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5.1.1.12 MME - CSS
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Legend:
Diameter: This protocol supports transferring of CSG subscription data for roaming subscribers only between MME and CSS (S7a). Diameter is defined in RFC 3588 [31].
Stream Control Transmission Protocol (SCTP): This protocol transfers signalling messages. SCTP is defined in RFC 4960 [35].
Figure 5.1.1.12-1: Control Plane for S7a interface
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5.1.1.13 MME - RCAF
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Legend:
Nq-AP: This application layer protocol supports the IMSI and APN retrieval procedure between the RCAF and the MME.
Stream Control Transmission Protocol (SCTP): This protocol transfers signalling messages. SCTP is defined in RFC 4960 [35].
Figure 5.1.1.13-1: Control Plane for Nq interface
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5.1.2 User Plane
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5.1.2.1 UE - P‑GW user plane with E-UTRAN
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Legend:
- GPRS Tunnelling Protocol for the user plane (GTP‑U): This protocol tunnels user data between eNodeB and the S‑GW as well as between the S‑GW and the P‑GW in the backbone network. GTP shall encapsulate all end user packets. End user Ethernet packets are only used with a combined PDN GW+SMF (as specified in TS 23.501 [83]).
- MME controls the user plane tunnel establishment and establishes User Plane Bearers between eNodeB and S‑GW.
- UDP/IP: These are the backbone network protocols used for routing user data and control signalling.
- LTE-Uu: The radio protocols of E-UTRAN between the UE and the eNodeB are specified in TS 36.300 [5].
Figure 5.1.2.1-1: User Plane
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5.1.2.2 eNodeB - S‑GW
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Legend:
- GPRS Tunnelling Protocol for the user plane (GTP‑U): This protocol tunnels user data between eNodeB and S‑GW.
- User Datagram Protocol (UDP): This protocol transfers user data. UDP is defined in RFC 768 [26].
Figure 5.1.2.2-1: User Plane for eNodeB – S‑GW
NOTE: Refer to TS 36.300 [5] for the corresponding user plane for the HeNB Subsystem - S-GW.
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5.1.2.3 UE - PDN GW user plane with 2G access via the S4 interface
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Legend:
- GPRS Tunnelling Protocol for the user plane (GTP‑U): This protocol tunnels user data between SGSN and the S‑GW as well as between the S‑GW and the P‑GW in the backbone network. GTP shall encapsulate all end user IP packets.
- UDP/IP: These are the backbone network protocols used for routing user data and control signalling.
- Protocols on the Um and the Gb interfaces are described in TS 23.060 [7].
Figure 5.1.2.3-1: User Plane for A/Gb mode
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5.1.2.4 UE - PDN GW user plane with 3G access via the S12 interface
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Legend:
- GPRS Tunnelling Protocol for the user plane (GTP‑U): This protocol tunnels user data between UTRAN and the S‑GW as well as between the S‑GW and the P‑GW in the backbone network. GTP shall encapsulate all end user IP packets.
- UDP/IP: These are the backbone network protocols used for routing user data and control signalling.
- Protocols on the Uu interface are described in TS 23.060 [7].
- SGSN controls the user plane tunnel establishment and establish a Direct Tunnel between UTRAN and S‑GW as shown in Figure 5.1.2.4-1.
Figure 5.1.2.4-1: User Plane for UTRAN mode and Direct Tunnel on S12
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5.1.2.5 UE - PDN GW user plane with 3G access via the S4 interface
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NOTE: Please refer to TS 23.402 [2] for the corresponding stack for PMIP based S5/S8.
Legend:
- GPRS Tunnelling Protocol for the user plane (GTP‑U): This protocol tunnels user data between UTRAN and the SGSN, between SGSN and S‑GW as well as between the S‑GW and the P‑GW in the backbone network. GTP shall encapsulate all end user IP packets.
- UDP/IP: These are the backbone network protocols used for routing user data and control signalling.
- Protocols on the Uu and the Iu interfaces are described in TS 23.060 [7].
- SGSN controls the user plane tunnel establishment and establishes a tunnel between SGSN and S‑GW. If Direct Tunnel is established between UTRAN and S‑GW, see Figure 5.1.2.4-1.
Figure 5.1.2.5-1: User Plane for Iu mode
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5.1.2.6 UE - P‑GW user plane with Control Plane CIoT EPS Optimisations
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Legend:
- GTP-u (GPRS Tunnelling Protocol User plane): This protocol tunnels user data between MME and the S‑GW as well as between the S‑GW and the P‑GW in the backbone network. GTP shall encapsulate all end user packets. End user Ethernet packets are only used with a combined PDN GW+SMF (as specified in TS 23.501 [83]).
- UDP/IP: These are the backbone network protocols used for routing user data and control signalling.
- NAS: this is the Non-Access Stratum Layer used to carry Data between UE and MME and may include Header compression and security functions of user plane IP data. Whether a convergence protocol sublayer may be required for this purpose is a stage 3 matter.
Figure 5.1.2.6-1: User Plane with Control Plane CIoT EPS Optimisations
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5.2 Identities
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5.2.1 EPS bearer identity
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An EPS bearer identity uniquely identifies an EPS bearer for one UE accessing via E-UTRAN. The EPS Bearer Identity is allocated by the MME. When using an EPS Radio Bearer, there is a one to one mapping between EPS RB and EPS Bearer, and the mapping between EPS RB Identity and EPS Bearer Identity is made by E-UTRAN. The E-RAB ID value used at S1 and X2 interfaces to identify an E-RAB is the same as the EPS Bearer ID value used to identify the associated EPS Bearer. When using Control Plane CIoT EPS Optimisation for user data transport for the PDN connectivity service, the MME (for uplink) and UE (for downlink) uses the EPS Bearer Identity contained within the NAS PDUs to identify the associated EPS bearer.
When there is a mapping between an EPS bearer and a PDP context, the same identity value is used for the EPS bearer ID and the NSAPI/RAB ID.
In some SM signalling messages in GERAN/UTRAN, transaction identifier (TI) represents NSAPI. The TI is dynamically allocated by the UE for UE-requested PDP context activation, and by the network for network-requested PDP context activation. A corresponding allocation is also needed for EPS Bearers in order to successfully transfer Bearers to GERAN/UTRAN. The TI is deallocated when a PDP context/EPS Bearer has been deactivated. TI usage is defined in TS 23.060 [7].
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5.2.2 Globally Unique Temporary UE Identity
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The MME shall allocate a Globally Unique Temporary Identity (GUTI) to the UE. The GUTI is defined in TS 23.003 [9].
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5.2.3 Tracking Area Identity (TAI)
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This is the identity used to identify tracking areas. The Tracking Area Identity is constructed from the MCC (Mobile Country Code), MNC (Mobile Network Code) and TAC (Tracking Area Code).
A TAI should be associated with a single time zone. All TAIs served by one eNodeB shall be in the same time zone.
NOTE: Changes in the TAI of a cell can occur but are normally infrequent and linked with O+M activity.
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5.2.4 eNodeB S1-AP UE Identity (eNodeB S1-AP UE ID)
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This is the temporary identity used to identify a UE on the S1-MME reference point within the eNodeB. It is unique within the eNodeB.
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5.2.5 MME S1-AP UE Identity (MME S1-AP UE ID)
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This is the temporary identity used to identify a UE on the S1-MME reference point within the MME. It is unique within the MME.
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5.2.6 Closed Subscriber Group ID
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A CSG ID is a unique identifier within the scope of PLMN defined in TS 23.003 [9] which identifies a Closed Subscriber Group (CSG) in the PLMN associated with a CSG cell or group of CSG cells.
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5.2.7 UE Radio Capability ID
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The UE Radio Capability ID is a short pointer with format defined in TS 23.003 [9] that is used to uniquely identify a set of UE Radio Capabilities (excluding UTRAN and NB-IoT capabilities). The UE Radio Capability ID is assigned either by the serving PLMN or by the UE manufacturer, as follows:
- UE manufacturer-assigned: The UE Radio Capability ID may be assigned by the UE manufacturer in which case it includes the UE manufacturer information (i.e. a Vendor ID). In this case, the UE Radio Capability ID uniquely identifies a set of UE radio capabilities and the UE Radio Capability for Paging for this manufacturer in any PLMN.
- PLMN-assigned: If a UE manufacturer-assigned UE Radio Capability ID is not used by the UE or the serving network, or it is not recognised by the serving PLMN UCMF, the UCMF may allocate UE Radio Capability IDs for the UE corresponding to different sets of UE radio capabilities the PLMN may receive from the UE at different times. In this case, the UE Radio Capability IDs the UE receives are applicable to the serving PLMN and uniquely identify the corresponding sets of UE radio capabilities and the UE Radio Capability for Paging(s) in this PLMN. The PLMN assigned UE Radio Capability ID includes a Version ID in its format. The value of the Version ID is the one configured in the UCMF, at time the UE Radio Capability ID value is assigned. The Version ID value makes it possible to detect whether a UE Radio Capability ID is current or outdated.
NOTE: For the case the PLMN is configured to store PLMN assigned IDs in the UE manufacturer-assigned operation requested list defined in clause 5.11.3a, then the algorithm for assignment of PLMN Assigned UE Radio Capability ID shall assign different UE Radio Capability IDs for UEs with different IMEI/TAC value.
The type of UE Radio Capability ID (UE manufacturer-assigned or PLMN-assigned) is distinguished when a UE Radio Capability ID is signalled.
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5.3 Authentication, security and location management
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5.3.1 IP address allocation
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5.3.1.1 General
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The procedures of clause 5.3.1 apply to UEs activating a PDN connection of PDN Type IPv4, IPv6 or IPv4v6. Part of it also applies for PDN Type Non-IP when SGi PtP Tunnelling based on UDP/IP, see clause 4.3.17.8, is used. The procedures of clause 5.3.1 do not apply to UEs activating a PDN connection of PDN Type Ethernet.
A UE shall perform the address allocation procedures for at least one IP address (either IPv4 address or IPv6 prefix) after the default bearer activation if no IPv4 address is allocated during the default bearer activation.
One of the following ways shall be used to allocate IP addresses for the UE:
a) The HPLMN allocates the IP address to the UE when the default bearer is activated (dynamic or static HPLMN address);
b) The VPLMN allocates the IP address to the UE when the default bearer is activated (dynamic VPLMN address); or
c) The PDN operator or administrator allocates an (dynamic or static) IP address to the UE when the default bearer is activated (External PDN Address Allocation).
The IP address allocated for the default bearer shall also be used for the dedicated bearers within the same PDN connection. IP address allocation for PDN connections, which are activated by the UE requested PDN connectivity procedure, is handled with the same set of mechanisms as those used within the Attach procedure.
PDN types IPv4, IPv6 and IPv4v6 are supported. An EPS Bearer of PDN type IPv4v6 may be associated with one IPv6 prefix only or with both one IPv4 address and one IPv6 prefix. PDN type IPv4 is associated with an IPv4 address. PDN type IPv6 is associated with an IPv6 prefix. PDN types IPv4 and IPv6 are utilised for the UE and/or the PDN GW support IPv4 addressing only or IPv6 prefix only; or operator preferences dictate the use of a single IP version only, or the subscription is limited to IPv4 only or IPv6 only for this APN. In addition, PDN type IPv4 and IPv6 are utilised for interworking with nodes of earlier releases.
The way that the UE sets the requested PDN type may be pre-configured in the device per APN. Unless otherwise configured (including when the UE does not send any APN), the UE sets the PDN type during the Attach or PDN Connectivity procedures based on its IP stack configuration as follows:
- A UE which is IPv6 and IPv4 capable shall request for PDN type IPv4v6.
- A UE which is only IPv4 capable shall request for PDN type IPv4.
- A UE which is only IPv6 capable shall request for PDN type IPv6.
- When the IP version capability of the UE is unknown in the UE (as in the case when the MT and TE are separated and the capability of the TE is not known in the MT), the UE shall request for PDN type IPv4v6.
NOTE 1: At intersystem changes between GERAN/UTRAN and E-UTRAN there is a 1-to-1 mapping between PDP type IPv4v6 and PDN type IPv4v6 without re-negotiation of the PDP/PDN type used for a PDN connection.
The HSS stores one PDN type per APN in the subscription data. During the Attach or UE requested PDN connectivity procedure the MME compares the requested PDN type to the PDN type in the subscription records for the given APN and sets the PDN type as follows:
- If the requested PDN type is allowed by subscription, the MME sets the PDN type as requested.
- If the requested PDN type is IPv4v6 and subscription data only allows PDN type IPv4 or only allows PDN type IPv6, the MME sets the PDN type according to the subscribed value. A reason cause shall be returned to the UE indicating that only the assigned PDN type is allowed. In this case the UE shall not request another PDN connection to the same APN for the other IP version during the existence of the PDN connection.
- If the requested PDN type is IPv4 or IPv6, and either the requested PDN type or PDN type IPv4v6 are subscribed, the MME sets the PDN type as requested. Otherwise the PDN connection request is rejected.
- If the requested PDN type is IPv4v6, and both IPv4 and IPv6 PDN types are allowed by subscription but not IPv4v6, the MME shall set the PDN type to IPv4 or IPv6 where the selection between IPv4 and IPv6 is implementation specific. The UE should then initiate the UE requested PDN connectivity procedure to this APN in order to activate a second PDN connection with the other single address PDN type which was not allocated by the network.
NOTE 2: If the MT and TE are separated, the UE might not be able to use reason cause "single address bearers only" as a trigger for activating a second single-stack EPS bearer.
The PDN GW may restrict the usage of a PDN type IPv4v6 as follows.
- If the PDN GW receives a request for PDN type IPv4v6, but the PDN GW operator preferences dictate the use of IPv4 addressing only or IPv6 prefix only for this APN, the PDN type shall be changed to a single address PDN type (IPv4 or IPv6) and a reason cause shall be returned to the UE indicating that only the assigned PDN type is allowed. In this case the UE shall not request another PDN connection to the same APN for the other IP version during the existence of the PDN connection.
- If the PDN GW receives a request for PDN type IPv4v6, but the MME does not set the Dual Address Bearer Flag due to the MME operator using single addressing per bearer to support interworking with nodes of earlier releases the PDN type shall be changed to a single IP version only and a reason cause shall be returned to the UE indicating that only single IP version per PDN connection is allowed. In this case the UE should request another PDN connection for the other IP version using the UE requested PDN connectivity procedure to the same APN with a single address PDN type (IPv4 or IPv6) other than the one already activated.
During inter-RAT mobility between E‑UTRAN and UTRAN/GERAN, an EPS bearer with PDN type IPv4v6 shall be mapped one-to-one to PDP type IPv4v6.
During inter-RAT mobility between E-UTRAN and UTRAN/GERAN, an EPS bearer with PDN type IPv4 shall be mapped one-to-one to a PDP context of PDP type IPv4. An EPS bearer with PDN type IPv6 shall be mapped one-to-one to a PDP context of PDP type IPv6.
It is the HPLMN operator that shall define in the subscription whether a dynamic HPLMN or VPLMN address may be used.
The EPS UE may indicate to the network within the Protocol Configuration Options element that the UE wants to obtain the IPv4 address with DHCPv4, which is a deferred IPv4 address allocation option, or during the default bearer activation procedure. This implies the following behaviour both for static and dynamic address allocation:
- the UE may indicate that it prefers to obtain an IPv4 address as part of the default bearer activation procedure. In such a case, the UE relies on the EPS network to provide IPv4 address to the UE as part of the default bearer activation procedure.
- the UE may indicate that it prefers to obtain the IPv4 address after the default bearer setup by DHCPv4. That is, when the EPS network supports DHCPv4 and allows that, it does not provide the IPv4 address for the UE as part of the default bearer activation procedures. The network may respond to the UE by setting the PDN Address to 0.0.0.0. After the default bearer establishment procedure is completed, the UE uses the connectivity with the EPS and initiates the IPv4 address allocation on its own using DHCPv4. However, if the EPS network provides IPv4 address to the UE as part of the default bearer activation procedure, the UE should accept the IPv4 address indicated in the default bearer activation procedure.
- if the UE sends no Address Allocation Preference, the PDN GW determines whether DHCPv4 is used between the UE and the PDN GW (for the deferred IPv4 address allocation) or not, based on per APN configuration
Both EPS network elements and UE shall support the following mechanisms:
a. IPv4 address allocation via default bearer activation, if IPv4 is supported.
b. /64 IPv6 prefix allocation via IPv6 Stateless Address autoconfiguration according to RFC 4862 [18], if IPv6 is supported;
Furthermore, the Protocol Configuration Options may be used during bearer activation to configure parameters which are needed for IP address allocation.
Both EPS network elements and UE may support the following mechanisms:
a. IPv4 address allocation and IPv4 parameter configuration after the attach procedure via DHCPv4 according to RFC 2131 [19] and RFC 4039 [25];
b. IPv6 parameter configuration via Stateless DHCPv6 according to RFC 8415 [94].
c. Allocation of IPv6 prefixes using DHCPv6 according to RFC 8415 [94].
EPS network elements may support the following mechanism:
a. Allocation of a static IPv4 address and/or a static IPv6 prefix based on subscription data in the HSS.
If the static IP address/prefix is not stored in the HSS subscription record, it may be configured on a per-user per-APN basis in the DHCP/Radius/Diameter server and the PDN GW retrieves the IP address/prefix for the UE from the DHCP/Radius/Diameter server. In this case, static IP address/prefix is allocated by the same procedures as the dynamic IP address/prefix allocation (i.e. in such cases it is transparent to the PDN GW if the IP address is static or dynamic).
If the static IP address/prefix is stored in the HSS subscription record, during the default bearer establishment the PDN GW receives this static IP address/prefix from Serving GW. In this case the PDN GW shall deliver the received address/prefix to the UE. The static IP address/prefix is delivered to the UE in the same way as a dynamic IP address/prefix. Thus it is transparent to the UE whether the PLMN or the external PDN allocates the IP address and whether the IP address is static or dynamic.
The following clauses describe how the above listed IP address allocation mechanisms work when GTP based S5/S8 is used. The way of working of the IP address allocation mechanisms for PMIP based S5/S8 can be found in TS 23.402 [2].The procedures can be used both for PLMN (VPLMN/HPLMN) or external PDN based IP address allocation.
In order to support DHCP based IP address configuration, the PDN GW shall act as the DHCP server towards the UE for both HPLMN assigned dynamic and static IP addressing and for VPLMN assigned dynamic IP addressing. When DHCP is used for external PDN assigned addressing and parameter configuration, the PDN GW shall act as the DHCP server towards the UE and it shall act as the DHCP client towards the external DHCP server. The Serving GW does not have any DHCP functionality. It forwards packets, including DHCP packets, between the UE and the PDN GW.
IPv6 Stateless Address autoconfiguration specified in RFC 4862 [18] is the basic mechanism to allocate /64 IPv6 prefix to the UE.
During default bearer establishment, the PDN GW sends the IPv6 prefix and Interface Identifier to the S‑GW, and then the S‑GW forwards the IPv6 prefix and Interface Identifier to the MME or to the SGSN. The MME or the SGSN forwards the IPv6 Interface Identifier to the UE. The MME does not forward the IPv6 prefix to the UE. If the UE receives the IPv6 prefix from the SGSN during PDP Context Activation procedure, it shall ignore it.
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5.3.1.2 IP address allocation, renewal and release mechanisms for GTP based S5/S8
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5.3.1.2.1 IPv4 address allocation via default bearer activation and release via PDN connection release
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An IPv4 address may be provided to the UE as part of the default bearer activation and the IPv4 address is released when PDN connection associated with the IPv4 address is released.
When the PLMN allocates an IPv4 address, it is the PDN GW responsibility to allocate and release the IPv4 address. The PDN GW may use an internal IPv4 address pool in this case. The PDN GW allocates an IPv4 address upon default bearer activation and it releases the IPv4 address upon PDN connection release associated with the IPv4 address for a given UE.
NOTE: If the PDN type is IPv4v6, when the PDN Connection is released, the IPv6 address is also released.
When an IPv4 address is allocated from an external PDN, it is the PDN GW responsibility to obtain the IPv4 address from the external PDN, and to allocate, renew and release the IPv4 address. The PDN GW may use DHCPv4 to obtain, renew and release the IPv4 address from the external PDN. If RADIUS or Diameter is used towards the external PDN, as described in TS 29.061 [38], the IP address can be obtained, renewed and released as part of these procedures. If DHCPv4 is used, the PDN GW functions as a DHCPv4 Client. If RADIUS is used, the PDN GW functions as a RADIUS Client. If Diameter is used, the PDN GW functions as a Diameter Client.
After releasing the IPv4 address, the PDN GW should not assign that IPv4 address to other user immediately.
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5.3.1.2.2 Allocation, renewal and release of the IPv6 default prefix via IPv6 stateless address autoconfiguration
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When the PLMN allocates an IPv6 prefix, it is the PDN GW responsibility to allocate and release the IPv6 prefix. The PDN GW may use an internal IPv6 prefix pool in this case. The PDN GW allocates a globally unique /64 IPv6 prefix via Router Advertisement to a given UE.
When an IPv6 prefix is allocated from an external PDN, it is the PDN GW responsibility to obtain the IPv6 prefix from the external PDN and to allocate, renew and release the IPv6 prefix. The PDN GW may use DHCPv6 to obtain the IPv6 prefix from the external PDN. In this case, the PDN GW functions as a DHCPv6 client. If RADIUS or Diameter is used towards the external PDN as described in TS 29.061 [38], the IPv6 prefix can be obtained, renewed and released as part of these procedures. If RADIUS is used, the PDN GW functions as the RADIUS Client. If Diameter is used, the PDN GW functions as the Diameter Client.
The procedure of stateless IPv6 address autoconfiguration is the following: After default bearer establishment the UE may send a Router Solicitation message to the PDN GW to solicit a Router Advertisement message. The PDN GW sends a Router Advertisement message (solicited or unsolicited) to the UE. The Router Advertisement messages shall contain the same IPv6 prefix as the one provided during default bearer establishment. If the UE receives an IPv6 prefix from a SGSN during the PDP Context activation procedure, it shall ignore it.
After the UE has received the Router Advertisement message, it constructs a full IPv6 address via IPv6 Stateless Address autoconfiguration in accordance with RFC 4862 [18]. To ensure that the link-local address generated by the UE does not collide with the link-local address of the PDN GW, the PDN GW shall provide an interface identifier (see RFC 4862 [18]) to the UE and the UE shall use this interface identifier to configure its link-local address. For stateless address autoconfiguration however, the UE can choose any interface identifier to generate IPv6 addresses, other than link-local, without involving the network. However, the UE shall not use any identifiers defined in TS 23.003 [9] as the basis for generating the interface identifier. For privacy, the UE may change the interface identifier used to generate full IPv6 address, as defined in TS 23.221 [27] without involving the network.
Any prefix that the PDN GW advertises to the UE is globally unique. The PDN GW shall also record the relationship between the UE's identity (IMSI) and the allocated IPv6 prefix. Because any prefix that the PDN GW advertises to the UE is globally unique, there is no need for the UE to perform Duplicate Address Detection for any IPv6 address configured from the allocated IPv6 prefix. Even if the UE does not need to use Neighbor Solicitation messages for Duplicate Address Detection, the UE may, for example, use them to perform Neighbor Unreachability Detection towards the PDN GW, as defined in RFC 4861 [32]. Therefore, the PDN GW shall respond with a Neighbor Advertisement upon receiving a Neighbor Solicitation message from the UE.
In order to renew the allocated IPv6 prefix, the PDN GW sends a Router Advertisement (solicited or unsolicited) to the UE with the same prefix and new non-zero values in preferred and valid lifetime fields.
In order to release the allocated IPv6 prefix, the PDN GW shall initiate the PDN connection release procedure. Upon release of the PDN connection, the UE shall implicitly release the prefix for the corresponding PDN connection.
NOTE 2: If the PDN type is IPv4v6, when the PDN Connection is released, the IPv4 address is also released.
After releasing the IPv6 prefix, the PDN GW should not assign that IPv6 prefix to other user immediately.
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5.3.1.2.3 IPv6 parameter configuration via stateless DHCPv6
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The UE may use stateless DHCPv6 for additional parameter configuration. The PDN GW acts as the DHCP server. When PLMN based parameter configuration is used, the PDN GW provides the requested parameters from locally provisioned database. When external PDN based parameter configuration is used, the PDN GW obtains the requested configuration parameters from the external PDN as described in the previous clauses. When the PDN GW acts as a DHCPv6 server towards the UE, the PDN GW may act as DHCPv6 client towards the external PDN to request the configuration parameters for the UE. If RADIUS or Diameter is used towards the external PDN as described in TS 29.061 [38], the requested configuration parameters can be fetched as part of these procedures.
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5.3.1.2.4 IPv4 address allocation, renewal and release and IPv4 parameter configuration via DHCPv4
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When the PLMN allocates an IPv4 address, it is the PDN GW responsibility to allocate, renew and release the IPv4 address.
When external PDN allocation is used, the PDN GW functions as a DHCPv4 server towards the UE. The PDN GW may act as a DHCP Client when interacting with a DHCPv4 server in the external PDN in order to obtain, renew and release the IPv4 address and to obtain the configuration parameters. Or, if RADIUS or Diameter is used towards the external PDN as described in TS 29.061 [38], the IPv4 address and the requested configuration parameters can be obtained, renewed and released as part of these procedures.
If dynamic policy provisioning is deployed, and the PCRF was not informed about the IPv4 address at IP-CAN session establishment, the PDN GW shall initiate an IP-CAN Session Modification procedure to inform the PCRF about an allocated IPv4 address. If the IPv4 address is released, the PDN GW shall inform the PCRF about the de-allocation of an IPv4 address.
If the UE sends DHCPv4 lease renewal message to renew the lease of the allocated IPv4 address, the PDN GW shall renew the lease of the allocated IPv4 address. If the IPv4 address was obtained from an external PDN, the PDN GW shall perform the DHCPv4 lease renewal procedure with the external PDN if DHCPv4 was used for obtaining IPv4 address from external PDN. If Diameter or RADIUS procedures where used to obtain the IPv4 address from external PDN, the PDN GW may perform corresponding update procedures as applicable. If the external PDN extends lease of the allocated IPv4 address, the PDN GW responds accordingly to the UE. Otherwise, if the external PDN does not extend the lease of the allocated IPv4 address, the PDN GW responds with the remaining lease time of the IPv4 address. If there is no PDN address allocated to the UE for this PDN connection, the PDN GW shall perform PDN GW initiated bearer deactivation procedure as defined in clause 5.4.4.1.
If the UE sends DHCPv4 release message to release the allocated IPv4 address for the PDN connection, the PDN GW may any time thereafter release the IPv4 address. If the PDN connection has no allocated PDN address, the PDN GW may at any time initiate PDN GW initiated bearer deactivation procedure as defined in clause 5.4.4.1.
NOTE: If the PDN type is IPv4v6 the release of the allocated IPv4 address does not mean that there is no allocated PDN address for the PDN connection, as the IPv6 prefix still remains allocated to that PDN connection.
If the PDN connection is released without any DHCPv4 release signalling with the UE, the UE and the PDN GW shall release the IPv4 address implicitly, as soon as the PDN connection is released.
After releasing the IPv4 address, the PDN GW should not assign that IPv4 address to any other user immediately.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.1.2.5 Void
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.1.2.6 IPv6 Prefix Delegation via DHCPv6
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Optionally a single network prefix shorter than the default /64 prefix may be assigned to a PDN connection. In this case, the /64 default prefix used for IPv6 stateless autoconfiguration will be allocated from this network prefix; the remaining address space from the network prefix can be delegated to the PDN connection using prefix delegation after the default bearer establishment and IPv6 prefix allocation via IPv6 stateless address autoconfiguration as defined in clause 5.3.1.2.2. When PLMN based parameter configuration is used, the PDN GW provides the requested IPv6 prefix from a locally provisioned pool. When external PDN based IPv6 prefix allocation is used, the PDN GW obtains the prefix from the external PDN.
NOTE: Allocation of IPv6 prefixes with flexible prefix length can leverage e.g. local configuration on the PDN GW or interaction with the AAA server.
The address space provided is maintained as an IPv6 address space pool available to the PDN connection for DHCPv6 IPv6 prefix requests with the exclusion of the IPv6 prefix that is allocated to the PDN connection during default bearer establishment as defined in clause 5.3.1.2.2. The total IPv6 address space available for the PDN connection (UE default bearer prefix and UE PDN connection IPv6 address space pool) shall be possible to aggregate into one IPv6 prefix that will represent all IPv6 addresses that the UE may use. If the UE had indicated that it supports prefix exclusion and the prefix to be delegated to the UE includes the /64 prefix that was allocated to the PDN Connection, the PDN GW shall utilise the prefix exclusion feature as specified for DHCPv6 Prefix Delegation in IETF RFC 6603 [70].
The UE uses DHCPv6 to request additional IPv6 prefixes (i.e. prefixes in addition to the default prefix) from the PDN GW after completing stateless IPv6 address autoconfiguration procedures. The UE acts as a "Requesting Router" as described in RFC 8415 [94] and inserts one or more IA_PD option(s) into a DHCPv6 Solicit message sent from the UE to the PDN GW. The PDN GW acts as the DHCP server and fulfils the role of a "Delegating Router" according to RFC 8415 [94]. The UE optionally includes the RAPID_COMMIT option in the DHCPv6 Solicit message to trigger two-message DHCPv6 procedure instead of the four-message DHCPv6 procedure. The UE shall include OPTION_PD_EXCLUDE option code in an OPTION_ORO option to indicate support for prefix exclusion. In response to the DHCPv6 Solicit message, the UE receives a DHCPv6 Reply message with one or more IA_PD prefix(es) for every IA_PD option that it sent in the DHCPv6 Solicit message. The PDN GW delegates a prefix excluding the default prefix with help of OPTION_PD_EXCLUDE. Prefix exclusion procedures shall follow IETF RFC 6603 [70].
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.2 Attach procedure
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.2.1 E-UTRAN Initial Attach
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A UE/user needs to register with the network to receive services that require registration. This registration is described as Network Attachment. The always-on connectivity for UE/users of the EPS may be enabled by establishing a default EPS bearer during Network Attachment. The PCC rules applied to the default EPS bearer may be predefined in the PDN GW and activated in the attachment by the PDN GW itself. The Attach procedure may trigger one or multiple Dedicated Bearer Establishment procedures to establish dedicated EPS bearer(s) for that UE. During the attach procedure, the UE may request for an IP address allocation. Terminals utilising only IETF based mechanisms for IP address allocation are also supported.
During the Initial Attach procedure the Mobile Equipment Identity is obtained from the UE. The MME operator may check the ME Identity with an EIR. The MME passes the ME Identity (IMEISV) to the HSS and to the PDN GW.
During the Initial Attach procedure, if the MME supports SRVCC and if any of the conditions described in step 8 in Figure 5.3.2.1-1 are satisfied, the MME informs the HSS with the UE SRVCC capability e.g. for further IMS registration.
The E-UTRAN Initial Attach procedure is used for Emergency Attach by UEs that need to perform emergency services but cannot gain normal services from the network. These UEs are in limited service state as defined in TS 23.122 [10]. Also UEs that had attached for normal services and do not have emergency bearers established and are camped on a cell in limited service state (e.g. restricted Tracking Area or not allowed CSG) shall initiate the Attach procedures indicating that the attach is to receive emergency services. UEs that camp normally on a cell, i.e. UEs that are not in limited service state, should initiate normal initial attach when not already attached and shall initiate the UE Requested PDN Connectivity procedure to receive emergency EPS bearer services.
The E-UTRAN Initial Attach procedure is used for RLOS Attach by UEs in limited service state as defined in TS 23.122 [10], as well as UEs attached for normal services but moved to a cell in limited service state (e.g. restricted Tracking Area or not allowed CSG).
NOTE 1: A UE that is emergency or RLOS attached performs initial attach procedure before being able to obtain normal services.
In order to limit load on the network, only when performing an E-UTRAN Attach with a new PLMN (i.e. not the registered PLMN or an equivalent PLMN of the registered PLMN), a UE configured to perform Attach with IMSI at PLMN change (see TS 24.368 [69]) shall identify itself by its IMSI instead of any stored temporary identifier.
This procedure is also used to establish the first PDN connection over E-UTRAN when the UE already has active PDN connections over a non-3GPP access network and wants to establish simultaneous PDN connections to different APNs over multiple accesses.
During the Attach procedure, a Multi-USIM UE may indicate to the MME a Requested IMSI Offset, as described in clause 4.3.33, with the aim of modifying the timing of the Paging Occasions to avoid paging collisions.
NOTE 2: As an exception, during the Attach procedure a Multi-USIM UE implementation can decide to indicate to the MME a Requested IMSI Offset even if it does not know whether the MME supports it.
Figure 5.3.2.1-1: Attach procedure
NOTE 3: For a PMIP-based S5/S8, procedure steps (A), (B), and (C) are defined in TS 23.402 [2]. Steps 7, 10, 13, 14, 15 and 23a/b concern GTP based S5/S8.
NOTE 4: The Serving GWs and PDN GWs involved in steps 7 and/or 10 may be different to those in steps 13‑15.
NOTE 5: The steps in (D) are executed only upon handover from non-3GPP access or if Presence Reporting Area Information is received from the MME.
NOTE 6: More detail on procedure steps (E) is defined in the procedure steps (B) in clause 5.3.8.3.
NOTE 7: More detail on procedure steps (F) is defined in the procedure steps (B) in clause 5.3.8.4.
NOTE 8: Some deployments cannot support all system features, for example they cannot support user plane establishment and user plane data transfer, when operating in S&F Mode in the example split MME deployment as described in Annex O.
1. A UE, camping on an E-UTRAN cell reads the related System Information Broadcast.
An E-UTRAN cell for a PLMN that supports CIoT enhancements shall broadcast:
For the NB-IoT case:
- Whether it can connect to an MME which supports EPS Attach without PDN Connectivity.
For the WB-E-UTRAN case:
- Whether it supports Control Plane CIoT EPS Optimisation and it can connect to an MME which supports Control Plane CIoT EPS Optimisation.
- Whether it supports User Plane CIoT EPS Optimisation and it can connect to an MME which supports User Plane CIoT EPS Optimisation.
- Whether it can connect to an MME which supports EPS Attach without PDN Connectivity.
If the PLMN does not advertise support of EPS attach without PDN connectivity and the UE can only attach without PDN connectivity, then the UE shall not attach to the PLMN in this cell and shall proceed as specified in TS 23.122 [10].
In the case of WB-E-UTRAN, if the PLMN does not support Control Plane CIoT EPS Optimisation, and the UE only supports Control Plane CIoT EPS Optimisation and cannot otherwise attach, then the UE shall not proceed with the Attach to the PLMN in this cell and shall proceed as specified in TS 23.122 [10].
An E-UTRAN cell for a PLMN that supports Restricted Local Operator Service shall broadcast:
- Whether it supports Restricted Local Operator Service.
If the PLMN does not advertise support for Restricted Local Operator Services, the UE shall not proceed with the Attach with indication that the attach is to receive Restricted Local Operator Services to the PLMN in this cell.
If a Service Gap timer is running in the UE (see clause 4.3.17.9) and the Attach Type is not Emergency Attach and it is not an Attach without PDN connectivity, then the UE shall not send Attach Requests to this PLMN or any other PLMN as long as the timer is running.
If the UE can proceed to attach, it initiates the Attach procedure by the transmission, to the eNodeB, of an Attach Request (IMSI or old GUTI, Old GUTI type, last visited TAI (if available), UE Core Network Capability, UE Specific DRX parameters, extended idle mode DRX parameters, UE paging probability information, Attach Type, ESM message container (Request Type, PDN Type, Protocol Configuration Options, Ciphered Options Transfer Flag, Header Compression Configuration), KSIASME, NAS sequence number, NAS-MAC, additional GUTI, P-TMSI signature, Voice domain preference and UE's usage setting, Preferred Network behaviour, MS Network Capability, Support for restriction of use of Enhanced Coverage, UE has UE Radio Capability ID assigned for the selected PLMN, Requested IMSI Offset) message together with RRC parameters indicating the Selected Network and the old GUMMEI.
In the RRC connection establishment signalling associated with the Attach Request, the UE indicates its support of the CIoT EPS Optimisations, relevant for MME selection.
The UE shall also include an IAB-Indication in the RRC connection establishment signalling, if the UE is an IAB-node, as defined in TS 36.331 [37].
If the UE identifies itself with the old GUTI, the UE shall set the Old GUTI Type to indicate whether the Old GUTI is a native GUTI or is mapped from a P-TMSI and RAI. The old GUTI may be derived from a P‑TMSI and RAI. IMSI shall be included if the UE does not have a valid GUTI or a valid P‑TMSI available, or if the UE is configured to perform Attach with IMSI at PLMN change and is accessing a new PLMN. The UE stores the TIN in detached state. If the UE's TIN indicates "GUTI" or "RAT-related TMSI" and the UE holds a valid GUTI then the old GUTI indicates this valid GUTI. If the UE's TIN indicates "P‑TMSI" and the UE holds a valid P‑TMSI and related RAI then these two elements are indicated as the old GUTI. Mapping a P‑TMSI and RAI to a GUTI is specified in TS 23.003 [9]. If the UE holds a valid GUTI and the old GUTI indicates a GUTI mapped from a P-TMSI and RAI, then the UE indicates the GUTI as additional GUTI. If the old GUTI indicates a GUTI mapped from a P-TMSI and RAI and the UE has a valid P-TMSI signature associated to it, the P-TMSI signature shall be included. The UE sets the voice domain preference and UE's usage setting according to its configuration, as described in clause 4.3.5.9.
Alternatively, when a UE only supports E-UTRAN, if the UE has a GUTI available and the UE is accessing the same PLMN (or ePLMN), then it identifies itself with the old GUTI and sets the Old GUTI Type to 'native', otherwise the UE configuration determines whether the UE identifies itself with its IMSI or the Old GUTI.
The UE includes the extended idle mode DRX parameters information element if the UE needs to enable extended idle mode DRX.
The UE may include UE paging probability information if it supports the assignment of WUS Assistance Information from the MME to assist the eNodeB's Wake-Up Signal (WUS) group decision (see TS 36.300 [5]).
If available, the last visited TAI shall be included in order to help the MME produce a good list of TAIs for any subsequent Attach Accept message. Selected Network indicates the PLMN that is selected for network sharing purposes. The RRC parameter "old GUMMEI" takes its value from the "old GUTI" contained in the Attach Request. UE Network Capability is described in UE capabilities, see clause 5.11.
If the UE has valid security parameters, the Attach Request message shall be integrity protected by the NAS-MAC in order to allow validation of the UE by the MME. KSIASME, NAS sequence number and NAS-MAC are included if the UE has valid EPS security parameters. NAS sequence number indicates the sequential number of the NAS message. If the UE does not have a valid EPS security association, then the Attach Request message is not integrity protected. In this case the security association is established in step 5a. The UE network capabilities indicate also the supported NAS and AS security algorithms.
PDN type indicates the requested IP version (IPv4, IPv4/IPv6, IPv6). For a UE that support CIoT EPS Optimisations, the PDN type may also be "Non-IP". PDN type may also indicate Ethernet.
Protocol Configuration Options (PCO) are used to transfer parameters between the UE and the PDN GW, and sent transparently through the MME and the Serving GW. The Protocol Configuration Options may include the Address Allocation Preference indicating that the UE prefers to obtain an IPv4 address only after the default bearer activation by means of DHCPv4. If the UE intends to send PCO which require ciphering (e.g., PAP/CHAP usernames and passwords) or send an APN, or both, the UE shall set the Ciphered Options Transfer Flag and send PCO or APN or both only after authentication and NAS security setup have been completed (see below).
NOTE 9: External network operators wanting to use PAP for authentication are warned that PAP is an obsolete protocol from a security point of view. CHAP provides stronger security than PAP.
If the UE supports 3GPP PS Data Off, it shall include in the PCO the 3GPP PS Data Off UE Status, which indicates whether the user has activated or deactivated 3GPP PS Data Off.
If the UE has UTRAN or GERAN capabilities, it shall send the NRSU in the PCO to indicate the support of the network requested bearer control in UTRAN/GERAN. The UE sends the ETFTU in the PCO to indicate the support of the extended TFT filter format. Request Type is included in the ESM message container and indicates "Handover" when the UE has already an activated PDN GW/HA due to mobility with non-3GPP accesses.
If a UE indicates support of CIoT EPS Optimisations in the RRC message, it may omit the ESM message container. If the ESM message container is omitted the MME shall not establish a PDN connection as part of the Attach procedure. In this case steps 6, 12 to 16 and 23 to 26 are not executed. In addition, for the case of UEs attaching with Control Plane CIoT EPS Optimisation with no user plane establishment, steps 17 to 22 are replaced by S1 AP NAS Transport and RRC Direct Transfer messages that just transport the NAS Attach Accept and NAS Attach Complete messages.
Attach Type indicates whether it is an EPS attach or a combined EPS/IMSI attach or an Emergency Attach or an RLOS Attach. Emergency Attach and RLOS Attach shall not be indicated when the UE is using NB-IoT. When using CIoT EPS Optimisations, the UE may indicate EPS attach and request SMS by setting the "SMS transfer without Combined Attach" flag in the Preferred Network Behaviour IE.
If a UE includes a Preferred Network Behaviour, this defines the Network Behaviour the UE is expecting to be available in the network as defined in clause 4.3.5.10.
If a UE indicated Control Plane CIoT EPS Optimisation supported in Preferred Network Behaviour, and the UE included the ESM message container, and the PDN type was IPv4 or IPv6 or IPv4v6, and the UE supports header compression, it shall include the Header Compression Configuration. The Header Compression Configuration includes the information necessary for the ROHC channel setup. Optionally, the Header Compression Configuration may include additional header compression context setup parameters if the UE already has the application traffic information, e.g. the target server IP address.
For an Emergency Attach the UE shall set both the Attach Type and the Request Type to "Emergency" and the IMSI shall be included if the UE does not have a valid GUTI or a valid P-TMSI available. The IMEI shall be included when the UE has no IMSI, no valid GUTI and no valid P-TMSI.
For RLOS attach, the UE shall set the Attach Type to "RLOS" and the Request Type to "RLOS", the IMSI shall be included if available and if the UE does not have a valid GUTI or a valid P-TMSI available. The IMEI shall be included when the UE has no IMSI, no valid GUTI and no valid P-TMSI.
If the UE supports RACS as defined in clause 5.11.3a, and if the UE is provisioned with a UE Radio Capability ID for use in the selected PLMN (i.e. PLMN-assigned for the specific PLMN or UE manufacturer-assigned), the UE includes a flag that indicates it has an assigned UE Radio Capability ID for use in the selected PLMN but the actual UE Radio Capability ID is provided to MME after security context is established in step 5a (see below).
If a Multi-USIM UE needs to modify the Paging Occasions in order to avoid paging collisions, it sends a Requested IMSI Offset to the MME, in order to signal an alternative IMSI as described in clause 4.3.33.
2. The eNodeB derives the MME address from the RRC parameters carrying the old GUMMEI, the indicated Selected Network and the RAT (NB-IoT or WB-E-UTRAN). If that MME is not associated with the eNodeB or the old GUMMEI is not available, the eNodeB selects an MME as described in clause 4.3.8.3 on "MME selection function". The eNodeB forwards the Attach Request message in a S1-MME control message (Initial UE message) together with the Selected Network, CSG access mode, CSG ID, L-GW address, TAI+ECGI of the cell from where it received the message to the new MME. CSG ID is provided if the UE attaches via a CSG cell or hybrid cell. CSG access mode is provided if the UE attaches via a hybrid cell. If the CSG access mode is not provided but the CSG ID is provided, the MME shall consider the cell as a CSG cell. If the eNodeB has a collocated L-GW, it includes the L-GW address in the Initial UE message to the MME.
If the IAB-Indication is received from the UE in step 1, the eNodeB selects an MME that supports IAB operation and includes the IAB-Indication in the Initial UE message to the MME.
If the MME is not configured to support Emergency Attach the MME shall reject any Attach Request that indicates Attach Type "Emergency".
If the MME is not configured to support RLOS Attach, the MME shall reject any Attach Request that indicates Attach Type "RLOS".
If the UE has included the Preferred Network Behaviour, and what the UE indicated it supports in Preferred Network Behaviour is incompatible with the network support e.g. the UE indicated support only for Control Plane CIoT EPS Optimisation and the MME only supports User Plane CIoT EPS Optimisation, the MME shall reject the Attach Request with an appropriate cause value (e.g. one that avoids retries on this PLMN).
To assist Location Services, the eNodeB indicates the UE's Coverage Level to the MME.
If the UE supports MT-EDT as indicated in the UE Network Capability, the MME shall consider this parameter to provide the MT-EDT indication towards Serving GW during PDN Connection establishment or mobility procedures, and handle the data size information that the MME may receive during Downlink Data Notification procedures as defined in clause 5.3.4B.6, and clause 5.3.5B.
In the case of satellite access for Cellular IoT, the MME may verify the UE location and determine whether the PLMN is allowed to operate at the UE location, as described in clause 4.13.4. If the UE receives an Attach Reject message with cause value indicating that the selected PLMN is not allowed to operate at the present UE location, the UE shall attempt to select a PLMN as specified in TS 23.122 [10].
In the case of satellite access over NB-IoT, the eNB may request the MME to provide the Coarse Location information to the eNB, as described in TS 36.300 [5] and TS 36.413 [36].
If the MME is operating in S&F Mode, the MME may reject the Attach Request and optionally provide to the UE in the Attach Reject message any of the following: a S&F Wait Timer, a S&F Monitoring List (see clause 4.13.9).
3. If the UE identifies itself with GUTI and the MME has changed since detach, the new MME determines the type of the old node, i.e. MME or SGSN, as specified in clause 4.3.19, uses the GUTI received from the UE to derive the old MME/SGSN address, and sends an Identification Request (old GUTI, complete Attach Request message) to the old MME/SGSN to request the IMSI. If the request is sent to an old MME, the old MME first verifies the Attach Request message by NAS MAC and then responds with Identification Response (IMSI, MM Context). If the request is sent to an old SGSN, the old SGSN first verifies the Attach Request message by the P-TMSI signature and then responds with Identification Response (MM Context). If the UE is not known in the old MME/SGSN or if the integrity check or P-TMSI signature check for the Attach Request message fails, the old MME/SGSN responds with an appropriate error cause. The MM context contains security related information as well as other parameters (including IMSI) as described in clause 5.7.2 (Information Storage for MME).
The additional GUTI in the Attach Request message allows the new MME to find any already existing UE context stored in the new MME when the old GUTI indicates a GUTI mapped from a P-TMSI and RAI.
For an Emergency Attach or a RLOS Attach, if the UE identifies itself with a temporary identity that is not known to the MME the MME immediately requests the IMSI from the UE. If the UE identifies itself with IMEI, the IMSI request shall be skipped.
During inter PLMN mobility, the new MME shall delete the UE Radio Capability ID received from the old MME, unless the operator policy indicates that all UE Radio Capability IDs used in the old PLMN are also valid in the new PLMN.
NOTE 10: A SGSN always responds with the UMTS security parameters and the MME may store it for later use.
4. If the UE is unknown in both the old MME/SGSN and new MME, the new MME sends an Identity Request to the UE to request the IMSI. The UE responds with Identity Response (IMSI).
5a If no UE context for the UE exists anywhere in the network, if the Attach Request (sent in step 1) was not integrity protected, or if the check of the integrity failed, then authentication and NAS security setup to activate integrity protection and NAS ciphering are mandatory. Otherwise it is optional. If NAS security algorithm is to be changed, the NAS security setup is performed in this step. The authentication and NAS security setup functions are defined in clause 5.3.10 on "Security Function".
If the UE supports RACS as indicated in the UE Network Capability, and if the UE indicated that it has UE Radio Capability ID assigned for use in the selected PLMN in step 1, then authentication and NAS security setup to activate integrity protection and NAS ciphering are mandatory and the MME shall request the UE to provide the UE Radio Capability ID in Security Mode Command and the UE shall include the UE Radio Capability ID in Security Mode Command Accept for the supported UE radio capabilities.
For satellite access over NB-IoT, it the UE indicated support for reporting its Coarse Location Information, the MME may request the UE to send its Coarse Location Information by setting the Coarse Location Information Request in the Security Mode Command message and the UE then reports its Coarse Location Information in the Security Mode Complete message to the MME. To perform UE location verification as described in clause 4.13.4, the MME provides the reported Coarse Location Information to the E-SMLC as described in clause 9.1.17 of TS 23.271 [57]. If the eNB requested the MME to provide the Coarse Location Information to the eNB, the MME provides the Coarse Location Information to the eNB in a following S1-AP message as described in TS 36.413 [36]. The eNB may use it as specified in TS 36.300 [5].
If the MME is configured to support Emergency Attach for unauthenticated IMSIs and the UE indicated Attach Type "Emergency" the MME skips the authentication and security setup or the MME accepts that the authentication may fail and continues the attach procedure.
If the MME is configured to support RLOS Attach and the UE indicated Attach Type "RLOS", based on local regulation and operator policy, the MME may skip the authentication and security setup, or the MME may perform authentication if security information is available or obtainable from HSS and continues the attach procedure regardless of the authentication result.
After step 5a, all NAS messages shall be protected by the NAS security functions (integrity and ciphering) indicated by the MME unless the UE is emergency or RLOS attached and not successfully authenticated.
5b. The ME Identity (IMEISV) shall be retrieved from the UE. The ME identity shall be transferred encrypted unless the UE performs Emergency Attach or RLOS Attach and cannot be authenticated.
For an Emergency Attach or RLOS Attach, the UE may have included the IMEI in the Emergency Attach or RLOS Attach. If so, the ME Identity retrieval is skipped.
In order to minimise signalling delays, the retrieval of the ME Identity may be combined with NAS security setup in step 5a. The MME may send the ME Identity Check Request (ME Identity, IMSI) to the EIR. The EIR shall respond with ME Identity Check Ack (Result). Dependent upon the Result, the MME decides whether to continue with this Attach procedure or to reject the UE.
For an Emergency Attach or RLOS Attach, the IMEI check to the EIR may be performed. If the IMEI is blocked, operator policies determine whether the Emergency Attach or RLOS Attach procedure continues or is stopped.
If the UE supports RACS, as indicated in the UE Core Network Capability IE, the MME shall use the IMEI of the UE to obtain the IMEI/TAC for the purpose of RACS operation.
6. If the UE has set the Ciphered Options Transfer Flag in the Attach Request message, the Ciphered Options i.e. PCO or APN or both, shall now be retrieved from the UE.
In order to handle situations where the UE may have subscriptions to multiple PDNs, if the Protocol Configuration Options contains user credentials (e.g. user name/password within PAP or CHAP parameters) then the UE should also send the APN to the MME.
7. If there are active bearer contexts in the new MME for this particular UE (i.e. the UE re-attaches to the same MME without having properly detached before), the new MME deletes these bearer contexts by sending Delete Session Request (LBI) messages to the GWs involved. The GWs acknowledge with Delete Session Response (Cause) message. If a PCRF is deployed, the PDN GW employs an IP-CAN Session Termination procedure to indicate that resources have been released.
8. If the MME has changed since the last detach, or if there is no valid subscription context for the UE in the MME, or if the UE provides an IMSI or the UE provides an old GUTI which doesn't refer to a valid context in the MME, or for some network sharing scenario (e.g. GWCN) if the PLMN-ID of the TAI supplied by the eNodeB is different from that of the GUTI in the UE's context, the MME sends an Update Location Request (MME Identity, IMSI, ME Identity (IMEISV), MME Capabilities, ULR-Flags, Homogeneous Support of IMS Voice over PS Sessions, UE SRVCC capability, equivalent PLMN list) message to the HSS. The MME capabilities indicate the MME's support for regional access restrictions functionality. ULR-Flags indicates "Initial-Attach-Indicator" as this is an Attach procedure. The inclusion of the equivalent PLMN list indicates that the MME supports the inter-PLMN handover to a CSG cell in an equivalent PLMN using the subscription information of the target PLMN. The "Homogenous Support of IMS Voice over PS Sessions" indication (see clause 4.3.5.8A) shall not be included unless the MME has completed its evaluation of the support of "IMS Voice over PS Session" as specified in clause 4.3.5.8.
NOTE 11: At this step, the MME may not have all the information needed to determine the setting of the IMS Voice over PS Session Supported indication for this UE (see clause 4.3.5.8). Hence the MME can send the "Homogenous Support of IMS Voice over PS Sessions" later on in this procedure.
If the UE performs Initial or Handover Attach in a VPLMN supporting Autonomous CSG Roaming and the HPLMN has enabled Autonomous CSG Roaming in the VPLMN (via Service Level Agreement) and the MME needs to retrieve the CSG subscription information of the UE from the CSS, the MME initiates the Update CSG Location Procedure with CSS as described in clause 5.3.12.
If the MME determines that only the UE SRVCC capability has changed, the MME sends a Notify Request to the HSS to inform about the changed UE SRVCC capability.
If there is a valid subscription context for the UE in the MME with a Service Gap timer running and the Attach Type is not Emergency Attach and it is not an Attach without PDN connectivity, the MME rejects the Attach Request from the UE with an appropriate cause value. In addition, MME may also provide a UE with a Mobility Management Back-off Timer set to the remaining value of the Service Gap timer.
For an Emergency Attach in which the UE was not successfully authenticated, the MME shall not send an Update Location Request to the HSS.
For an RLOS Attach the MME shall not send an Update Location Request to the HSS.
When the UE indicated "S&F Capability" in the UE Core Network Capability and MME is operating in S&F Mode, the MME proceeds as follows:
- If the MME has rejected the UE request in step 2, based on configuration the MME may send an Update Location Request including an indication that this is a provisional Update Location Request and may include a timestamp, see clause 4.13.9.
- If the MME has accepted the UE request in step 2, the MME sends an Update Location Request that may include a timestamp, see clause 4.13.9.
9. The HSS sends Cancel Location (IMSI, Cancellation Type) to the old MME. The old MME acknowledges with Cancel Location Ack (IMSI) and removes the MM and bearer contexts. If the ULR-Flags indicates "Initial-Attach-Indicator" and the HSS has the SGSN registration, then the HSS sends Cancel Location (IMSI, Cancellation Type) to the old SGSN. The Cancellation Type indicates the old MME/SGSN to release the old Serving GW resource.
10. If there are active bearer contexts in the old MME/SGSN for this particular UE, the old MME/SGSN deletes these bearer contexts by sending Delete Session Request (LBI) messages to the GWs involved. The GWs return Delete Session Response (Cause) message to the old MME/SGSN. If a PCRF is deployed, the PDN GW employs an IP‑CAN Session Termination procedure as defined in TS 23.203 [6] to indicate that resources have been released.
11. The HSS acknowledges the Update Location message by sending an Update Location Ack (IMSI, Subscription data) message to the new MME. The Subscription Data contain one or more PDN subscription contexts. Each PDN subscription context contains an 'EPS subscribed QoS profile' and the subscribed APN-AMBR (see clause 4.7.3) and the WLAN offloadability indication (see clause 4.3.23). The new MME validates the UE's presence in the (new) TA.
If due to regional subscription restrictions or access restrictions (e.g. CSG restrictions) the UE is not allowed to attach in the TA or due to subscription checking fails for other reasons, the new MME rejects the Attach Request with an appropriate cause. If all checks are successful then the new MME constructs a context for the UE. If the APN provided by the UE is not allowed by subscription, based on operator policy, the MME may reject the Attach Request from the UE with an appropriate cause, or accept the Attach Request by replacing the UE requested APN with a network supported APN. The MME uses that network supported APN for the remainder of this procedure, except that the MME provides to the UE the same APN that the UE requested. If the Update Location is rejected by the HSS, the new MME rejects the Attach Request from the UE with an appropriate cause.
The Subscription Data may contain CSG subscription information for the registered PLMN and for the equivalent PLMN list requested by MME in step 8.
The Subscription Data may contain the IAB-Operation Allowed indication the IAB operation. The MME shall use the IAB-Opeation Allowed indication to authorize the UE's IAB operation.
The subscription data may contain Enhanced Coverage Restricted parameter. If received from the HSS, MME stores this Enhanced Coverage Restricted parameter in the MME MM context.
The subscription data may contain Service Gap Time parameter. If received from the HSS, MME stores this Service Gap Time in the MME MM context and passes it to the UE in the Attach Accept message.
The subscription data may contain Subscribed Paging Time Window parameter that applies to the UEs on a specific RAT, e.g. NB-IoT. If received from the HSS, MME stores this Subscribed Paging Time Window parameter in the MME MM context.
The subscription data may contain an indication that the UE is subscribed to receive time reference information in access stratum. If received from the HSS and if supported by the MME, the MME stores this indication in the MME MM context.
If the UE provided APN is authorized for LIPA according to the user subscription, the MME shall use the CSG Subscription Data to authorize the connection.
For an Emergency Attach or RLOS Attach, the MME shall not check for access restrictions, regional restrictions or subscription restrictions (e.g. CSG restrictions). For an Emergency Attach, the MME shall ignore any unsuccessful Update Location Response from HSS and continue with the Attach procedure.
12. If an ESM container was not included in the Attach Request, steps 12, 13,14,15,16 are skipped. If the attach type is not set to "Emergency" or "RLOS", and the ESM container was included in the Attach Request, and the UE has indicated support for Attach without PDN Connectivity, and the network supports Attach without PDN Connectivity, and the PDN Connection Restriction is set in the subscriber data, then the new MME shall not establish PDN connection, and steps 12, 13, 14, 15 and 16 are skipped.
For an Emergency Attach the MME applies the parameters from MME Emergency Configuration Data for the emergency bearer establishment performed in this step and any potentially stored IMSI related subscription data are ignored by the MME.
For a RLOS Attach, the MME applies the parameters from MME RLOS Configuration Data for the RLOS default bearer establishment performed in this step and any potentially stored IMSI related subscription data are ignored by the MME.
If the UE performs Initial or Handover Attach via a CSG cell and there is no subscription for that CSG or the CSG subscription is expired the MME shall reject the Attach Request with an appropriate cause. If the UE has this CSG ID and associated PLMN on its Allowed CSG list the UE shall remove the CSG ID and associated PLMN from the list when receiving this reject cause.
If a subscribed PDN address is allocated for the UE for this APN, the PDN subscription context contains the UE's IPv4 address and/or the IPv6 prefix and optionally the PDN GW identity. If the PDN subscription context contains a subscribed IPv4 address and/or IPv6 prefix, the MME indicates it in the PDN address. For Request Type indicating "Initial request", if the UE does not provide an APN, the MME shall use the PDN GW corresponding to the default APN for default bearer activation. If the UE provides an APN, this APN shall be employed for default bearer activation. For Request Type indicating "Handover", if the UE provides an APN, the MME shall use the PDN GW corresponding to the provided APN for default bearer activation, If the UE does not provide an APN, and the subscription context from HSS contains a PDN GW identity corresponding to the default APN, the MME shall use the PDN GW corresponding to the default APN for default bearer activation. The case where the Request Type indicates "Handover" and the UE does not provide an APN, and the subscription context from HSS does not contain a PDN GW identity corresponding to the default APN constitutes an error case. If the Request Type indicates "Initial request" and the selected PDN subscription context contains no PDN GW identity the new MME selects a PDN GW as described in clause 4.3.8.1 on PDN GW selection function (3GPP accesses). If the PDN subscription context contains a dynamically allocated PDN GW identity and the Request Type does not indicate "Handover" the MME may select a new PDN GW as described in clause PDN GW selection function, e.g. to allocate a PDN GW that allows for more efficient routing.
For initial and handover Emergency Attach the MME uses the PDN GW Selection function defined in clause 4.3.12.4 to select a PDN GW.
For initial RLOS Attach, the MME uses the PDN GW Selection function defined in clause 4.3.12a.4 to select a PDN GW.
If the subscription context does not indicate that the APN is for a PDN connection to an SCEF, the new MME selects a Serving GW as described in clause 4.3.8.2 on Serving GW selection function and allocates an EPS Bearer Identity for the Default Bearer associated with the UE. Then it sends a Create Session Request (IMSI, MSISDN, MME TEID for control plane, PDN GW address, PDN Address, APN, RAT type, LTE-M RAT type reporting to PGW flag, Default EPS Bearer QoS, PDN Type, APN-AMBR, EPS Bearer Identity, Protocol Configuration Options, Handover Indication, ME Identity (IMEISV), User Location Information (ECGI and TAI), UE Time Zone, User CSG Information, MS Info Change Reporting support indication, Selection Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger Id, OMC Identity, Maximum APN Restriction, Dual Address Bearer Flag, the Protocol Type over S5/S8, Serving Network, APN Rate Control Status) message to the selected Serving GW. If Control Plane CIoT EPS Optimisation applies, then the MME shall also indicate S11-U tunnelling of NAS user data and send its own S11-U IP address and MME DL TEID for DL data forwarding by the SGW. User CSG Information includes CSG ID, access mode and CSG membership indication.
For PDN type "non-IP" when Control Plane CIoT EPS Optimisations are enabled for the UE, if APN subscription data indicate a SCEF connection needs to be used, then the MME allocates an EPS Bearer Identity for the Default Bearer associated with the UE and establishes a connection to the SCEF address indicated in subscription data as per TS 23.682 [74] and the steps 12,13,14,15,16 are not executed. The rest of the interactions with the UE apply as specified below.
If the MME determines the PDN connection shall only use the Control Plane CIoT EPS Optimisation, the MME shall include a Control Plane Only PDN Connection Indicator in Create Session Request.
If the Request Type indicates "Emergency" or "RLOS", Maximum APN restriction control shall not be performed.
For emergency attached or RLOS attached UEs IMSI is included if available and if the IMSI cannot be authenticated then the IMSI shall be marked as unauthenticated.
The RAT type is provided in this message for the later PCC decision. The RAT type shall distinguish between NB-IoT, LTE-M and WB-E-UTRA RAT types as specified in clause 4.3.5.3. The subscribed APN‑AMBR for the APN is also provided in this message. The MSISDN is included if provided in the subscription data from the HSS. Handover Indication is included if the Request Type indicates handover. Selection Mode indicates whether a subscribed APN was selected, or a non-subscribed APN sent by the UE was selected. Charging Characteristics indicates which kind of charging the bearer context is liable for. The MME may change the requested PDN type according to the subscription data for this APN as described in clause 5.3.1.1. The MME shall set the Dual Address Bearer Flag when the PDN type is set to IPv4v6 and all SGSNs which the UE may be handed over to are Release 8 or above supporting dual addressing, which is determined based on node pre-configuration by the operator. The Protocol Type over S5/S8 is provided to Serving GW which protocol should be used over S5/S8 interface.
The charging characteristics for the PS subscription and individually subscribed APNs as well as the way of handling Charging Characteristics and whether to send them or not to the P‑GW is defined in TS 32.251 [44]. The MME shall include Trace Reference, Trace Type, Trigger Id, and OMC Identity if S‑GW and/or P‑GW trace is activated. The MME shall copy Trace Reference, Trace Type, and OMC Identity from the trace information received from the HLR or OMC.
The Maximum APN Restriction denotes the most stringent restriction as required by any already active bearer context. If there are no already active bearer contexts, this value is set to the least restrictive type (see clause 15.4 of TS 23.060 [7]). If the P‑GW receives the Maximum APN Restriction, then the P‑GW shall check if the Maximum APN Restriction value does not conflict with the APN Restriction value associated with this bearer context request. If there is no conflict the request shall be allowed, otherwise the request shall be rejected with sending an appropriate error cause to the UE.
If the MME requires the eNodeB to check whether the UE radio capabilities are compatible with the network configuration (e.g. whether the SRVCC or frequency support by the UE matches that of the network) to be able to set the IMS voice over PS Session Supported Indication (see clause 4.3.5.8), then the MME may send a UE Radio Capability Match Request to the eNodeB as defined in clause 5.3.14.
The MME includes the latest APN Rate Control status if it has stored it.
Based on UE and Serving GW capability of supporting MT-EDT, Communication Pattern parameters or local policy, the MME may indicate to Serving GW that MT-EDT is applicable for the PDN connection.
13. The Serving GW creates a new entry in its EPS Bearer table and sends a Create Session Request (IMSI, MSISDN, APN, Serving GW Address for the user plane, Serving GW TEID of the user plane, Serving GW TEID of the control plane, RAT type, Default EPS Bearer QoS, PDN Type, PDN Address, subscribed APN-AMBR, EPS Bearer Identity, Protocol Configuration Options, Handover Indication, ME Identity, User Location Information (ECGI), UE Time Zone, User CSG Information, MS Info Change Reporting support indication, PDN Charging Pause Support indication, Selection Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger Id, OMC Identity, Maximum APN Restriction, Dual Address Bearer Flag, Serving Network, APN Rate Control Status) message to the PDN GW indicated by the PDN GW address received in the previous step. After this step, the Serving GW buffers any downlink packets it may receive from the PDN GW without sending a Downlink Data Notification message to the MME until it receives the Modify Bearer Request message in step 23 below. The MSISDN is included if received from the MME.
If the Serving GW has received the Control Plane Only PDN Connection Indicator in step 12, the Serving GW informs the PDN GW this information in Create Session Request. The Serving GW and PDN GW shall indicate the use of CP only on their CDRs.
PDN GWs shall not perform any checks of Maximum APN Restriction if Create Session Request includes the emergency APN or RLOS APN.
For emergency attached or RLOS attached UEs IMSI is included if available and if the IMSI cannot be authenticated then the IMSI shall be marked as unauthenticated.
In the case of handover attach, and if the PDN GW detects that the 3GPP PS Data Off UE Status is active, the PDN GW shall indicate this status to the charging system for offline and online charging.
14. If dynamic PCC is deployed and the Handover Indication is not present, the PDN GW performs an IP-CAN Session Establishment procedure as defined in TS 23.203 [6], and thereby obtains the default PCC rules for the UE. If the UE is accessing over WB-E-UTRA, this may lead to the establishment of a number of dedicated bearers following the procedures defined in clause 5.4.1 in association with the establishment of the default bearer, which is described in Annex F.
The IMSI, APN, UE IP address, User Location Information (ECGI), UE Time Zone, Serving Network, RAT type, APN-AMBR, Default EPS Bearer QoS, ETFTU (if ETFTU is not provided it means UE and/or the PDN GW does not support the extended TFT filter format) are provided to the PCRF by the PDN GW if received by the previous message. The User Location Information and UE Time Zone are used for location based charging. For emergency attached or RLOS attached UEs which are unauthenticated the PDN GW provides the IMEI as the UE Identity instead of IMSI, to the PCRF. If the PCRF decides that the PDN connection may use the extended TFT filter format, it shall return the ETFTN indicator to the PDN GW for inclusion in the protocol Configuration Options returned to the UE.
The PCRF may modify the APN-AMBR and the QoS parameters (QCI and ARP) associated with the default bearer in the response to the PDN GW as defined in TS 23.203 [6].
If the PCC is configured to support emergency services and if dynamic PCC is deployed, the PCRF, based on the emergency APN, sets the ARP of the PCC rules to a value that is reserved for emergency services and the authorization of dynamic PCC rules as described in of TS 23.203 [6]. If dynamic PCC is not deployed, the PDN GW uses the ARP of the default emergency EPS bearer for any potentially initiated dedicated emergency EPS bearer. The P‑GW determines that emergency services are requested based on the emergency APN received in Create Session Request message.
If the PCC is configured to support Restricted Local Operator Services and if dynamic PCC is deployed, the PCRF, based on the RLOS APN, sets the ARP of the PCC rules to a value based on operator policy and the authorization of dynamic PCC rules as described in of TS 23.203 [6].
NOTE 12: While the PDN GW/PCEF may be configured to activate predefined PCC rules for the default bearer, the interaction with the PCRF is still required to provide e.g. the UE IP address information to the PCRF.
NOTE 13: If the IP address is not available when the PDN GW performs the IP-CAN Session Establishment procedure with the PCRF, the PDN GW initiates an IP-CAN Session Modification procedure to inform the PCRF about an allocated IP address as soon as the address is available. In this version of the specification, this is applicable only to IPv4 address allocation.
If dynamic PCC is deployed and the Handover Indication is present, the PDN GW executes a PCEF Initiated IP‑CAN Session Modification procedure with the PCRF as specified in TS 23.203 [6] to report the new IP‑CAN type. Depending on the active PCC rules, the establishment of dedicated bearers for the UE may be required. The establishment of those bearers shall take place in combination with the default bearer activation as described in Annex F. This procedure can continue without waiting for a PCRF response. If changes to the active PCC rules are required, the PCRF may provide them after the handover procedure is finished.
In both cases (Handover Indication is present or not), if dynamic PCC is not deployed, the PDN GW may apply local QoS policy. If the UE is accessing over WB-E-UTRA, this may lead to the establishment of a number of dedicated bearers for the UE following the procedures defined in clause 5.4.1 in combination with the establishment of the default bearer, which is described in Annex F.
If the CSG information reporting triggers are received from the PCRF, the PDN GW should set the CSG Information Reporting Action IE accordingly.
If 3GPP PS Data Off status is received in the PCO from the UE and PDN GW supports 3GPP PS Data Off, the PDN GW shall provide the 3GPP PS Data Off status to the PCRF. If the PCRF supports 3GPP PS Data Off, it shall return 3GPP PS Data Off support to the PDN GW for inclusion in the PCO returned to the UE.
The additional behaviour of the PDN GW for 3GPP PS Data Off is defined in TS 23.203 [6].
If received, the PDN GW may take the APN Rate Control Status into account when encoding the APN Rate Control parameters in Protocol Configuration Options and when enforcing the APN Rate Control as described in clause 4.7.7.3.
15. The P‑GW creates a new entry in its EPS bearer context table and generates a Charging Id for the Default Bearer. The new entry allows the P‑GW to route user plane PDUs between the S‑GW and the packet data network, and to start charging. The way the P‑GW handles Charging Characteristics that it may have received is defined in TS 32.251 [44].
The PDN GW returns a Create Session Response (PDN GW Address for the user plane, PDN GW TEID of the user plane, PDN GW TEID of the control plane, PDN Type, PDN Address, EPS Bearer Identity, EPS Bearer QoS, Protocol Configuration Options, Charging Id, Prohibit Payload Compression, APN Restriction, Cause, MS Info Change Reporting Action (Start) (if the PDN GW decides to receive UE's location information during the session), CSG Information Reporting Action (Start) (if the PDN GW decides to receive UE's User CSG information during the session), Presence Reporting Area Action (if the PDN GW decides to receive notifications about a change of UE presence in Presence Reporting Area), PDN Charging Pause Enabled indication (if PDN GW has chosen to enable the function), APN-AMBR, Delay Tolerant Connection) message to the Serving GW.
The PDN GW takes into account the received PDN type, the Dual Address Bearer Flag and the policies of operator when the PDN GW selects the PDN type to be used as follows. If the received PDN type is IPv4v6 and both IPv4 and IPv6 addressing is possible in the PDN but the Dual Address Bearer Flag is not set, or only single IP version addressing for this APN is possible in the PDN, the PDN GW selects a single IP version (either IPv4 or IPv6). If the received PDN type is IPv4 or IPv6 or "Non-IP" or "Ethernet", the PDN GW uses the received PDN type if it is supported in the PDN, otherwise an appropriate error cause will be returned. For IPv4, IPv6 and IPv4v6, the PDN GW allocates a PDN Address according to the selected PDN type. If the PDN GW has selected a PDN type different from the received PDN Type, the PDN GW indicates together with the PDN type IE a reason cause to the UE why the PDN type has been modified, as described in clause 5.3.1.1. The PDN GW shall either accept or reject (but not modify) the PDN type if the PDN type is set to "Non-IP" or "Ethernet". PDN Address may contain an IPv4 address for IPv4 and/or an IPv6 prefix and an Interface Identifier, or be omitted for PDN types "Non-IP" and "Ethernet". If the PDN has been configured by the operator so that the PDN addresses for the requested APN shall be allocated by usage of DHCPv4 only, or if the PDN GW allows the UE to use DHCPv4 for address allocation according to the Address Allocation Preference received from the UE, the PDN Address shall be set to 0.0.0.0, indicating that the IPv4 PDN address shall be negotiated by the UE with DHCPv4 after completion of the Default Bearer Activation procedure. For external PDN addressing for IPv6, the PDN GW obtains the IPv6 prefix from the external PDN using either RADIUS or Diameter client function. In the PDN Address field of the Create Session Response, the PDN GW includes the Interface Identifier and IPv6 prefix. The PDN GW sends Router Advertisement to the UE after default bearer establishment with the IPv6 prefix information for all cases.
If the PDN address is contained in the Create Session Request, the PDN GW shall allocate the IPv4 address and/or IPv6 prefix contained in the PDN address to the UE. The IP address allocation details are described in clause 5.3.1 on "IP Address Allocation". The PDN GW derives the BCM based on the NRSU and operator policy. The PDN GW derives whether the extended TFT filter format is to be used based on the ETFTU, ETFTN received from the PCRF and operator policy. Protocol Configuration Options contains the BCM, ETFTN as well as optional PDN parameters that the P‑GW may transfer to the UE. These optional PDN parameters may be requested by the UE, or may be sent unsolicited by the P‑GW. Protocol Configuration Options are sent transparently through the MME.
The PDN GW includes a Delay Tolerant Connection indication if the PDN GW supports receiving a rejection cause from the SGW indicating that the UE is temporarily not reachable due to power saving and holding mobile terminated procedures, until the PDN GW receives a message indicating that the UE is available for end to end signalling.
When the Handover Indication is present, the PDN GW does not yet send downlink packets to the S‑GW; the downlink path is to be switched at step 23a.
If the PDN GW is an L-GW, it does not forward downlink packets to the S-GW. The packets will only be forwarded to the HeNB at step 20 via the direct user plane path.
If the 3GPP PS Data Off UE Status was present in the Create Session Request PCO and the network supports 3GPP PS Data Off feature, the PDN GW shall include the 3GPP PS Data Off Support Indication in the Create Session Response PCO.
16. The Serving GW returns a Create Session Response (PDN Type, PDN Address, Serving GW address for User Plane, Serving GW TEID User Plane, Serving GW TEID for control plane, EPS Bearer Identity, EPS Bearer QoS, PDN GW addresses and TEIDs (GTP-based S5/S8) or GRE keys (PMIP-based S5/S8) at the PDN GW(s) for uplink traffic, Protocol Configuration Options, Prohibit Payload Compression, APN Restriction, Cause, MS Info Change Reporting Action (Start), Presence Reporting Area Action, CSG Information Reporting Action (Start), APN-AMBR, Delay Tolerant Connection) message to the new MME.
If Control Plane CIoT EPS Optimisation applies, and if the MME does not include Control Plane Only PDN Connection Indicator in the Create Session Request:
- If separation of S11-U from S1-U is required, the Serving GW shall include the Serving GW IP address and TEID for S11-U and additionally the Serving GW IP address and TEID for S1-U in Create Session Response.
- Otherwise, if separation of S11-U from S1-U is not required, the Serving GW includes the Serving GW IP address and TEID for S11-U in Create Session Response.
17. If an APN Restriction is received, then the MME shall store this value for the Bearer Context and the MME shall check this received value with the stored value for the Maximum APN Restriction to ensure there are no conflicts between values. If the Bearer Context is accepted, the MME shall determine a (new) value for the Maximum APN Restriction. If there is no previously stored value for Maximum APN Restriction, then the Maximum APN Restriction shall be set to the value of the received APN Restriction. MME shall not deactivate bearer(s) with emergency ARP, if present, to maintain valid APN restriction combination.
The P-GW shall ignore Maximum APN restriction if the request includes the Emergency APN.
If the MS Info Change Reporting Action (Start) and/or the CSG Information Reporting Action (Start) are received for this bearer context, then the MME shall store this for the bearer context and the MME shall report to that P-GW via the S-GW whenever a UE's location and/or User CSG information change occurs that meets the P-GW request, as described in clause 15.1.1a of TS 23.060 [7]. If Presence Reporting Area Action is received for this bearer context, the MME shall store this information for the bearer context and shall report to that P-GW via the S-GW whenever a change of UE presence in a Presence Reporting Area is detected, as described in clause 5.9.2.2.
The MME determines the UE AMBR to be used by the eNodeB based on the subscribed UE-AMBR and the APN‑AMBR for the default APN, see clause 4.7.3.
For emergency attach or RLOS attach the MME determines the UE-AMBR to be used by the eNodeB from the APN AMBR received from the S-GW.
If new MME hasn't received, from Step 12, Voice Support Match Indicator for the UE from the eNodeB then, based on implementation, the MME may set IMS Voice over PS session supported Indication and update it at a later stage.
The new MME sends an Attach Accept (GUTI, TAI List, Session Management Request (APN, PDN Type, PDN Address, EPS Bearer Identity, Protocol Configuration Options, Header Compression Configuration, Control Plane Only Indicator, Connection Release Supported, Paging Cause Indication for Voice Service Supported, Reject Paging Request Supported, Paging Restriction Supported, Paging Timing Collision Control Supported), NAS sequence number, NAS-MAC, IMS Voice over PS session supported Indication, Emergency Service Support indicator, LCS Support Indication, Supported Network Behaviour, Service Gap Time, Enhanced Coverage Restricted, Indication for support of 15 EPS bearers per UE, PLMN-assigned UE Radio Capability ID, indication for PLMN-assigned UE Radio Capability ID deletion, Accepted IMSI Offset, Forbidden TAI(s), Enhanced Discontinuous Coverage Support, Return To Coverage Notification Not Required, Maximum Time Offset, Start of Unavailability Period, Unavailability Period Duration, Time Reference Information Distribution Indication) message to the eNodeB. GUTI is included if the new MME allocates a new GUTI. PDN Type and PDN Address are omitted if the Attach Request (step 1) did not contain an ESM message container. The MME indicates the CIoT EPS Optimisations it accepts in the Supported Network Behaviour information as defined in clause 4.3.5.10. Service Gap Time is included if Service Gap Time is present in the subscription information (step 11) and the UE has indicated UE Service Gap Control Capability. This message is contained in an S1_MME control message Initial Context Setup Request, unless the MME has selected to use the Control Plane CIoT EPS Optimisation, or, the UE did not include the ESM message container in the Attach Request (step 1), in which case an S1-AP Downlink NAS transport message is used. The S1-AP Initial Context Setup Request message also includes the AS security context information for the UE, the Handover Restriction List, the EPS Bearer QoS, the UE-AMBR, EPS Bearer Identity, as well as the TEID at the Serving GW used for user plane and the address of the Serving GW for user plane and whether User Plane CIoT EPS Optimisation is allowed for the UE. If the PDN type is set to "Non-IP" the MME includes it in the S1-AP Initial Context Setup Request so that the eNodeB disables header compression. If the PDN type is set to "Ethernet" the MME includes it in the S1-AP Initial Context Setup Request so that any eNodeB header compression functionality can act appropriately. In addition, if the PDN connection is established for Local IP Access, the corresponding S1 Initial Context Setup Request message includes a Correlation ID for enabling the direct user plane path between the HeNB and the L-GW. If the PDN connection is established for SIPTO at the Local Network with L-GW function collocated with the (H)eNB, the corresponding S1-AP Initial Context Setup Request message includes a SIPTO Correlation ID for enabling the direct user plane path between the (H)eNB and the L-GW. LIPA and SIPTO do not apply to Control Plane CIoT EPS Optimisation.
NOTE 14: In this release of the 3GPP specification the Correlation ID and SIPTO Correlation ID is set equal to the user plane PDN GW TEID (GTP-based S5) or GRE key (PMIP-based S5) that the MME has received in step 16.
If Control Plane CIoT EPS Optimisation applies for an IP PDN connection, and the UE has sent in the Attach Request the Header Compression Configuration, and the MME supports the header compression parameters, the MME shall include the Header Compression Configuration in the PDN Connectivity Accept message. The MME also binds the uplink and downlink ROHC channels to support header compression feedback signalling. If the UE has included header compression context setup parameters in Header Compression Configuration in the Attach Request, the MME may acknowledge the header compression context setup parameters. If the ROHC context is not established during the attach procedure for the PDN connection, before using the compressed format for sending the data, the UE and the MME need to establish the ROHC context with ROHC IR packet based on Header Compression Configuration.
If the MME based on local policy determines the PDN connection shall only use the Control Plane CIoT EPS Optimisation, the MME shall include a Control Plane Only Indicator in the Session Management Request. For PDN connections with an SCEF, the MME shall always include the Control Plane Only Indicator. A UE receiving the Control Plane Only Indicator, for a PDN connection shall only use the Control Plane CIoT EPS Optimisation for this PDN connection.
If the ESM container was not included in the Attach Request in step 1, then the Attach Accept message shall not include PDN related parameters, and the Downlink NAS transfer S1-AP message shall not include Access stratum context related information but may include CSG related information.
If the attach type is not set to "Emergency", and the ESM container was included in Attach Request in step 1, and the UE indicated support of Attach without PDN Connection in the Attach Request, and the MME supports Attach without PDN Connection, and PDN connection restriction is set in subscriber data, then the MME shall discard the ESM container in the Attach Request message, and shall not include PDN related parameters in the Attach Accept, but may include CSG related information.
In the Attach Accept message, the MME does not include the IPv6 prefix within the PDN Address. The MME includes the EPS Bearer QoS parameter QCI and APN-AMBR into the Session Management Request. Furthermore, if the UE has UTRAN or GERAN capabilities and the network supports mobility to UTRAN or GERAN, the MME uses the EPS bearer QoS information to derive the corresponding PDP context parameters QoS Negotiated (R99 QoS profile), Radio Priority, Packet Flow Id and TI and includes them in the Session Management Request. If the UE indicated in the UE Network Capability it does not support BSS packet flow procedures, then the MME shall not include the Packet Flow Id. Handover Restriction List is described in clause 4.3.5.7 "Mobility Restrictions". The MME sets the IMS Voice over PS session supported Indication as described in clause 4.3.5.8. LCS Support Indication indicates whether the network supports the EPC-MO-LR and/or CS-MO-LR as described in TS 23.271 [57]. The MME may include an indication whether the traffic of this PDN Connection is allowed to be offloaded to WLAN, as described in clause 4.3.23. Indication for support of 15 EPS bearers per UE indicates the network support for up to 15 EPS bearers per UE as defined in clause 4.12.
If the UE initiates the Attach procedure at a hybrid cell, the MME shall check whether the CSG ID is contained in the CSG subscription and is not expired. The MME shall send an indication whether the UE is a CSG member to the RAN along with the S1-MME control message. Based on this information, the RAN may perform differentiated treatment for CSG and non-CSG members.
If the MME or PDN GW has changed the PDN Type, an appropriate reason cause shall be returned to the UE as described in clause 5.3.1.1. If the UE has indicated PDN type "Non-IP" or "Ethernet", the MME and PDN GW shall not change PDN type.
For an emergency attached UE, i.e. for UEs that have only emergency EPS bearers established, there is no AS security context information included in the S1 control messages and there is no NAS level security when the UE cannot be authenticated. The Emergency Service Support indicator informs the UE that Emergency bearer services are supported, i.e. the UE is allowed to request PDN connectivity for emergency services.
For RLOS attached UEs, i.e. for UEs that have only RLOS PDN connection established, there is no AS security context information included in the S1 control messages and there is no NAS level security when the UE cannot be successfully authenticated.
If the UE included extended idle mode DRX parameters information element, the MME includes extended idle mode DRX parameters information element if it decides to enable extended idle mode DRX with Paging Time Window length assigned considering Subscribed Paging Time Window (if available) and the local policy. Additionally, for a UE using an eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the MME may consider the use of discontinuous coverage as described in clause 4.13.8.2 when determining extended idle mode DRX parameters.
If the UE provided the UE paging probability information in Step 1, the MME takes it into account when generating the WUS Assistance Information. If the MME has determined WUS Assistance Information for the UE, the MME shall send the WUS Assistance Information to the UE (see TS 36.300 [5]).
If the UE included support for restriction of use of Enhanced Coverage in step 1, the MME sends Enhanced Coverage Restricted parameter to the eNodeB in S1-AP Initial Context Set-up Request message. MME also sends Enhanced Coverage Restricted parameter to the UE in the Attach Accept message.
If the UE has indicated support for dual connectivity with NR in the Attach Request and the UE is not allowed to use NR as Secondary RAT, the MME indicates that to the UE in the Attach Accept message.
If RACS is supported in the MME and MME has received UE Radio Capability ID earlier in this procedure, it signals the UE Radio Capability ID to the eNodeB in S1-AP Initial Context Set-up Request message. If the eNodeB does not have mapping between the specific UE Radio Capability ID and the UE radio capabilities, it shall use the procedure described in TS 36.413 [36] to retrieve the mapping from the MME.
When the UE supports RACS, and the MME needs to configure the UE with a UE Radio Capability ID, and the MME already has the UE radio capabilities for the UE, the MME may provide the UE with the UE Radio Capability ID for the UE radio capabilities the UCMF returns to the MME for this UE.
If MME has authorized the UE's IAB operation in step 11 based on the IAB-Operation Allowed indication, it shall include an "IAB Authorized" indication in the S1-AP Initial Context Set-up Request message to the eNodeB.
If the UE had included a UE Specific DRX parameter for NB-IoT in the Attach Request, the MME includes the Accepted NB-IoT DRX parameter.
If the UE provided a Requested IMSI Offset in step 1, but the network prefers a different value, the MME provides the UE with an Accepted IMSI Offset different from the one provided in step 1. Otherwise the value of the Accepted IMSI Offset the MME sends is the value of the Requested IMSI Offset sent by the UE in step 1. The MME stores the value of the alternative IMSI derived from the Accepted IMSI Offset (see clause 4.3.33) provided to the UE in the UE context.
If a Multi-USIM mode UE does not provide a Requested IMSI Offset in step 1, the MME erases any Alternative IMSI value in the UE context.
If the Multi-USIM UE has indicated one or more Multi-USIM specific capabilities are supported in the UE Core Network Capability in step 1, the MME shall indicate whether the corresponding one or more Multi-USIM specific features described in clause 4.3.33 are supported based on network capability and preference by the network (i.e. based on local network policy) by providing one or more of the Connection Release Supported, Paging Cause Indication for Voice Service Supported, Reject Paging Request Supported, Paging Restriction Supported and Paging Timing Collision Control Supported indications. The MME shall only indicate Paging Restriction Supported together with either Connection Release Supported or Reject Paging Request Supported. The UE shall only use Multi-USIM specific features that the MME indicated as being supported. In the case of Emergency Attach, the MME shall not indicate support for any Multi-USIM feature to the UE.
If the MME receives multiple TAIs from E-UTRAN in step 2 and determines that some, but not all, TAIs in the received list of TAIs are forbidden by subscription or by operator policy, the MME shall include the forbidden TAI(s) in the Attach Accept message.
If both UE and network support discontinuous coverage, the MME provides the Enhanced Discontinuous Coverage Support indication as described in clause 4.13.8.1. The MME may provide Start of Unavailability Period and/or Unavailability Period Duration to UE in the Attach Accept message as described in clause 4.13.8.2.
For a UE using a eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the MME may provide Return To Coverage Notification Not Required, which requests the UE in ECM_IDLE state to not perform the TAU procedure when it returns to coverage as described in clause 4.13.8.2. The MME may also provide a Maximum Time Offset as described in clause 4.13.8.6.
If supported by the MME and if the UE is subscribed to receive time reference information, then the MME provides the Time Reference Information Distribution Indication to the eNodeB.
If the UE indicated "S&F Capability" in the UE Core Network Capability and the MME is operating in S&F Mode, the MME may optionally provide to the UE in the Attach Accept message any of the following: a S&F Wait Timer, a S&F Monitoring List, an Estimated S&F UL Delivery Time (see clause 4.13.9).
18. If the eNodeB received an S1-AP Initial Context Setup Request the eNodeB sends the RRC Connection Reconfiguration message including the EPS Radio Bearer Identity to the UE, and the Attach Accept message will be sent along to the UE.
If the eNodeB received an S1-AP Downlink NAS Transport message (e.g. containing the Attach Accept message), the eNode B sends a RRC Direct Transfer message to the UE.
The UE shall store the QoS Negotiated, Radio Priority, Packet Flow Id and TI, which it received in the Session Management Request, for use when accessing via GERAN or UTRAN. The APN is provided to the UE to notify it of the APN for which the activated default bearer is associated. For further details, see TS 36.331 [37]. The UE may provide EPS Bearer QoS parameters to the application handling the traffic flow(s). The application usage of the EPS Bearer QoS is implementation dependent. The UE shall not reject the RRC Connection Reconfiguration on the basis of the EPS Bearer QoS parameters contained in the Session Management Request.
If the UE receives Enhanced Coverage Restricted parameter in the Attach Accept message, UE shall store this information and shall use the value of Enhanced Coverage Restricted parameter to determine if enhanced coverage feature should be used or not. If the UE receives a Service Gap Time in the Attach Accept message, the UE shall store this parameter and apply Service Gap Control (see clause 4.3.17.9).
If the attach procedure is initiated by manual CSG selection and occurs via a CSG cell, the UE upon receiving the Attach accept shall check if the CSG ID and associated PLMN of the cell where the UE has sent the Attach Request message is contained in its Allowed CSG list. If the CSG ID and associated PLMN is not in the UE's Allowed CSG list, the UE shall add the CSG ID and associated PLMN to its Allowed CSG list. Manual CSG selection is not supported when an emergency service has been initiated.
NOTE 15: If the UE receives an Attach Accept message via a hybrid cell, the UE does not add the corresponding CSG ID and associated PLMN to its Allowed CSG list. Adding a CSG ID and associated PLMN to the UE's local Allowed CSG list for a hybrid cell is performed only by OTA or OMA DM procedures.
When receiving the Attach Accept message the UE shall set its TIN to "GUTI" as no ISR Activated is indicated.
If the UE receives an IPv4 address set to 0.0.0.0, it may negotiate the IPv4 address with DHCPv4 as specified in TS 29.061 [38]. If the UE receives an IPv6 interface identifier, it may wait for the Router Advertisement from the network with the IPv6 prefix information or it may send a Router Solicitation if necessary.
NOTE 16: The IP address allocation details are described in clause 5.3.1 on "IP Address Allocation".
If Control Plane CIoT EPS Optimisation applies or the UE has not included the ESM message container in the Attach Request in step 1, then the steps 19 and 20 are not executed.
19. The UE sends the RRC Connection Reconfiguration Complete message to the eNodeB. For further details, see TS 36.331 [37].
20. The eNodeB sends the Initial Context Response message to the new MME. This Initial Context Response message includes the TEID of the eNodeB and the address of the eNodeB used for downlink traffic on the S1_U reference point.
The MME shall be prepared to receive this message either before or after the Attach Complete message (sent in step 22).
If the Correlation ID or SIPTO Correlation ID was included in the Initial Context Setup Request message, the eNodeB shall use the included information to establish direct user plane path with the L-GW and forward uplink data for Local IP Access or SIPTO at the Local Network with L-GW function collocated with the (H)eNB accordingly.
21. The UE sends a Direct Transfer message to the eNodeB, which includes the Attach Complete (EPS Bearer Identity, NAS sequence number, NAS-MAC) message. If the UE omitted the ESM message container from the Attach Request message in step 1, then the EPS Bearer Identity is omitted from the Attach Complete message.
22. The eNodeB forwards the Attach Complete message to the new MME in an Uplink NAS Transport message.
If the ESM message container was included in step 1, after the Attach Accept message and once the UE has obtained (if applicable to the PDN type) a PDN Address, the UE can then send uplink packets towards the eNodeB which will then be tunnelled to the Serving GW and PDN GW. If Control Plane CIoT EPS Optimisations apply, UL data is sent as specified in clause 5.3.4B. If the UE requested for a dual address PDN type (IPv4v6) to a given APN and was granted a single address PDN type (IPv4 or IPv6) by the network with a reason cause indicating that only single IP version per PDN connection is allowed sent together with the PDN type, the UE should request for the activation of a parallel PDN connection to the same APN with a single address PDN type (IPv4 or IPv6) other than the one already activated. If the UE receives no reason cause in step 18 in response to an IPv4v6 PDN type and it receives an IPv6 Interface Identifier apart from the IPv4 address or 0.0.0.0 in the PDN Address field, it considers that the request for a dual address PDN was successful. It can wait for the Router Advertisement from the network with the IPv6 prefix information or it may send Router Solicitation if necessary.
23. Upon reception of both, the Initial Context Response message in step 20 and the Attach Complete message in step 22, the new MME sends a Modify Bearer Request (EPS Bearer Identity, eNodeB address, eNodeB TEID, Handover Indication, Presence Reporting Area Information, RAT type, LTE-M RAT type reporting to PGW) message to the Serving GW. If the Control Plane CIoT EPS Optimisation applies and the PDN connection is not served by a SCEF and if the MME does not need to report a change of UE presence in Presence Reporting Area, sending of Modify Bearer Request and steps 23a, 23b and 24 are skipped; otherwise if the PDN connection is served by SCEF, steps 23,24, 25, and 26 are not executed. If the MME has been requested to report a change of UE presence in Presence Reporting Area, the MME includes in this message the Presence Reporting Area Information comprising the PRA identifier(s) and indication(s) on whether the UE is inside or outside the area(s). When receiving the request for reporting change of UE presence in Presence Reporting Area, and the MME decides not to activate reporting UE presence in one or more of the received Presence Reporting Area(s), the MME reports also the inactive Presence Reporting Area(s) in this message. The RAT type information element is included if the UE is using the LTE-M RAT type. If PDN GW expects the LTE-M RAT type reporting as specified in clause 5.11.5, the MME also includes the LTE-M RAT type reporting to PGW flag to indicate that the Serving GW needs to forward the LTE-M RAT type to the PGW.
23a. If the Handover Indication is included in step 23, the Serving GW sends a Modify Bearer Request (Handover Indication) message to the PDN GW to prompt the PDN GW to tunnel packets from non 3GPP IP access to 3GPP access system and immediately start routing packets to the Serving GW for the default and any dedicated EPS bearers established. If Presence Reporting Area Information is included in step 23, the Serving GW sends a Modify Bearer Request (Presence Reporting Area Information) message to the PDN GW. If the LTE-M RAT type and the LTE-M RAT type reporting to PGW flag were received at step 23, the Serving GW shall include the LTE-M RAT type in the Modify Bearer Request message to the PGW. Otherwise the Serving GW includes RAT type WB-E-UTRAN.
NOTE 17: The PDN GW is expected to handle the uplink packets sent by the UE via 3GPP access after step 22, even if they arrive before path switch in step 23.
NOTE 18: The PDN GW forwards the Presence Reporting Area Information to the PCRF, to the OCS or to both as defined in TS 23.203 [6].
23b. The PDN GW acknowledges by sending Modify Bearer Response to the Serving GW.
24. The Serving GW acknowledges by sending Modify Bearer Response (EPS Bearer Identity) message to the new MME. The Serving GW can then send its buffered downlink packets.
If there is a "Availability after DDN Failure" monitoring event or a "UE Reachability" monitoring event configured for the UE in the EMM Context of the MME, the MME sends an event notification (see TS 23.682 [74] for further information).
25. After the MME receives Modify Bearer Response (EPS Bearer Identity) message, if Request Type does not indicate handover and an EPS bearer was established and the subscription data indicates that the user is allowed to perform handover to non-3GPP accesses, and if the MME selected a PDN GW that is different from the PDN GW identity which was indicated by the HSS in the PDN subscription context, the MME shall send a Notify Request including the APN and PDN GW identity to the HSS for mobility with non-3GPP accesses. The message shall include information that identifies the PLMN in which the PDN GW is located.
If the ME identity of the UE has changed and step 8 has not been performed, the MME sends a Notify Request (ME Identity) message to inform the HSS of the updated ME identity.
For an unauthenticated or roaming UE, if the Request Type of the UE requested connectivity procedure indicates "Emergency", the MME shall not send any Notify Request to an HSS. For a non-roaming authenticated UE, based on operator configuration (e.g. on whether Voice over WLAN is supported or not by the operator, on whether the operator uses a fixed PDN GW for emergency calls, etc.), if the Request Type indicates "Emergency", the MME may send a Notify Request to the HSS including the "PDN GW currently in use for emergency services", which comprises the PDN GW address and an indication that the PDN connection is for emergency services. The HSS shall store it as part of the UE context for emergency services.
For any UEs, if Request Type of the UE requested connectivity procedure indicates "RLOS", the MME shall not send any Notify Request to an HSS.
After step 8, and in parallel to any of the preceding steps, the MME shall send a Notify Request (Homogeneous Support of IMS Voice over PS Sessions) message to the HSS:
- If the MME has evaluated the support of IMS Voice over PS Sessions, see clause 4.3.5.8, and
- If the MME determines that it needs to update the Homogeneous Support of IMS Voice over PS Sessions, see clause 4.3.5.8A.
26. In the case of non-emergency services, the HSS stores the APN and PDN GW identity pair. In the case of emergency services, the HSS stores the "PDN GW currently in use for emergency services". The HSS then sends a Notify Response to the MME.
NOTE 19: For handover from non-3GPP access, the PDN GW initiates resource allocation deactivation procedure in the trusted/untrusted non-3GPP IP access as specified in TS 23.402 [2].
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5.3.2.2 UTRAN/GERAN Initial Attach
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When a UE attaches to UTRAN/GERAN, it executes the normal attach procedure as defined in TS 23.060 [7]. When the UE needs an IP address, it initiates PDP context activation procedure as defined in TS 23.060 [7].
This procedure along with PDP context activation is also used to establish the first PDN connection over UTRAN/GERAN when the UE already has active PDN connections over a non-3GPP access network and wants to establish simultaneous PDN connections to different APNs over multiple accesses.
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5.3.3 Tracking Area Update procedures
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5.3.3.0 Triggers for tracking area update
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A stand-alone tracking area update (with or without S‑GW change, described in clauses 5.3.3.1 and 5.3.3.2 respectively) occurs when a GPRS-attached or E‑UTRAN-attached UE experiences any of the following conditions:
- UE detects it has entered a new TA that is not in the list of TAIs that the UE registered with the network (except for the case of a UE configured to perform Attach with IMSI when entering a TA in a new non-equivalent PLMN in RRC-IDLE mode);
- the periodic TA update timer has expired;
- UE was in UTRAN PMM_Connected state (e.g. URA_PCH) when it reselects to E‑UTRAN;
- UE was in GPRS READY state when it reselects to E‑UTRAN;
- the TIN indicates "P-TMSI" when the UE reselects to E-UTRAN (e.g. due to bearer configuration modifications performed on GERAN/UTRAN);
- the RRC connection was released with release cause "load re-balancing TAU required";
- the RRC layer in the UE informs the UE's NAS layer that an RRC connection failure (in either E-UTRAN or UTRAN) has occurred;
- a change of the UE Network Capability and/or MS Network Capability and/or UE Specific DRX Parameters and/or TS 24.008 [47] MS Radio Access capability (e.g. due to GERAN radio capability change, E-UTRAN, NG-RAN capability change or cdma2000 Radio Access Technology Capability change) information of the UE.
- for UE supporting RACS in ECM-IDLE as defined in clause 5.11.3a, a change in UE Radio Access capability (e.g. due to GERAN radio capability change, E-UTRAN, NG-RAN capability change or cdma2000 Radio Access Technology Capability change) corresponding to signalling a different UE Radio Capability ID.
- at every change between a cell that does not broadcast SystemInformationBlockType31(-NB) and an E-UTRA cell that broadcasts SystemInformationBlockType31(-NB).
- a change in conditions in the UE require a change in the extended idle mode DRX parameters previously provided by the MME.
- for a UE supporting CS fallback, or configured to support IMS voice, or both, a change of the UE's usage setting or voice domain preference for E-UTRAN.
- for a SR-VCC capable UE, a change of MS Classmark 2 and/or MS Classmark 3 and/or Supported Codecs.
- UE manually selects a CSG cell whose CSG ID and associated PLMN is absent from both the UE's Allowed CSG list and the UE's Operator CSG list.
- UE receives a paging request from the MME while the Mobility Management back off timer is running and the UE's TIN indicates "P-TMSI".
- a change in any of the values of information included in Preferred Network Behaviour as defined in clause 4.3.5.10 that would create incompatibility with the Supported Network Behaviour provided by the serving MME.
- with satellite access for Cellular IoT upon changing to a suitable cell indicating one or more TACs for the RPLMN all of which are outside the UE's Tracking Area List in both ECM-CONNECTED and ECM-IDLE.
- a UE that is using a RAN that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage) is about to leave the satellite network coverage as described in clause 4.13.8.2.
- when the UE has informed the network that it is unreachable and now returns to coverage using either satellite or terrestrial access as described in clause 4.13.8.2.
NOTE 1: The complete list of TAU triggers is specified in TS 24.301 [46].
NOTE 2: With satellite access for Cellular IoT, more than one TAC can be indicated to a UE for each PLMN in any cell, see clause 4.13.6.
The procedure is initiated by an UE in either ECM-IDLE state or ECM-CONNECTED state. The decision to perform S‑GW change during the tracking area update procedure is made by the MME independently from the triggers above.
If SIPTO is allowed for the APN associated with a PDN connection, the MME should re-evaluate whether the PDN GW location is still acceptable. If the MME determines that PDN GW re-location is needed, the MME may initiate PDN deactivation with reactivation requested according to clause 5.10.3 at the end of the tracking area/routing area update procedure.
NOTE 3: It depends on the operator's configuration in the MME whether to use the deactivation with reactivation request or allow the continued usage of the already connected GW.
If SIPTO at the local network is allowed for the APN associated with a PDN connection the MME handles the SIPTO at the Local Network PDN connection as follows.
For a L‑GW collocated with (H)eNB:
- For intra-MME mobility, upon completion of the TAU procedure the MME shall deactivate the SIPTO at the local Network PDN connection with the "reactivation requested" cause value according to clause 5.10.3. If the UE has no other PDN connection, the MME initiates "explicit detach with reattach required" procedure according to clause 5.3.8.3.
- For Inter-MME/SGSN mobility, as part of the Tracking Area Update procedure, the source MME shall remove the bearer(s) corresponding to the SIPTO at Local Network PDN connection and shall release the core network resources associated to the SIPTO at the Local Network PDN connection by performing the MME-initiated PDN Connection Deactivation before sending the Context Response message.
For a stand-alone GW:
- For intra-MME mobility, upon completion of the TAU procedure the MME checks that the Local Home Network ID has changed and decides whether to deactivate the SIPTO at the local Network PDN connection with the "reactivation requested" cause value according to clause 5.10.3. If the UE has no other PDN connection, the MME initiates "explicit detach with reattach required" procedure according to clause 5.3.8.3.
- For Inter-MME/SGSN mobility, upon completion of the TAU/RAU procedure the new MME/SGSN checks that the Local Home Network ID has changed and decides whether to deactivate the SIPTO at the Local Network PDN connection with the "reactivation requested" cause value according to clause 5.10.3. If the UE has no other PDN connection, the MME initiates "explicit detach with reattach required" procedure according to clause 5.3.8.3.
If LIPA is active for a PDN connection of the UE, the source MME (or S4-SGSN) shall not include LIPA bearer(s) in the EPS bearer Context during Tracking Area Update procedure and shall release the core network resources of this LIPA PDN connection by performing the MME requested PDN disconnection procedure according to steps 2 to 6 of clause 5.10.3 before it responds with the Context Response message in the case of inter-MME/SGSN mobility or after it receives Tracking Area Update Request in the case of intra-MME mobility.
NOTE 4: The source MME may not be able to release the LIPA PDN connection after the Context Response is sent as when there is no S-GW relocation, the S-GW will assign the S11 control tunnel of the UE to the new MME after the new MME updates the context information.
During the Tracking Area Update procedure, if the MME supports SRVCC and if the UE SRVCC capability has changed, the MME informs the HSS with the UE SRVCC capability e.g. for further IMS registration.
The cell selection for UTRAN is described in TS 25.304 [12] and TS 25.331 [33].
If during the Tracking Area Update procedure the MME detects that the Serving GW or/and the MME needs be relocated, the old MME may reject any PDN GW initiated EPS bearer(s) request received since the Tracking Area Update procedure started and if rejected, the old MME shall include an indication that the request has been temporarily rejected due to mobility procedure in progress. The rejection is forwarded by the Serving GW to the PDN GW, with the indication that the request has been temporarily rejected.
In the case of satellite access for Cellular IoT, upon receiving the TAU Request message, the MME may verify the UE location and determine whether the PLMN is allowed to operate at the UE location, as described in clause 4.13.4. If the UE receives a TAU Reject message with cause value indicating that the selected PLMN is not allowed to operate at the present UE location, the UE shall attempt to select a PLMN as specified in TS 23.122 [10].
Upon reception of a rejection for an EPS bearer(s) PDN GW initiated procedure with an indication that the request has been temporarily rejected due to mobility procedure in progress, the PDN GW start a locally configured guard timer. The PDN GW shall re-attempt, up to a pre-configured number of times, when either it detects that the Tracking Area Update procedure is completed or has failed using message reception or at expiry of the guard timer.
A Multi-USIM UE may trigger a TAU to send a Requested IMSI Offset in order to derive an alternative IMSI as defined in clause 4.3.33.
NOTE 5: As an exception, during a TAU procedure due to mobility to a new Tracking Area outside the Tracking Area List and detecting paging collision at the same time, a Multi-USIM UE implementation can decide to indicate to the MME a Requested IMSI Offset even if it does not know whether the MME serving the new Tracking Area supports it.
5.3.3.0A Provision of UE's TAI to MME in ECM-CONNECTED state
The eNodeB shall include the TAI+ECGI of the current cell in every S1-AP UPLINK NAS TRANSPORT message. If Dual Connectivity is activated for the UE, the eNodeB shall also include the PSCell ID in every S1-AP UPLINK NAS TRANSPORT message.
NOTE: An eNodeB can contain cells from more than one Tracking Area and intra-eNodeB cell changes are not normally notified to the MME. However, the MME needs to know the UE's current TAI in order to correctly produce a TAU accept message.
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5.3.3.1 Tracking Area Update procedure with Serving GW change
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Figure 5.3.3.1-1: Tracking Area Update procedure with Serving GW change
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 9 and 10 concern GTP based S5/S8.
NOTE 2: In the case of Tracking Area Update without MME change the signalling in steps 4, 5, 7 and steps 12-17 are skipped.
NOTE 3: Some deployments cannot support all system features, for example they cannot support user plane establishment and user plane data transfer, when operating in S&F Mode in the example split MME deployment as described in Annex O.
1. One of the triggers described in clause 5.3.3.0 for starting the TAU procedure occurs.
2. The UE initiates the TAU procedure by sending, to the eNodeB, a TAU Request (UE Core Network Capability, MS Network Capability, Preferred Network behaviour, Support for restriction of use of Enhanced Coverage, old GUTI, Old GUTI type, last visited TAI, active flag, signalling active flag, EPS bearer status, P‑TMSI Signature, additional GUTI, eKSI, NAS sequence number, NAS-MAC, KSI, Voice domain preference and UE's usage setting, UE has UE Radio Capability ID assigned for the selected PLMN, Requested IMSI Offset, Release Request indication, Paging Restriction Information, Unavailability Period Duration, Start of Unavailability Period) message together with RRC parameters indicating the Selected Network and the old GUMMEI. An exception is that, if the TAU was triggered for load re-balancing purposes (see clause 4.3.7.3), the old GUMMEI is not included in the RRC parameters. The UE shall set the Old GUTI Type to indicate whether the Old GUTI is a native GUTI or is mapped from a P-TMSI and RAI.
If the UE's TIN indicates "GUTI" or "RAT‑related TMSI" and the UE holds a valid GUTI then the old GUTI indicates this valid GUTI. If the UE's TIN indicates "P‑TMSI" and the UE holds a valid P‑TMSI and related RAI then these two elements are indicated as the old GUTI. Mapping a P‑TMSI and RAI to a GUTI is specified in Annex H. When the UE is in connected mode (e.g. in URA_PCH) when it reselects to E‑UTRAN, the UE shall set its TIN to "P‑TMSI".
If the UE holds a valid GUTI and the old GUTI indicates a GUTI mapped from a P-TMSI and RAI, then the UE indicates the GUTI as additional GUTI. If the old GUTI indicates a GUTI mapped from a P-TMSI and RAI, and the UE has a valid P-TMSI signature, the P-TMSI signature shall be included.
The additional GUTI in the Tracking Area Update Request message allows the new MME to find any already existing UE context stored in the new MME when the old GUTI indicates a value mapped from a P-TMSI and RAI.
Alternatively, when a UE only supports E-UTRAN, it identifies itself with the old GUTI and sets the Old GUTI Type to 'native'.
The RRC parameter "old GUMMEI" takes its value from the identifier that is signalled as the old GUTI according to the rules above. For a combined MME/SGSN the eNodeB is configured to route the MME‑code(s) of this combined node to the same combined node. This eNodeB is also configured to route MME‑code(s) of GUTIs that are generated by the UE's mapping of the P‑TMSIs allocated by the combined node. Such an eNodeB configuration may also be used for separate nodes to avoid changing nodes in the pool caused by inter RAT mobility.
The last visited TAI shall be included in order to help the MME produce a good list of TAIs for any subsequent TAU Accept message. Selected Network indicates the network that is selected. Active flag is a request by UE to activate the radio and S1 bearers for all the active EPS Bearers by the TAU procedure when the UE is in ECM-IDLE state. Signalling active flag is a request by UE using Control Plane CIoT EPS Optimisation to maintain the NAS signalling connection after Tracking Area Update Procedure is completed in order to transmit pending Data using the Data Transport in Control Plane CIoT EPS Optimisation or NAS signalling. The EPS bearer status indicates each EPS bearer that is active in the UE. The TAU Request message shall be integrity protected by the NAS-MAC as described in TS 33.401 [41]. eKSI, NAS sequence number and NAS-MAC are included if the UE has valid EPS security parameters. NAS sequence number indicates the sequential number of the NAS message. KSI is included if the UE indicates a GUTI mapped from a P‑TMSI in the information element "old GUTI".
In the RRC connection establishment signalling associated with the TAU Request, the UE indicates its support of the CIoT EPS Optimisations relevant for MME selection.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no active flag or EPS bearer status included in the TAU Request message. For a UE with a running Service Gap timer in the UE the UE shall not set the active flag and the signalling active flag in the TAU request message (see clause 4.3.17.9) except for network access for regulatory prioritized services like Emergency services or exception reporting.
If the UE has any PDN connection of PDN Type "non-IP" or "Ethernet", the UE shall send the EPS bearer status in the TAU Request message.
The UE sets the voice domain preference and UE's usage setting according to its configuration, as described in clause 4.3.5.9.
The UE includes extended idle mode DRX parameters information element if it needs to enable extended idle mode DRX, even if extended idle mode DRX parameters were already negotiated before.
The UE may include UE paging probability information if it supports the assignment of WUS Assistance Information from the MME to assist the eNodeB's Wake-Up Signal (WUS) group decision (see TS 36.300 [5]).
If a UE includes a Preferred Network Behaviour, this defines the Network Behaviour the UE is expecting to be available in the network as defined in clause 4.3.5.10.
If the UE supports RACS as defined in clause 5.11.3a, and if the UE is provisioned with a UE Radio Capability ID for use in the selected PLMN (i.e. PLMN-assigned for the specific PLMN or manufacturer-assigned), the UE includes a flag that indicates it has an assigned UE Radio Capability ID for use in the selected PLMN but the actual UE Radio Capability ID is provided to MME after security context is established in step 6 (see below).
If a Multi-USIM UE wants to enter ECM-IDLE state it includes the Release Request indication and optionally provides Paging Restriction Information.
If a Multi-USIM UE needs to modify the Paging Occasions in order to avoid paging collisions, it sends a Requested IMSI Offset to the MME, in order to signal an alternative IMSI as described in clause 4.3.33
In the case of satellite access for Cellular IoT, the MME may verify the UE location and determine whether the PLMN is allowed to operate at the UE location, as described in clause 4.13.4. If the UE receives a TAU Reject message with cause value indicating that the selected PLMN is not allowed to operate at the present UE location, the UE shall attempt to select a PLMN as specified in TS 23.122 [10].
If the UE is using a eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the UE may include an Unavailability Period Duration and Start of Unavailability Period, see clause 4.13.8.2.
3. The eNodeB derives the MME address from the RRC parameters carrying the old GUMMEI, the indicated Selected Network and the RAT (NB-IoT or WB-E-UTRAN). If that MME is not associated with that eNodeB or the GUMMEI is not available or the UE indicates that the TAU procedure was triggered by load re-balancing, the eNodeB selects an MME as described in clause 4.3.8.3 on "MME Selection Function".
The eNodeB forwards the TAU Request message together with the CSG access mode, CSG ID, TAI+ECGI of the cell from where it received the message and with the Selected Network to the new MME. CSG ID is provided by RAN if the UE sends the TAU Request message via a CSG cell or a hybrid cell. CSG access mode is provided if the UE sends the TAU Request message via a hybrid cell. If the CSG access mode is not provided but the CSG ID is provided, the MME shall consider the cell as a CSG cell. For SIPTO at the Local Network with stand-alone GW architecture the eNodeB includes the Local Home Network ID in the Initial UE Message and in Uplink NAS Transport message if the target cell is in a Local Home Network.
To assist Location Services, the eNodeB indicates the UE's Coverage Level to the MME.
If the MME supports RACS, and the MME detects that the selected PLMN is different from the currently registered PLMN for the UE, the MME provides the UE Radio Capability ID of the newly selected PLMN in the UE context to the eNodeB as described in clause 5.11.3a.
In the case of satellite access over NB-IoT, as described in TS 36.300 [5] and TS 36.413 [36], the eNB may request the MME to provide the Coarse Location information to the eNB, as described in TS 36.300 [5] and TS 36.413 [36].
If the MME is operating in S&F Mode, the MME may reject the TAU Request and optionally provide to the UE in the TAU Reject message any of the following: a S&F Wait Timer, a S&F Monitoring List (see clause 4.13.9).
4. The new MME differentiates the type of the old node, i.e. MME or SGSN, as specified in clause 4.3.19, uses the GUTI received from the UE to derive the old MME/S4 SGSN address, and sends a Context Request (old GUTI, complete TAU Request message, P‑TMSI Signature, MME Address, UE validated, CIoT EPS Optimisation support indication) message to the old MME/old S4 SGSN to retrieve user information. UE Validated indicates that the new MME has validated the integrity protection of the TAU message, e.g. based on native EPS security context for the UE. To validate the Context Request the old MME uses the complete TAU Request message and the old S4 SGSN uses the P‑TMSI Signature and responds with an appropriate error if integrity check fails in old MME/S4 SGSN. This shall initiate the security functions in the new MME. If the security functions authenticate the UE correctly, the new MME shall send a Context Request (IMSI, complete TAU Request message, MME Address, UE Validated) message to the old MME/S4 SGSN with the UE Validated set. If the new MME indicates that it has authenticated the UE or if the old MME/old S4 SGSN correctly validates the UE, then the old MME/old S4 SGSN starts a timer.
If the UE with emergency bearers is not authenticated in the old MME/old S4 SGSN (in a network supporting unauthenticated UEs) the old MME/old S4 SGSN continues the procedure with sending a Context Response and starting the timer also when it cannot validate the Context Request.
If a RLOS attached UE is not successfully authenticated in the old MME, the old MME continues the procedure with sending a Context Response and starting the existing timer also when it cannot validate the Context Request.
If the new MME supports CIoT EPS Optimisation, CIoT EPS Optimisation support indication is included in the Context Request indicating support for various CIoT EPS Optimisations (e.g. support for header compression for CP CIoT EPS Optimisation, etc.).
5. If the Context Request is sent to an old MME the old MME responds with a Context Response (IMSI, MSISDN, ME Identity (IMEISV), MM Context, EPS Bearer Context(s), Serving GW signalling Address and TEID(s), ISR Supported, MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone, UE Core Network Capability, UE Specific DRX Parameters, Remaining Running Service Gap timer, LTE-M UE Indication) message. If the new MME supports CIoT EPS Optimisation and the use of header compression has been negotiated between the UE and the old MME, the Context Response also includes the Header Compression Configuration which includes the information necessary for the ROHC channel setup but not the RoHC context itself.
If the Context Request is sent to an old S4 SGSN the old S4 SGSN responds with a Context Response (MM Context, EPS Bearer Context(s), Serving GW signalling Address and TEID(s), ISR Supported, MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone, UE Core Network Capability, UE Specific DRX Parameters). If the source MME has not yet reported a non-zero MO Exception Data Counter to the PDN GW, the Context Response also includes the MO Exception Data Counter as described in TS 29.274 [43].
The MM Context contains security related information as well as other parameters (including IMSI and ME Identity (if available)) as described in clause 5.7.2 (Information Storage for MME). The unused Authentication Quintets in the MM Context are also maintained in the SGSN. TS 33.401 [41] gives further details on the transfer of security related information.
If the MM Context received with the Context Response message did not include IMEISV and the MME does not already store the IMEISV of the UE, the MME shall retrieve the ME Identity (IMEISV) from the UE.
The PDN GW Address and TEID(s) (for GTP-based S5/S8) or GRE Keys (PMIP-based S5/S8 at the PDN GW(s) for uplink traffic) and the TI(s), is part of the EPS Bearer Context. If the UE is not known in the old MME/old S4 SGSN or if the integrity check for the TAU Request message fails, the old MME/old S4 SGSN responds with an appropriate error cause. ISR Supported is indicated if the old MME/old S4 SGSN and associated Serving GW are capable to activate ISR for the UE.
If the UE receives emergency bearer services from the old MME/old S4 SGSN and the UE is UICCless, IMSI can not be included in the Context Response. For emergency attached UEs, if the IMSI cannot be authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available.
For a RLOS attached UE, the old MME includes an RLOS indication to the new MME. If the RLOS attached UE in the old MME does not have a USIM, IMSI can not be included in the Context Response. If the RLOS attached UE has USIM but the IMSI cannot be successfully authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available.
If SIPTO at the Local Network is active for a PDN connection in the architecture with stand-alone GW, the old MME/old S4 SGSN shall include the Local Home Network ID of the old cell in the EPS Bearer context corresponding to the SIPTO at the Local Network PDN connection.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no EPS Bearer Context(s) included in the Context Response message.
Based on the CIoT EPS Optimisation support indication, old MME only transfers the EPS Bearer Context(s) that the new MME supports. If the new MME does not support CIoT EPS Optimisation, EPS Bearer Context(s) of non-IP PDN connection are not transferred to the new MME. If the new MME does not support Ethernet PDN Type, EPS Bearer Context(s) of Ethernet PDN type are not transferred to the new MME. If the EPS Bearer Context(s) of a PDN connection has not been transferred, the old MME shall consider all bearers of that PDN connection as failed and release that PDN connection by triggering the MME requested PDN disconnection procedure specified in clause 5.10.3. The buffered data in the old MME is discarded after receipt of Context Acknowledgement.
If the EPS Bearer Context(s) are to be transferred to the new MME, the old MME also includes the Serving GW IP address and TEID for both S1-U and S11-U, if available.
If the Old MME is aware the UE is a LTE-M UE, it provides the LTE-M UE Indication to the new MME. During inter PLMN mobility, the new MME shall delete the UE Radio Capability ID received from the old MME, unless the operator policy indicates that all UE Radio Capability IDs used in the old PLMN are also valid in the new PLMN.
6. If the integrity check of TAU Request message (sent in step 2) failed, then authentication is mandatory. The authentication functions are defined in clause 5.3.10 on "Security Function". Ciphering procedures are described in clause 5.3.10 on "Security Function". If GUTI allocation is going to be done and the network supports ciphering, the NAS messages shall be ciphered.
If this TAU request is received for a UE which is already in ECM_CONNECTED state and the PLMN-ID of the TAI sent by the eNodeB in Step 3 is different from that of the GUTI, included in the TAU Request message, the MME shall delay authenticating the UE until after Step 21 (TAU Complete message).
NOTE 4: The MME delays the authentication such that the UE first updates its registered PLMN-ID to the new PLMN-ID selected by the RAN during handover. The new PLMN-ID is provided by the MME to the UE as part of the GUTI in the TAU accept message in Step 20. Doing this ensures that the same PLMN-ID is used in the derivation of the Kasme key by both the network and the UE.
If the new MME is configured to allow emergency bearer services for unauthenticated UE the new MME behave as follows:
- where a UE has only emergency bearer services, the MME either skip the authentication and security procedure or accepts that the authentication may fail and continues the Tracking Area Update procedure; or
- where a UE has both emergency and non-emergency bearer services and authentication fails, the MME continues the Tracking Area Update procedure and deactivates all the non-emergency PDN connections as specified in clause 5.10.3.
If the new MME is configured to allow Restricted Local Operator Services, the new MME, based on local regulation and operator policy, may skip the authentication and security procedure, or may perform authentication if security parameters are available, or obtainable from HSS, and continues the Tracking Area Update procedure regardless of the authentication result.
If the UE indicated it has a UE Radio Capability ID assigned for use in the selected PLMN in step 2, the MME may request the UE to provide the UE Radio Capability ID in Security Mode Command, if the MME needs to get the UE Radio Capability ID from the UE e.g. at inter-PLMN mobility. If enquired by the MME the UE shall include the UE Radio Capability ID in Security Mode Command Accept for the supported UE radio capabilities.
In the case of satellite access for NB-IoT, if the UE indicated support for reporting its Coarse Location Information, the MME may request the UE to report its Coarse Location Information by setting the Coarse Location Information Request in the Security Mode Command message and the UE then reports its Coarse Location Information in the Security Mode Complete message. To perform UE location verification as described in clause 4.13.4, the MME provides the reported Coarse Location Information to the E-SMLC as described in clause 9.1.17 of TS 23.271 [57]. If the eNB requested the MME to provide the Coarse Location Information to the eNB, the MME provides the Coarse Location Information to the eNB in a following S1-AP message as described in TS 36.413 [36]. The eNB may use it as specified in TS 36.300 [5].
7. The MME (if the MME has changed then it is the new MME) determines to relocate the Serving GW. The Serving GW is relocated when the old Serving GW cannot continue to serve the UE. The MME (if the MME has changed then it is the new MME) may also decide to relocate the Serving GW if a new Serving GW is expected to serve the UE longer and/or with a more optimal UE to PDN GW path, or if a new Serving GW can be co-located with the PDN GW. Selection of a new Serving GW is performed according to clause 4.3.8.2 on "Serving GW selection function".
If the MME has changed the new MME sends a Context Acknowledge (Serving GW change indication) message to the old MME/old S4 SGSN. Serving GW change indication indicates a new Serving GW has been selected. The old MME/old S4 SGSN marks in its UE context that the information in the GWs is invalid. And, if the old node is an MME, the old MME marks in its UE context that the information in the HSS is invalid. This ensures that the old MME/old S4 SGSN updates the GWs, and the old MME updates the HSS, if the UE initiates a TAU or RAU procedure back to the old MME/old S4 SGSN before completing the ongoing TAU procedure.
NOTE 5: Updating the GWs refers to deletion of session(s) on the Serving GW followed by re-creation of session(s) on the Serving GW. The re-creation of session(s) on the Serving GW will result in successful re-establishment of the S5/S8 tunnel between the selected Serving GW and the PDN GW.
If the security functions do not authenticate the UE correctly, then the TAU shall be rejected, and the new MME shall send a reject indication to the old MME/old S4 SGSN. The old MME/old S4 SGSN shall continue as if the Identification and Context Request was never received.
ISR is not indicated in the Context Acknowledge as ISR is not activated due to the S‑GW change.
For UE using CIoT EPS Optimisation without any activated PDN connection, the steps 8, 9, 10, 11, 18 and 19 are skipped.
8. If the MME has changed the new MME verifies the EPS bearer status received from the UE with the bearer contexts received from the old MME/old S4 SGSN. If the MME has not changed the MME verifies EPS bearer status from the UE with the bearer contexts available in the MM context. The MME releases any network resources related to EPS bearers that are not active in the UE. If there is no bearer context at all, the MME rejects the TAU Request.
NOTE 6: If the MME has changed, the new MME executes the Create Session Request procedure before releasing any network resources related to EPS bearers that are not active in the UE.
If the MME selected a new Serving GW it sends a Create Session Request (IMSI, MSISDN, bearer contexts, MME Address and TEID, Type, the Protocol Type over S5/S8, RAT type, LTE-M RAT type reporting to PGW flag, Serving Network, UE Time Zone, MO Exception data counter) message per PDN connection to the selected new Serving GW. The PDN GW address and TFT (for PMIP-based S5/S8) are indicated in the bearer Contexts. Type indicates to the Serving GW to send the Modify Bearer Request to the PDN GW. The Protocol Type over S5/S8 is provided to Serving GW which protocol should be used over S5/S8 interface. RAT type indicates a change in radio access. If it is a mobility from a SGSN to a MME and if the MME supports location information change reporting, the MME shall include the User Location Information (according to the supported granularity) in the Create Session Request, regardless of whether location information change reporting had been requested in the previous RAT by the PDN GW. If it is an inter MME mobility and if the PDN GW requested location information change reporting, the MME includes the User Location Information IE in this message if it is different compared to the previously sent information. If the PDN GW requested User CSG information, the MME also includes the User CSG Information IE in this message. If Control Plane CIoT EPS Optimisation applies, the MME may also indicate S11-U tunnelling of NAS user data and send its own S11-U IP address and MME DL TEID for DL data forwarding by the SGW. The MME shall include the MO Exception data counter if it has received the counter for RRC cause "MO Exception data" in the Context Response message.
If only the Control Plane CIoT EPS Optimisation is used, the MME shall include a Control Plane Only PDN Connection Indicator in Create Session Request.
If the new MME receives the EPS bearer context with SCEF, then the new MME updates the SCEF as defined in TS 23.682 [74].
If the UE is using the LTE-M RAT type and the PDN GW expects the LTE-M RAT type reporting as specified in clause 5.11.5, the MME also includes the LTE-M RAT type reporting to PGW flag to indicate to the Serving GW to forward the LTE-M RAT type to the PDN GW.
9. The Serving GW informs the PDN GW(s) about the change of for example the RAT type that e.g. can be used for charging, by sending the message Modify Bearer Request (Serving GW Address and TEID, RAT type, Serving Network, PDN Charging Pause Support Indication) per PDN connection to the PDN GW(s) concerned. User Location Information IE and/or UE Time Zone IE and/or User CSG Information IE and/or MO Exception data counter are also included if they are present in step 8. The Serving GW and PDN GW indicate each use of the RRC establishment cause "MO Exception Data" by the related counter on its CDR.
If the Serving GW has received the Control Plane Only PDN Connection Indicator in step 8, the Serving GW indicates the use of CP only on its CDR.
If LTE-M RAT type and the LTE-M RAT type reporting to PGW flag were received at step 8, the Serving GW shall include the LTE-M RAT type in the Modify Bearer Request message to the PGW. Otherwise the Serving GW includes RAT type WB-E-UTRAN.
9a If dynamic PCC is deployed, and RAT type information needs to be conveyed from the PDN GW to the PCRF, then the PDN GW shall send RAT type information to the PCRF by means of an IP‑CAN Session Modification procedure as defined in TS 23.203 [6].
NOTE 7: The PDN GW does not need to wait for the PCRF response, but continues in the next step. If the PCRF response leads to an EPS bearer modification the PDN GW should initiate a bearer update procedure.
10. The PDN GW updates its bearer contexts and returns a Modify Bearer Response (MSISDN, Charging Id, PDN Charging Pause Enabled Indication (if PDN GW has chosen to enable the function)) message. The MSISDN is included if the PDN GW has it stored in its UE context. If there has been a RAT change towards E-UTRAN and location information change reporting is required and supported in the target MME, the PDN GW shall provide MS Info Change Reporting Action in the Modify Bearer Response.
If the Serving GW is relocated, the PDN GW shall send one or more "end marker" packets on the old path immediately after switching the path in order to assist the reordering function in the target eNodeB. If the Serving GW has no downlink user plane established, the Serving GW shall discard the "end marker" received from the PDN GW and shall not send Downlink Data Notification. Otherwise the Serving GW shall forward the "end marker" packets to the source eNodeB or source S4 SGSN.
11. The Serving GW updates its bearer context. This allows the Serving GW to route bearer PDUs to the PDN GW when received from eNodeB.
The Serving GW returns a Create Session Response (Serving GW address and TEID for user plane and control plane and PDN GW TEIDs (for GTP-based S5/S8) or GRE keys (for PMIP-based S5/S8) for uplink traffic and control plane, MS Info Change Reporting Action) message to the new MME.
If Control Plane CIoT EPS Optimisation applies and if the MME does not include Control Plane Only PDN Connection Indicator in the Create Session Request:
- If separation of S11-U from S1-U is required, the Serving GW shall include the Serving GW IP address and TEID for S11-U and additionally the Serving GW IP address and TEID for S1-U in the Create Session Response.
- Otherwise, if separation of S11-U from S1-U is not required, the Serving GW includes the Serving GW IP address and TEID for S11-U in Create Session Response.
When the MME receives the Create Session Response message, the MME checks if there is a "Availability after DDN Failure" monitoring event or a "UE Reachability" monitoring event configured for the UE in the MME and in such a case sends an event notification (see TS 23.682 [74] for further information).
12. The new MME verifies whether it holds subscription data for the UE identified by the GUTI, the additional GUTI or by the IMSI received with the context data from the old CN node.
If there are no subscription data in the new MME for this UE, or for some network sharing scenario (e.g. GWCN) if the PLMN-ID of the TAI supplied by the eNodeB is different from that of the GUTI in the UE's context, then the new MME sends an Update Location Request (MME Identity, IMSI, ULR-Flags, MME Capabilities, Homogeneous Support of IMS Voice over PS Sessions, UE SRVCC capability, equivalent PLMN list, ME Identity (IMEISV)) message to the HSS. ULR-Flags indicates that update location is sent from an MME and the MME registration shall be updated in HSS. The HSS does not cancel any SGSN registration. The MME capabilities indicate the MME's support for regional access restrictions functionality. The inclusion of the equivalent PLMN list indicates that the MME supports the inter-PLMN handover to a CSG cell in an equivalent PLMN using the subscription information of the target PLMN. The "Homogenous Support of IMS Voice over PS Sessions" indication (see clause 4.3.5.8A) shall not be included unless the MME has completed its evaluation of the support of "IMS Voice over PS Session" as specified in clause 4.3.5.8. The ME Identity is included if step 5 caused the MME to retrieve the IMEISV from the UE.
NOTE 8: At this step, the MME may not have all the information needed to determine the setting of the IMS Voice over PS Session Supported indication for this UE (see clause 4.3.5.8). Hence the MME can send the "Homogenous Support of IMS Voice over PS Sessions" later on in this procedure.
If the UE initiates the TAU procedure in a VPLMN supporting Autonomous CSG Roaming and the HPLMN has enabled Autonomous CSG Roaming in the VPLMN (via Service Level Agreement) and the MME needs to retrieve the CSG subscription information of the UE from the CSS, the MME initiates the Update CSG Location Procedure with CSS as described in clause 5.3.12.
If the MME determines that only the UE SRVCC capability has changed, the MME sends a Notify Request to the HSS to inform about the changed UE SRVCC capability.
If all the EPS bearers of the UE have emergency ARP value, the new MME may skip the update location procedure or proceed even if the update location fails.
If the UE is RLOS attached, the new MME skips the Update Location procedure.
13. The HSS sends the message Cancel Location (IMSI, Cancellation Type) to the old MME with Cancellation Type set to Update Procedure.
14. If the timer started in step 4 is not running, the old MME removes the MM context. Otherwise, the contexts are removed when the timer expires. It also ensures that the MM context is kept in the old MME for the case the UE initiates another TAU procedure before completing the ongoing TAU procedure to the new MME. The old MME acknowledges with the message Cancel Location Ack (IMSI).
15. When old S4 SGSN receives the Context Acknowledge message and if the UE is in Iu Connected, the old S4 SGSN sends an Iu Release Command message to the RNC after the timer started in step 4 has expired.
16. The RNC responds with an Iu Release Complete message.
17. The HSS acknowledges the Update Location Request message by sending an Update Location Ack (IMSI, Subscription Data) message to the new MME. The Subscription Data may contain the CSG subscription data for the registered PLMN and for the equivalent PLMN list requested by MME in step 12.
The subscription data may contain Enhanced Coverage Restricted parameter. If received from the HSS, MME stores this Enhanced Coverage Restricted parameter in the MME MM context.
The subscription data may contain a Service Gap Time. If received from the HSS, the MME stores this Service Gap Time in the MME MM context for the UE and passes it to the UE in the Tracking Area Update Accept message.
The subscription data may contain Subscribed Paging Time Window parameter that applies to the UEs on a specific RAT, e.g. NB-IoT. If received from the HSS, MME stores this Subscribed Paging Time Window parameter in the MME MM context.
The subscription data may contain an indication that the UE is subscribed to receive time reference information in access stratum. If received from the HSS, and if supported by the MME, the MME stores this indication in the MME MM context.
If the Update Location is rejected by the HSS, the new MME rejects the TAU Request from the UE with an appropriate cause. In such cases, the new MME releases any local MME EPS Bearer contexts for this particular UE, and additionally deletes the EPS bearer resources in the new Serving GW by sending the Delete Session Request (Cause, Operation Indication) messages to the new Serving GW. The Operation Indication flag shall not be set. Therefore, the new Serving GW receiving this request shall not initiate a delete procedure towards the PDN GW.
If the UE initiates the TAU procedure at a CSG cell, the new MME shall check whether the CSG ID and associated PLMN is contained in the CSG subscription and is not expired. If the CSG ID and associated PLMN is not present or expired, the MME shall send a Tracking Area Update reject message to the UE with an appropriate cause value. The UE shall remove the CSG ID and associated PLMN from its Allowed CSG list if present. If the UE has ongoing emergency bearer services no CSG access control shall be performed.
If all checks are successful then the new MME constructs a context for the UE.
18. If the MME has changed, when the timer started in step 4 expires the old MME/old S4 SGSN releases any local MME or SGSN bearer resources and additionally the old MME/old S4 SGSN deletes the EPS bearer resources by sending the Delete Session Request (Cause, Operation Indication) messages to the old Serving GW if it received the Serving GW change indication in the Context Acknowledge message in step 7. When the Operation Indication flag is not set, that indicates to the old Serving GW that the old Serving GW shall not initiate a delete procedure towards the PDN GW. If ISR is activated the Cause indicates to the old S‑GW that the old S‑GW shall delete the bearer resources on the other old CN node by sending Delete Bearer Request message(s) to that CN node.
If the MME has not changed, step 11 triggers the release of the EPS bearer resources at the old Serving GW.
19. The Serving GW acknowledges with Delete Session Response (Cause) messages. The Serving GW discards any packets buffered for the UE.
20. If due to regional subscription restrictions or access restrictions (e.g. CSG restrictions) (received in update location procedure in step 17) the UE is not allowed to access the TA:
- The MME rejects the Tracking Area Update Request with an appropriate cause to the UE.
- For UEs with emergency EPS bearers, i.e. at least one EPS bearer has an ARP value reserved for emergency services, the new MME accepts the Tracking Area Update Request and deactivates all non-emergency PDN connections as specified in clause 5.10.3. If the Tracking Area Update procedure is initiated in ECM-IDLE state, all non-emergency EPS bearers are deactivated by the Tracking Area Update procedure without bearer deactivation signalling between the UE and the MME.
If the TAU request message includes Paging Restriction Information, the MME may accept or reject the Paging Restriction Information requested by the UE based on operator policy. If the MME rejects the Paging Restriction Information, the MME removes any stored Paging Restriction Information from the UE context and discards the UE requested Paging Restriction Information. If the MME accepts the Paging Restriction Information from the UE, the MME stores the Paging Restriction Information from the UE in the UE context and then enforces it in the Network Triggered Service Request procedure as described in clause 5.3.4.3. The MME informs the UE about the acceptance/rejection of the requested Paging Restriction Information in the TAU Accept message. If the TAU Request message does not include any Paging Restriction Information, the MME shall delete any stored Paging Restriction Information for this UE and stop restricting paging accordingly.
If the TAU Request message includes a Release Request indication, the MME does not activate the user plane setup procedure in the subsequent steps and triggers the S1 release procedure as described in clause 5.3.5 after the completion of TAU procedure.
The MME sends a TAU Accept (GUTI, TAI list, EPS bearer status, NAS sequence number, NAS-MAC, IMS Voice over PS session supported, Emergency Service Support indicator, LCS Support Indication, Supported Network Behaviour, Service Gap Time, Enhanced Coverage Restricted, Indication of support of 15 EPS bearers per UE, PLMN-assigned UE Radio Capability ID, indication for PLMN-assigned UE Radio Capability ID deletion, Accepted IMSI Offset, Connection Release Supported, Paging Cause Indication for Voice Service Supported, Reject Paging Request Supported, Paging Restriction Supported, Paging Timing Collision Control Supported, Paging Restriction Information acceptance/rejection, Forbidden TAI(s), Enhanced Discontinuous Coverage Support, Return To Coverage Notification Not Required, Unavailability Period Duration, Start of Unavailability Period, Maximum Time Offset) message to the UE. If the active flag is set the MME may provide the eNodeB with Handover Restriction List. GUTI is included if the MME allocates a new GUTI. If the active flag is set in the TAU Request message the user plane setup procedure can be activated in conjunction with the TAU Accept message. If the DL Data Buffer Expiration Time for the UE in the MME has not expired, the user plane setup procedure is activated even if the MME did not receive the active flag in the TAU Request message. If the new MME receives the Downlink Data Notification message or any downlink signalling message while the UE is still connected, the user plane setup procedure may be activated even if the new MME did not receive the active flag in the TAU Request message. The procedure is described in detail in TS 36.300 [5]. The message sequence should be the same as for the UE triggered Service Request procedure specified in clause 5.3.4.1 from the step when MME establishes the bearer(s). The MME indicates the EPS bearer status IE to the UE. The UE removes any internal resources related to bearers that are not marked active in the received EPS bearer status. If the EPS bearer status information was in the TAU Request, the MME shall indicate the EPS bearer status to the UE. Handover Restriction List is described in clause 4.3.5.7 "Mobility Restrictions". The MME sets the IMS Voice over PS session supported as described in clause 4.3.5.8.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no EPS bearer status included in the TAU Accept message.
The MME indicates the CIoT EPS Optimisations it supports and prefers in the Supported Network Behaviour information as defined in clause 4.3.5.10.
If there is a Service Gap timer running for the UE in the MME, and the active flag or the signalling active flag is received in the TAU Request message, the MME shall ignore the active flag and signalling active flag and not perform any of the actions related to these flags except if the TAU Request message has been received when the UE has a PDN connection for emergency bearer services established or is establishing a PDN connection for emergency bearer services or if the UE is configured to use high priority access (AC 11-15) in selected PLMN.
The MME shall include the Service Gap Time in the TAU Accept message if the UE has indicated Service Gap Control capability and either if Service Gap Time was received in step 17 from HSS in the subscription information or if the Service Gap Time in the subscription information has been updated by HSS User Profile management (i.e. the Insert Subscriber Data procedure in clause 5.3.9.2).
If the UE included support for restriction of use of Enhanced Coverage in step 1, the MME sends Enhanced Coverage Restricted parameter to the eNodeB in the S1-AP message as defined in clause 4.3.28. The MME also sends the Enhanced Coverage Restricted parameter to the UE in the TAU Accept message. UE shall store Enhanced Coverage Restricted parameter and shall use the value of Enhanced Coverage Restricted parameter to determine if enhanced coverage feature should be used or not.
If the MME successfully obtained Header Compression Configuration parameters in step 5 it indicates the continued use of previous negotiated configuration to the UE in the Header Compression Context Status for each EPS Bearer of the UE. When Header Compression Context Status indicates that the previous negotiated configuration can no longer be used for some EPS bearers, the UE shall stop performing header compression and decompression, when sending or receiving data using Control Plane CIoT EPS Optimisation on these EPS bearers.
If the MME did not receive the Voice Support Match Indicator in the MM Context, then the MME may send a UE Radio Capability Match Request to the eNodeB as described in clause 5.3.14. If the MME hasn't received Voice Support Match Indicator from the eNodeB then, based on implementation, MME may set IMS Voice over PS session supported Indication and update it at a later stage. After step 12, and in parallel to any of the preceding steps, the MME shall send a Notify Request (Homogeneous Support of IMS Voice over PS Sessions) message to the HSS:
- If the MME has evaluated the support of IMS Voice over PS Sessions, see clause 4.3.5.8, and
- If the MME determines that it needs to update the Homogeneous Support of IMS Voice over PS Sessions, see clause 4.3.5.8A.
The Emergency Service Support indicator informs the UE that Emergency bearer services are supported. LCS Support Indication indicates whether the network supports the EPC-MO-LR and/or CS-MO-LR as described in TS 23.271 [57]. Indication for support of 15 EPS bearers per UE indicates the network support for up to 15 EPS bearers per UE as defined in clause 4.12.
If the UE included extended idle mode DRX parameters information element, the MME includes extended idle mode DRX parameters information element if it decides to enable extended idle mode DRX with Paging Time Window length assigned considering Subscribed Paging Time Window (if available) and the local policy. Additionally, for a UE using an eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the MME may consider Unavailability Period Duration and/or Start of Unavailability Period as described in clause 4.13.8.2 when determining idle mode DRX parameters.
If the UE provided the UE paging probability information in Step 2, the MME takes it into account when generating the WUS Assistance Information. If the MME has determined WUS Assistance Information for the UE, the MME shall send the WUS Assistance Information to the UE (see TS 36.300 [5]).
When receiving the TAU Accept message and there is no ISR Activated indication the UE shall set its TIN to "GUTI".
For a S‑GW change, ISR Activated is never indicated by the MME as it needs a RAU with the same S‑GW first to activate ISR. For an MME change, ISR is not activated by the new MME to avoid context transfer procedures with two old CN nodes.
If the TAU procedure is initiated by manual CSG selection and occurs via a CSG cell, the UE upon receiving the TAU Accept message shall add the CSG ID and associated PLMN to its Allowed CSG list if it is not already present. Manual CSG selection is not supported if the UE has emergency bearers established.
If the user plane setup is performed in conjunction with the TAU Accept message and the TAU is performed via a hybrid cell, then the MME shall send an indication whether the UE is a CSG member to the RAN along with the S1-MME control message. Based on this information, the RAN may perform differentiated treatment for CSG and non-CSG members.
NOTE 9: If the UE receives a TAU Accept message via a hybrid cell, the UE does not add the corresponding CSG ID and associated PLMN to its Allowed CSG list. Adding a CSG ID and associated PLMN to the UE's local Allowed CSG list for a hybrid cell is performed only by OTA or OMA DM procedures.
If the UE receives a Service Gap Time in the TAU Accept message, the UE shall store this parameter and apply Service Gap Control (see clause 4.3.17.9).
If the UE has indicated support for dual connectivity with NR in the TAU Request and the UE is not allowed to use NR as Secondary RAT, the MME indicates that to the UE in the TAU Accept message.
If the user plane setup is performed and if RACS is supported and MME has UE Radio Capability ID in UE context, valid for the PLMN the UE is currently in, it signals the UE Radio Capability ID to the eNodeB as defined in clause 5.11.3a. If the eNodeB does not have mapping between the specific UE Radio Capability ID and the UE radio capabilities, it shall use the procedure described in TS 36.413 [36] to retrieve the mapping from the Core Network.
When the UE supports RACS, and the MME needs to configure the UE with a UE Radio Capability ID, and the MME already has the UE radio capabilities for the UE, the MME may provide the UE with the UE Radio Capability ID for the UE radio capabilities the UCMF returns to the MME for this UE.
If the UE had included a UE Specific DRX parameter for NB-IoT in the Tracking Area Update Request, the MME includes the Accepted NB-IoT DRX parameter.
If the UE provided a Requested IMSI Offset in step 2, but the network prefers a different value, the MME provides the UE with an Accepted IMSI Offset different from the one provided in step 2. Otherwise the value of the Accepted IMSI Offset the MME sends is the value of the Requested IMSI Offset sent by the UE in step 2. The MME stores the value of the alternative IMSI derived (see clause 4.3.33) from the Accepted IMSI Offset provided to the UE in the UE context.
If a Multi-USIM UE does not provide a Requested IMSI Offset in step 1, the MME erases any alternative IMSI value in the UE context.
NOTE 10: The MME does not remove IMSI Offset value if the Tracking Area Update Request is for periodic Tracking Area Update.
If the Multi-USIM UE has indicated one or more Multi-USIM specific Capabilities are supported in the UE Core Network Capability in step 2, the MME shall indicate whether the corresponding one or more Multi-USIM specific features described in clause 4.3.33 are supported based on network capability and preference by the network (based on local network policy) by providing one or more of the Connection Release Supported, Paging Cause Indication for Voice Service Supported, Reject Paging Request Supported, Paging Restriction Supported and Paging Timing Collision Control Supported indications. The MME shall only indicate Paging Restriction Supported together with either Connection Release Supported or Reject Paging Request Supported. The UE shall only use Multi-USIM specific features that the MME indicated as being supported. In the case of Emergency attached UE, the MME shall not indicate support for any Multi-USIM feature to the UE.
If the MME receives multiple TAIs from E-UTRAN in step 3 and determines that some, but not all, TAIs in the received list of TAIs are forbidden by subscription or by operator policy, the MME shall include the forbidden TAI(s) in the TAU Accept message.
If both UE and network support discontinuous coverage, the MME provides the Enhanced Discontinuous Coverage Support indication as described in clause 4.13.8.1.
For a UE using an eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the MME may provide Return To Coverage Notification Not Required, which requests the UE in ECM_IDLE state to not perform the TAU procedure when it returns to coverage, and/or provide the UE with an Unavailability Period Duration and/or Start of Unavailability Period if available, as described in clause 4.13.8.2. The MME may also provide a Maximum Time Offset as described in clause 4.13.8.6.
If supported by the MME and if the UE is subscribed to receive time reference information, then the MME provides the Time Reference Information Distribution Indication to the eNodeB.
If the UE indicated "S&F Capability" in the UE Core Network Capability and the MME is operating in S&F Mode, the MME may optionally provide to the UE in the TAU Accept message any of the following: a S&F Wait Timer, a S&F Monitoring List, an Estimated S&F UL Delivery Time (see clause 4.13.9).
21. If GUTI was included in the TAU Accept, or the MME indicates an Accepted IMSI Offset to the UE in step 20, the UE acknowledges the received message by returning a TAU Complete message to the MME.
When the "Active flag" is not set in the TAU Request message and the Tracking Area Update was not initiated in ECM-CONNECTED state, the new MME releases the signalling connection with UE, according to clause 5.3.5. For a UE using Control Plane CIoT EPS Optimisation, when the "Signalling active flag" is set, the new MME shall not release the NAS signalling connection with the UE immediately after the TAU procedure is completed.
NOTE 11: The new MME may initiate E‑RAB establishment (see TS 36.413 [36]) after execution of the security functions, or wait until completion of the TA update procedure. For the UE, E‑RAB establishment may occur any time after the TA update request is sent.
In the case of a rejected tracking area update operation, due to regional subscription, roaming restrictions or access restrictions (see TS 23.221 [27] and TS 23.008 [28]) the new MME should not construct an MM context for the UE. In the case of receiving the subscriber data from HSS, the new MME may construct an MM context and store the subscriber data for the UE to optimise signalling between the MME and the HSS. A reject shall be returned to the UE with an appropriate cause and the S1 connection shall be released. Upon return to idle, the UE shall act according to TS 23.122 [10].
The new MME shall determine the Maximum APN restriction based on the received APN Restriction of each bearer context in the Context Response message and then store the new Maximum APN restriction value.
The bearer contexts shall be prioritized by the new MME. If the new MME is unable to support the same number of active bearer contexts as received from old MME/SGSN, the prioritisation is used to decide which bearer contexts to maintain active and which ones to delete. In any case, the new MME shall first update all contexts in one or more P‑GWs and then deactivate the bearer context(s) that it cannot maintain as described in the clause "MME Initiated Dedicated Bearer Deactivation Procedure". This shall not cause the MME to reject the tracking area update.
The new MME shall not deactivate emergency service related EPS bearers, i.e. EPS bearers with ARP value reserved for emergency services.
NOTE 12: If MS (UE) was in PMM-CONNECTED state the bearer contexts are sent already in the Forward Relocation Request message as described in the clause "Serving RNS relocation procedures" of TS 23.060 [7].
If the tracking area update procedure fails a maximum allowable number of times, or if the MME returns a Tracking Area Update Reject (Cause) message, the UE shall enter EMM DEREGISTERED state.
If the new MME identifies that the RAT type has changed, the MME checks the subscription information to identify for each APN whether to maintain the PDN connection, disconnect the PDN connection with a reactivation request, or, disconnect the PDN connection without reactivation request. If the MME decides to deactivate a PDN connection it performs MME-initiated PDN Connection Deactivation procedure after the tracking area update procedure is completed but before the S1/RRC interface connection is released. Existing ESM cause values as specified in TS 24.301 [46] (e.g. #39, "reactivation requested"; #66 "Requested APN not supported in current RAT and PLMN combination"; and for a dedicated bearer, possibly #37 "EPS QoS not accepted") are used to cause predictable UE behaviour. If all the PDN connections are disconnected and the UE does not support "attach without PDN connectivity", the MME shall request the UE to detach and reattach.
5.3.3.1A Tracking Area Update procedure with Serving GW change and data forwarding
Figure 5.3.3.1A-1: Tracking Area Update procedure with Serving GW change and data forwarding
NOTE 1: The procedure steps (A) and (B) are defined in clause 5.3.3.1. Step 5 in the figure above has compared to clause 5.3.3.1 one additional parameter which is described below.
4. The timer setting by the old S4 SGSN or MME in step 4 (as in clause 5.3.3.1) shall ensure that the buffered data in the old Serving GW can be forwarded before the old Serving GW resource is released.
5. DL data is being buffered in the old Serving GW and the DL Data Expiration Time has not expired, therefore the old MME/old S4-SGSN indicates Buffered DL Data Waiting in the Context Response. This triggers the new MME to setup the user plane and invoke data forwarding. For Control Plane CIoT EPS Optimisation, if the DL data is buffered in the old Serving GW, and when the Buffered DL Data Waiting is indicated, the new MME shall setup the S11 user plane with the new Serving GW and invoke data forwarding. If the DL data is buffered in the old MME and the DL Data Expiration Time has not expired, the old MME shall discard the buffered DL data.
11-12. The user plane is setup. These procedure steps are defined in clause 5.3.4.1, steps 4-7 and steps 8-12 respectively in the UE Triggered Service Request procedure.
NOTE 2: It is assumed that Pause of PGW Charging is not invoked by SGW that is performing extended data buffering.
For Control Plane CIoT EPS Optimisation, steps 11 and 12 are skipped.
13. Since it was indicated in step 5 that buffered DL data is waiting, the new MME sets up forwarding parameters by sending Create Indirect Data Forwarding Tunnel Request (target eNodeB addresses and TEIDs for forwarding) to the Serving GW. The Serving GW sends a Create Indirect Data Forwarding Tunnel Response (target Serving GW addresses and TEIDs for forwarding) to the target MME. For Control Plane CIoT EPS Optimisation, the new MME sets up forwarding parameters by sending Create Indirect Data Forwarding Tunnel Request (target MME address and TEID for forwarding) to the Serving GW. Upon receipt of the Create Indirect Data Forwarding Tunnel Response message the new MME starts a timer for release of resources if resources for indirect forwarding were allocated in the new S-GW.
Indirect forwarding may be performed via a Serving GW which is different from the Serving GW used as the anchor point for the UE.
14. This procedure step is defined in clause 5.3.3.1, step 7. In addition the new MME includes the F-TEID where buffered DL data should be forwarded and a Forwarding indication in the Context Acknowledge message. The F-TEID is the F-TEID for the indirect forwarding received from step 13 or it may be the F-TEID of the eNodeB (when eNodeB supports forwarding).
15. A Modify Bearer Request( F-TEID ) is sent to the old Serving GW. The F-TEID is the Forwarding F-TEID where the buffered DL data shall be forwarded.
16. The old Serving GW forwards its buffered data towards the received F-TEID in step 15. The buffered DL data is sent to the UE over the radio bearers established in step 11. For Control Plane CIoT EPS Optimisation, the buffered DL data is sent to the new MME from the new Serving GW and is sent to the UE as described in steps 12-14 of clause 5.3.4B.3.
17-18. As steps 15-16, 18-19 in clause 5.3.3.1.
19. If indirect forwarding was used, then the expiry of the timer at the new MME started at step 13 triggers the new MME to send a Delete Indirect Data Forwarding Tunnel Request message to the new S-GW to release temporary resources used for indirect forwarding that were allocated at step 13.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.3.2 E-UTRAN Tracking Area Update without S‑GW Change
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Figure 5.3.3.2-1: E-UTRAN Tracking Area Update without S‑GW change
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402 [2]. Steps 12 and 14 concern GTP based S5/S8.
NOTE 2: In the case of Tracking Area Update without MME change the signalling in steps 4, 5, 7 and steps 9-19 are skipped. A change of UE Time Zone, User CSG information or Serving Network is signalled in the next Service Request. If TAI change need to be reported to the PDN GW, location information change reporting procedure described in clause 5.9.2 is performed.
NOTE 3: Deferred reporting of UE Time Zone, or Serving Network per NOTE 2 may fail when inter-MME/SGSN mobility occurs before a UE sends SERVICE REQUEST and the target MME/SGSN (e.g. pre-Release 10) does not support the "Change to Report" flag.
NOTE 4: Some deployments cannot support all system features, for example they cannot support user plane establishment and user plane data transfer, when operating in S&F Mode in the example split MME deployment as described in Annex O.
1. One of the triggers described in clause 5.3.3.0 for starting the TAU procedure occurs.
2. The UE initiates a TAU procedure by sending, to the eNodeB, a Tracking Area Update Request (UE Core Network Capability, MS Network Capability, Preferred Network behaviour, Support for restriction of use of Enhanced Coverage, active flag, signalling active flag, EPS bearer status, old GUTI, Old GUTI Type, last visited TAI, P-TMSI signature, additional GUTI, KSISGSN, KSIASME, NAS sequence number, NAS-MAC, Voice domain preference and UE's usage setting, UE has UE Radio Capability ID assigned for the selected PLMN, Requested IMSI Offset, Release Request indication, Paging Restriction Information, Unavailability Period Duration, Start of Unavailability Period) message together with RRC parameters indicating the Selected Network and the old GUMMEI. An exception is that, if the TAU was triggered for load re-balancing purposes (see clause 4.3.7.3), the old GUMMEI is not included in the RRC parameters. The UE shall set the Old GUTI Type to indicate whether the Old GUTI is a native GUTI or is mapped from a P-TMSI and RAI.
If the UE's TIN indicates "GUTI" or "RAT‑related TMSI" and the UE holds a valid GUTI then the old GUTI indicates this valid GUTI. If the UE's TIN indicates "P‑TMSI" and the UE holds a valid P‑TMSI and related RAI then these two elements are indicated as the old GUTI. Mapping a P‑TMSI and RAI to a GUTI is specified in Annex H. When the UE is in connected mode (e.g. in URA_PCH) when it reselects to E-UTRAN, the UE shall set its TIN to "P‑TMSI".
If the UE holds a valid GUTI and the old GUTI indicates a GUTI mapped from a P-TMSI and RAI, then the UE indicates the GUTI as additional GUTI. If the old GUTI indicates a GUTI mapped from a P-TMSI and RAI, and the UE has a valid P-TMSI signature, the P-TMSI signature shall be included.
The additional GUTI in the Tracking Area Update Request message allows the new MME to find any already existing UE context stored in the new MME when the old GUTI indicates a value mapped from a P-TMSI and RAI.
Alternatively, when a UE only supports E-UTRAN, it identifies itself with the old GUTI and sets the Old GUTI Type to 'native'.
The RRC parameter "old GUMMEI" takes its value from the identifier that is signalled as the old GUTI according to the rules above. For a combined MME/SGSN the eNodeB is configured to route the MME‑code(s) of this combined node to the same combined node. This eNodeB is also configured to route MME‑code(s) of GUTIs that are generated the UE's mapping of the P‑TMSIs allocated by the combined node. Such an eNodeB configuration may also be used for separate nodes to avoid changing nodes in the pool caused by inter RAT mobility.
The last visited TAI shall be included in order to help the MME produce a good list of TAIs for any subsequent TAU Accept message. Selected Network indicates the network that is selected. Active flag is a request by the UE to activate the radio and S1 bearers for all the active EPS Bearers by the TAU procedure. Signalling active flag is a request by UE using Control Plane CIoT EPS Optimisation to maintain the NAS signalling connection after Tracking Area Update Procedure is completed in order to transmit pending Data using the Data Transport in Control Plane CIoT EPS Optimisation or NAS signalling. The UE's ISR capability is included in the UE Core Network Capability element. The EPS bearer status indicates each EPS bearer that is active in the UE. The TAU Request message shall be integrity protected by the NAS-MAC as described in TS 33.401 [41]. KSIASME is included if the UE has valid security parameters. NAS sequence number indicates the sequential number of the NAS message.
In the RRC connection establishment signalling associated with the TAU Request, the UE indicates its support of the CIoT EPS Optimisations relevant for MME selection.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no active flag or EPS bearer status included in the TAU Request message. For a UE with a running Service Gap timer in the UE the UE shall not set the active flag or the signalling active flag in the TAU request message (see clause 4.3.17.9) except for network access for regulatory prioritized services like Emergency services or exception reporting.
If the UE has any PDN connection of PDN Type "non-IP" or "Ethernet", the UE shall send the EPS bearer status in the TAU Request message.
KSISGSN is included if the UE indicates a GUTI mapped from a P‑TMSI in the information element "old GUTI".
The UE sets the voice domain preference and UE's usage setting according to its configuration, as described in clause 4.3.5.9.
The UE includes extended idle mode DRX parameters information element if it needs to enable extended idle mode DRX, even if extended idle mode DRX parameters were already negotiated before.
If a UE includes a Preferred Network Behaviour, this defines the Network Behaviour the UE is expecting to be available in the network as defined in clause 4.3.5.10.
If the UE supports RACS as defined in clause 5.11.3a, and if the UE is provisioned with a UE Radio Capability ID for use in the selected PLMN (i.e. PLMN-assigned for the specific PLMN or manufacturer-assigned), the UE includes a flag that indicates it has an assigned UE Radio Capability ID for use in the selected PLMN but the actual UE Radio Capability is provided to MME after security context is established in step 6 (see below).
If a Multi-USIM UE wants to enter ECM-IDLE state it includes the Release Request indication and optionally provides Paging Restriction Information.
If a Multi-USIM UE needs to modify the Paging Occasions in order to avoid paging collisions, it sends a Requested IMSI Offset to the MME, in order to signal an alternative IMSI as described in clause 4.3.33.
If the UE is using a eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the UE may include an Unavailability Period Duration and Start of Unavailability Period, see clause 4.13.8.2.
3. The eNodeB derives the MME address from the RRC parameters carrying the old GUMMEI, the indicated Selected Network and the RAT (NB-IoT or WB-E-UTRAN). If that GUMMEI is not associated with the eNodeB, or the GUMMEI is not available or the UE indicates that the TAU procedure was triggered by load re-balancing, the eNodeB selects the MME as described in clause 4.3.8.3 on "MME Selection Function". The eNodeB forwards the TAU Request message together with the CSG access mode, CSG ID, TAI+ECGI of the cell from where it received the message and with the Selected Network to the MME. CSG ID is provided by RAN if the UE sends the TAU Request message via a CSG cell or a hybrid cell. CSG access mode is provided if the UE sends the TAU Request message via a hybrid cell. If the CSG access mode is not provided but the CSG ID is provided, the MME shall consider the cell as a CSG cell. For SIPTO at the Local Network with stand-alone GW architecture the eNodeB includes the Local Home Network ID in the Initial UE Message and in Uplink NAS Transport message if the target cell is in a Local Home Network.
To assist Location Services, the eNodeB indicates the UE's Coverage Level to the MME.
If the MME supports RACS, and the MME detects that the selected PLMN is different from the currently registered PLMN for the UE, the MME provides the UE Radio Capability ID of the newly selected PLMN in the UE context to the eNodeB as described in clause 5.11.3a.
In the case of satellite access for Cellular IoT, the MME may verify the UE location and determine whether the PLMN is allowed to operate at the UE location, as described in clause 4.13.4. If the UE receives a TAU Reject message with cause value indicating that the selected PLMN is not allowed to operate at the present UE location, the UE shall attempt to select a PLMN as specified in TS 23.122 [10].
In the case of satellite access over NB-IoT, the eNB may request the MME to provide the Coarse Location information to the eNB, as described in TS 36.300 [5] and TS 36.413 [36].
If the MME is operating in S&F Mode, the MME may reject the TAU Request and optionally provide to the UE in the TAU Reject message any of the following: a S&F Wait Timer, a S&F Monitoring List (see clause 4.13.9).
4. The new MME differentiates the type of the old node, i.e. MME or SGSN, as specified in clause 4.3.19, uses the GUTI received from the UE to derive the old MME/S4 SGSN address and sends a Context Request (old GUTI, MME Address, UE Validated, complete TAU Request message, P‑TMSI Signature, CIoT EPS Optimisation support indication) message to the old MME/S4 SGSN to retrieve the user information. UE Validated indicates that the new MME has validated the integrity protection of the TAU message, e.g. based on native EPS security context for the UE. To validate the Context Request the old MME uses the complete TAU Request message and the old S4 SGSN uses the P-TMSI Signature and responds with an appropriate error if integrity check fails in old MME/S4 SGSN. This shall initiate the security functions in the new MME. If the security functions authenticate the UE correctly, the new MME shall send a Context Request (IMSI, complete TAU Request message, MME Address, UE Validated) message to the old MME/S4 SGSN with the UE Validated set. If the new MME indicates that it has authenticated the UE or if the old MME/old S4 SGSN authenticates the UE, the old MME/old S4 SGSN starts a timer.
If the UE with emergency bearers is not authenticated in the old MME/old S4 SGSN (in a network supporting unauthenticated UEs) the old MME/old S4 SGSN continues the procedure with sending a Context Response and starting the timer also when it cannot validate the Context Request.
If a RLOS attached UE is not successfully authenticated in the old MME and/or the Context Request cannot be validated, the old MME continues the procedure with sending a Context Response and starting the existing timer.
If the new MME supports CIoT EPS Optimisation, CIoT EPS Optimisation support indication is included in the Context Request indicating support for various CIoT EPS Optimisations (e.g. support for header compression for CP CIoT EPS Optimisation, etc.).
5. If the Context Request is sent to an old MME the old MME responds with a Context Response (IMSI, ME Identity (IMEISV), unused EPS Authentication Vectors, KSIASME, KASME, EPS Bearer Context(s), Serving GW signalling Address and TEID(s), MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone, UE Core Network Capability, UE Specific DRX Parameters, Change to Report (if present), Remaining Running Service Gap timer, LTE-M UE Indication) message. If the new MME supports CIoT EPS Optimisation and the use of header compression has been negotiated between the UE and old MME, the Context Response also includes the Header Compression Configuration which includes the information necessary for the ROHC channel setup but not the RoHC context itself.
If the Context Request is sent to an old S4 SGSN the old S4 SGSN responds with a Context Response (IMSI, ME Identity (if available), unused Authentication Quintets, CK, IK, KSISGSN, EPS Bearer Context(s), Serving GW signalling Address and TEID(s), ISR Supported, MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone, UE Core Network Capability, UE Specific DRX Parameters, Change to Report (if present)) message. The Authentication Quintets are maintained by the old S4 SGSN. TS 33.401 [41] gives further details on the transfer of security related information.
Change to Report flag is included by the old MME or the old S4 SGSN if reporting of change of UE Time Zone, or Serving Network, or both towards Serving GW / PDN GW was deferred by the old MME or old S4 SGSN.
If the Context Response message did not include IMEISV and the MME does not already store the IMEISV of the UE, the MME shall retrieve the ME Identity (IMEISV) from the UE.
The PDN GW Address and TEID(s) (for GTP-based S5/S8) or GRE Keys (PMIP-based S5/S8 at the PDN GW(s) for uplink traffic and the TI(s), is part of the EPS Bearer Context. ISR Supported is indicated if the old SGSN and associated Serving GW are capable to activate ISR for the UE.
The new MME shall ignore the UE Core Network Capability contained in the Context Response only when it has previously received an UE Core Network Capability in the Tracking Area Update Request. If the UE is not known in the old MME/old S4 SGSN or if the integrity check for the TAU request message fails, the old MME/old S4 SGSN responds with an appropriate error cause.
If the DL Data Buffer Expiration Time for the UE has not expired (see High latency communication in clause 4.3.17.7), the old MME/old S4-SGSN indicates Buffered DL Data Waiting in the Context Response. When this is indicated, the new MME shall setup the user plane in conjunction to the TAU procedure for delivery of the buffered DL data.
If the UE receives emergency bearer services from the old MME/old S4 SGSN and the UE is UICCless, IMSI can not be included in the Context Response. For emergency attached UEs, if the IMSI cannot be authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available.
For a RLOS attached UE, the old MME includes an RLOS indication to the new MME. If the RLOS attached UE in the old MME does not have a USIM, IMSI can not be included in the Context Response. If the RLOS attached UE has USIM but the IMSI cannot be successfully authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available.
If SIPTO at the Local Network is active for a PDN connection in the architecture with stand-alone GW, the old MME/old S4 SGSN shall include the Local Home Network ID of the old cell in the EPS Bearer context corresponding to the SIPTO at the Local Network PDN connection.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no EPS Bearer Context(s) included in the Context Response message.
Based on the CIoT EPS Optimisation support indication, old MME only transfers the EPS Bearer Context(s) that the new MME supports. If the new MME does not support CIoT EPS Optimisation, EPS Bearer Context(s) of non-IP PDN connection are not transferred to the new MME. If the new MME does not support Ethernet PDN Type, EPS Bearer Context(s) of Ethernet PDN type are not transferred to the new MME. If the EPS Bearer Context(s) of a PDN connection has not been transferred, the old MME shall consider all bearers of that PDN connection as failed and release that PDN connection by triggering the MME requested PDN disconnection procedure specified in clause 5.10.3. The buffered data in the old MME is discarded after receipt of Context Acknowledgement.
If the EPS Bearer Context(s) are to be transferred to the new MME, the old MME also includes the Serving GW IP address and TEID for both S1-U and S11-U, if available.
If the Old MME is aware the UE is a LTE-M UE, it provides the LTE-M UE Indication to the new MME.
6. If the integrity check of TAU Request message (sent in step 2) failed, then authentication is mandatory. The authentication functions are defined in clause 5.3.10 on "Security Function". Ciphering procedures are described in clause 5.3.10 on "Security Function". If GUTI allocation is going to be done and the network supports ciphering, the NAS messages shall be ciphered.
If this TAU request is received for a UE which is already in ECM_CONNECTED state and the PLMN-ID of the TAI sent by the eNodeB in Step 3 is different from that of the GUTI included in the TAU Request message, the MME shall delay authenticating the UE until after Step 21 (TAU Complete message).
NOTE 5: The MME delays the authentication such that the UE first updates its registered PLMN-ID to the new PLMN-ID selected by the RAN during handover. The new PLMN-ID is provided by the MME to the UE as part of the GUTI in the TAU accept message in Step 20. Doing this ensures that the same PLMN-ID is used in the derivation of the Kasme key by both the network and the UE.
If the new MME is configured to allow emergency bearer services for unauthenticated UE the new MME behave as follows:
- where a UE has only emergency bearer services, the MME either skip the authentication and security procedure or accepts that the authentication may fail and continues the Tracking Area Update procedure; or
- where a UE has both emergency and non-emergency bearer services and authentication fails, the MME continues the Tracking Area Update procedure and deactivates all the non-emergency PDN connections as specified in clause 5.10.3.
If the new MME is configured to support Restricted Local Operator Services, the new MME, based on local regulation and operator policy, may skip the authentication and security procedure, or may perform authentication if security parameters are available or obtainable from HSS and continues the Tracking Area Update procedure regardless of the authentication result.
If the UE indicated it has a UE Radio Capability ID assigned for use in the selected PLMN in step 2, the MME may request the UE to provide the UE Radio Capability ID in Security Mode Command, if the MME needs to get the UE Radio Capability ID from the UE e.g. at inter-PLMN mobility. If enquired by the MME the UE shall include the UE Radio Capability ID in Security Mode Command Accept for the supported UE radio capabilities.
In the case of satellite access for NB-IoT, if the UE indicated support for reporting its Coarse Location Information, the MME may request the UE to report its Coarse Location Information by setting the Coarse Location Information Request in the Security Mode Command message and the UE then reports its Coarse Location Information in the Security Mode Complete message to the MME. To perform UE location verification as described in clause 4.13.4, the MME provides the reported Coarse Location Information to the E-SMLC as described in clause 9.1.17 of TS 23.271 [57]. If the eNB requested the MME to provide the Coarse Location Information to the eNB, the MME provides the Coarse Location Information to the eNB in a following S1-AP message as described in TS 36.413 [36]. The eNB may use it as specified in TS 36.300 [5].
7. If the old node is an old MME the new MME sends a Context Acknowledge message to the old MME. The old MME marks in its context that the information in the GW and the HSS are invalid. This ensures that the MME updates the GWs and the HSS if the UE initiates a TAU procedure back to the MME before completing the ongoing TAU procedure.
NOTE 6: Updating the GWs refers to modification of session(s) on the Serving GW. This will result in successful re-establishment of the S11/S4 tunnel between the MME/SGSN and the Serving GW.
If the old node is an old S4 SGSN the MME sends a Context Acknowledge (ISR Activated) message to the old SGSN. Unless ISR Activated is indicated by the MME, the old S4 SGSN marks in its context that the information in the GWs is invalid. This ensures that the old S4 SGSN updates the GWs if the UE initiates a RAU procedure back to the old S4 SGSN before completing the ongoing TAU procedure. If ISR Activated is indicated to the old S4 SGSN, this indicates that the old S4 SGSN shall maintain its UE context including authentication quintets and stop the timer started in step 4. In this case, if the Implicit Detach timer is running, the old S4 SGSN shall re-start it with a slightly larger value than the UE's GERAN/UTRAN Deactivate ISR timer. Also, in this case, if the old SGSN has maintained the Serving GW address for user plane and S4 GTP-U TEID, the old SGSN shall remove Serving GW address for user plane and S4 GTP-U TEID locally. When ISR Activated is not indicated and this timer expires the old SGSN deletes all bearer resources of that UE. As the Context Acknowledge from the MME does not include any S‑GW change the S4 SGSN does not send any Delete Session Request message to the S‑GW. The MME shall not activate ISR if the associated Serving GW does not support ISR.
If the security functions do not authenticate the UE correctly, then the TAU shall be rejected, and the MME shall send a reject indication to the old MME/old S4 SGSN. The old MME/old S4 SGSN shall continue as if the Identification and Context Request was never received.
For UE using CIoT EPS Optimisation without any activated PDN connection, the steps 9, 10, 11, 12 and 13 are skipped.
8. Void.
9. If the MME has changed the new MME adopts the bearer contexts received from the old MME/SGSN as the UE's EPS bearer contexts to be maintained by the new MME. The MME establishes the EPS bearer(s) in the indicated order. The MME deactivates the EPS bearers which cannot be established.
The MME verifies the EPS bearer status received from the UE with the EPS bearer contexts it maintains and releases any network resources related to EPS bearers that are not active in the UE. If there is no bearer context at all, the MME rejects the TAU Request. If the MME has changed the new MME sends a Modify Bearer Request (new MME address and TEID, ISR Activated, RAT type, LTE-M RAT type reporting to PGW flag) message per PDN connection to the Serving GW. If there is no need for the SGW to send the signalling to the PDN GW, the MME may send Modify Access Bearers Request (new MME address and TEID) per UE to the Serving GW to optimise the signalling. The PDN GW address is indicated in the bearer contexts. If indicated, the information ISR Activated indicates that ISR is activated. If it is a mobility from a SGSN to a MME and if the MME supports location information change reporting, the MME shall include the User Location Information (according to the supported granularity) in the Modify Bearer Request, regardless of whether location information change reporting had been requested in the previous RAT by the PDN GW. If it is an inter MME mobility and if the PDN GW requested location information change reporting, the MME includes the User Location Information IE in this message if it is different compared to the previously sent information. If the PDN GW requested User CSG information, the MME also includes the User CSG Information IE in this message. If either the UE Time Zone has changed or Context Response message indicated pending UE Time Zone change reporting (via Change to Report flag), the MME includes the UE Time Zone IE in this message. If either the Serving Network has changed or Context Response message indicated pending Serving Network change reporting (via Change to Report flag) the MME includes the new Serving Network IE in this message. In network sharing scenarios Serving Network denotes the serving core network. If the old node is an old MME at a Tracking Area Update with a MME change ISR Activated shall not be indicated.
NOTE 7: The User CSG Information IE is only sent in step 9 if the "Active flag" is set in the TAU Request message.
When the Modify Access Bearers Request or Modify Bearer Request does not indicate ISR Activated the S‑GW deletes any ISR resources by sending a Delete Bearer Request to the other CN node that has bearer resources on the S‑GW reserved.
If the new MME receives the EPS bearer context with SCEF, then the new MME updates the SCEF as defined in TS 23.682 [74].
For Control Plane CIoT EPS Optimisation, if the DL data is buffered in the Serving GW, and if this is a Tracking Area Update without MME change and the DL Data Buffer Expiration Time in the MM context for the UE in the MME has not expired, or if this is a Tracking Area Update with MME change and the old MME/old S4-SGSN indicated Buffered DL Data Waiting in the Context Response in step 5, the MME shall also indicate S11-U tunnelling of NAS user data and include its own S11-U IP address and MME DL TEID for DL data forwarding by the SGW in the Modify Bearer Request. The MME may also do so without DL data buffered in the SGW.
If the UE is using the LTE-M RAT type and the PDN GW expects the LTE-M RAT type reporting as specified in clause 5.11.5, the MME also includes the LTE-M RAT type reporting to PGW flag to indicate to the Serving GW to forward the LTE-M RAT type to the PDN GW.
10. If the RAT type has changed, or the Serving GW has received the User Location Information IE or the UE Time Zone IE or User CSG Information IE and/or the Serving Network IE from the MME in step 9, the Serving GW informs the PDN GW(s) about this information that e.g. can be used for charging, by sending the message Modify Bearer Request (RAT type) per PDN connection to the PDN GW(s) concerned. User Location Information IE and/or UE Time Zone IE and/or User CSG Information IE and/or Serving Network IE are also included if they are present in step 9.
If the Modify Bearer Request message is not sent because of above reasons and the PDN GW charging is paused, then the SGW shall send Modify Bearer Request message with PDN Charging Pause Stop Indication to inform the PDN GW that the charging is no longer paused. Other IEs are not included in this message.
If LTE-M RAT type and the LTE-M RAT type reporting to PGW flag were received at step 9, the Serving GW shall include the LTE-M RAT type in the Modify Bearer Request message to the PGW. Otherwise the Serving GW includes RAT type WB-E-UTRAN.
11. If dynamic PCC is deployed, and RAT type information or UE location information needs to be conveyed from the PDN GW to the PCRF, then the PDN GW shall send this information to the PCRF by means of an IP‑CAN Session Modification procedure as defined in TS 23.203 [6].
NOTE 8: The PDN GW does not need to wait for the PCRF response, but continues in the next step. If the PCRF response leads to an EPS bearer modification the PDN GW should initiate a bearer update procedure.
12. The PDN GW updates its context field to allow DL PDUs to be routed to the correct Serving GW. PDN GW returns a Modify Bearer Response (MSISDN) to the Serving GW. The MSISDN is included if the PDN GW has it stored in its UE context. If there has been a RAT change towards E-UTRAN and location information change reporting is required and supported in the target MME, the PDN GW shall provide MS Info Change Reporting Action in the Modify Bearer Response.
13. The Serving GW updates its bearer context. If ISR Activated is indicated in step 9 and RAT Type received in step 9 indicates E‑UTRAN, then the Serving GW only updates the MME Control Plane Address stored locally and keep the SGSN related information unchanged. Also, in this case, if the Serving GW has maintained the SGSN address for user plane and S4 GTP-U TEID, the Serving GW removes the SGSN address for user plane and S4 GTP-U TEID locally. Otherwise the Serving GW shall update all of the information stored locally for this UE with the related information received from the MME. This allows the Serving GW to route Bearer PDUs to the PDN GW when received from eNodeB. The Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic, MS Info Change Reporting Action) message to the new MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message. If the Serving GW cannot serve the MME Request in the Modify Access Bearers Request message without S5/S8 signalling other than to unpause charging in the PDN GW or without corresponding Gxc signalling when PMIP is used over the S5/S8 interface, it shall respond to the MME with indicating that the modifications are not limited to S1-U bearers, and the MME shall repeat its request using Modify Bearer Request message per PDN connection.
When the MME receives the Modify Bearer Response or the Modify Access Bearers Response message, the MME checks if there is a "Availability after DDN Failure" monitoring event or a "UE Reachability" monitoring event configured for the UE in the MME and in such a case sends an event notification (see TS 23.682 [74] for further information).
For Control Plane CIoT EPS Optimisation, if the MME address and MME DL TEID are provided in step 9, the Serving GW includes Serving GW address and Serving GW UL TEID in the Modify Bearer Response message. The DL data is sent to the MME from the Serving GW.
The buffered DL data is sent to the UE as described in steps 12-14 of clause 5.3.4B.3.
14. The new MME verifies whether it holds subscription data for the UE identified by the GUTI, the additional GUTI or by the IMSI received with the context data from the old CN node.
If there are no subscription data in the new MME for this UE, or for some network sharing scenario (e.g. GWCN) if the PLMN-ID of the TAI supplied by the eNodeB is different from that of the GUTI in the UE's context, then the new MME informs the HSS of the change of MME by sending an Update Location Request (MME Id, IMSI, ULR-Flags, MME Capabilities, Homogenous Support of IMS Voice over PS Sessions, UE SRVCC capability, equivalent PLMN list, ME Identity (IMEISV)) message to the HSS. ULR-Flags indicates that update location is sent from an MME and the MME registration shall be updated in HSS. The HSS does not cancel any SGSN registration. The MME capabilities indicate the MME's support for regional access restrictions functionality. The inclusion of the equivalent PLMN list indicates that the MME supports the inter-PLMN handover to a CSG cell in an equivalent PLMN using the subscription information of the target PLMN. The "Homogenous Support of IMS Voice over PS Sessions" indication (see clause 4.3.5.8A) shall not be included unless the MME has completed its evaluation of the support of "IMS Voice over PS Session" as specified in clause 4.3.5.8. The ME Identity is included if step 5 caused the MME to retrieve the IMEISV from the UE.
NOTE 9: At this step, the MME may not have all the information needed to determine the setting of the IMS voice over PS Session Supported indication for this UE (see clause 4.3.5.8). Hence the MME can send the "Homogenous Support of IMS Voice over PS Sessions" later on in this procedure.
If the UE initiates the TAU procedure in a VPLMN supporting Autonomous CSG Roaming and the HPLMN has enabled Autonomous CSG Roaming in the VPLMN (via Service Level Agreement) and the MME needs to retrieve the CSG subscription information of the UE from the CSS, the MME initiates the Update CSG Location Procedure with CSS as described in clause 5.3.12.
If the MME determines that only the UE SRVCC capability has changed, the MME sends a Notify Request to the HSS to inform about the changed UE SRVCC capability.
If all the EPS bearers of the UE have emergency ARP value, the new MME may skip the update location procedure or proceed even if the update location fails.
If the UE is RLOS attached, the new MME skips the update location procedure and the TAU procedure proceeds.
15. The HSS sends a Cancel Location (IMSI, Cancellation type) message to the old MME with a Cancellation Type set to Update Procedure.
16. When receiving a Cancel Location message and the timer started in step 4 is not running, the old MME removes the MM and bearer contexts. Otherwise, the contexts are removed when the timer expires. It also ensures that the MM context is kept in the old MME for the case the UE initiates another TAU procedure before completing the ongoing TAU procedure to the new MME. The old MME acknowledges with a Cancel Location Ack (IMSI) message.
NOTE 10: ISR Activated is never indicated from new to old MME.
So an old MME deletes all the bearer resources of the UE in any case when the timer started in step 4 expires, which is independent on receiving a Cancel Location message.
17. When receiving the Context Acknowledge message and if the UE is Iu Connected, the old SGSN sends an Iu Release Command message to the RNC after the timer started in step 4 has expired.
18. The RNC responds with an Iu Release Complete message.
19. The HSS acknowledges the Update Location Request by returning an Update Location Ack (IMSI, Subscription Data) message to the new MME after the cancelling of the old MME context is finished. If all checks are successful, the MME constructs an MM context for the UE. The Subscription Data may contain the CSG subscription data for the registered PLMN and for the equivalent PLMN list requested by MME in step 14.
The subscription data may contain Enhanced Coverage Restricted parameter. If received from the HSS, MME stores this Enhanced Coverage Restricted parameter in the MME MM context.
The subscription data may contain Service Gap Time. If received from the HSS, the MME stores this Service Gap Time in the MME MM context for the UE and passes it to the UE in the Tracking Area Update Accept message if the UE has indicated Service Gap Control capability.
The subscription data may contain Subscribed Paging Time Window parameter that applies to the UEs on a specific RAT, e.g. NB-IoT. If received from the HSS, MME stores this Subscribed Paging Time Window parameter in the MME MM context.
The subscription data may contain an indication that the UE is subscribed to receive time reference information in access stratum. If received from the HSS, and if supported by the MME, the MME stores this indication in the MME MM context.
If the UE initiates the TAU procedure at a CSG cell, the new MME shall check whether the CSG ID and associated PLMN is contained in the CSG subscription and is not expired. If the CSG ID and associated PLMN is not present or expired, the MME shall send a Tracking Area Update reject message to the UE with an appropriate cause value. The UE shall remove the CSG ID and associated PLMN from its Allowed CSG list if present.
If the Update Location is rejected by the HSS, the new MME rejects the TAU Request from the UE with an appropriate cause sent in the TAU Reject message to the UE. In such cases, the new MME releases any local MME EPS Bearer contexts for this particular UE.
20. If due to regional subscription restrictions or access restrictions (e.g. CSG restrictions) (received in update location procedure in step 19) the UE is not allowed to access the TA:
- The MME rejects the Tracking Area Update Request with an appropriate cause to the UE.
- For UEs with emergency EPS bearers, i.e. at least one EPS bearer has an ARP value reserved for emergency services, the new MME accepts the Tracking Area Update Request and deactivates all non-emergency PDN connections as specified in clause 5.10.3. If the Tracking Area Update procedure is initiated in ECM-IDLE state, all non-emergency EPS bearers are deactivated by the Tracking Area Update procedure without bearer deactivation signalling between the UE and the MME.
If the TAU request message includes Paging Restriction Information, the MME may accept or reject the Paging Restriction Information requested by the UE based on operator policy. If the MME rejects the Paging Restriction Information, the MME removes any stored Paging Restriction Information from the UE context and discards the UE requested Paging Restriction Information. If the MME accepts the Paging Restriction Information from the UE, the MME stores the Paging Restriction Information from the UE in the UE context and then enforces it in the Network Triggered Service Request procedure as described in clause 5.3.4.3. The MME informs the UE about the acceptance/rejection of the requested Paging Restriction Information in the TAU Accept message. If the TAU Request message does not include any Paging Restriction Information, the MME shall delete any stored Paging Restriction Information for this UE and stop restricting paging accordingly.
If the TAU Request message includes a Release Request indication, the MME does not activate the user plane setup procedure in the subsequent steps and triggers the S1 release procedure as described in clause 5.3.5 after the completion of TAU procedure.
The MME responds to the UE with a Tracking Area Update Accept (GUTI, TAI-list, EPS bearer status, NAS sequence number, NAS-MAC, ISR Activated, IMS Voice over PS session supported, Emergency Service Support indicator, LCS Support Indication, Supported Network Behaviour, Service Gap Time, Enhanced Coverage Restricted, Indication of support of 15 EPS bearers per UE, PLMN-assigned UE Radio Capability ID, Accepted IMSI Offset, Paging Restriction Information acceptance/rejection, Enhanced Discontinuous Coverage Support, Return To Coverage Notification Not Required, Unavailability Period Duration, the Start of Unavailability Period, Maximum Time Offset) message. If the active flag is set the Handover Restriction List may be sent to eNodeB as eNodeB handles the roaming restrictions and access restrictions in the Intra E-UTRAN case. If the active flag is set in the TAU Request message the user plane setup procedure is activated in conjunction with the TAU Accept message. If this is a Tracking Area Update without MME change and the DL Data Buffer Expiration Time in the MM context for the UE in the MME has not expired, or if this is a Tracking Area Update with MME change and the old MME/old S4-SGSN indicated Buffered DL Data Waiting in the Context Response in step 5, the user plane setup procedure is activated even if the MME did not receive the active flag in the TAU Request message. If the new MME receives the Downlink Data Notification message or any downlink signalling message while the UE is still connected, the user plane setup procedure may be activated even if the new MME did not receive the active flag in the TAU Request message. The procedure is described in detail in TS 36.300 [5]. The message sequence should be the same as for the UE triggered Service Request procedure specified in clause 5.3.4.1 from the step when MME establish the bearers(s). The EPS bearer status indicates the active bearers in the network. The UE removes any internal resources related to bearers not marked active in the received EPS bearer status. If the EPS bearer status information was in the TAU Request, the MME shall indicate the EPS bearer status to the UE. If ISR Activated is indicated to the UE, this indicates that its P-TMSI and RAI shall remain registered with the network and shall remain valid in the UE. At a Tracking Area Update with an MME change ISR Activated shall not be indicated. At a Tracking Area Update without an MME change, if ISR is activated for the UE when the MME receives the Tracking Area Update Request, the MME should maintain ISR by indicating ISR Activated in the Tracking Area Update Accept message. Handover Restriction List is described in clause 4.3.5.7 "Mobility Restrictions". The MME sets the IMS Voice over PS session supported as described in clause 4.3.5.8.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no EPS bearer status included in the TAU Accept message.
The MME indicates the CIoT EPS Optimisations it supports and prefers in the Supported Network Behaviour information as defined in clause 4.3.5.10.
If there is a Service Gap timer running for the UE in the MME, the MME shall ignore the active flag and signalling active flag and not perform any of the actions related to these flags except if the TAU Request message has been received when the UE has a PDN connection for emergency bearer services established or is establishing a PDN connection for emergency bearer services or if the UE is configured to use high priority access (AC 11-15) in selected PLMN.
The MME shall include the Service Gap Time in the TAU Accept message if the UE has indicated Service Gap Control capability and either if Service Gap Time was received in step 19 from HSS in the subscription information or if the Service Gap Time in the subscription information has been updated by HSS User Profile management (i.e. the Insert Subscriber Data procedure in clause 5.3.9.2).
If the UE included support for restriction of use of Enhanced Coverage in step 1, the MME sends Enhanced Coverage Restricted parameter to the eNodeB in the S1-AP message as defined in clause 4.3.28. The MME also sends the Enhanced Coverage Restricted parameter to the UE in the TAU Accept message. UE shall store Enhanced Coverage Restricted parameter and shall use the value of Enhanced Coverage Restricted parameter to determine if enhanced coverage feature should be used or not.
If the MME successfully obtained Header Compression Configuration parameters in step 5 it indicates he continued use of previous negotiated configuration to the UE in the Header Compression Context Status for each EPS Bearer of the UE. When Header Compression Context Status indicates that the previous negotiated configuration can no longer be used for some EPS bearers, the UE shall stop performing header compression and decompression when sending or receiving data using Control Plane CIoT EPS Optimisation on these EPS bearers.
The MME checks if there is a "Availability after DDN Failure" monitoring event or a "UE Reachability" monitoring event configured for the UE in the MME for which an event notification has not yet been sent. In such a case an event notification is sent (see TS 23.682 [74] for further information).
If the MME did not receive the Voice support match indicator in the MM Context, then the MME may send a UE Radio Capability Match Request to the eNodeB as described in clause 5.3.14. If the MME hasn't received Voice support match indicator from the eNodeB then based on implementation MME may set IMS Voice over PS session supported Indication and update it at a later stage. After step 14, and in parallel to any of the preceding steps, the MME shall send a Notify Request (Homogeneous Support of IMS Voice over PS Sessions) message to the HSS:
- If the MME has evaluated the support of IMS Voice over PS Sessions, see clause 4.3.5.8, and
- If the MME determines that it needs to update the Homogeneous Support of IMS Voice over PS Sessions, see clause 4.3.5.8A.
The Emergency Service Support indicator informs the UE that Emergency bearer services are supported. LCS Support Indication indicates whether the network supports the EPC-MO-LR and/or CS-MO-LR as described in TS 23.271 [57]. Indication for support of 15 EPS bearers per UE indicates the network supports 15 EPS bearers as defined in clause 4.12.
When receiving the TAU Accept message and there is no ISR Activated indication the UE shall set its TIN to "GUTI". When ISR Activated is indicated and the UE's TIN indicates "GUTI" the UE's TIN shall not be changed. When ISR Activated is indicated and the TIN is "P‑TMSI" or "RAT‑related TMSI" the UE shall set its TIN to "RAT‑related TMSI".
For an MME change ISR is not activated by the new MME to avoid context transfer procedures with two old CN nodes.
For an emergency attached UE, emergency ISR is not activated.
If the TAU procedure is initiated by manual CSG selection and occurs via a CSG cell, the UE upon receiving TAU Accept message shall add the CSG ID and associated PLMN to its Allowed CSG list if it is not already present. Manual CSG selection is not supported if the UE has emergency bearers established.
If the UE included extended idle mode DRX parameters information element, the MME includes extended idle mode DRX parameters information element in the TAU accept if it decides to enable extended idle mode DRX with Paging Time Window length assigned considering Subscribed Paging Time Window (if available) and the local policy. Additionally, for a UE using an eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the MME may consider Unavailability Period Duration and/or Start of Unavailability Period as described in clause 4.13.8.2 when determining extended idle mode DRX parameters.
If the user plane setup is performed in conjunction with the TAU Accept message and the TAU is performed via a hybrid cell, then the MME shall send an indication whether the UE is a CSG member to the RAN along with the S1-MME control message. Based on this information, the RAN may perform differentiated treatment for CSG and non-CSG members.
NOTE 11: If the UE receives a TAU Accept message via a hybrid cell, the UE does not add the corresponding CSG ID and associated PLMN to its Allowed CSG list. Adding a CSG ID and associated PLMN to the UE's local Allowed CSG list for a hybrid cell is performed only by OTA or OMA DM procedures.
If the UE receives a Service Gap Time in the TAU Accept message, the UE shall store this parameter and apply Service Gap Control (see clause 4.3.17.9).
If the UE has indicated support for dual connectivity with NR in the TAU Request and the UE is not allowed to use NR as Secondary RAT, the MME indicates that to the UE in the TAU Accept message.
If the user plane setup is performed and if RACS is supported and MME has UE Radio Capability ID in UE context, valid for the PLMN the UE is currently in, it signals the UE Radio Capability ID to the eNodeB as defined in clause 5.11.3a. If the eNodeB does not have mapping between the specific UE Radio Capability ID and the UE radio capabilities, it shall use the procedure described in TS 36.413 [36] to retrieve the mapping from the Core Network.
When the UE supports RACS, and the MME needs to configure the UE with a UE Radio Capability ID, and the MME already has the UE radio capabilities for the UE, the MME may provide the UE with the UE Radio Capability ID for the UE radio capabilities the UCMF returns to the MME for this UE.
If the UE had included a UE Specific DRX parameter for NB-IoT in the Tracking Area Update Request, the MME includes the Accepted NB-IoT DRX parameter.
If the UE provided a Requested IMSI Offset in step 2, but the network prefers a different value, the MME provides the UE with an Accepted IMSI Offset different from the one provided in step 2. Otherwise the value of the Accepted IMSI Offset the MME sends is the value of the Requested IMSI Offset sent by the UE in step 2. The MME stores the value of the alternative IMSI derived (see clause 4.3.33) from the Accepted IMSI Offset provided to the UE in the UE context.
If a Multi-USIM UE does not provide a Requested IMSI Offset in step 1, the MME erases any alternative IMSI value in the UE context.
NOTE 12: The MME does not remove IMSI Offset value if the Tracking Area Update Request is for periodic Tracking Area Update.
If the Multi-USIM UE has indicated one or more Multi-USIM specific Capabilities are supported in the UE Core Network Capability in step 2, the MME shall indicate whether the corresponding one or more Multi-USIM specific features described in clause 4.3.33 are supported based on network capability and preference by the network (based on local network policy) by providing one or more of the Connection Release Supported, Paging Cause Indication for Voice Service Supported, Reject Paging Request Supported, Paging Restriction Supported and Paging Timing Collision Control Supported indications. The MME shall only indicate Paging Restriction Supported together with either Connection Release Supported or Reject Paging Request Supported. The UE shall only use Multi-USIM specific features that the MME indicated as being supported. In case of Emergency attached UE, the MME shall not indicate support for any Multi-USIM feature to the UE.
If both UE and network support discontinuous coverage, the MME provides the Enhanced Discontinuous Coverage Support indication as described in clause 4.13.8.1.
For a UE using a eNodeB that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), the MME may provide Return To Coverage Notification Not Required, which requests the UE in ECM_IDLE state to not perform the TAU procedure when it returns to coverage, and/or provide the UE with an Unavailability Period Duration and/or Start of Unavailability Period if available, as described in clause 4.13.8.2. The MME may also provide a Maximum Time Offset as described in clause 4.13.8.6.
If supported by the MME and if the UE is subscribed to receive time reference information, then the MME provides the Time Reference Information Distribution Indication to the eNodeB.
If the UE indicated "S&F Capability" in the UE Core Network Capability and the MME is operating in S&F Mode, the MME may optionally provide to the UE in the TAU Accept message any of the following: a S&F Wait Timer, a S&F Monitoring List, an Estimated S&F UL Delivery Time (see clause 4.13.9).
21. If the GUTI was changed, or the MME indicates an Accepted IMSI Offset to the UE in step 20, the UE acknowledges the new GUTI or the Accepted IMSI Offset value by returning a Tracking Area Update Complete message to the MME.
When the "Active flag" is not set in the TAU Request message and the Tracking Area Update was not initiated in ECM-CONNECTED state, the MME releases the signalling connection with UE, according to clause 5.3.5. For a UE using Control Plane CIoT EPS Optimisation, when the "Signalling active flag" is set, the new MME shall not release the NAS signalling connection with the UE immediately after the TAU procedure is completed.
NOTE 13: The new MME may initiate E‑RAB establishment (see TS 36.413 [36]) after execution of the security functions, or wait until completion of the TA update procedure. For the UE, E‑RAB establishment may occur any time after the TA update request is sent.
In the case of a rejected tracking area update operation, due to regional subscription, roaming restrictions, or access restrictions (see TS 23.221 [27] and TS 23.008 [28]) the new MME should not construct an MM context for the UE. In the case of receiving the subscriber data from HSS, the new MME may construct an MM context and store the subscriber data for the UE to optimise signalling between the MME and the HSS. A reject shall be returned to the UE with an appropriate cause and the S1 connection shall be released. Upon return to idle, the UE shall act according to TS 23.122 [10].
If the new MME is unable to update the bearer context in one or more P‑GWs, the new MME shall deactivate the corresponding bearer contexts as described in clause "MME Initiated Dedicated Bearer Deactivation Procedure". This shall not cause the MME to reject the tracking area update.
The new MME shall determine the Maximum APN restriction based on the received APN Restriction of each bearer context in the Context Response message and then store the new Maximum APN restriction value.
The bearer contexts shall be prioritized by the new MME. If the new MME is unable to support the same number of active bearer contexts as received from old MME/SGSN, the prioritisation is used to decide which bearer contexts to maintain active and which ones to delete. In any case, the new MME shall first update all contexts in one or more P‑GWs and then deactivate the context(s) that it cannot maintain as described in clause "MME Initiated Dedicated Bearer Deactivation Procedure". This shall not cause the MME to reject the tracking area update.
The new MME shall not deactivate emergency service related EPS bearers, i.e. EPS bearers with ARP value reserved for emergency services.
NOTE 14: If MS (UE) was in PMM-CONNECTED state the bearer contexts are sent already in the Forward Relocation Request message as described in clause "Serving RNS relocation procedures" of TS 23.060 [7].
If the tracking area update procedure fails a maximum allowable number of times, or if the MME returns a Tracking Area Update Reject (Cause) message, the UE shall enter EMM DEREGISTERED state.
If the new MME identifies that the RAT type has changed, the MME checks the subscription information to identify for each APN whether to maintain the PDN connection, disconnect the PDN connection with a reactivation request, or, disconnect the PDN connection without reactivation request. If the MME decides to deactivate a PDN connection it performs MME-initiated PDN Connection Deactivation procedure after the tracking area update procedure is completed but before the S1/RRC interface connection is released. Existing ESM cause values as specified in TS 24.301 [46] (e.g. #39, "reactivation requested"; #66 "Requested APN not supported in current RAT and PLMN combination"; and for a dedicated bearer, possibly #37 "EPS QoS not accepted") are used to cause predictable UE behaviour. If all the PDN connections are disconnected and the UE does not support "attach without PDN connectivity", the MME shall request the UE to detach and reattach.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.3.3 Routing Area Update with MME interaction and without S‑GW change
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The Routing Area Update without S‑GW change procedure takes place when a UE that is registered with an MME selects a UTRAN or GERAN cell and the S‑GW is not changed by the procedure. In this case, the UE changes to a Routing Area that the UE has not yet registered with the network. This procedure is initiated by an ECM-IDLE state UE and may also be initiated if the UE is in ECM-CONNECTED state. The RA update case is illustrated in Figure 5.3.3.3-1.
NOTE 1: This procedure covers the MME to 2G or 3G SGSN RAU.
Figure 5.3.3.3-1: Routing Area Update with MME interaction and without S‑GW change
NOTE 2: For a PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 8 and 10 concern GTP based S5/S8.
1. The UE selects a UTRAN or GERAN cell. This cell is in a Routing Area that the UE not yet registered with the network, or the UE reselects a UTRAN or GERAN cell and the TIN indicates "GUTI". The UE in ECM‑CONNECTED state may change to the GERAN cell through Network Assisted Cell Change (NACC).
2a. The UE sends a Routing Area Update Request (old P-TMSI, P-TMSI Type, old RAI, UE Core Network Capability, MS Network Capability, P‑TMSI Signature, additional P‑TMSI/RAI, KSI, Voice domain preference and UE's usage setting) message to the new SGSN. The UE shall set the P-TMSI Type to indicate whether the P-TMSI is a native P-TMSI or is mapped from a GUTI.
If the UE's internal TIN indicates "GUTI" and the UE holds a valid GUTI then the UE indicates the GUTI as the old P‑TMSI and old RAI. If the UE's TIN indicates "P‑TMSI" or "RAT‑related TMSI" and the UE holds a valid P‑TMSI and related RAI then these two elements are indicated as old P‑TMSI and old RAI. Mapping a GUTI to a P‑TMSI and an RAI is specified in TS 23.003 [9].
If the UE holds a valid P‑TMSI and related RAI and the old P-TMSI and old RAI indicate a P-TMSI/RAI mapped from a GUTI, then the UE indicates these parameters as additional P‑TMSI/RAI.
The old P‑TMSI is indicated in the RAU Request message for Iu‑mode only. For Gb mode the TLLI is derived from the value that is determined as the old P‑TMSI according to the rules above. The routing parameter that is signalled in the RRC signalling to the RNC for routing to the SGSN is derived from the identifier that is signalled as the old P‑TMSI according to the rules above. For a combined MME/SGSN the RAN is configured to route the NRI(s) of this combined node to the same combined node. The RAN is also configured to route NRI(s) of P‑TMSIs that are generated by the UE's mapping of the GUTIs allocated by the combined node. Such a RAN configuration may also be used for separate nodes to avoid changing nodes in the pool caused by inter RAT mobility.
If the UE has a follow-on request, i.e. if there is pending uplink traffic (signalling or data), the 3G SGSN may use, as an implementation option, the follow-on request indication to release or keep the Iu connection after the completion of the RA update procedure.
KSI is mapped from an eKSI identifying a KASME if the UE indicates a P‑TMSI mapped from GUTI in the information element "old P‑TMSI". KSI identifies a (CK, IK) pair if the UE indicates a P‑TMSI in the information element "old P‑TMSI".
The UE sets the voice domain preference and UE's usage setting according to its configuration, as described in clause 4.3.5.9.
2b. The RNC shall add the Routing Area Identity, CSG access mode, CSG ID before forwarding the message to the SGSN. This RA identity corresponds to the RAI in the MM system information sent by the RNC to the UE. The BSS shall add the Cell Global Identity (CGI) of the cell where the UE is located before passing the message to the new SGSN. CSG ID is provided by RAN if the UE sends the RAU Request message via a CSG cell or a hybrid cell. CSG access mode is provided if the UE sends the RAU Request message via a hybrid cell. If the CSG access mode is not provided but the CSG ID is provided, the SGSN shall consider the cell as a CSG cell. For SIPTO at the Local Network the with stand-alone GW architecture the RNC includes the Local Home Network ID in the Initial UE Message and in Direct Transfer message if the target cell is in a Local Home Network.
3. The new S4 SGSN determines the type of the old node, i.e. MME or SGSN, as specified in clause 4.3.19, uses the old RAI received from the UE to derive the old MME address, and sends a Context Request (P‑TMSI, old RAI, New SGSN Address, P‑TMSI Signature) message to the old MME to get the context for the UE. To validate the Context Request the old MME uses a NAS token mapped from the P‑TMSI Signature. If the UE is not known in the old MME, the old MME responds with an appropriate error cause. If integrity check fails in the old MME, the old MME responds with an appropriate error cause which shall initiate the security functions in the new S4 SGSN. If the security functions authenticate the UE correctly, the new S4 SGSN shall send a Context Request (IMSI, old RAI, New SGSN Address, UE Validated) message to the old MME.UE Validated indicates that the new S4 SGSN has authenticated the UE. If the new S4 SGSN indicates that it has authenticated the UE or if the old MME authenticates the UE, the old MME starts a timer.
If the UE with emergency bearers is not authenticated in the old MME (in a network supporting unauthenticated UEs) the old MME continues the procedure with sending a Context Response and starting the timer also when it cannot validate the Context Request.
4. The old MME responds with one Context Response (IMSI, ME Identity (if available), KSI, CK, IK, unused Authentication Quintets, EPS Bearer Contexts, Serving GW signalling Address and TEID(s), ISR Supported, MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone, UE Core Network Capability, UE Specific DRX Parameters, Change to Report (if present)) message. The PDN GW Address and TEID(s) (for GTP-based S5/S8) or GRE Keys (PMIP-based S5/S8) for uplink traffic and control plane, and the TI(s) is part of the EPS Bearer context(s). The unused Authentication Quintets in the MM Context may be sent if stored by the MME and the MME received the unused Authentication Quintets from the same SGSN previously. ISR Supported is indicated if the old MME and associated Serving GW are capable to activate ISR for the UE.
If the UE receives emergency bearer services from the old MME and the UE is UICCless, IMSI can not be included in the Context Response. For emergency attached UEs, if the IMSI cannot be authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available.
The new S4 SGSN shall ignore the UE Core Network Capability contained in the Context Response only when it has previously received an UE Core Network Capability in the Routing Area Update Request. If UE is not known in the old MME, the old MME responds with an appropriate error cause.
Change to Report flag is included by the old MME if reporting of change of UE Time Zone, or Serving Network, or both towards Serving GW / PDN GW was deferred by the old MME.
The new SGSN maps the EPS bearers to PDP contexts 1-to-1 and maps the EPS Bearer QoS parameter values of an EPS bearer to the Release 99 QoS parameter values of a PDP context as defined in Annex E. The PDP context(s) are established in the indicated order. The SGSN deactivates the PDP contexts which cannot be established.
If SIPTO at the Local Network is active for a PDN connection in the architecture with stand-alone GW, the old MME shall include the Local Home Network ID of the old cell in the EPS Bearer context corresponding to the SIPTO at the Local Network PDN connection.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no EPS Bearer Context(s) included in the Context Response message.
The old MME only transfers the EPS Bearer Context(s) that the new SGSN supports. If not supported, EPS Bearer Context(s) of non-IP PDN connection are not transferred to the new SGSN. EPS Bearer Context(s) of Ethernet PDN connection type are not transferred to the new SGSN. If the EPS Bearer Context(s) of a PDN connection has not been transferred, the old MME shall consider all bearers of that PDN connection as failed and release that PDN connection by triggering the MME requested PDN disconnection procedure specified in clause 5.10.3.
5. Security functions may be executed. Procedures are defined in clause 5.3.10 on "Security Function".
If the new SGSN is configured to allow emergency bearer services for unauthenticated UE the new SGSN behave as follows:
- where a UE has only emergency bearer services, the SGSN either skip the authentication and security procedure or accepts that the authentication may fail and continues the Routing Area Update procedure; or
- where a UE has both emergency and non-emergency bearer services and authentication fails, the SGSN continues the Routing Area Update procedure and deactivates all the non-emergency PDP contexts as specified in TS 23.060 [7].
6. The new S4 SGSN sends a Context Acknowledge (ISR Activated) message to the old MME. Unless ISR is indicated by the new S4 SGSN, the old MME marks in its context that the information in the GWs is invalid. This ensures that the old MME updates the GW if the UE initiates a TAU procedure back to the old MME before completing the ongoing RAU procedure.
NOTE 3: Updating the GWs refers to modification of session(s) on the Serving GW. This will result in successful re-establishment of the S11/S4 tunnel between the MME/SGSN and the Serving GW.
ISR Activated indicates to the old MME that it shall maintain the UE's contexts and the MME stops the timer started in step 3. In this case, if the Implicit Detach timer is running, the old MME shall re-start it with a slightly larger value than the UE's E-UTRAN Deactivate ISR timer. When ISR Activated is not indicated and this timer expires the old MME deletes all bearer resources of that UE. As the Context Acknowledge from the new S4 SGSN does not include any S‑GW change the old MME does not send any Delete Session Request message to the S‑GW. The SGSN shall not activate ISR if the associated Serving GW does not support ISR.
If the security functions do not authenticate the UE correctly, then the RAU is rejected, and the new S4 SGSN sends a reject indication to the old MME. The old MME shall continue as if the Identification and Context Request was never received.
For UE using CIoT EPS Optimisation without any activated PDN connection, the steps 7, 8, 9, 10, and 11 are skipped.
If the new SGSN identifies that the RAT type has changed, the SGSN checks the subscription information to identify for each APN whether to maintain the PDN connection, disconnect the PDN connection with a reactivation request or disconnect PDN connection without reactivation request. If the SGSN decides to deactive a PDN connection it performs SGSN-initiated PDN Connection Deactivation procedure after tracking area procedure is completed. Existing SM cause values as specified in TS 24.008 [47] (e.g. #39, "reactivation requested"; #66 "Requested APN not supported in current RAT and PLMN combination"; and for a dedicated bearer, possibly #37 "QoS not accepted") are used to cause predictable UE behaviour.
7. In this procedure flow the Serving GW is not relocated. The SGSN sends a Modify Bearer Request (new SGSN Address and TEID, RAT type, ISR Activated) message per PDN connection to the Serving GW. If indicated, the information ISR Activated indicates that ISR is activated. As it is a mobility from E-UTRAN, if the target SGSN supports location information change reporting, the target SGSN shall include the User Location Information (according to the supported granularity) in the Modify Bearer Request, regardless of whether location information change reporting had been requested in the previous RAT by the PDN GW. If the PDN GW requested User CSG information, the SGSN also includes the User CSG information IE in this message. If either the UE Time Zone has changed, or Context Response message from old MME indicated pending UE Time Zone change reporting (via Change to Report flag), the SGSN includes the UE Time Zone IE in this message. If either the Serving Network has changed, or Context Response message from old MME indicated pending Serving Network change reporting (via Change to Report flag) the SGSN includes the new Serving Network IE in this message. In network sharing scenarios Serving Network denotes the serving core network.
When the Modify Bearer Request does not indicate ISR Activated the S‑GW deletes any ISR resources by sending a Delete Bearer Request to the other CN node that has bearer resources on the S‑GW reserved. RAT type indicates a change in radio access.
If ISR Activated is indicated or SGSN and SGW are configured to release S4 U-Plane when EPS Bearer Contexts associated with the released RABs are to be preserved, the SGSN does not send SGSN address and TEID for U-Plane in Modify Bearer Request.
NOTE 4: The User CSG Information IE is not sent in step 7 if the "follow-on request indication" indicates releasing the Iu connection after the completion of the RA update procedure.
8. If the RAT type has changed or the Serving GW has received the User Location Information IE and/or the UE Time Zone IE and/or User CSG information IE and/or the Serving Network IE from the MME in step 7 the Serving GW informs the PDN GW(s) about the change of this information that e.g. can be used for charging, by sending the message Modify Bearer Request (RAT type) per PDN connection to the PDN GW(s) concerned. User Location Information IE and/or UE Time Zone IE and/or User CSG information IE and/or Serving Network IE are also included if they are present in step 7.
9. If dynamic PCC is deployed, and RAT type information or UE location information needs to be conveyed from the PDN GW to the PCRF, then the PDN GW shall send this information to the PCRF by means of an IP‑CAN Session Modification procedure as defined in TS 23.203 [6].
NOTE 5: The PDN GW does not need to wait for the PCRF response, but continues in the next step. If the PCRF response leads to an EPS bearer modification the PDN GW should initiate a bearer update procedure.
10. The PDN GW updates its context field and returns a Modify Bearer Response (MSISDN) message to the Serving GW. MSISDN is included if the PDN GW has it stored in its UE context. If location information change reporting is required and supported in the target SGSN, the PDN GW shall provide MS Info Change Reporting Action in the Modify Bearer Response.
11. The Serving GW updates its context fields. If ISR Activated is indicated in step 7 and RAT Type received in step 7 indicates UTRAN or GERAN, then the Serving GW only updates the SGSN Control Plane Address and keeps the MME related information unchanged. Otherwise the Serving GW shall update all of the information stored locally for this UE with the related information received from the SGSN. Then the Serving GW returns a Modify Bearer Response (Serving GW address and TEID for uplink traffic, MS Info Change Reporting Action) message.
When the SGSN receives the Modify Bearer Response message, the SGSN checks if there is a "Availability after DDN Failure" monitoring event or a "UE Reachability" monitoring event configured for the UE in the SGSN and in such a case sends an event notification (see TS 23.682 [74] for further information).
12. The new SGSN verifies whether it holds subscription data for the UE identified by the P‑TMSI, the additional PTMSI/RAI or by the IMSI received with the context data from the old CN node.
The additional P-TMSI/RAI allows the new SGSN to find any already existing UE context stored in the new SGSN. If there are no subscription data in the new SGSN for this UE, or for some network sharing scenario (e.g. GWCN) if the PLMN-ID of the RAI supplied by the RNC is different from that of the RAI in the UE's context, then the new SGSN informs the HSS of the change of the SGSN by sending an Update Location (SGSN Number, SGSN Address, IMSI, Homogenous Support of IMS Voice over PS Sessions, UE SRVCC capability, equivalent PLMN list) message to the HSS. For "Homogenous Support of IMS Voice over PS Sessions", see clause 5.3.8A of TS 23.060 [7]. The inclusion of the equivalent PLMN list indicates that the SGSN supports the inter-PLMN handover to a CSG cell in an equivalent PLMN using the subscription information of the target PLMN.
If the UE initiates the RAU procedure in a VPLMN supporting Autonomous CSG Roaming and the HPLMN has enabled Autonomous CSG Roaming in the VPLMN (via Service Level Agreement) and the SGSN needs to retrieve the CSG subscription information of the UE from the CSS, the SGSN initiates the Update CSG Location Procedure with CSS as described in clause 5.3.12.
13. The HSS sends a Cancel Location (IMSI, Cancellation Type) message to the old SGSN with the Cancellation Type set to Update Procedure.
When receiving the Cancel Location message the old SGSN removes all the UE contexts. The old SGSN acknowledges with a Cancel Location Ack (IMSI) message.
14. When receiving the Context Acknowledge message from the new SGSN and if the old MME has an S1-MME association for the UE, the source MME sends a S1-U Release Command to the source eNodeB after the timer started in step 3 has expired. The RRC connection is released by the source eNodeB. The source eNodeB confirms the release of the RRC connection and of the S1-U connection by sending a S1-U Release Complete message to the source MME.
15. The HSS acknowledges the Update Location message by sending an Update Location Ack (IMSI, Subscription Data) to the new SGSN. The Subscription Data may contain the CSG subscription data for the registered PLMN and for the equivalent PLMN list requested by SGSN in step 12.
If the UE initiates the RAU procedure at a CSG cell, the new S4 SGSN shall check whether the CSG ID and associated PLMN is contained in the CSG subscription and is not expired. If the CSG ID and associated PLMN is not present or expired, the S4 SGSN shall send a RAU reject message to the UE with an appropriate cause value. The UE shall remove the CSG ID and associated PLMN from its Allowed CSG list if present.
If the Update Location is rejected by the HSS, the new SGSN rejects the RAU Request from the UE with an appropriate cause sent in the RAU Reject message to the UE. In such cases, the new SGSN releases any local SGSN EPS Bearer contexts for this particular UE.
16. Void.
17. Void.
18. If due to regional subscription restrictions or access restrictions (e.g. CSG restrictions) the UE is not allowed to access the RA:
- For UEs with ongoing emergency bearer services, the new SGSN accept the Routing Area Update Request and deactivates the non-emergency PDP contexts as specified in clause 9.2.4.2 in TS 23.060 [7]. If the Routing Area Update procedure is initiated in PMM-IDLE/STANDBY state, all non-emergency PDP Contexts are deactivated by the Routing Area without PDP Context deactivation signalling between the UE and the SGSN
- For all other cases, the new SGSN rejects Routing Area Update Request with an appropriate cause to the UE and notifies the HSS of rejection (details of this notification is covered in stage 3).
The new SGSN responds to the UE with a Routing Area Update Accept (P-TMSI, P-TMSI signature, ISR Activated, Emergency Service Support indicator, PDP context status) message to the UE. P-TMSI is included if the SGSN allocates a new P-TMSI. The Emergency Service Support indicator informs the UE that Emergency bearer services are supported over UTRAN.
If ISR Activated is indicated to the UE, its GUTI and list of TAs shall remain registered with the network and shall remain valid in the UE.
When receiving the RAU Accept message and there is no ISR Activated indication the UE shall set its TIN to "P‑TMSI". When ISR Activated is indicated and the UE's TIN indicates "P‑TMSI" the TIN shall not be changed. When ISR Activated is indicated and the UE's TIN indicates "GUTI" or "RAT‑related TMSI" the UE shall set its TIN to "RAT‑related TMSI".
If an SGSN change ISR is not activated by the new SGSN to avoid context transfer procedures with two old CN nodes.
If the RAU procedure is initiated by manual CSG selection and occurs via a CSG cell, the UE upon receiving the RAU Accept shall add the CSG ID and associated PLMN to its Allowed CSG list if it is not already present. Manual CSG selection is not supported if the UE has emergency bearers established.
In Iu mode, if after step 7 the new SGSN receives a Downlink Data Notification message or any other downlink signalling message while the UE is still connected, the new SGSN may prolong the PS signalling connection with the UE.
If there is DL data buffered for a UE using power saving functions (i.e. the DL Data Buffer Expiration Time in the MM context for the UE in the SGSN has not expired), the user plane setup is performed in conjunction with the RAU Accept message.
With the PDP context status information, the UE shall deactivate all those bearers contexts locally which are active in the UE, but are indicated by the SGSN as being inactive.
If the user plane setup is performed in conjunction with the RAU Accept message and the RAU is performed via a hybrid cell, then the SGSN shall send an indication whether the UE is a CSG member to the RAN along with the RANAP message. Based on this information, the RAN may perform differentiated treatment for CSG and non-CSG members.
NOTE 6: If the UE receives a RAU Accept message via a hybrid cell, the UE does not add the corresponding CSG ID and associated PLMN to its Allowed CSG list. Adding a CSG ID and associated PLMN to the UE's local Allowed CSG list for a hybrid cell is performed only by OTA or OMA DM procedures.
19. If P-TMSI was included in the Routing Area Update Accept message, the UE acknowledges the new P-TMSI by returning a Routing Area Update Complete message to the SGSN.
20. For Iu-mode, if the UE has uplink data or signalling pending it shall send a Service Request (P-TMSI, CKSN, Service Type) message to the new SGSN. If a P-TMSI was allocated in step 18, that P-TMSI is the one included in this message. Service Type specifies the requested service. Service Type shall indicate one of the following: Data or Signalling.
21. If the UE has sent the Service Request, the new 3G SGSN requests the RNC to establish a radio access bearer by sending a RAB Assignment Request (RAB ID(s), QoS Profile(s), GTP SNDs, GTP SNUs, PDCP SNUs) message to the RNC. If Direct Tunnel is established the SGSN provides to the RNC the Serving GW's Address for User Plane and TEID for uplink data.
22. If the SGSN established Direct Tunnel in step 21) it shall send Modify Bearer Request per PDN connection to the Serving GW and include the RNC's Address for User Plane and downlink TEID for data. The Serving GW updates the Address for User Plane and TEID for downlink data and return a Modify Bearer Response.
NOTE 7: EPS does not support any CAMEL procedures.
NOTE 8: The new SGSN may initiate RAB establishment after execution of the security functions (step 5), or wait until completion of the RA update procedure. For the MS, RAB establishment may occur any time after the RA update request is sent (step 2).
In the case of a rejected routing area update operation, due to regional subscription, roaming restrictions or access restrictions (see TS 23.221 [27] and TS 23.008 [28]) the new SGSN should not construct an MM context. In the case of receiving the subscriber data from HSS, the new SGSN may construct an MM context and store the subscriber data for the UE to optimise signalling between the SGSN and the HSS. A reject shall be returned to the UE with an appropriate cause and the PS signalling connection shall be released. Upon return to idle, the UE shall act according to TS 23.122 [10].
If the network supports the MOCN configuration for network sharing, the SGSN may, if the UE is not a 'Network Sharing Supporting MS', in this case decide to initiate redirection by sending a Reroute Command to the RNS, as described in TS 23.251 [24] instead of rejecting the routing area update.
If the new SGSN is unable to update the bearer context in one or more P‑GWs, the new SGSN shall deactivate the corresponding bearer contexts as described in clause "SGSN-initiated PDP Context Deactivation Procedure" of TS 23.060 [7]. This shall not cause the SGSN to reject the routing area update.
The new SGSN shall determine the Maximum APN restriction based on the received APN Restriction of each bearer context in the Context Response message and then store the new Maximum APN restriction value.
The PDP contexts shall be prioritized by the new SGSN. If the new SGSN is unable to support the same number of active PDP contexts as received from the old MME, the prioritisation is used to decide which PDP contexts to maintain active and which ones to delete. In any case, the new SGSN shall first update all PDP contexts in one or more P‑GWs and then deactivate the PDP context(s) that it cannot maintain as described in clause "SGSN-initiated PDP Context Deactivation Procedure" of TS 23.060 [7]. This shall not cause the SGSN to reject the routing area update.
NOTE 9: If the UE was in PMM-CONNECTED state the bearer contexts are sent already in the Forward Relocation Request message as described in clause "Serving RNS relocation procedures" of TS 23.060 [7].
If the routing area update procedure fails a maximum allowable number of times, or if the SGSN returns a Routing Area Update Reject (Cause) message, the UE shall enter PMM DETACHED state.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.3.4 Void
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.3.5 Void
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.3.6 Routing Area Update with MME interaction and with S‑GW change
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The Routing Area Update with S‑GW change procedure takes place when a UE that is registered with an MME selects a UTRAN or GERAN cell and the S‑GW is changed by the procedure. In this case, the UE changes to a Routing Area that the UE has not yet registered with the network. This procedure is initiated by an ECM-IDLE state UE and may also be initiated if the UE is in ECM-CONNECTED state. This RA update case is illustrated in Figure 5.3.3.6-1.
NOTE 1: This procedure covers the MME to 2G or 3G SGSN RAU.
Figure 5.3.3.6-1: Routing Area Update with MME interaction and with S‑GW change
NOTE 2: For a PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 8 and 10 concern GTP based S5/S8
1. The UE selects a UTRAN or GERAN cell. This cell is in a Routing Area that the UE not yet registered with the network or the UE reselects a UTRAN or GERAN cell and the TIN indicates "GUTI". The UE in ECM‑CONNECTED state may change to the GERAN cell through Network Assisted Cell Change (NACC).
2a. The UE sends a Routing Area Update Request (old RAI, old P-TMSI, P-TMSI Type, UE Core Network Capability, MS Network Capability, P‑TMSI Signature, additional P‑TMSI/RAI, KSI, Voice domain preference and UE's usage setting) message to the new SGSN. The UE shall set the P-TMSI Type to indicate whether the P-TMSI is a native P-TMSI or is mapped from a GUTI.
If the UE's TIN indicates "GUTI" and the UE holds a valid GUTI then the UE indicates the GUTI as the old P‑TMSI and old RAI. If the UE's TIN indicates "P‑TMSI" or "RAT‑related TMSI" and the UE holds a valid P‑TMSI and related RAI then these two elements are indicated as old P‑TMSI and old RAI. Mapping a GUTI to a P‑TMSI and an RAI is specified in TS 23.003 [9].
If the UE holds a valid P‑TMSI and related RAI and the old P-TMSI and old RAI indicate a P-TMSI/RAI mapped from a GUTI, then the UE indicates these parameters as additional P‑TMSI/RAI.
The old P‑TMSI is indicated in the RAU Request message for Iu‑mode only. For Gb mode the TLLI is derived from the value that is determined as the old P‑TMSI according to the rules above. The routing parameter that is signalled in the RRC signalling to the RNC for routing to the SGSN is derived from the identifier that is signalled as the old P‑TMSI according to the rules above. For a combined MME/SGSN the RAN is configured to route the NRI(s) of this combined node to the same combined node. The RAN is also configured to route NRI(s) of P‑TMSIs that are generated by the UE's mapping of the GUTIs allocated by the combined node. Such a RAN configuration may also be used for separate nodes to avoid changing nodes in the pool caused by inter RAT mobility.
If the UE has a follow-on request, i.e. if there is pending uplink traffic (signalling or data), the 3G-SGSN may use, as an implementation option, the follow-on request indication to release or keep the Iu connection after the completion of the RA update procedure.
KSI is mapped from an eKSI identifying a KASME if the UE indicates a P‑TMSI mapped from GUTI in the information element "old P‑TMSI". KSI identifies a (CK, IK) pair if the UE indicates a P‑TMSI in the information element "old P‑TMSI".
The UE sets the voice domain preference and UE's usage setting according to its configuration, as described in clause 4.3.5.9.
2b. The RNC shall add the Routing Area Identity, CSG access mode, CSG ID before forwarding the message to the SGSN. This RA identity corresponds to the RAI in the MM system information sent by the RNC to the UE. The BSS shall add the Cell Global Identity (CGI) of the cell where the UE is located before passing the message to the new SGSN. CSG ID is provided by RAN if the UE sends the RAU Request message via a CSG cell or a hybrid cell. CSG access mode is provided if the UE sends the RAU Request message via a hybrid cell. If the CSG access mode is not provided but the CSG ID is provided, the SGSN shall consider the cell as a CSG cell. For SIPTO at the Local Network the with stand-alone GW architecture the RNC includes the Local Home Network ID in the Initial UE Message and in Direct Transfer message if the target cell is in a Local Home Network.
3. The new S4 SGSN determines the type of the old node, i.e. MME or SGSN, as specified in clause 4.3.19, uses the old RAI received from the UE to derive the old MME address, and the new S4 SGSN sends a Context Request (P‑TMSI, old RAI, New SGSN Address, P‑TMSI Signature) message to the old MME to get the context for the UE. To validate the Context Request the old MME uses a NAS token mapped from the P-TMSI Signature. If the UE is not known in the old MME, the old MME responds with an appropriate error cause. If integrity check fails in the old MME, the old MME responds with an appropriate error cause which should initiate the security functions in the new S4 SGSN. If the security functions authenticate the UE correctly, the new S4 SGSN shall send a Context Request (IMSI, old RAI, New SGSN Address, UE Validated) message to the old MME. UE Validated indicates that the new S4 SGSN has authenticated the UE. If the new S4 SGSN indicates that it has authenticated the UE or if the old MME authenticates the UE, the old MME starts a timer.
If the UE with emergency bearers is not authenticated in the old MME (in a network supporting unauthenticated UEs) the old MME continues the procedure with sending a Context Response and starting the timer also when it cannot validate the Context Request.
4. The old MME responds with a Context Response (MM Context, EPS Bearer Contexts, Serving GW signalling Address and TEID(s), MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone and ISR Supported) message. The MM context contains security related information as well as other parameters (including IMSI) as described in clause 5.7.2 (Information Storage for MME). The PDN GW Address and TEID(s) (for GTP-based S5/S8) or GRE Keys (PMIP-based S5/S8) for uplink traffic and control plane, and the TI(s) is part of the EPS Bearer context(s). The unused Authentication Quintets in the MM Context may be sent if stored by the MME and if the MME received the unused Authentication Quintets from the same SGSN previously.
If the UE receives only emergency bearer services from the old MME and the UE is UICCless, IMSI can not be included in the Context Response. For emergency attached UEs, if the IMSI cannot be authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available. ISR Supported is indicated if the old MME and associated Serving GW are capable to activate ISR for the UE.
The new SGSN shall ignore the UE Core Network Capability in the MM Context of the Context Response only when it has previously received an UE Core Network Capability in the Routing Area Request. If UE is not known in the old MME, the old MME responds with a appropriate error cause.
The new SGSN maps the EPS bearers to PDP contexts 1-to-1 and maps the EPS Bearer QoS parameter values of an EPS bearer to the Release 99 QoS parameter values of a bearer context as defined in Annex E. The PDP context(s) are established in the indicated order. The SGSN deactivates the PDP contexts which cannot be established.
If SIPTO at the Local Network is active for a PDN connection in the architecture with stand-alone GW, the old MME shall include the Local Home Network ID of the old cell in the EPS Bearer context corresponding to the SIPTO at the Local Network PDN connection.
If the UE uses power saving functions and the DL Data Buffer Expiration Time for the UE has not expired (see High latency communication in clause 4.3.17.7), the old MME indicates Buffered DL Data Waiting in the Context Response. When this is indicated, the new SGSN shall invoke data forwarding (corresponding to clause 5.3.3.1A) and setup the user plane in conjunction to the RAU procedure for delivery of the buffered DL data to the UE.
For UE using CIoT EPS Optimisation without any activated PDN connection, there is no EPS Bearer Context(s) included in the Context Response message.
The old MME only transfers the EPS Bearer Context(s) that the new SGSN supports. If not supported, EPS Bearer Context(s) of non-IP PDN connection are not transferred to the new SGSN. EPS Bearer Context(s) of Ethernet PDN connection type are not transferred to the new SGSN. If the EPS Bearer Context(s) of a PDN connection has not been transferred, the old MME shall consider all bearers of that PDN connection as failed and release that PDN connection by triggering the MME requested PDN disconnection procedure specified in clause 5.10.3.
5. Security functions may be executed. Procedures are defined in clause 5.3.10 on "Security Function".
For ongoing emergency services only, if the new SGSN is configured to support emergency bearer services in limited service state, it may skip the authentication procedure or proceed even if authentication fails. If the new SGSN does not support emergency bearer services in limited service state, then it rejects the RAU request with an appropriate reject cause.
6. If the new SGSN identifies that the RAT type has changed, the SGSN checks the subscription information to identify for each APN whether to maintain the PDN connection, disconnect the PDN connection with a reactivation request or disconnect PDN connection without reactivation request. If the SGSN decides to deactive a PDN connection it performs SGSN-initiated PDN Connection Deactivation procedure after tracking area procedure is completed. Existing SM cause values as specified in TS 24.008 [47] (e.g. #39, "reactivation requested"; #66 "Requested APN not supported in current RAT and PLMN combination"; and for a dedicated bearer, possibly #37 "QoS not accepted") are used to cause predictable UE behaviour.
The new SGSN determines to relocate the Serving GW. The Serving GW is relocated when the old Serving GW cannot continue to serve the UE. The new SGSN may also decide to relocate the Serving GW if a new Serving GW is expected to serve the UE longer and/or with a more optimal UE to PDN GW path, or if a new Serving GW can be co-located with the PDN GW. Selection of a new Serving GW is performed according to clause 4.3.8.2 on "Serving GW selection function".
The new SGSN sends a Context Acknowledge (Serving GW change indication) message to the old MME. Serving GW change indication indicates a new Serving GW has been selected. The old MME marks in its context that the information in the GWs is invalid. This ensures that the old MME updates the GWs if the UE initiates a TAU procedure back to the old MME before completing the ongoing RAU procedure.
NOTE 3: Updating the GWs refers to deletion of session(s) on the Serving GW followed by re-creation of session(s) on the Serving GW. The re-creation of session(s) on the Serving GW will result in successful re-establishment of the S5/S8 tunnel between the selected Serving GW and the PDN GW.
The old MME deletes all bearer resources of the UE when the timer started in step 3 expires.
If the security functions do not authenticate the UE correctly, then the RAU is rejected, and the new S4 SGSN sends a reject indication to the old MME. The MME shall continue as if the Identification and Context Request was never received.
For UE using CIoT EPS Optimisation without any activated PDN connection, the steps 7, 8, 9, 10, 11, 16 and 17 are skipped.
7. In this procedure flow the Serving GW is relocated. The SGSN sends a Create Session Request (IMSI, bearer contexts, SGSN Address and TEID for the control plane, RAT Type, Type, the Protocol Type over S5/S8, Serving Network, UE Time Zone, etc) message per PDN connection to the selected new Serving GW. The PDN GW address is indicated in the bearer contexts. Type indicates to the Serving GW to send the Modify Bearer Request to the PDN GW. The Protocol Type over S5/S8 is provided to Serving GW which protocol should be used over S5/S8 interface. RAT type indicates a change in radio access. As it is a mobility from E-UTRAN, if the target SGSN supports location information change reporting, the target SGSN shall include the User Location Information (according to the supported granularity) in the Modify Bearer Request, regardless of whether location information change reporting had been requested in the previous RAT by the PDN GW. If the PDN GW requested User CSG information, the SGSN also includes the User CSG Information IE in this message.
8. The new Serving GW sends the message Modify Bearer Request (Serving GW Address, Serving GW TEID, RAT type, Serving Network) per PDN connection to the PDN GW concerned. User Location Information IE and/or UE Time Zone IE and/or User CSG Information IE are also included if they are present in step 7.
9. If dynamic PCC is deployed, and RAT type information or UE location information or UE Time Zone needs to be conveyed from the PDN GW to the PCRF, then the PDN GW shall send this information to the PCRF by means of an IP-CAN Session Modification procedure as defined in TS 23.203 [6].
NOTE 4: The PDN GW does not need to wait for the PCRF response, but continues in the next step. If the PCRF response leads to an EPS bearer modification the PDN GW should initiate a bearer update procedure.
10. The PDN GW updates its context field and returns a Modify Bearer Response (Charging Id, MSISDN) message to the Serving GW. The MSISDN is included if the PDN GW has it stored in its UE context. If location information change reporting is required and supported in the target SGSN, the PDN GW shall provide MS Info Change Reporting Action in the Modify Bearer Response.
If the Serving GW is relocated, the PDN GW shall send one or more "end marker" packets on the old path immediately after switching the path. If the source Serving GW has no downlink user plane established, the Serving GW shall discard the "end marker" received from the PDN GW and shall not send Downlink Data Notification. Otherwise the Serving GW shall forward the "end marker" packets to the source eNodeB.
11. The new Serving GW updates its bearer context. This allows the Serving GW to route Bearer PDUs to the PDN GW when received from RNC. The new Serving GW returns a Create Session Response (Serving GW address and TEID, PDN GW Address and TEIDs (for GTP-based S5/S8) or GRE keys (for PMIP-based S5/S8, MS Info Change Reporting Action) at the PDN GW(s) for uplink traffic) message to the SGSN.
When the SGSN receives the Create Session Response message, the SGSN checks if there is a "Availability after DDN Failure" monitoring event or a "UE Reachability" monitoring event configured for the UE in the SGSN and in such a case sends an event notification (see TS 23.682 [74] for further information).
12. The new SGSN verifies whether it holds subscription data for the UE identified by the P‑TMSI, the additional P‑TMSI/RAI or by the IMSI received with the context data from the old CN node.
The additional P-TMSI/RAI allows the new SGSN to find any already existing UE context stored in the new SGSN. If there are no subscription data in the new SGSN for this UE, or for some network sharing scenario (e.g. GWCN) if the PLMN-ID of the RAI supplied by the RNC is different from that of the RAI in the UE's context, then the new SGSN informs the HSS of the change of SGSN by sending an Update Location (SGSN Number, SGSN Address, IMSI, Homogenous Support of IMS Voice over PS Session, UE SRVCC capability, equivalent PLMN list) message to the HSS. For "Homogenous Support of IMS Voice over PS Sessions", see clause 5.3.8A of TS 23.060 [7]. The inclusion of the equivalent PLMN list indicates that the SGSN supports the inter-PLMN handover to a CSG cell in an equivalent PLMN using the subscription information of the target PLMN.
If the UE initiates the RAU procedure in a VPLMN supporting Autonomous CSG Roaming and the HPLMN has enabled Autonomous CSG Roaming in the VPLMN (via Service Level Agreement) and the SGSN needs to retrieve the CSG subscription information of the UE from the CSS, the SGSN initiates the Update CSG Location Procedure with CSS as described in clause 5.3.12.
13. The HSS sends a Cancel Location (IMSI, Cancellation Type) message to the old SGSN with the Cancellation Type set to Update Procedure.
When receiving the Cancel Location message the old SGSN removes all the UE contexts. The old SGSN acknowledges with a Cancel Location Ack (IMSI) message.
14. When receiving the Context Acknowledge message from the new S4 SGSN and if the old MME has an S1-MME association for the UE, the source MME sends a S1-U Release Command to the source eNodeB after the timer started in step3 has expired. The RRC connection is released by the source eNodeB. The source eNodeB confirms the release of the RRC connection and of the S1-U connection by sending a S1-U Release Complete message to the source MME.
15. The HSS acknowledges the Update Location message by sending an Update Location Ack (IMSI, Subscription Data) to the new SGSN. If the Update Location is rejected by the HSS, the new SGSN rejects the RAU Request from the UE with an appropriate cause. In such cases, the SGSN releases any local SGSN EPS Bearer contexts for this particular UE, and additionally deletes the EPS bearer resources in the new Serving GW by sending the Delete Session Request (Cause, Operation Indication) messages to the new Serving GW. The Operation Indication flag shall not be set. Therefore, the new Serving GW receiving this request shall not initiate a delete procedure towards the PDN GW.
The new SGSN validates the UE's presence in the (new) RA. If due to regional subscription restrictions or access restrictions (e.g. CSG restrictions) the UE is not allowed to be attached in the RA, the SGSN rejects the Routing Area Update Request with an appropriate cause to the UE and notifies the HSS of the rejection. The Subscription Data may contain the CSG subscription data for the registered PLMN and for the equivalent PLMN list requested by SGSN in step 12.
If the UE initiates the RAU procedure at a CSG cell, the new S4 SGSN shall check whether the CSG ID and associated PLMN is contained in the CSG subscription and is not expired. If the CSG ID and associated PLMN is not present or expired, the S4 SGSN shall send a RAU reject message to the UE with an appropriate cause value. The UE shall remove the CSG ID and associated PLMN from its Allowed CSG list if present.
16. When the timer started in step 3 expires and the old MME received the Serving GW change indication in the Context Acknowledge message, the old MME deletes the EPS bearer resources by sending Delete Session Request (Cause, Operation Indication) messages to the old Serving GW. The operation Indication flag is not set, that indicates to the old Serving GW that the old Serving GW shall not initiate a delete procedure towards the PDN GW. If ISR is activated the cause indicates to the old S‑GW that the old S‑GW shall delete the bearer resources on the other old CN node by sending Delete Bearer Request message(s) to that CN node.
17. The old Serving GW acknowledges with Delete Session Response (Cause) messages. The old Serving GW discards any packets buffered for the UE.
18. If due to regional subscription restrictions or access restrictions the UE is not allowed to access the RA:
- For UEs with ongoing emergency bearer services, the new SGSN accept the Routing Area Update Request and deactivates the non-emergency PDP contexts as specified in clause 9.2.4.2 of TS 23.060 [7]. If the Routing Area Update procedure is initiated in PMM-IDLE/STANDBY state, all non-emergency PDP Contexts are deactivated by the Routing Area Update procedure without PDP Context deactivation signalling between the UE and the SGSN.
- For all other cases, the new SGSN rejects Routing Area Update Request with an appropriate cause to the UE and notifies the HSS of rejection (details of this notification is specified in stage 3).
The new SGSN responds to the UE with a Routing Area Update Accept (P-TMSI, P-TMSI Signature, Emergency Service Support indicator, PDP context status) message. The Emergency Service Support indicator informs the UE that Emergency bearer services are supported over UTRAN.
For an S‑GW change ISR Activated is never indicated by the SGSN to the UE as it needs a TAU with the same S‑GW first to activate ISR. For an SGSN change ISR is not activated by the new SGSN to avoid context transfer procedures with two old CN nodes.
When receiving the RAU Accept message, as there is no ISR Activated indication, the UE shall set its TIN to "P‑TMSI".
In Iu mode, if after step 7 the new SGSN receives a Downlink Data Notification message or any other downlink signalling message while the UE is still connected, the new SGSN may prolong the PS signalling connection with the UE.
If there is DL data buffered for a UE using power saving functions (i.e. the DL Data Buffer Expiration Time in the MM context for the UE in the SGSN has not expired), the user plane setup is performed in conjunction with the RAU Accept message.
If the RAU procedure is initiated by manual CSG selection and occurs via a CSG cell, the UE upon receiving the RAU Accept message shall add the CSG ID and associated PLMN to its Allowed CSG list if it is not already present. Manual CSG selection is not supported if the UE has emergency bearers established.
With the PDP context status information, the UE shall deactivate all those bearers contexts locally which are active in the UE, but are indicated by the SGSN as being inactive.
If the user plane setup is performed in conjunction with the RAU Accept message and the RAU is performed via a hybrid cell, then the SGSN shall send an indication whether the UE is a CSG member to the RAN along with the RANAP message. Based on this information, the RAN may perform differentiated treatment for CSG and non-CSG members.
NOTE 5: If the UE receives a RAU Accept message via a hybrid cell, the UE does not add the corresponding CSG ID and associated PLMN to its Allowed CSG list. Adding a CSG ID and associated PLMN to the UE's local Allowed CSG list for a hybrid cell is performed only by OTA or OMA DM procedures.
NOTE 6: When ISR Activated is indicated and the UE's TIN indicates "P‑TMSI" the TIN is not changed. When ISR Activated is indicated and the UE's TIN indicates "GUTI" or "RAT‑related TMSI" the UE shall set its TIN to "RAT‑related TMSI".
19. If the P-TMSI was included in the RAU Accept message, the UE acknowledges the new P-TMSI by returning a Routing Area Update Complete message to the SGSN.
20. For Iu-mode, if the UE has uplink data or signalling pending it shall send a Service Request (P-TMSI, CKSN, Service Type) message to the new SGSN. If a P-TMSI was allocated in step 18, that P-TMSI is the one included in this message. Service Type specifies the requested service. Service Type shall indicate one of the following: Data or Signalling.
21. If the UE has sent the Service Request, the new 3G SGSN requests the RNC to establish a radio access bearer by sending a RAB Assignment Request (RAB ID(s), QoS Profile(s), GTP SNDs, GTP SNUs, PDCP SNUs) message to the RNC. If Direct Tunnel is established the SGSN provides to the RNC the Serving GW's Address for User Plane and TEID for uplink data.
22. If the SGSN established Direct Tunnel in step 21) it shall send Modify Bearer Request to the Serving GW and include the RNC's Address for User Plane and downlink TEID for data. The Serving GW updates the Address for User Plane and TEID for downlink data and return a Modify Bearer Response.
NOTE 7: EPS does not support any CAMEL procedures.
In the case of a rejected routing area update operation, due to regional subscription, roaming restrictions, access restrictions (see TS 23.221 [27] and TS 23.008 [28]) or because the SGSN cannot determine the HLR address to establish the locating updating dialogue, the new SGSN should not construct an MM context. In the case of receiving the subscriber data from HLR, the new SGSN may construct an MM context and store the subscriber data for the UE to optimise signalling between the SGSN and the HSS. A reject shall be returned to the UE with an appropriate cause and the PS signalling connection shall be released. Upon return to idle, the UE shall act according to TS 23.122 [10].
If the new SGSN is unable to update the bearer context in one or more P‑GWs, the new SGSN shall deactivate the corresponding bearer contexts as described in clause "SGSN-initiated PDP Context Deactivation Procedure" of TS 23.060 [7]. This shall not cause the SGSN to reject the routing area update.
The new SGSN shall determine the Maximum APN restriction based on the received APN Restriction of each bearer context in the Context Response message and then store the new Maximum APN restriction value.
The PDP contexts shall be prioritized by the new SGSN. If the new SGSN is unable to support the same number of active PDP contexts as received from old MME, the prioritisation is used to decide which PDP contexts to maintain active and which ones to delete. In any case, the new SGSN shall first update all PDP contexts in one or more P‑GWs and then deactivate the PDP context(s) that it cannot maintain as described in clause "SGSN-initiated PDP Context Deactivation Procedure" of TS 23.060 [7]. This shall not cause the SGSN to reject the routing area update.
If the routing area update procedure fails a maximum allowable number of times, or if the SGSN returns a Routing Area Update Reject (Cause) message, the MS shall enter IDLE state.
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495b59b986f98d41912141cabbec196e
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5.3.4 Service Request procedures
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.4.1 UE triggered Service Request
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Figure 5.3.4.1-1: UE triggered Service Request procedure
The Service Request procedure in this clause is triggered by the UE in:
a) ECM-IDLE state to establish user plane radio bearers for the UE;
b) ECM-IDLE state to establish user plane radio bearers even if the UE applies Control Plane CIoT EPS Optimisation, when the UE and MME supports S1-U data transfer or User Plane EPS Optimisation in addition to Control Plane CIoT EPS Optimisation;
c) ECM-CONNECTED state to request, if the UE is a Multi-USIM UE and wants to release of the UE connection, stop of any data transmission, discard of any pending data and, optionally, Paging Restriction Information; or
d) ECM-IDLE state to request, if the UE is a Multi-USIM UE wants to remove the Paging Restriction Information.
e) ECM-IDLE state, if the UE is a Multi-USIM UE and wants to respond to paging with a Reject Paging Indication that indicates that S1 connection shall be released and no user plane radio bearers shall be established, unless it is unable to do so, e.g. due to UE implementation constraints. The UE optionally provides the Paging Restriction Information.
NOTE 1: It is not expected that a Multi-USIM UE will execute UE triggered service request procedure with Release Request indication if regulatory prioritized services (e.g. emergency service, emergency callback waiting) are ongoing.
NOTE 2: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402 [2]. Steps 9 and 11 concern GTP-based S5/S8.
1. The UE sends NAS message Service Request towards the MME encapsulated in an RRC message to the eNodeB. The RRC message(s) that can be used to carry the S-TMSI and this NAS message are described in TS 36.300 [5].
The Multi-USIM UE in ECM-CONNECTED state may include the Release Request indication and optionally Paging Restriction Information in the Service Request message, if the UE intends to return to ECM-IDLE state.
2. The eNodeB forwards NAS message to MME. NAS message is encapsulated in either an S1-AP: Initial UE Message (NAS message, TAI+ECGI of the serving cell, S-TMSI, CSG ID, CSG access Mode, RRC establishment cause), or another S1-AP message (e.g. Uplink NAS Transport Message) used for the UE in ECM-CONNECTED. Details of this step are described in TS 36.300 [5]. If the MME can't handle the Service Request it will reject it. CSG ID is provided if the UE sends the Service Request message via a CSG cell or a hybrid cell. CSG access mode is provided if the UE sends the Service Request message via a hybrid cell. If the CSG access mode is not provided but the CSG ID is provided, the MME shall consider the cell as a CSG cell.
If a CSG ID is indicated and CSG access mode is not provided, and there is no subscription data for this CSG ID and associated PLMN or the CSG subscription is expired, the MME rejects the Service Request with an appropriate cause. The UE shall remove the CSG ID and associated PLMN of the cell where the UE has initiated the service request procedure from the Allowed CSG list, if present.
For UEs with emergency EPS bearers, i.e. at least one EPS bearer has an ARP value reserved for emergency services, if CSG access restrictions do not allow the UE to get normal services the MME shall deactivate all non-emergency bearers and accept the Service Request.
If LIPA is active for a PDN connection and if the cell accessed by the UE does not link to the L-GW where the UE initiated the LIPA PDN Connection, the MME shall not request the establishment of the bearers of the LIPA PDN connection from the eNodeB in step 4 and shall request disconnection of the LIPA PDN connection according to clause 5.10.3. If the UE has no other PDN connection then the MME shall reject the Service Request with an appropriate cause value resulting in the UE detaching, skip the following steps of the procedure and initiate the release of the core network resources with the implicit MME-initiated Detach procedure according to clause 5.3.8.3.
If there is a "Availability after DDN Failure" monitoring event or a "UE Reachability" monitoring event configured for the UE in the MME, the MME sends an event notification (see TS 23.682 [74] for further information).
To assist Location Services, the eNodeB indicates the UE's Coverage Level to the MME.
If the MME supports RACS, and the MME detects that the selected PLMN is different from the currently registered PLMN for the UE, the MME provides the UE Radio Capability ID of the newly selected PLMN in the UE context to the eNodeB as described in clause 5.11.3a.
If the Service Request message is received from a UE in ECM-IDLE state without a Release Request indication, the MME shall delete any stored Paging Restriction Information for this UE and stop restricting paging accordingly and the procedure continues form the next step 3.
If the Service Request message includes a Release Request indication or Reject Paging Indication, then:
- If the Service Request message includes Paging Restriction Information, the MME may accept or reject the Paging Restriction Information requested by the UE based on operator policy. If the MME rejects the Paging Restriction Information, the MME removes any stored Paging Restriction Information from the UE context and discards the UE requested Paging Restriction Information. If the MME accepts the Paging Restriction Information from the UE, the MME stores the received Paging Restriction Information from the UE in the UE context. The MME informs the UE about the acceptance/rejection of the requested Paging Restriction Information in the Service Accept message. If no Paging Restriction Information is provided, no paging restrictions apply;
- no S1 bearer is established (steps 4-7 are skipped);
- the MME Triggers the S1 release procedure as described in clause 5.3.5 and no further steps of this procedure are executed. The MME may however trigger the NAS Authentication/Security in step 3 before releasing the UE.
In the case of satellite access for Cellular IoT, the MME may verify the UE location and determine whether the PLMN is allowed to operate at the UE location, as described in clause 4.13.4. If the UE receives a Service Reject message with cause value indicating that the selected PLMN is not allowed to operate at the present UE location, the UE shall attempt to select a PLMN as specified in TS 23.122 [10].
In the case of satellite access over NB-IoT, the eNB may request the MME to provide the Coarse Location information to the eNB, as described in TS 36.300 [5] and TS 36.413 [36].
3. NAS authentication/security procedures as defined in clause 5.3.10 on "Security function" may be performed.
If the MME is configured to support RLOS and the UE indicated Attach Type "RLOS", based on local regulation and operator policy, the MME may skip the authentication and security setup, or the MME may perform authentication if security information is available or obtainable from a HSS, and continue the Service Request procedure regardless of the authentication result.
In the case of satellite access for NB-IoT, if the UE indicated support for reporting its Coarse Location Information, the MME may request the UE to report its Coarse Location Information by setting the Coarse Location Information Request in the Security Mode Command message and the UE then reports its Coarse Location Information in the Security Mode Complete message to the MME. To perform UE location verification as described in clause 4.13.4, the MME provides the reported Coarse Location Information to the E-SMLC as described in clause 9.1.17 of TS 23.271 [57]. If the eNB requested the MME to provide the Coarse Location Information to the eNB, the MME provides the Coarse Location Information to the eNB in an S1-AP message as described in TS 36.413 [36]. The eNB may use it as specified in TS 36.300 [5].
4. If there is a Service Gap timer running in the MME MM Context for the UE and the MME is not waiting for a MT paging response from the UE, the MME rejects the Service Request with an appropriate cause. In addition, MME may also provide a UE with a Mobility Management Back-off timer set to the remaining value of the Service Gap timer.
The MME deletes S11-U related information in UE context if there is any, including TEID(DL) for the S11-U for Control Plane CIoT EPS Optimisation if data buffering is in the MME, ROHC context for Control Plane CIoT EPS Optimisation, etc, but not the Header Compression Configuration. The MME sends S1-AP Initial Context Setup Request (Serving GW address, S1-TEID(s) (UL), EPS Bearer QoS(s), Security Context, MME Signalling Connection Id, Handover Restriction List, CSG Membership Indication) message to the eNodeB. If there is a PDN connection established for Local IP Access, this message includes a Correlation ID for enabling the direct user plane path between the HeNB and the L-GW. If there is a PDN connection established for SIPTO at the Local Network with L-GW function collocated with the (H)eNB, this message includes a SIPTO Correlation ID for enabling the direct user plane path between the (H)eNB and the L‑GW. This step activates the radio and S1 bearers for all the active EPS Bearers. The eNodeB stores the Security Context, MME Signalling Connection Id, EPS Bearer QoS(s) and S1-TEID(s) in the UE RAN context. The step is described in detail in TS 36.300 [5]. Handover Restriction List is described in clause 4.3.5.7 "Mobility Restrictions".
NOTE 3: In this release of the 3GPP specification the Correlation ID and SIPTO Correlation ID is set equal to the user plane PDN GW TEID (GTP-based S5) or GRE key (PMIP-based S5) which is specified in clause 5.3.2.1 and clause 5.10.2.
If the UE included support for restriction of use of Enhanced Coverage, the MME sends Enhanced Coverage Restricted parameter to the eNodeB in the S1-AP message.
The MME shall only request to establish Emergency EPS Bearer if the UE is not allowed to access the cell where the UE initiated the service request procedure due to CSG access restriction.
If the MME receives multiple TAIs from E-UTRAN in step 2 and determines that some, but not all, TAIs in the received list of TAIs are forbidden by subscription or by operator policy, the MME shall include the forbidden TAI(s) as in the Service Reject message.
If the Service Request is performed via a hybrid cell, CSG Membership Indication indicating whether the UE is a CSG member shall be included in the S1-AP message from the MME to the RAN. Based on this information, the RAN can perform differentiated treatment for CSG and non-CSG members.
If RACS is supported and MME has UE Radio Capability ID in UE context, valid for the PLMN the UE is currently in, it signals the UE Radio Capability ID to the eNodeB as defined in clause 5.11.3a. If the eNodeB does not have mapping between the specific UE Radio Capability ID and the UE radio capabilities, it shall use the procedure described in TS 36.413 [36] to retrieve the mapping from the Core Network.
If supported by the MME and if the UE is subscribed to receive time reference information, then the MME provides a Time Reference Information Distribution indication to the eNodeB.
5. The eNodeB performs the radio bearer establishment procedure. The user plane security is established at this step, which is described in detail in TS 36.300 [5]. When the user plane radio bearers are setup. EPS bearer state synchronization is performed between the UE and the network, i.e. the UE shall locally remove any EPS bearer for which no radio bearers are setup and, if the radio bearer for a default EPS bearer is not established, the UE shall locally deactivate all EPS bearers associated to that default EPS bearer.
6. The uplink data from the UE can now be forwarded by eNodeB to the Serving GW. The eNodeB sends the uplink data to the Serving GW address and TEID provided in the step 4. The Serving GW forwards the uplink data to the PDN GW.
7. The eNodeB sends an S1-AP message Initial Context Setup Complete (eNodeB address, List of accepted EPS bearers, List of rejected EPS bearers, S1 TEID(s) (DL)) to the MME. This step is described in detail in TS 36.300 [5]. If the Correlation ID or SIPTO Correlation ID is included in step 4, the eNodeB shall use the included information to establish a direct user plane path to the L-GW and forward uplink data for Local IP Access or SIPTO at the Local Network with L-GW function collocated with the (H)eNB accordingly.
8. The MME sends a Modify Bearer Request message (eNodeB address, S1 TEID(s) (DL) for the accepted EPS bearers, Delay Downlink Packet Notification Request, RAT Type, MO Exception data counter) per PDN connection to the Serving GW. If the Serving GW supports Modify Access Bearers Request procedure and if there is no need for the Serving GW to send the signalling to the PDN GW, the MME may send Modify Access Bearers Request (eNodeB address(es) and TEIDs for downlink user plane for the accepted EPS bearers, Delay Downlink Packet Notification Request) per UE to the Serving GW to optimise the signalling. The Serving GW is now able to transmit downlink data towards the UE. The usage of the Delay Downlink Packet Notification Request Information Element is specified in clause 5.3.4.2 below. If the PDN GW requested UE's location and/or User CSG information and the UE's location and/or User CSG information has changed, the MME also includes the User Location Information IE and/or User CSG Information IE in this message. If ISR is activated or if the Serving Network IE has changed compared to the last reported Serving Network IE then the MME also includes the Serving Network IE in this message. If the UE Time Zone has changed compared to the last reported UE Time Zone then the MME shall include the UE Time Zone IE in this message. If the internal flag Pending Network Initiated PDN Connection Signalling is set, the MME indicates UE available for end to end signalling in the Modify Bearer Request message and reset the flag.
The MME only includes the MO Exception data counter if the RRC establishment cause is set to "MO exception data" and the UE is accessing via the NB-IoT RAT. The MME maintains the MO Exception Data Counter for Serving PLMN Rate Control purposes (see clause 4.7.7.2). The MME may immediately send the MO Exception Data Counter to the Serving GW. Alternatively, in order to reduce signalling, the MME may send the MO Exception Data Counter to the Serving GW as described in TS 29.274 [43].
The MME and the Serving GW clears the DL Data Buffer Expiration Time in their UE contexts if it was set, to remember that any DL data buffered for a UE using power saving functions has been delivered and to avoid any unnecessary user plane setup in conjunction with a later TAU.
If a default EPS bearer is not accepted by the eNodeB, all the EPS bearers associated to that default bearer shall be treated as non-accepted bearers. The MME releases the non-accepted bearers by triggering the bearer release procedure as specified in clause 5.4.4.2. If the Serving GW receives a DL packet for a non-accepted bearer, the Serving GW drops the DL packet and does not send a Downlink Data Notification to the MME.
9. If the RAT Type has changed compared to the last reported RAT Type or if the UE's Location and/or Info IEs and/or UE Time Zone and/or if ISR is not activated and Serving Network id and/or the indication UE available for end to end signalling are present in step 8, the Serving GW shall send the Modify Bearer Request message (RAT Type, MO Exception data counter) per PDN connection to the PDN GW. User Location Information IE and/or User CSG Information IE and/or Serving Network IE and/or UE Time Zone and/or the indication UE available for end to end signalling are also included if they are present in step 8.
If the Modify Bearer Request message is not sent because of above reasons and the PDN GW charging is paused, then the SGW shall send a Modify Bearer Request message with PDN Charging Pause Stop Indication to inform the PDN GW that the charging is no longer paused. Other IEs are not included in this message.
If the Modify Bearer Request message is not sent because of above reasons but the MME indicated the MO Exception data counter, then the Serving Gateway should notify the PDN GW that this RRC establishment cause has been used by the MO Exception Data Counter (see TS 29.274 [43]). The Serving GW indicates each use of this RRC establishment cause by the related counter on its CDR.
10. If dynamic PCC is deployed, the PDN GW interacts with the PCRF to get the PCC rule(s) according to the RAT Type by means of a PCEF initiated IP‑CAN Session Modification procedure as defined in TS 23.203 [6]. If dynamic PCC is not deployed, the PDN GW may apply local QoS policy.
The PDN GW indicates each use of the RRC establishment cause "MO Exception Data" by the related counter on its CDR.
11. The PDN GW sends the Modify Bearer Response to the Serving GW.
12. The Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic) to the MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message. If the Serving GW cannot serve the MME Request in the Modify Access Bearers Request message without S5/S8 signalling other than to unpause charging in the PDN GW or without corresponding Gxc signalling when PMIP is used over the S5/S8 interface, it shall respond to the MME with indicating that the modifications are not limited to S1-U bearers, and the MME shall repeat its request using a Modify Bearer Request message per PDN connection.
If SIPTO at the Local Network is active for a PDN connection with stand-alone GW deployment and the Local Home Network ID for stand-alone accessed by the UE differs from the Local Home Network ID where the UE initiated the SIPTO@LN PDN Connection, the MME shall request disconnection of the SIPTO at the local network PDN connection(s) with the "reactivation requested" cause value according to clause 5.10.3. If the UE has no other PDN connection, the MME initiated "explicit detach with reattach required" procedure according to clause 5.3.8.3.
If SIPTO at the Local Network is active for a PDN connection with collocated LGW deployment and the L-GW CN address of the cell accessed by the UE differs from the L-GW CN address of the cell where the UE initiated the SIPTO at the Local Network PDN Connection, the MME shall request disconnection of the SIPTO at the local network PDN connection(s) with the "reactivation requested" cause value according to clause 5.10.3. If the UE has no other PDN connection, the MME initiated "explicit detach with reattach required" procedure according to clause 5.3.8.3.
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495b59b986f98d41912141cabbec196e
|
23.401
|
5.3.4.2 Handling of abnormal conditions in UE triggered Service Request
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Under certain conditions, the current UE triggered Service Request procedure can cause unnecessary Downlink Packet Notification messages which increase the load of the MME.
This can occur when uplink data sent in step 6 causes a response on the downlink which arrives at the Serving GW before the Modify Bearer Request message, step 8. This data cannot be forwarded from the Serving GW to the eNodeB and hence it triggers a Downlink Data Notification message.
If the MME receives a Downlink Data Notification after step 2 and before step 9, the MME shall not send S1 interface paging messages. However, across all the UEs on that MME, the MME shall monitor the rate at which these events occur. If the rate becomes significant (as configured by the operator) and the MME's load exceeds an operator configured value, the MME shall indicate "Delay Downlink Packet Notification Request" with parameter D to the Serving Gateway, where D is the requested delay given as an integer multiple of 50 ms, or zero. The Serving GW then uses this delay in between receiving downlink data and sending the Downlink Data Notification message.
NOTE 1: A low rate of reception of Downlink Data Notifications between steps 2 and 9 should be considered a normal circumstance, e.g. due to the chance that a UE Terminating call/session is initiated at roughly the same time as the UE triggered Service Request procedure.
NOTE 2: It is recommended that this rate is determined over 60 second periods.
The MME shall use the step 8 Modify Access Bearers Request or Modify Bearer Request of the UE initiated Service Request procedure to indicate "Delay Downlink Packet Notification Request" to the Serving GW.
To determine the amount of delay requested by a given MME, the Serving GW either uses the last Modify Access Bearers Request or Modify Bearer Request message which is part of a Service Request procedure, or, just uses one of the Service Request procedure's Modify Access Bearers Request or Modify Bearer Request messages received within the preceding 30 seconds. The latter mode of operation shall be taken into account when implementing the MME.
The MME is responsible for setting the value of D. The exact algorithm for setting the value is implementation dependent, two examples are given below to serve as a guideline:
EXAMPLE 1: The MME adaptively increases the value of D when the rate of unnecessary Downlink Data Notifications is too high; and correspondingly it decreases the value when the rate is not too high.
EXAMPLE 2: When unnecessary Downlink Data Notifications arrive, the MME measures the average time from the reception of the unnecessary Downlink Data Notification to the reception of the Modify Access Bearers Request or Modify Bearer Response from the Serving GW in the same UE triggered Service Request Procedure. The value of D is calculated from this average, by adding a safety margin.
Normally, upon receipt of a downlink data packet for which there is no DL-TEID of the S1 user plane tunnel, the S‑GW shall send the Downlink Data Notification message to the MME without delay.
If the S‑GW determines from the last Modify Access Bearers Request or Modify Bearer Request message which is part of a Service Request procedure that a given MME request delaying of the Downlink Packet Notification by a delay of D, it shall (only for UEs of that MME) buffer the Downlink Data for a period D. If the DL-TEID and eNodeB address for the UE is received before the expiry of the timer, the timer shall be cancelled and the Network triggered Service Request procedure is finished without sending the Downlink Data Notification message to the MME, i.e. DL data are sent to the UE. Otherwise the Downlink Data Notification message is sent to the MME when the timer expires.
NOTE 3: The above procedure and indicated time values are intended to ensure that the procedure is "stable"; avoids RAN impacts; and, that the negative impacts of shortening the DRX interval on UE battery life are avoided.
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495b59b986f98d41912141cabbec196e
|
23.401
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5.3.4.3 Network Triggered Service Request
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Figure 5.3.4.3-1: Network triggered Service Request procedure
If the MME needs to signal with the UE that is in ECM-IDLE state, e.g. to perform the MME/HSS-initiated detach procedure for the ECM-IDLE mode UE or the S‑GW receives control signalling (e.g. Create Bearer Request or Update Bearer Request), the MME starts network triggered service request procedure from step 3a in the Network Triggered Service request procedure.
If the MME wishes to use the Control Plane CIoT EPS Optimisation for mobile terminating services, then the procedure of clause 5.3.4B.3 is used to replace the procedure of this clause.
If ISR is activated, when the Serving GW receives a Create Bearer Request or Update Bearer Request for a UE, and the S‑GW does not have a downlink S1-U and the SGSN has notified the Serving GW that the UE has moved to PMM-IDLE or STANDBY state, the Serving GW buffers signalling messages and sends a Downlink Data Notification to trigger the MME and SGSN to page the UE. If the Serving GW, while waiting for the user plane to be established, is triggered to send a second Downlink Data Notification with higher priority (i.e. ARP priority level) than the first Downlink Data Notification was sent with, the Serving GW sends a new Downlink Data Notification message indicating the higher priority to the MME. If the Serving GW receives additional downlink signalling messages for a bearer with same or lower priority than the first Downlink Data Notification was sent for or if the Serving GW has sent the second Downlink Data Notification message indicating the higher priority and receives additional downlink signalling messages for this UE, the Serving GW buffers these downlink signalling messages and does not send a new Downlink Data Notification. The S‑GW will be notified about the current RAT type based on the UE triggered service request procedure. The S‑GW will go on executing the dedicated bearer activation or dedicated bearer modification procedure, i.e. send the corresponding buffered signalling to MME or SGSN which UE resides in now and inform the current RAT type to the PDN GW if the RAT type has been changed compared to the last reported RAT Type. If dynamic PCC is deployed, the current RAT type information shall also be conveyed from the PDN GW to the PCRF. If the PCRF response leads to an EPS bearer modification the PDN GW should initiate a bearer update procedure as specified in clause 5.4.2.1 below.
When the Serving GW sends a Downlink Data Notification, it shall include both EPS Bearer ID and ARP. If the Downlink Data Notification is triggered by the arrival of downlink data packets at the Serving GW, the Serving GW shall include the EPS Bearer ID and ARP associated with the bearer on which the downlink data packet was received. If the Downlink Data Notification is triggered by the arrival of control signalling, the Serving GW shall include the EPS Bearer ID and ARP if present in the control signalling. If the ARP is not present in the control signalling, the Serving GW shall include the ARP in the stored EPS bearer context.
If a LIPA PDN connection exists, when the L-GW receives the downlink data for a UE that is in ECM-IDLE state, the L-GW sends the first downlink user packet to Serving GW and buffers all other downlink user packets. The Serving GW will trigger the MME to page the UE.
1. When the Serving GW receives a downlink data packet/control signalling for a UE known as not user plane connected (i.e. the S‑GW context data indicates no downlink user plane TEID), it buffers the downlink data packet and identifies which MME or SGSN is serving that UE.
If that MME has requested the Serving GW to throttle downlink low priority traffic and if the downlink data packet is received on a low priority bearer to be throttled (see clause 4.3.7.4.1a), the SGW drops the downlink data. The steps below are not executed.
If that MME has requested the S‑GW to delay sending the Downlink Data Notification (see clause 5.3.4.2 on "Handling of abnormal conditions in UE triggered Service Request"), the Serving GW buffers the downlink data and waits until the timer expires before continuing with step 2. If the DL-TEID and eNodeB address for that UE is received before the expiry of the timer, the timer shall be cancelled and the Network triggered Service Request procedure is finished without executing the steps below, i.e. DL data are sent to the UE.
If the Serving GW receives additional downlink data packets/control signalling for this UE before the expiry of the timer, the Serving GW does not restart this timer.
2. The Serving GW sends a Downlink Data Notification message (ARP, EPS Bearer ID, Paging Policy Indication) to the MME and SGSN nodes for which it has control plane connectivity for the given UE. The ARP and EPS Bearer ID are always set in Downlink Data Notification. The MME and SGSN respond to the S‑GW with a Downlink Data Notification Ack message. When supporting Paging Policy Differentiation, the Serving GW indicates in the message the Paging Policy Indication related to the downlink data that triggered the Downlink Data Notification message, as described in clause 4.9.
NOTE 1: The ARP, the EPS Bearer ID and optionally the Paging Policy Indication are sent to the SGSN as well as MME, but the usage of these parameters at SGSN is not specified in this release of the specification.
An MME and an SGSN that detects that the UE is in a power saving state (e.g. Power Saving Mode or extended idle mode DRX) or is only in coverage intermittently (e.g. the UE is using satellite access with a known maximum interval between coverage occasions) and cannot be reached by paging at the moment, shall invoke extended buffering depending on operator configuration, except for cases described in next paragraphs. MME/SGSN derives the expected time before radio bearers can be established to the UE. The MME/SGSN then indicates DL Buffering Requested to the Serving GW in the Downlink Data Notification Ack message and includes a DL Buffering Duration time and optionally a DL Buffering Suggested Packet Count. The MME/SGSN stores a new value for the DL Data Buffer Expiration Time in the MM context for the UE based on the DL Buffering Duration time and skips the remaining steps of this procedure. The DL Data Buffer Expiration Time is used for UEs using power saving state or if the UE is only in coverage intermittently (e.g. the UE is using satellite access with a known maximum interval between coverage occasions) and indicates that there are buffered data in the Serving GW and that the user plane setup procedure is needed when the UE makes signalling with the network. When the DL Data Buffer Expiration Time has expired, the MME/SGSN considers no DL data to be buffered and no indications of Buffered DL Data Waiting are sent during context transfers at TAU procedures.
If there is a "Availability after DDN Failure" monitoring event configured for the UE in the MME/SGSN, the MME/SGSN does not invoke extended buffering. Instead, the MME/SGSN sets the Notify-on-available-after-DDN-failure flag to remember to send an "Availability after DDN Failure" notification when the UE becomes available. If there is a "UE Reachability" monitoring event configured for the UE in the MME/SGSN, the MME/SGSN should not need to invoke extended buffering.
NOTE 2: When "Availability after DDN failure" and "UE reachability" monitoring events are used for a UE, the application server is assumed to send data when the UE is reachable or about to become reachable, hence no extended buffering is needed. If there are multiple application servers, the event notifications and extended buffering may be needed simultaneously. It is assumed this is handled through additional information based on SLA as described in the next paragraph.
The MME/SGSN may use additional information based on a SLA with the MTC user for when to invoke extended buffering, e.g. only invoke it for a certain APN, do not invoke it for certain subscribers, invoke extended buffering in conjunction with "Availability after DDN failure" and "UE reachability" monitoring events, etc.
A Serving GW that receives a DL Buffering Requested indication in a Downlink Data Notification Ack message stores a new value for the DL Data Buffer Expiration Time based on the DL Buffering Duration time and does not send any additional Downlink Data Notification if subsequent downlink data packets are received in the Serving GW before the buffer time DL Data Buffer Expiration Time has expired for the UE.
If the Serving GW, while waiting for the user plane to be established, is triggered to send a second Downlink Data Notification for a bearer with higher priority (i.e. ARP priority level) than the first Downlink Data Notification was sent for, the SGW sends a new Downlink Data Notification message indicating the higher priority to the MME. If the Serving GW receives additional downlink data packets for a bearer with same or lower priority than the first Downlink Data Notification was sent for or if the Serving GW has sent the second Downlink Data Notification message indicating the higher priority and receives additional downlink data packets for this UE, the Serving GW buffers these downlink data packets and does not send a new Downlink Data Notification.
If the Serving GW, while waiting for the user plane to be established, receives a Modify Bearer Request message from MME or SGSN other than the one it sent a Downlink Data Notification message to, the Serving GW re-sends the Downlink Data Notification message only to the new MME or SGSN from which it received the Modify Bearer Request message even if ISR is active.
If the Tracking Area Update procedure with MME change or the Routing Area Update procedure is in progress when the old MME receives a Downlink Data Notification message, the old MME may reject a Downlink Data Notification message with an indication that the Downlink Data Notification message has been temporarily rejected.
Similarly, if the Routing Area Update procedure with SGSN change or the Tracking Area Update procedure is in progress when the old SGSN receives a Downlink Data Notification message, the old SGSN may reject a Downlink Data Notification message with an indication that the Downlink Data Notification message has been temporarily rejected.
If the MME holds stored Paging Restriction Information (see clause 4.3.33.6) for the UE that restricts the Downlink Data from causing paging, the MME sends Downlink Data Notification Ack message with an indication that the Downlink Data Notification message has been temporarily rejected.
Upon reception of a Downlink Data Notification Ack message with an indication that the Downlink Data Notification message has been temporarily rejected and if the Downlink Data Notification is triggered by the arrival of downlink data packets at the Serving GW, the Serving GW may start a locally configured guard timer and buffers all downlink user packets received to the given UE and waits for a Modify Bearer Request message to come. Upon reception of a Modify Bearer Request message, the Serving GW re-sends the Downlink Data Notification message only to the new MME or SGSN from which it received the Modify Bearer Request message even if ISR is active. Otherwise the Serving GW releases buffered downlink user packets at expiry of the guard timer or receiving the Delete Session Request message from MME/SGSN.
Upon reception of a Downlink Data Notification Ack message with an indication that the Downlink Data Notification message has been temporarily rejected and if the Downlink Data Notification is triggered by the arrival of signalling messages at the Serving GW, the Serving GW may reject the PDN GW initiated EPS bearer(s) request with the same indication that the request has been temporarily rejected. Upon reception of a rejection for an EPS bearer(s) PDN GW initiated procedure with an indication that the request has been temporarily rejected, the PDN GW may start a locally configured guard timer. The PDN GW may re-attempt, up to a pre-configured number of times, when either it detects the UE accesses via a new SGW or at expiry of the guard timer.
3a. If the UE is registered in the MME and considered reachable for paging, the MME sends a Paging message (NAS ID for paging, TAI(s), UE identity based DRX index, Paging DRX length, list of CSG IDs for paging, Paging Priority indication, Enhanced Coverage Restricted, CE mode B Restricted, Assistance Data for Recommended Cells, WUS Assistance Information, Voice Service Indication) to each eNodeB belonging to the tracking area(s) in which the UE is registered. The step is described in detail in TS 36.300 [5] and TS 36.413 [36]. Steps 3-4 are omitted if the MME already has a signalling connection over S1-MME towards the UE but the S1-U tunnel has not yet been established.
If the MME holds stored Paging Restriction Information for the UE, the MME may block the paging for this UE, based on local policy and the stored Paging Restriction Information (see clause 4.3.33.6).
If extended idle mode DRX is enabled for the UE, the MME pages the UE just before the occurrence of the UE's next paging occasion, which is determined as described in TS 23.682 [74].
NOTE 3: Steps 3a and 4a are performed also when the UE and the network support User Plane CIoT EPS Optimisation and the previous RRC connection has been suspended.
Paging priority indication is included only:
- if the MME receives a Downlink Data Notification or Create/Update Bearer Request with an ARP priority level associated with MPS or other priority services, as configured by the operator.
- One Paging Priority level can be used for multiple ARP priority level values. The mapping of ARP priority level values to Paging Priority level (or levels) is configured by operator policy.
During a congestion situation the eNodeB may prioritise the paging of UEs according to the Paging Priority indications.
NOTE 4: Paging priority indication is also included for MT-SMS related requests from the SMS-GMSC as per TS 23.272 [58].
If the MME, while waiting for a UE response to the Paging Request message sent without Paging Priority indication, receives an Update Bearer Request, Create Bearer Request or Downlink Data Notification, any of which indicates an ARP priority level associated with MPS or other priority services, as configured by the operator, the MME shall send another paging message with the suitable Paging Priority.
When the MME is configured to support CSG paging optimisation in the CN, the MME should avoid sending Paging messages to those eNodeB(s) with CSG cells for which the UE does not have a CSG subscription. When the MME is configured to support CSG paging optimisation in the HeNB Subsystem, the list of CSG IDs for paging is included in the Paging message. For CSG paging optimisation, the CSG IDs of expired CSG subscriptions and valid CSG subscriptions are both included in the list. If the UE has emergency bearer service the MME shall not perform the CSG paging optimisation.
NOTE 5: An expired CSG subscription indicates that the UE is not allowed service in the CSG. However, since the removal of the CSG from the UE is pending, it is possible the UE will camp on that CSG and therefore the UE is still paged for the CSG.
NOTE 6: The eNodeB reports to the MME the CSG ID supported. For More detail of this procedure refer to TS 36.413 [36].
When the MME supports SIPTO at Local Network and LIPA paging for traffic arriving on the PDN connection with L-GW function collocated with the (H)eNB the MME should only page this (H)eNB to avoid sending Paging messages to eNodeB(s) that are not handling this specific PDN connection.
Paging strategies may be configured in the MME for different combinations of APN, Paging Policy Indication from SGW when available (see clause 4.9) and other EPS bearer context information e.g. QCI. APN and any EPS bearer context information are identified by EPS bearer ID received in Downlink Data Notification. Paging strategies may include:
- paging retransmission scheme (e.g. how frequently the paging is repeated or with what time interval);
- determining whether to send the Paging message to the eNodeBs during certain MME high load conditions;
- whether to apply sub-area based paging (e.g. first page in the last known ECGI or TA and retransmission in all registered TAs).
If extended idle mode DRX was enabled in the UE, the MME may additionally take into account the Paging Time Window length for paging retransmission schemes.
NOTE 7: The Paging priority in the Paging message is set based on priority level of the ARP IE received in Downlink Data Notification or Create/Update Bearer Request message and is independent from any paging strategy.
The MME and the E-UTRAN may support further paging optimisations in order to reduce the signalling load and the network resources used to successfully page a UE by one or several following means:
- by the MME implementing specific paging strategies (e.g. the S1 Paging message is sent to the eNodeB that served the UE last);
- by the MME considering Information On Recommended Cells And eNodeBs provided by the E-UTRAN at transition to ECM IDLE. The MME takes the eNodeB related part of this information into account to determine the eNodeBs to be paged, and provides the information on recommended cells within the S1 Paging message to each of these eNodeBs;
- by the E-UTRAN considering the Paging Attempt Count Information provided by the MME at paging.
When implementing such optimisations/strategies, the MME shall take into account any PSM active timer and the DRX interval for the UE.
The MME shall ensure that the correct Paging DRX Length is provided based on the accepted UE Specific DRX of the current RAT.
If the UE Radio Capability for Paging Information is available in the MME for the RAT corresponding to the TAI(s) in the S1 Paging message, the MME shall add the UE Radio Capability for Paging Information for that RAT in the S1 Paging message to the eNodeB.
If the Information On Recommended Cells And eNodeBs For Paging is available in the MME, the MME shall take that information into account to determine the eNodeBs for paging and, when paging an eNodeB, the MME may transparently convey the information on recommended cells to the eNodeB.
The MME may include in the S1AP Paging message(s) the paging attempt count information. The paging attempt count information shall be the same for all eNodeBs selected by the MME for paging.
The MME may include in the S1AP Paging message(s) the WUS Assistance Information, if available.
If the MME has Information for Enhanced Coverage stored and Enhanced Coverage is not restricted then the MME shall include Information for Enhanced Coverage in the Paging message for all eNodeBs selected by the MME for paging. For including the Enhanced Coverage Restricted parameter in the paging message, see clause 4.3.28.
For including the CE mode B Restricted parameter in the Paging message, see clause 4.3.27a.
If the network supports the Paging Cause Indication for Voice Service feature if the UE context in the MME indicates that the UE supports the Paging Cause for Voice Service feature, the MME should provide the Voice Service Indication in the S1AP Paging message only when the MME detects that the downlink data which triggers the Paging message is related to voice service, as specified in clause 4.3.
3b. If the UE is registered in the SGSN, the SGSN sends paging messages to RNC/BSS, which is described in detail in TS 23.060 [7].
4a. If eNodeBs receive paging messages from the MME, the UE is paged by the eNodeBs. The step is described in detail in TS 36.300 [5] and TS 36.304 [34]. If the WUS Assistance Information is included in Step 3a, the eNodeB takes it into account when paging the UE (see TS 36.300 [5]).
If the UE and eNodeB support WUS, then:
- if the S1-AP Paging message contains the Assistance Data for Recommended Cells IE (see TS 36.413 [36]), the eNodeB shall only broadcast the UE's Wake Up Signal in the last used cell;
- else (i.e. the Assistance Data for Recommended Cells IE is not included in the S1-AP Paging message) the eNodeB should not broadcast the UE's Wake Up Signal.
If the Voice Service Indication is included in step 3a, the eNodeB supporting the Paging Cause Indication for Voice Service feature should include the Voice Service Indication in the paging message to the UE, see TS 36.300 [5].
4b. If RNC/BSS nodes receive paging messages from the SGSN the UE is paged by the RNSC/BSS, which is described in detail in TS 23.060 [7].
5. When UE is in the ECM-IDLE state, upon reception of paging indication in E-UTRAN access, the UE initiates the UE triggered Service Request procedure (clause 5.3.4.1) or, if the UE is enabled to use User Plane CIoT EPS Optimisation and there is suspended access stratum context stored in the UE, the UE initiates the Connection Resume procedure (clause 5.3.5A). If the MME already has a signalling connection over S1-MME towards the UE but the S1-U tunnel has not yet been established, then the messages sequence performed start from the step when MME establishes the bearer(s).
If the Multi-USIM UE is in ECM-IDLE state, upon reception of paging indication in E-UTRAN access and if the UE decides not to accept the paging, the UE attempts to send a Reject Paging Indication via the UE Triggered Service Request procedure (clause 5.3.4.1) unless it is unable to do so, e.g. due to UE implementation constraints.
Upon reception of paging indication in UTRAN or GERAN access, the MS shall respond in respective access as specified TS 24.008 [47] and the SGSN shall notify the S‑GW.
The MME and/or SGSN supervises the paging procedure with a timer. If the MME and/or SGSN receives no response from the UE to the Paging Request message, it may repeat the paging according to any applicable paging strategy described in step 2.
If the MME and/or SGSN receives no response from the UE after this paging repetition procedure, it shall use the Downlink Data Notification Reject message to notify the Serving GW about the paging failure, if paging was triggered by a Downlink Data Notification message, unless the MME or SGSN is aware of an ongoing MM procedure that prevents the UE from responding, i.e. the MME or SGSN received a Context Request message indicating that the UE performs TAU or RAU procedure with another MME or SGSN. If paging was triggered by control signalling from the Serving GW and if the MME or SGSN receives no response from the UE after this paging repetition procedure, the MME or SGSN shall reject that control signalling. When a Downlink Data Notification Reject message is received, if ISR is not activated, the Serving GW deletes the buffered packet(s). If ISR is activated and the Serving GW receives Downlink Data Notification Reject message from both SGSN and MME, the Serving GW deletes the buffered packet(s) or rejects the control signalling which triggers the Service Request procedure. The Serving GW may invoke the procedure PDN GW Pause of Charging (clause 5.3.6A) if UE is in ECM IDLE and the PDN GW has enabled "PDN charging pause" feature.
NOTE 8: The Serving GW may initiate the procedure PDN GW Pause of Charging at any time before step 5 if the UE is in ECM IDLE and the PDN GW has indicated that the feature is enabled for this PDN. See clause 5.3.6A.
5a. After receiving the Reject Paging Indication, the MME uses the Downlink Data Notification Failure Indication message to notify the Serving GW that the UE rejected the page and no user plane radio bearers will be established. The UE remains reachable for future paging attempts based on stored (if any) Paging Restriction Information.
6a. If ISR is activated and paging response is received in E‑UTRAN access the Serving GW sends a "Stop Paging" message to the SGSN.
6b. If ISR is activated and paging response is received in UTRAN or GERAN access the Serving GW sends a "Stop Paging" message to the MME.
The Serving GW transmits downlink data towards the UE via the RAT which performed the Service Request procedure.
For a LIPA PDN connection, after the UE enters connected mode, the packets buffered in the L-GW are forwarded to the HeNB on the direct path. If the UE enters connected mode at a different cell than the one where the L-GW is collocated, the MME shall deactivate the LIPA PDN connection as defined in clause 5.3.4.1 step 2.
If the network triggered service request fails due to no response from the UE, then MME and/or SGSN may be based on operator policy initiate the Dedicated Bearer Deactivation procedure for preserved GBR bearers. For details, see clause 5.4.4.2 for MME and TS 23.060 [7] for SGSN.
5.3.4A Connection Suspend procedure
This procedure is used by the network to suspend the connection if the UE and the network support User Plane CIoT EPS Optimisation (see TS 36.300 [5]).
Figure 5.3.4A-1: eNodeB initiated Connection Suspend procedure
1. The eNodeB initiates the Connection Suspend procedure to the MME, see TS 36.413 [36]. The eNodeB indicates to the MME that the UE's RRC connection is to be suspended upon which MME enters ECM-IDLE. Data related to the S1AP association, UE Context and bearer context, necessary to resume the connection is kept in the eNodeB, UE and the MME.
If the eNodeB supports WUS, the eNodeB should include the Information On Recommended Cells And eNodeBs For Paging in the S1 UE Context Suspend Request message; otherwise, the eNodeB may include the Information On Recommended Cells And eNodeBs For Paging in the S1 UE Context Suspend Request message. If available, the MME shall store this information to be used when paging the UE.
The eNodeB includes Information for Enhanced Coverage, if available, in the S1 UE Context Suspend Request message.
If the PLMN has configured secondary RAT reporting and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included.
If Dual Connectivity was activated by that eNodeB at the time of the Connection Suspend or earlier by that eNodeB, the eNodeB shall include the last known PSCell ID and the time elapsed since the Dual Connectivity was released.
If Service Gap Control is being applied to the UE (see clause 4.3.17.9) and the Service Gap timer is not already running, the Service Gap timer shall be started in the MME when entering ECM-IDLE, unless the connection was initiated after a paging of an MT event, after a TAU procedure without any active flag or signalling active flag set or after a TAU procedure for network access for regulatory prioritized services like Emergency services or exception reporting.
1a-d. If the eNodeB provided Secondary RAT usage data in step 1 and if PGW secondary RAT usage data reporting is active, the MME initiates the Secondary RAT usage data reporting procedure in clause 5.7A.3 as illustrated in figure 5.7A.3-2.
2. The MME sends a Release Access Bearers Request (Secondary RAT usage data) message to the Serving GW that requests the release of all S1-U bearers for the UE. If Secondary RAT usage data was received in step 1, Secondary RAT usage data is included in this message. The message indicates that the SGW is the target for the reporting.
3. The Serving GW releases all eNodeB related information (address and downlink TEIDs) for the UE and responds with a Release Access Bearers Response message to the MME. Other elements of the UE's Serving GW context are not affected. If downlink packets arrive for the UE, the Serving GW starts buffering downlink packets received for the UE and initiating the "Network Triggered Service Request" procedure, described in clause 5.3.4.3.
NOTE: Based on operator policy any received Indication of "Abnormal Release of Radio Link" may be used by Serving GW in subsequent decisions to trigger PDN charging pause if the feature has been enabled on that PDN.
The Serving GW informs the MME in the Release Access Bearer Response message about release of S1-U bearers.
4. The MME sends an S1AP: UE Context Suspend Response message to the eNodeB to successfully terminate the Connection Suspend procedure initiated by the eNodeB, see TS 36.413 [36].
5. The eNodeB sends RRC message to suspend the RRC Connection towards the UE, see TS 36.300 [5]).
If Service Gap Control is being applied for the UE (see clause 4.3.17.9) and the Service Gap timer is not already running, the Service Gap timer shall be started in the UE when entering ECM-IDLE, unless the connection was initiated as a response to paging of an MT event, after a TAU procedure without any active flag or signalling active flag set or after a TAU procedure for network access for regulatory prioritized services like Emergency services or exception reporting.
5.3.4B Data Transport in Control Plane CIoT EPS Optimisation
5.3.4B.1 General
If the UE and MME use the Control Plane CIoT EPS Optimisation, they can transfer data in NAS PDUs including the EPS Bearer Identity of the PDN connection they relate to, for which there is no S1-U bearers established (i.e. when an S1-U bearer is established the UE shall use S1-U to transfer data PDUs). All PDN types are supported. If the UE and the MME support Control Plane CIoT EPS Optimisation, then for SMS transfer and EPC Mobile Originated Location Request (EPC-MO-LR) or EPC Mobile Terminated Location Request (EPC-MT-LR) the Service Request procedures defined in clause 5.3.4 are not used for MO and MT SMS or for EPC-MO-LR and EPC-MT-LR, but instead UE and MME shall be using the Data Transport in Control Plane CIoT EPS Optimisation.
This is accomplished by using the NAS transport capabilities of RRC and S1-AP protocols and the data transport of GTP-u tunnels between MME and S-GW and between S-GW and P-GW, or if a Non-IP connection is provided by via the MME with the SCEF, then data transfer occurs as indicated in TS 23.682 [74].
For IP data, the UE and MME may perform header compression based on ROHC framework IETF RFC 5795 [77]. For uplink IP data, UE implements ROHC compressor, and MME implements the decompressor. For downlink IP data, MME implements the ROHC compressor, and UE implements the decompressor. The uplink and downlink ROHC channels are bound by UE and MME to support feedback. The configurations for the header compression are established during the PDN connection establishment procedure.
To minimise potential conflicts between NAS signalling PDUs and NAS Data PDUs, the MME should complete any security related procedures (e.g. Authentication, Security Mode Command, GUTI reallocation) before alerting the HSS, MSC or SGW of the UE's entry into ECM-CONNECTED state, and before commencing downlink transfer of NAS Data PDUs. The priority handling between the EMM/ESM NAS signalling PDUs and NAS Data PDUs is specified in TS 24.301 [46].
5.3.4B.2 Mobile Originated Data Transport in Control Plane CIoT EPS Optimisation with P-GW connectivity
Figure 5.3.4B.2-1: MO Data transport in NAS PDU
0. The UE is ECM-IDLE.
1. The UE establishes a RRC connection or sends the RRCEarlyDataRequest message as defined in TS 36.300 [5] and sends as part of it an integrity protected NAS PDU. The NAS PDU carries the EPS Bearer ID and encrypted Uplink Data. For IP PDN type PDN connections configured to support Header Compression, the UE shall apply header compression before encapsulating data into the NAS message. The UE may also indicate in a NAS Release Assistance Information in the NAS PDU whether no further Uplink or Downlink Data transmissions are expected, or only a single Downlink data transmission (e.g. Acknowledgement or response to Uplink data) subsequent to this Uplink Data transmission is expected.
1b. In the NB-IoT case, the eNodeB, based on configuration, may retrieve the EPS negotiated QoS profile from the MME, if not previously retrieved. The MME Code within the S-TMSI in the RRCConnectionRequest message is used to identify the MME. In the case of network sharing, the MME Codes shall be unique within the area of overlapping MME pools of the participating operators. The eNodeB may apply prioritisation between requests from different UEs before triggering step 2 and throughout the RRC connection. The eNodeB may retrieve additional parameters (e.g., UE Radio Capabilities - see TS 36.413 [36]).
2. The NAS PDU sent in step 1 is relayed to the MME by the eNodeB using a S1-AP Initial UE message. If the RRCEarlyDataRequest message was received in step 1, the eNodeB includes the "EDT Session" indication in the S1-AP Initial UE message.
To assist Location Services, the eNodeB indicates the UE's Coverage Level to the MME.
If the NAS Release Assistance Information is received from the UE it overrides the Traffic Profile (see TS 23.682 [74]) and the MME does not send the Traffic Profile to the eNodeB.
In the case of satellite access over NB-IoT, the eNB may request the MME to provide the Coarse Location information to the eNB, as described in TS 36.300 [5] and TS 36.413 [36].
3. If there is a Service Gap timer running in the MME MM Context for the UE and the MME is not waiting for a MT paging response from the UE, the MME rejects the request by discarding the NAS data PDU and sending a Service Reject message to the UE with an appropriate cause. The MME may also provide UE with a Mobility Management Back-off timer set to the remaining value of Service Gap timer, followed by executing step 15.
The MME checks the integrity of the incoming NAS PDU and decrypts the data it contains. When the ROHC is configured to be used, the MME shall decompress the IP header if header compression applies to the PDN connection.
The MME performs (and the UE responds to) any EMM or ESM procedures if necessary, e.g. the security related procedures. Steps 4 to 9 can continue in parallel to this, however, steps 10 and 11 shall await completion of all the EMM and ESM procedures.
If the MME is operating in S&F Mode, the MME may reject the NAS PDU sent in step 1 and optionally provide to the UE any of the following: a S&F Wait Timer, a S&F Monitoring List (see clause 4.13.9).
4a. If the S11-U connection is not established, the MME sends a Modify Bearer Request message (MME address, MME TEID DL, Delay Downlink Packet Notification Request, RAT Type, LTE-M RAT type reporting to PGW flag, MO Exception data counter) for each PDN connection to the Serving GW. The Serving GW is now able to transmit downlink data towards the UE. The usage of the Delay Downlink Packet Notification Request Information Element is specified in clause 5.3.4.2 with reference to the UE initiated service request procedure, but it equally applies in this case. The MME shall indicate S11-U tunnelling of NAS user data and send its own S11-U IP address and MME DL TEID for DL data forwarding by the SGW. Also, regardless of whether the S11-U was already established:
- If the PDN GW requested UE's location and/or User CSG information and the UE's location and/or User CSG information has changed, the MME shall send the Modify Bearer Request message and also includes the User Location Information IE and/or User CSG Information IE in this message.
- If the Serving Network IE has changed compared to the last reported Serving Network IE then the MME shall send the Modify Bearer Request message and also includes the Serving Network IE in this message.
- If the UE Time Zone has changed compared to the last reported UE Time Zone then the MME shall send the Modify Bearer Request message and include the UE Time Zone IE in this message.
If the RAT type currently used is NB-IOT this shall be reported as different from other E-UTRA flavours.
If the UE is using the LTE-M RAT type and the PDN GW expects the LTE-M RAT type reporting as specified in clause 5.11.5, the MME also includes the LTE-M RAT type reporting to PGW flag to indicate to the Serving GW to forward the LTE-M RAT type to the PDN GW.
The MME only includes MO Exception data counter if the RRC establishment cause is set to "MO exception data" and the UE is accessing via the NB-IoT RAT. The Serving GW indicates each use of this RRC establishment cause by the related counter on its CDR. The MME maintains the MO Exception Data Counter for Serving PLMN Rate Control purposes (see clause 4.7.7.2). The MME may immediately send the MO Exception Data Counter to the Serving GW. Alternatively, in order to reduce signalling, the MME may send the MO Exception Data Counter to the Serving GW as indicated in TS 29.274 [43].
4b If the S11-U connection is established and the UE is accessing via the NB-IoT RAT with the RRC establishment cause set to "MO exception data", the MME should notify the Serving Gateway. The MME maintains the MO Exception Data Counter for Serving PLMN Rate Control purposes (see clause 4.7.7.2). The MME may immediately send the MO Exception Data Counter to the Serving GW. Alternatively, in order to reduce signalling, the MME may send the MO Exception Data Counter to the Serving GW as indicated in TS 29.274 [43].
5. If the RAT Type has changed compared to the last reported RAT Type or if the UE's Location and/or Info IEs and/or UE Time Zone and Serving Network id are present in step 4, the Serving GW shall send the Modify Bearer Request message (RAT Type, MO Exception data counter) to the PDN GW. User Location Information IE and/or User CSG Information IE and/or Serving Network IE and/or UE Time Zone are also included if they are present in step 4.
If LTE-M RAT type and the LTE-M RAT type reporting to PGW flag were received at step 4a, the Serving GW shall include the LTE-M RAT type in the Modify Bearer Request message to the PGW. Otherwise the Serving GW includes RAT type WB-E-UTRAN.
If the Modify Bearer Request message is not sent because of above reasons and the PDN GW charging is paused, then the SGWS-GW shall send a Modify Bearer Request message with PDN Charging Pause Stop Indication to inform the PDN GW that the charging is no longer paused. Other IEs are not included in this message.
If the Modify Bearer Request message is not sent because of above reasons but the MME indicated MO Exception data counter, then the Serving Gateway should notify the PDN GW that this RRC establishment cause has been used by the indication of the MO Exception Data Counter (see TS 29.274 [43]). The Serving GW indicates each use of this RRC establishment cause by the related counter on its CDR.
6. The PDN GW sends the Modify Bearer Response to the Serving GW.
The PDN GW indicates each use of the RRC establishment cause "MO Exception Data" by the related counter on its CDR.
In the case of satellite access over NB-IoT, the eNB may request the MME to provide the Coarse Location information to the eNB, as described in TS 36.300 [5] and TS 36.413 [36].
7. If a Modify Bearer Request message was sent at step 4 the Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic) to the MME as a response to a Modify Bearer Request message. The Serving GW address for S11-U User Plane and Serving GW TEID are used by the MME to forward UL data to the SGW.
8. The MME sends Uplink data to the P-GW via the S-GW.
9. If no Downlink Data are expected based on the NAS Release Assistance Information from the UE in step 1, this means that all application layer data exchanges have completed with the UL data transfer, and if the MME is not aware of pending MT traffic and S1-U bearers are not established, step 10 is skipped and step 11 applies.
Otherwise, Downlink data may arrive at the P-GW and the P-GW sends them to the MME via the S-GW. If no data is received steps10-12 are skipped and the eNodeB may trigger step 14 after step 13 detects no activity. While the RRC connection is active, the UE may still send Uplink data and may receive Downlink data in NAS PDUs that are carried in a S1AP Uplink or (respectively) Downlink messages (not shown in the figure). At any time the UE has no user plane bearers established it may provide NAS Release Assistance Information with the Uplink data. In this case, to assist Location Services, the eNodeB may indicate, if needed, the UE's Coverage Level to the MME.
10. If Downlink data are received in step 9, the MME encrypts and integrity protects the Downlink data.
11. If step 10 is executed then Downlink data are encapsulated in a NAS PDU and sent to the eNodeB in a S1-AP Downlink NAS Message. If the configuration in the MME indicates that the eNodeB supports acknowledgements of downlink NAS data PDUs and if acknowledgements of downlink NAS data PDUs are enabled in the subscription information for the UE, the MME indicates in the S1-AP Downlink NAS message that acknowledgment is requested from the eNodeB. For IP PDN type PDN connections configured to support Header Compression, the MME shall apply header compression before encapsulating data into the NAS message. If step 10 is not executed, or NAS Service Accept message is not to be sent, the MME sends Connection Establishment Indication message to the eNodeB to complete the establishment of the UE-associated logical S1-connection. The UE Radio Capability may be provided from the MME to the eNodeB in the DL NAS Transport message or Connection Establishment Indication message, and the eNodeB shall store the received UE Radio Capability information as specified in TS 36.300 [5].
If the NAS Release Assistance Information was received with Uplink data and it indicated that Downlink data was expected, it means that the next downlink packet following the sending of the NAS Release Assistance Information is the last packet of the application layer data exchange, then for this case, unless the MME is aware of additional pending MT traffic and unless S1-U bearers are established, the MME sends a S1 UE Context Release Command immediately after the S1-AP message including the Downlink data encapsulated in NAS PDU as an indication that the eNodeB shall release the RRC connection promptly after successfully sending data to the UE. Alternatively, if "EDT Session" indication was received in step 2, the MME may include End Indication for no further data in the S1-AP message including the Downlink data encapsulated in NAS PDU. If the MME includes the End Indication indicating no further data and if the eNodeB does not proceed with RRC connection establishment, then the eNodeB skips step 12a and initiates step 12b.
If the NAS Release Assistance Information was received indicating no Downlink Data expected, it means that all application layer data exchanges have completed with the UL data transfer, then for this case, unless the MME is aware of additional pending MT traffic and unless S1-U bearers are established:
- the MME sends S1AP UE Context Release Command either:
- immediately after the S1AP DL NAS TRANSPORT (NAS Service Accept), in which case steps 12b and 14 are skipped, or
- immediately after S1AP CONNECTION ESTABLISHMENT INDICATION, in which case steps 12a, 12b, 13, and 14 are skipped.
- Alternatively, if the MME received "EDT Session" indication from the eNodeB in step 2, the MME should include End Indication with no further data in S1AP DL NAS TRANSPORT (NAS Service Accept) or S1AP CONNECTION ESTABLISHMENT INDICATION. If the eNodeB does not proceed with RRC connection establishment, the eNodeB skips step 12a and initiates stop 12b.
If the UE is accessing via an NB-IoT cell, or if it is accessing via an WB-E-UTRAN cell and is capable of CE mode B, to determine the NAS PDU retransmission strategy the MME should take into account the transmission delay of the NAS PDU and the CE mode B Restricted parameter stored in the MME's MM context and, if applicable, the CE mode, i.e. set the NAS timers long enough according to the worst transmission delay (see TS 24.301 [46]).
If the UE had indicated "S&F Capability" in the UE Core Network Capability and the MME is operating in S&F Mode, the MME may optionally provide in the NAS PDU message any of the following: a S&F Wait Timer, a S&F Monitoring List, an Estimated S&F UL Delivery Time (see clause 4.13.9).
12a. The eNodeB sends a RRC Downlink data message including the Downlink data encapsulated in NAS PDU. If in step 11 the S1-AP message with the NAS DATA PDU was followed by an S1 UE Context Release Command, step 15 is completed promptly after the Downlink Data transmission of the NAS PDU to the UE and the acknowledgement to MME in step 13 have been completed at the eNodeB, and the eNodeB does not need to enter step 14. If header compression was applied to the PDN, the UE would perform header decompression to rebuild the IP header.
If the eNB requested the MME to provide the Coarse Location Information to the eNB, the MME provides the Coarse Location Information to the eNB in an S1-AP message as described in TS 36.413 [36]. The eNB may use it as specified in TS 36.300 [3].
12b. If End Indication with no further data is received in S1AP message from the MME, the eNodeB may send the RRCEarlyDataComplete message with any NAS payload received from step 11 (either NAS data PDU or NAS service accept) as defined in TS 36.300 [5]. Step 14 is skipped in this case.
13. The eNodeB sends a NAS Delivery indication to the MME if requested. If the eNodeB reports an unsuccessful delivery with an S1-AP NAS Non Delivery Indication, the MME should wait for some time until the UE has potentially changed cell and re-established contact with the MME, by which MME should resend the Downlink S1-AP message to the eNodeB, otherwise the MME reports an unsuccessful delivery to the SCEF in the case of T6a procedure (see TS 23.682 [74], clause 5.13.3). If the eNodeB reports a successful delivery with an S1-AP NAS Delivery Indication and if the Downlink data was received over the T6a interface, the MME should respond to the SCEF (see TS 23.682 [74], clause 5.13.3). If the eNodeB does not support S1-AP NAS delivery indications, the MME indicates a cause code 'Success Unacknowledged Delivery' to the SCEF otherwise 'Success Acknowledged Delivery', for the SCEF to know if reliable delivery was possible or not.
14. If no NAS PDU activity exists for a while, the eNodeB starts an S1 release in step 15.
15. An S1 release procedure according to clause 5.3.5 triggered by the eNodeB or MME. Alternatively, if the MME in step 11 sent S1 UE Context Release Command then the procedure starts with step 5 in clause 5.3.5, or Connection Suspend Procedure defined in clause 5.3.4A. The UE and the MME shall store the ROHC configuration and context for the uplink/downlink data transmission when entering ECM_CONNECTED state next time.
5.3.4B.3 Mobile Terminated Data Transport in Control Plane CIoT EPS Optimisation with P-GW connectivity
Figure 5.3.4B.3-1: MT Data transport in NAS PDUs
0. The UE is EPS attached and in ECM-Idle mode.
1. When the S-GW receives a downlink data packet/control signalling for a UE, if the S- GW context data indicates no downlink user plane TEID towards the MME), it buffers the downlink data packet and identifies which MME is serving that UE.
If that MME has requested the Serving GW to throttle downlink low priority traffic and if the downlink data packet is received on a low priority bearer to be throttled (see clause 4.3.7.4.1a), the S-GW drops the downlink data. The steps below are not executed.
If that MME has requested the S‑GW to delay sending the Downlink Data Notification (see clause 5.3.4.2 on "Handling of abnormal conditions in UE triggered Service Request"), the Serving GW buffers the downlink data and waits until the timer expires before continuing with step 2. If the DL-TEID and MME address for that UE is received before the expiry of the timer, the timer shall be cancelled and the Mobile Terminated Data transport procedure is progressed from step 11 as Downlink data are sent to the UE.
If the Serving GW receives additional downlink data packets/control signalling for this UE before the expiry of the timer, the Serving GW does not restart this timer.
2. If the Serving GW is buffering data in step 1, the Serving GW sends a Downlink Data Notification message (ARP, EPS Bearer ID) to the MME for which it has control plane connectivity for the given UE. The ARP and EPS Bearer ID are always set in Downlink Data Notification. The MME responds to the S‑GW with a Downlink Data Notification Ack message.
An MME detects that the UE is in a power saving state (e.g. Power Saving Mode) and cannot be reached by paging at the time of receiving Downlink data notification, shall invoke extended buffering depending on operator configuration, except for cases described in next paragraphs. The MME derives the expected time before radio bearers can be established to the UE. The MME then indicates Downlink Buffering Requested to the Serving GW in the Downlink Data Notification Ack message and includes a Downlink Buffering Duration time and optionally a Downlink Buffering Suggested Packet Count. The MME stores a new value for the Downlink Data Buffer Expiration Time in the MM context for the UE based on the Downlink Buffering Duration time and skips the remaining steps of this procedure. The Downlink Data Buffer Expiration Time is used for UEs using power saving state and indicates that there are buffered data in the Serving GW and that the user plane setup procedure is needed when the UE makes signalling with the network. When the Downlink Data Buffer Expiration Time has expired, the MME considers no Downlink data to be buffered and no indications of Buffered Downlink Data Waiting are sent during context transfers at TAU procedures.
If there is an "Availability after DDN Failure" monitoring event configured for the UE in the MME, the MME does not invoke extended buffering. Instead, the MME sets the Notify-on-available-after-DDN-failure flag to remember to send an "Availability after DDN Failure" notification when the UE becomes available. If there is a "UE Reachability" monitoring event configured for the UE in the MME, the MME does not invoke extended buffering.
NOTE 1: When "Availability after DDN failure" and "UE reachability" monitoring events are used for a UE, the application server is assumed to send data only when the UE is reachable, hence no extended buffering is needed. If there are multiple application servers, the event notifications and extended buffering may be needed simultaneously. It is assumed this is handled through additional information based on SLA as described in the next paragraph.
The MME may use additional information based on a SLA with the MTC user for when to invoke extended buffering, e.g. only invoke it for a certain APN, do not invoke it for certain subscribers, invoke extended buffering in conjunction with "Availability after DDN failure" and "UE reachability" monitoring events, etc.
A Serving GW that receives a Downlink Buffering Requested indication in a Downlink Data Notification Ack message stores a new value for the Downlink Data Buffer Expiration Time based on the Downlink Buffering Duration time and does not send any additional Downlink Data Notification if subsequent downlink data packets are received in the Serving GW before the buffer time Downlink Data Buffer Expiration Time has expired for the UE.
If the Serving GW, while waiting for the user plane to be established, is triggered to send a second Downlink Data Notification for a bearer with higher priority (i.e. ARP priority level) than that of the bearer for which the first Downlink Data Notification was sent, the S-GW sends a new Downlink Data Notification message indicating the higher priority to the MME. If the Serving GW receives additional downlink data packets for a bearer with same or lower priority than the first Downlink Data Notification was sent for or if the Serving GW has sent the second Downlink Data Notification message indicating the higher priority and receives additional downlink data packets for this UE, the Serving GW buffers these downlink data packets and does not send a new Downlink Data Notification.
If the Serving GW, while waiting for the user plane to be established, receives a Modify Bearer Request message from an MME other than the one it sent a Downlink Data Notification message to, the Serving GW re-sends the Downlink Data Notification message but only to the new MME from which it received the Modify Bearer Request message.
If the MME holds stored Paging Restriction Information (see clause 4.3.33.6) for the UE that restricts the Downlink Data from causing paging, the MME sends Downlink Data Notification Ack message with an indication that the Downlink Data Notification message has been temporarily rejected.
Upon reception of a Downlink Data Notification Ack message with an indication that the Downlink Data Notification message has been temporarily rejected and if the Downlink Data Notification is triggered by the arrival of downlink data packets at the Serving GW, the Serving GW may start a locally configured guard timer and buffers all downlink user packets received to the given UE and waits for a Modify Bearer Request message to come. Upon reception of a Modify Bearer Request message, the Serving GW re-sends the Downlink Data Notification message but only to the new MME from which it received the Modify Bearer Request message. Otherwise the Serving GW releases buffered downlink user packets upon expiry of the guard timer or upon receiving the Delete Session Request message from MME.
If the S11-U is already established (buffering is in the MME), step 2 is not executed and step 11 is immediately executed. Steps 7,8,9,10 are executed only if conditions are met when the NAS control plane service request is received at step 6, as outlined below in the respective clauses.
An MME detecting that the UE is in a power saving state (e.g. Power Saving Mode) and cannot be reached by paging at the time of receiving Downlink data, shall start extended buffering depending on operator configuration, except for cases described in next paragraphs. The MME derives the expected time before radio bearers can be established to the UE, stores a new value for the Downlink Data Buffer Expiration Time in the MM context for the UE and skips the remaining steps of this procedure. When the Downlink Data Buffer Expiration Time has expired, the MME considers no Downlink data to be buffered.
Also for the case of buffering in the MME the "Availability after DDN Failure" monitoring event can be configured for the UE, even though the actual DDN is not received and the Downlink data is received. The "UE Reachability" monitoring event can also be configured. The extended buffering can also be configured as per what is described above in this step of the procedure for the case of buffering in S-GW.
3. If the UE is registered in the MME and considered reachable, the MME sends Paging message(s) as specified in step 3a of clause 5.3.4.3.
4. If eNodeBs receive paging messages from the MME, the UE is paged by the eNodeBs as specified in step 4a of clause 5.3.4.3.
5. As the UE is in the ECM-IDLE state, upon reception of paging indication, the UE sends Control Plane Service Request NAS message (as defined in TS 24.301 [46]) over RRC Connection request and S1-AP initial message. The Control Plane Service Request NAS message, when Control Plane CIoT EPS Optimisation applies, does not trigger Data radio bearer establishment by the MME and the MME can immediately send Downlink Data it receives using a NAS PDU to the eNodeB. The MME supervises the paging procedure with a timer. If the MME receives no response from the UE to the Paging Request message, it may repeat the paging according to any applicable paging strategy described in step 3.
If the Multi-USIM UE in ECM-IDLE state, upon reception of paging indication in E-UTRAN access and if the UE decides not to accept the paging, the UE attempts to send a Reject Paging Indication in the Control Plane Service Request NAS message (as defined in TS 24.301 [46]) over RRC Connection request and S1-AP initial message. If the Control Plane Service Request NAS message includes a Reject Paging Indication, then:
- If the Service Request message includes Paging Restriction Information, the MME may accept or reject the Paging Restriction Information requested by the UE based on operator policy. If the MME rejects the Paging Restriction Information, the MME removes any stored Paging Restriction Information from the UE context and discards the UE requested Paging Restriction Information. If the MME accepts the Paging Restriction Information from the UE, the MME stores the Paging Restriction Information from the UE in the UE context. The MME informs the UE about the acceptance/rejection of the requested Paging Restriction Information in the Service Accept message. If no Paging Restriction Information is provided, no paging restrictions apply;
- no Downlink or Uplink Data is sent (steps 7-20 are skipped);
- the MME triggers the S1 release procedure in step 21.
5b. In the NB-IoT case, the eNodeB, based on configuration, may retrieve the EPS negotiated QoS profile from the MME, if not previously retrieved. The MME Code within the S-TMSI in the RRCConnectionRequest message is used to identify the MME. In the case of network sharing, the MME Codes shall be unique within the area of overlapping MME pools of the participating operators. The eNodeB may apply prioritisation between requests from different UEs before triggering step 6 and throughout the RRC connection. The eNodeB may retrieve additional parameters (e.g., UE Radio Capabilities - see TS 36.413 [36]).
6. If the MME receives no response from the UE after this paging repetition procedure, it shall use the Downlink Data Notification Reject message to notify the Serving GW about the paging failure (or, equivalently, if the buffering is in the MME, the MME simply discards data for the UE locally), unless the MME is aware of an ongoing MM procedure that prevents the UE from responding, i.e. the MME received a Context Request message indicating that the UE performs TAU with another MME. When a Downlink Data Notification Reject message is received, the Serving GW deletes the buffered packet(s). The Serving GW may invoke the procedure PDN GW Pause of Charging (clause 5.3.6A) if UE is in ECM IDLE and the PDN GW has enabled "PDN charging pause" feature. If buffering is in the MME, Pause Charging is triggered by the MME via a Release Access Bearer Request to the S-GW(not shown in Figure 5.3.4B.3-1) including a "Abnormal Release of Radio Link" cause, which releases the S11-U.
NOTE 2: The Serving GW (or MME, in the case of buffering in the MME) may initiate the procedure P-GW Pause of Charging at any time before step 5 if the UE is in ECM IDLE and the P-GW has indicated that the feature is enabled for this PDN. See clause 5.3.6A.0.
To assist Location Services, the eNodeB indicates the UE's Coverage Level to the MME.
The MME performs (and the UE responds to) any EMM or ESM procedures if necessary, e.g. the security related procedures. Steps 7 to 11 can continue in parallel to this, however, steps 12 and 13 shall await completion of all the EMM and ESM procedures.
In the case of satellite access over NB-IoT, the eNB may request the MME to provide the Coarse Location information to the eNB, as described in TS 36.300 [5] and TS 36.413 [36].
7. If the S11-U is not established, the MME sends a Modify Bearer Request message (MME address, MME TEID DL, Delay Downlink Packet Notification Request, RAT Type, LTE-M RAT type reporting to PGW flag) for each PDN connection to the Serving GW. The Serving GW is now able to transmit downlink data towards the UE. The usage of the Delay Downlink Packet Notification Request Information Element is specified in clause 5.3.4.2 with reference to the UE initiated service request procedure, but it equally applies in this case. The MME shall indicate S11-U tunnelling of NAS user data and send its own S11-U IP address and MME DL TEID for DL data forwarding by the SGW. Also, regardless of whether the S11-U was already established:
- If the P-GW requested UE's location and/or User CSG information and the UE's location and/or User CSG information has changed, the MME shall send the Modify Bearer Request message and also includes the User Location Information IE and/or User CSG Information IE in this message.
- If the Serving Network IE has changed compared to the last reported Serving Network IE then the MME shall send the Modify Bearer Request message and also includes the Serving Network IE in this message.
- If the UE Time Zone has changed compared to the last reported UE Time Zone then the MME shall send the Modify Bearer Request message and include the UE Time Zone IE in this message.
If the RAT type currently used is NB-IOT this shall be reported as different from other -E-UTRA flavours.
If the UE is using the LTE-M RAT type and the PDN GW expects the LTE-M RAT type reporting as specified in clause 5.11.5, the MME also includes the LTE-M RAT type reporting to PGW flag to indicate to the Serving GW to forward the LTE-M RAT type to the PDN GW.
8. If the RAT Type has changed compared to the last reported RAT Type or if the UE's Location and/or Info IEs and/or UE Time Zone and Serving Network id are present in step 7, the Serving GW shall send the Modify Bearer Request message (RAT Type) to the P-GW. User Location Information IE and/or User CSG Information IE and/or Serving Network IE and/or UE Time Zone are also included if they are present in step 7.
If LTE-M RAT type and the LTE-M RAT type reporting to PGW flag were received at step 7, the Serving GW shall include the LTE-M RAT type in the Modify Bearer Request message to the PGW. Otherwise the Serving GW includes RAT type WB-E-UTRAN.
If the Modify Bearer Request message is not sent because of above reasons and the PDN GW charging is paused, then the S-GW shall send a Modify Bearer Request message with PDN Charging Pause Stop Indication to inform the PDN GW that the charging is no longer paused. Other IEs are not included in this message.
9. The PDN GW sends the Modify Bearer Response to the Serving GW.
10. If a Modify Bearer Request message was sent at step 7, the Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic) to the MME as a response to a Modify Bearer Request message. The Serving GW address for S11-U User Plane and Serving GW TEID are used by the MME to forward UL data to the SGW.
11. Buffered (if S11-U was not established) Downlink data is sent by the S-GW to the MME.
12-13. The MME encrypts and integrity protects Downlink data and sends it to the eNodeB using a NAS PDU carried by a Downlink S1-AP message. If the configuration in the MME indicates that the eNodeB supports acknowledgements of downlink NAS data PDUs and if acknowledgements of downlink NAS data PDUs are enabled in the subscription information for the UE, the MME indicates in the Downlink S1-AP message that acknowledgment is requested from the eNodeB. For IP PDN type PDN connections configured to support Header Compression, the MME shall apply header compression before encapsulating data into the NAS message. Alternatively and if the MME decides that S1-U bearers need to be established in the case that the UE and MME accept User Plane EPS Optimisation or S1-U data transfer, steps 4-12 from clause 5.3.4.1 are followed.
If the UE is accessing via an NB-IoT cell, or if it is accessing via an WB-E-UTRAN cell and is capable of CE mode B, to determine the NAS PDU retransmission strategy the MME should take into account the transmission delay of the NAS PDU and the CE mode B Restricted parameter stored in the MME's MM context and, if applicable, the CE mode, i.e. set the NAS timers long enough according to the worst transmission delay (see TS 24.301 [46]).
If the eNB requested the MME to provide the Coarse Location Information to the eNB, the MME provides the Coarse Location Information to the eNB in an S1-AP message as described in TS 36.413 [36]. The eNB may use it as specified in TS 36.300 [5].
14. The NAS PDU with data is delivered to the UE via a Downlink RRC message. This is taken by the UE as implicit acknowledgment of the Service Request message sent in step 5. If header compression was applied, to the PDN, the UE shall perform header decompression to rebuild the IP header.
15. The eNodeB sends a NAS Delivery indication to the MME if requested. If the eNodeB reports an unsuccessful delivery with an S1-AP NAS Non Delivery Indication, the MME should wait for some time until the UE has potentially changed cell and re-established contact with the MME, by which MME should resend the Downlink S1-AP message to the eNodeB, otherwise the MME reports an unsuccessful delivery to the SCEF in the case of T6a procedure (see TS 23.682 [74], clause 5.13.3). If the eNodeB reports a successful delivery with an S1-AP NAS Delivery Indication and if the Downlink data was received over the T6a interface, the MME should respond to the SCEF (see TS 23.682 [74], clause 5.13.3). If the eNodeB does not support S1-AP NAS delivery indications, the MME indicates a cause code 'Success Unacknowledged Delivery' to the SCEF otherwise 'Success Acknowledged Delivery', for the SCEF to know if reliable delivery was possible or not.
16. While the RRC connection is still up, further Uplink and Downlink data can be transferred using NAS PDUs. In step 17 an Uplink data transfer is shown using an Uplink RRC message encapsulating a NAS PDU with data. At any time the UE has no user plane bearers established, the UE may provide a Release Assistance Information with Uplink data in the NAS PDU.
For IP PDN type PDN connections configured to support Header Compression, the UE shall apply header compression before encapsulating it into the NAS message.
17. The NAS PDU with data is send to the MME in a Uplink S1-AP message.
To assist Location Services, the eNodeB may indicate, if changed, the UE's Coverage Level to the MME.
If the Release Assistance Information is received from the UE it overrides the Traffic Profile (see TS 23.682 [74]) and the MME does not send the Traffic Profile to the eNodeB.
18. The data is checked for integrity and decrypted. If header compression was applied to the PDN, the MME shall perform header decompression to rebuild the IP header.
19. The MME sends Uplink data to the PDN GW via the S-GW and executes any action related to the presence of Release Assistance Information as follows:
- for the case where the Release Assistance Information indicates there is no downlink data to follow the uplink data then unless the MME is aware of pending MT traffic, and unless S1-U bearers exist, the MME immediately releases the connection and therefore step 21 is executed.
- for the case where the Release Assistance Information indicates that downlink data will follow the uplink transmission then unless the MME is aware of additional pending MT traffic and unless S1-U bearers exist, the MME sends a S1 UE Context Release Command to the eNodeB immediately after the S1-AP message including the Downlink data encapsulated in NAS PDU.
20. If no NAS activity exists for a while the eNodeB detects inactivity and executes step 21.
21. The eNodeB starts an eNodeB initiated S1 release procedure according to clause 5.3.5 or Connection Suspend Procedure defined in clause 5.3.4A. The UE and the MME shall store the ROHC configuration and context for the uplink/downlink data transmission when entering ECM_CONNECTED state next time.
5.3.4B.4 Establishment of S1-U bearer during Data Transport in Control Plane CIoT EPS Optimisation
Figure 5.3.4B.4-1: Establishment of S1-U bearer during Data Transport in Control Plane CIoT EPS Optimisation
UE or MME can use this procedure if the UE and MME successfully negotiate S1-U data transfer or User Plane CIoT EPS Optimisation in addition to Control Plane CIoT EPS Optimisation based on the Preferred and Supported Network Behaviour as defined in clause 4.3.5.10. The MME either because it has received the NAS message as defined in steps 2-3 or the MME decides that S1-U based data transfer is now preferred e.g. determined by the size of data transferred in UL and DL using Control Plane CIoT EPS Optimisation triggers the establishment of S1-U bearer(s). The MME checks if the UE can support the establishment of required number of additional user plane radio bearers based on the maximum number of user plane radio bearers indicated by UE in the UE Network Capability IE as defined in clause 5.11.3. If the MME takes the decision that S1-U data transfer is now preferred steps 2-3 are not needed.
1. UE is sending and receiving data in NAS PDUs using the Control Plane CIoT EPS Optimisation.
2. The UE may be triggered to establish user plane bearers and sends a Control Plane Service Request with an active flag towards the MME encapsulated in an RRC message to the eNodeB. The RRC message and this NAS message are described in TS 36.300 [5] and TS 24.301 [46] respectively.
3. The eNodeB forwards the Control Plane Service Request with active flag to MME. NAS message is encapsulated in an S1-AP UL NAS Transport Message (NAS message, TAI+ECGI of the serving cell, S-TMSI, CSG ID, CSG access Mode). Details of this step are described in TS 36.300 [5]. If the MME receives the Control Plane Service Request with active flag defined in steps 2-3 it shall establish S1-U bearer(s) and execute the transfer. If the MME cannot handle the procedure associated to the Control Plane Service Request with active flag, it shall reject it. CSG ID is provided if the UE sends the NAS message via a CSG cell or a hybrid cell. CSG access mode is provided if the UE sends the NAS message via a hybrid cell. If the CSG access mode is not provided but the CSG ID is provided, the MME shall consider the cell as a CSG cell.If a CSG ID is indicated and CSG access mode is not provided, and there is no subscription data for this CSG ID and associated PLMN or the CSG subscription is expired, the MME rejects the Control Plane Service Request with an appropriate cause. The UE shall remove the CSG ID and associated PLMN of the cell where the UE has initiated the service request procedure from the Allowed CSG list, if present.
4. The MME shall send any remaining UL data over S11-U and in order to minimize the possible occurrence of out of order DL data e.g. caused by earlier DL data which were sent on the Control Plane may send a Release Access Bearers Request message to the Serving GW that requests the release of all S11-U bearers for the UE. The MME locally deletes any existing ROHC context used for Control Plane CIoT EPS Optimisation, and other S11-U related information in UE context, including TEID (DL) for the S11-U, etc, but not the Header Compression Configuration.
NOTE: The MME may use the "Delay Downlink Packet Notification Request" causing the Serving GW to not send Downlink Data Notifications as described in clause 5.3.4.2 to minimize the impact of possible Downlink Data Notifications this step may cause.
5. If the Serving GW receives the Release Access Bearers Request message it releases all MME related information (address and downlink TEIDs) for the UE and responds with a Release Access Bearers Response message to the MME. Other elements of the UE's Serving GW context are not affected. If downlink packets arrive for the UE, the Serving GW starts buffering downlink packets received for the UE and initiating the "Network Triggered Service Request" procedure, described in clause 5.3.4.3.
6. The MME sends S1-AP Initial Context Setup Request (Serving GW address, S1-TEID(s) (UL), EPS Bearer QoS(s), Security Context, MME Signalling Connection Id, Handover Restriction List, CSG Membership Indication, Service Accept) message to the eNodeB for all PDN connections that MME has not included Control Plane Only Indicator in ESM request. The MME responds to the UE with a Service Accept message. The eNodeB stores the Security Context, MME Signalling Connection Id, EPS Bearer QoS(s) and S1-TEID(s) in the UE RAN context. The step is described in detail in TS 36.300 [5]. Handover Restriction List is described in clause 4.3.5.7 "Mobility Restrictions".
7. If the Control Plane Service Request is performed via a hybrid cell, CSG Membership Indication indicating whether the UE is a CSG member shall be included in the S1-AP message from the MME to the RAN. Based on this information, the RAN can perform differentiated treatment for CSG and non-CSG members. The eNodeB performs the radio bearer establishment procedure. The user plane security is established at this step, which is described in detail in TS 36.300 [5]. The UE needs to locally delete any existing ROHC context used for Control Plane CIoT EPS Optimisation. When the user plane radio bearers are setup, EPS bearer state synchronization is performed between the UE and the network, i.e. the UE shall locally remove any EPS bearer for which the MME has not included Control Plane Only Indicator in ESM request and for which no radio bearers are setup. If the radio bearer for a default EPS bearer is not established, the UE shall locally deactivate all EPS bearers associated to that default EPS bearer.
8. As the user plane radio bearers are setup the UE shall use user plane bearers to transfer data PDUs, except for EPS bearers the MME has included Control Plane Only Indicator in ESM request and for which Control Plane CIoT EPS Optimisation is still be used. The uplink data from the UE can now be forwarded by eNodeB to the Serving GW. The eNodeB sends the uplink data to the Serving GW address and TEID provided in the step 6. The Serving GW forwards the uplink data to the PDN GW.
9. The eNodeB sends an S1-AP message Initial Context Setup Complete (eNodeB address, List of accepted EPS bearers, List of rejected EPS bearers, S1 TEID(s) (DL)) to the MME. This step is described in detail in TS 36.300 [5].
10. The MME sends a Modify Bearer Request message (eNodeB address, S1 TEID(s) (DL) for the accepted EPS bearers, Delay Downlink Packet Notification Request, RAT Type) per PDN connection to the Serving GW. If the Serving GW supports Modify Access Bearers Request procedure and if there is no need for the Serving GW to send the signalling to the PDN GW, the MME may send Modify Access Bearer Request (eNodeB address(es) and TEIDs for downlink user plane for the accepted EPS bearers, Delay Downlink Packet Notification Request) per UE to the Serving GW to optimise the signalling. The Serving GW is now able to transmit downlink data towards the UE.
11. The Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic) to the MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message. If the Serving GW cannot serve the MME Request in the Modify Access Bearers Request message without S5/S8 signalling other than to unpause charging in the PDN GW or without corresponding Gxc signalling when PMIP is used over the S5/S8 interface, it shall respond to the MME with indicating that the modifications are not limited to S1-U bearers, and the MME shall repeat its request using a Modify Bearer Request message per PDN connection.
5.3.4B.5 eNodeB Control Plane Relocation Indication procedure
For intra-NB-IoT mobility for UE and MME using Control Plane CIoT EPS Optimisation the eNodeB CP Relocation Indication procedures may be used. The purpose of the eNodeB CP Relocation Indication procedure is to request the MME to authenticate the UE's re-establishment request as described in TS 33.401 [41], and initiate the establishment of the UE's S1 connection and, if necessary, the S11-U connection after the UE has initiated a RRC Re-establishment procedure in a new eNodeB.
More details are defined in TS 36.300 [5].
5.3.4B.6 MT-EDT procedure for Control Plane CIoT EPS Optimization
The procedure is used by the network to initiate MT-EDT procedure if the UE and the network support Control Plane CIoT EPS Optimisation and there is single DL data transmission for the UE.
Figure 5.3.4B.6-1: MT-EDT procedure for Control Plane CIoT EPS Optimization
The call flow is the same as the Mobile Terminated Data Transport procedure documented in clause 5.3.4B.3 procedure for Control Plane CIoT EPS Optimisation with the following changes:
In step2, the Serving-GW may send the downlink data size to the MME if the downlink data is applicable for Control Plane CIoT EPS Optimisation and MT-EDT is applicable for this PDN Connection.
In step3, if MT-EDT is applicable for the PDN Connection, the MME may include the downlink data size in the Paging message to assist eNodeB to use MT-EDT.
In step 4, if data size is included in the Paging message from MME, the eNodeB may decide to use MT-EDT by adding a MT-EDT indication in the Paging message to the UE.
In step 5, the UE, upon reception of MT-EDT indication in the Paging message, triggers MO-EDT by sending the RRCEarlyDataRequest message as defined in TS 36.300 [5].
In step 13, if downlink data is received from the S-GW, the MME may include End Indication for no further data in the S1-AP message including the Downlink data encapsulated in NAS PDU.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.5 S1 release procedure
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This procedure is used to release the logical S1-AP signalling connection (over S1-MME) and all S1 bearers (in S1-U) for a UE. This Procedure releases the S11-U bearer in Control Plane CIoT EPS Optimisation (except in the case of buffering in MME), instead of the S1-U bearer. The procedure will move the UE from ECM-CONNECTED to ECM-IDLE in both the UE and MME, and all UE related context information is deleted in the eNodeB. When the S1-AP signalling connection is lost, e.g. due to loss of the signalling transport or because of an eNodeB or MME failure, the S1 release procedure is performed locally by the eNodeB and by the MME. When the S1 release procedure is performed locally by the eNodeB or by the MME each node performs locally its actions as described in the procedure flow below without using or relying on any of the signalling shown directly between eNodeB and MME.
If Service Gap Control shall be applied for the UE (see clause 4.3.17.9) and the Service Gap timer is not already running, the Service Gap timer shall be started in MME and UE when entering ECM-IDLE, unless the connection was initiated after a paging of an MT event, or after a TAU procedure without any active flag set or signalling active flag set.
The initiation of S1 Release procedure is either:
- eNodeB-initiated with cause e.g. O&M Intervention, Unspecified Failure, User Inactivity, Repeated RRC signalling Integrity Check Failure, Release due to UE generated signalling connection release, CS Fallback triggered, Inter-RAT Redirection, UE using satellite access moved out of PLMN serving area, etc. as defined in TS 36.413 [36]; or
- MME-initiated with cause e.g. authentication failure, detach, not allowed CSG cell (e.g. the CSG ID of the currently used CSG cell expires or is removed from the CSG subscription data), etc.
Both eNodeB-initiated and MME-initiated S1 release procedures are shown in Figure 5.3.5-1.
Figure 5.3.5-1: S1 Release Procedure
1a. In certain cases the eNodeB may release the UE's signalling connection before or in parallel to requesting the MME to release the S1 context, e.g. the eNodeB initiates an RRC Connection Release for CS Fallback by redirection. If the reason for the release is that the eNodeB received Release Assistance Indicator in Access Stratum as defined in TS 36.321 [87], the eNodeB should not immediately release the RRC connection, instead send S1 UE context Release Request with appropriate cause value e.g. user inactivity.
1b. If the eNodeB detects a need to release the UE's signalling connection and all radio bearers for the UE, the eNodeB sends an S1 UE Context Release Request (Cause) message to the MME. Cause indicates the reason for the release (e.g. O&M intervention, unspecified failure, user inactivity, repeated integrity checking failure, or release due to UE generated signalling connection release).
If the PLMN has configured secondary RAT reporting and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included in S1 UE Context Release Request.
NOTE 1: Step 1 is only performed when the eNodeB-initiated S1 release procedure is considered. Step 1 is not performed and the procedure starts with Step 2 when the MME-initiated S1 release procedure is considered.
The MME upon receiving S1 UE Context Release Request with Cause=user inactivity continues with the S1 release procedure unless the MME is aware of pending MT traffic or signalling and/or NAS Release Assistance Information that may have been received in NAS PDU when Control Plane CIoT EPS Optimisation is used, which indicates that downlink data is expected.
The MME upon receiving S1 UE Context Release Request with Cause indicating the release is requested due to a UE using satellite access moved out of PLMN serving area, may detach the UE as described in clause 5.3.8.3 before continuing with the S1 Release procedure.
For Control Plane CIoT EPS Optimisation with data buffering in the MME, step 2 and step 3 are skipped.
2. The MME sends a Release Access Bearers Request (Abnormal Release of Radio Link Indication, Secondary RAT usage data) message to the S‑GW that requests the release of all S1-U bearers for the UE, or the S11-U in Control Plane CIoT EPS Optimisation if buffering is in the S-GW. This message is triggered either by an S1 Release Request message from the eNodeB, or by another MME event. The Abnormal Release of Radio Link Indication is included if the S1 release procedure is due to an abnormal release of the radio link. If secondary RAT usage data was received in Step 1b, the MME includes Secondary RAT usage data in this message.
3. If the S-GW has received a Release Access Bearers Request, the S‑GW releases all eNodeB related information (address and TEIDs), or the MME TEIDs related information in Control Plane CIoT EPS Optimisation (address and TEIDs), for the UE and responds with a Release Access Bearers Response message to the MME. Other elements of the UE's S‑GW context are not affected. The S‑GW retains the S1-U configuration that the S‑GW allocated for the UE's bearers. The S‑GW starts buffering downlink packets received for the UE and initiating the "Network Triggered Service Request" procedure, described in clause 5.3.4.3, if downlink packets arrive for the UE. In Control Plane CIoT EPS Optimisation Downlink data triggers Mobile Terminated Data transport in NAS signalling defined in clause 5.3.4B.3.
NOTE 2: Based on operator policy any received Indication of "Abnormal Release of Radio Link" may be used by Serving GW in subsequent decisions to trigger PDN charging pause if the feature has been enabled on that PDN.
4. The MME releases S1 by sending the S1 UE Context Release Command (Cause) message to the eNodeB.
5. If the RRC connection is not already released, the eNodeB sends a RRC Connection Release message to the UE in Acknowledged Mode. Once the message is acknowledged by the UE, the eNodeB deletes the UE's context.
6. The eNodeB confirms the S1 Release by returning an S1 UE Context Release Complete (ECGI, TAI, Secondary RAT usage data) message to the MME. With this, the signalling connection between the MME and the eNodeB for that UE is released. This step shall be performed promptly after step 4, e.g. it shall not be delayed in situations where the UE does not acknowledge the RRC Connection Release.
If Dual Connectivity was activated by that eNodeB at the time of the release or earlier by that eNodeB, the eNodeB shall include the last known PSCell ID and the time elapsed since the Dual Connectivity was released.
If the eNodeB supports WUS, the eNodeB should include the Information On Recommended Cells And eNodeBs For Paging in the S1 UE Context Release Complete message; otherwise, the eNodeB may include the Information On Recommended Cells And eNodeBs For Paging in the S1 UE Context Release Complete message. If available, the MME shall store this information to be used when paging the UE.
The eNodeB includes Information for Enhanced Coverage, if available, in the S1 UE Context Release Complete message.
If the PLMN has configured secondary RAT usage data reporting, the eNodeB has not included Secondary RAT usage data at step 1b, and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included in this message. If Secondary RAT usage data was included at step 1b then MME ignores Secondary RAT usage data at step 6.
The MME deletes any eNodeB related information ("eNodeB Address in Use for S1-MME", "MME UE S1 AP ID" and "eNodeB UE S1AP ID") from the UE's MME context, but, retains the rest of the UE's MME context including the S‑GW's S1-U configuration information (address and TEIDs). All non-GBR EPS bearers established for the UE are preserved in the MME and in the Serving GW.
If the cause of S1 release is because of User I inactivity, Inter-RAT Redirection, the MME shall preserve the GBR bearers. If the cause of S1 release is because of CS Fallback triggered, further details about bearer handling are described in TS 23.272 [58]. Otherwise, e.g. Radio Connection With UE Lost, S1 signalling connection lost, eNodeB failure the MME shall trigger the MME Initiated Dedicated Bearer Deactivation procedure (clause 5.4.4.2) for the GBR bearer(s) of the UE after the S1 Release procedure is completed.
NOTE 3: EPC does not support the GPRS preservation feature with setting the MBR for GBR bearers to zero.
NOTE 4: The MME can defer the deactivation of GBR bearers for a short period (in the order of seconds) upon receipt of an S1AP UE Context Release Request due to radio reasons, so as to allow the UE to re-establish the corresponding radio and S1-U bearers and thus avoid deactivation of the GBR bearers.
If LIPA is active for a PDN connection, the HeNB informs the collocated L-GW by internal signalling to releases the direct user plane path to the HeNB. After the direct user plane path is released, if downlink packets arrive for the UE, the L-GW forwards the first packet on the S5 tunnel to the S‑GW to initiate the "Network Triggered Service Request" procedure, as described in clause 5.3.4.3.
7. If the eNodeB provided and MME accepted Secondary RAT usage data in step 6 (i.e. MME initiated S1 release), the MME initiates the Secondary RAT usage data reporting procedure in clause 5.7A.3 as illustrated in figure 5.7A.3-2 (steps 7a - 7d). If PGW secondary RAT usage reporting is active, steps 7b and 7c are performed, otherwise only steps 7a and 7d are performed.
If the eNodeB provided Secondary RAT usage data in step 1b (i.e. eNodeB initiated S1 release) and PGW secondary RAT usage data reporting is active, the MME initiates the Secondary RAT usage data reporting procedure in clause 5.7A.3 as illustrated in figure 5.7A.3-2.
5.3.5A Connection Resume procedure
This procedure is used by the UE to resume the ECM-connection if the UE and the network support User Plane CIoT EPS Optimisation and the UE has stored the necessary information to conduct the Connection Resume procedure (see TS 36.300 [5]) otherwise the Service Request procedures are used, see clause 5.3.4.
Figure 5.3.5A-1: UE initiated Connection Resume procedure
1. The UE triggers the Random Access procedure to the eNodeB, see TS 36.300 [5].
2. The UE triggers the RRC Connection Resume procedure including information needed by the eNodeB to access the UE's stored AS context, see TS 36.300 [5]. The E-UTRAN performs security checks. EPS bearer state synchronization is performed between the UE and the network, i.e. the UE shall locally remove any EPS bearer for which no radio bearer is setup and which is not a Control Plane CIoT EPS bearer. If the radio bearer for a default EPS bearer is not established, the UE shall locally deactivate all EPS bearers associated to that default EPS bearer.
3. The eNodeB notifies the MME that the UE's RRC connection is resumed in the S1-AP UE Context Resume Request message which includes an RRC resume cause. If the eNodeB is not able to admit all suspended bearers, the eNodeB shall indicate this in the list of rejected EPS bearers, see TS 36.413 [36].
When the UE attempts to establish a signalling connection and the following conditions are met:
the eNodeB serves more than one country (e.g. it supports E-UTRA satellite access); and
- the eNodeB knows in what country the UE is located; and
- the eNodeB is connected to MMEs serving different PLMNs of different countries; and
- the UE provides an S-TMSI or GUMMEI, which indicates an MME serving a different country to where the UE is currently located; and
- the eNodeB is configured to enforce selection of the MME based on the country the UE is currently located;
then the eNodeB shall select an MME serving a PLMN corresponding to the UE's current location and send the S1-AP UE Context Resume Request message to that MME (this is intended to cause the resume procedure to fail).
If there is a Service Gap timer running in the MME for the UE and the MME is not waiting for a MT paging response from the UE and the RRC Connection Establishment Cause for the Connection Resume Request is not 'mo-Signalling', the MME rejects the resume request by sending a S1-AP UE Context Resume Reject message to eNodeB.
NOTE: If the UE then sends a subsequent Service Request while the Service Gap timer is running, the MME will send a Service Reject NAS message to the UE with a Mobility Management back-off timer corresponding to the remaining time of the current Service Gap timer (see procedure in clause 5.3.4).
The MME enters the ECM-CONNECTED state. The MME identifies that the UE returns at the eNodeB for which MME has stored data related to the S1AP association, UE Context and bearer context including the DL TEID(s), necessary to resume the connection, see Connection Suspend procedure in clause 5.3.4A.
If a default EPS bearer is not accepted by the eNodeB, all the EPS bearers associated to that default bearer shall be treated as non-accepted bearers. The MME releases the non-accepted and non-established bearers by triggering the bearer release procedure as specified in clause 5.4.4.2.
To assist Location Services, the eNodeB indicates the UE's Coverage Level to the MME.
3a. If the S1-U connection is resumed and the UE is accessing via the NB-IoT RAT with the RRC resume cause set to "MO exception data", the MME should notify the Serving Gateway of each use of this establishment cause by the MO Exception Data Counter. The MME maintains the MO Exception Data Counter and sends it to the Serving GW as indicated in TS 29.274 [43].
3b. The Serving Gateway should notify the PDN GW if the RRC establishment cause "MO Exception Data" has been used by the MO Exception Data Counter (see TS 29.274 [43]). The Serving GW indicates each use of this RRC establishment cause by the related counter on its CDR.
3c. The PDN GW indicates each use of the RRC establishment cause "MO Exception Data" by the related counter on its CDR.
4. MME acknowledges the connection resumption in S1-AP UE Context Resume Response message. If the MME is not able to admit all suspended E-RABs the MME shall indicate this in the E-RABs Failed To Resume List IE.
5. If the MME included in step 4 a list of E-RABs failed to resume, the eNodeB reconfigures the radio bearers.
6. The uplink data from the UE can now be forwarded by eNodeB to the Serving GW. The eNodeB sends the uplink data to the Serving GW address and TEID stored during the Connection Suspend procedure, see clause 5.3.4A. The Serving GW forwards the uplink data to the PDN GW.
7. The MME sends a Modify Bearer Request message (eNodeB address, S1 TEID(s) (DL) for the accepted EPS bearers, Delay Downlink Packet Notification Request, RAT Type) per PDN connection to the Serving GW. If the Serving GW supports Modify Access Bearers Request procedure and if there is no need for the Serving GW to send the signalling to the PDN GW, the MME may send Modify Access Bearers Request (eNodeB address(es) and TEIDs for downlink user plane for the accepted EPS bearers, Delay Downlink Packet Notification Request) per UE to the Serving GW to optimise the signalling. The Serving GW is now able to transmit downlink data towards the UE.
The MME and the Serving GW clears the DL Data Buffer Expiration Time in their UE contexts if it was set, to remember that any DL data buffered for a UE using power saving functions has been delivered and to avoid any unnecessary user plane setup in conjunction with a later TAU.
8. The Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic) to the MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message. If the Serving GW cannot serve the MME Request in the Modify Access Bearers Request message without S5/S8 signalling other than to unpause charging in the PDN GW or without corresponding Gxc signalling when PMIP is used over the S5/S8 interface, it shall respond to the MME with indicating that the modifications are not limited to S1-U bearers, and the MME shall repeat its request using a Modify Bearer Request message per PDN connection.
If SIPTO at the Local Network is active for a PDN connection with stand-alone GW deployment and the Local Home Network ID for stand-alone accessed by the UE differs from the Local Home Network ID where the UE initiated the SIPTO@LN PDN Connection, the MME shall request disconnection of the SIPTO at the local network PDN connection(s) with the "reactivation requested" cause value according to clause 5.10.3. If the UE has no other PDN connection, the MME initiated "explicit detach with reattach required" procedure according to clause 5.3.8.3.
If SIPTO at the Local Network is active for a PDN connection with collocated LGW deployement and the L-GW CN address of the cell accessed by the UE differs from the L-GW CN address of the cell where the UE initiated the SIPTO at the Local Network PDN Connection, the MME shall request disconnection of the SIPTO at the local network PDN connection(s) with the "reactivation requested" cause value according to clause 5.10.3. If the UE has no other PDN connection, the MME initiated "explicit detach with reattach required" procedure according to clause 5.3.8.3.
5.3.5B MT-EDT procedure for User Plane CIoT EPS Optimisation
Figure 5.3.5B-1: MT-EDT procedure for User Plane CIoT EPS Optimization
1. Same as step 1 in clause 5.3.4.3.
2. Same as step 2 in clause 5.3.4.3, with the following addition:;
The Serving-GW may send the downlink data size to the MME for MT-EDT consideration if the downlink data is applicable for User Plane CIoT EPS Optimisation and MT-EDT is applicable for this PDN connection.
3. Same as step 3 in clause 5.3.4.3, with the following addition;
If MT-EDT is applicable for the PDN Connection, the MME may include the downlink data size in the Paging message to assist eNodeB to use MT-EDT.
4. Same as step 4 in cluse 5.3.4.3, with the following addition;
If data size is included in Paging message from MME, the eNodeB may decide to use MT-EDT, by adding a MT-EDT indication in the Paging message to the UE.
5-8. Follow the procedure as defined in clause 7.3b.3 in TS 36.300 [5].
9. SGW delivers downlink data to RAN.
10-11. The eNodeB can decide to use MT-EDT and move the UE to IDLE mode.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.6 Void
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5.3.6A PDN GW Pause of Charging procedure
The PDN GW Pause of Charging procedure is optionally supported by the Serving GW and PDN GW and has the purpose to limit a mismatch between PDN GW and Serving GW charging volume and packet counts. Generally, it aims for the PDN GW charging and usage monitoring data to more accurately reflect the downlink traffic actually sent to the E-UTRAN.
NOTE 1: A consequence of using this procedure is that PDN GW charging data does not correspond to the volume that traversed the PDN GW, and it is therefore not possible to count the downlink packets dropped between the PDN GW and the E-UTRAN.
The Serving GW may indicate support of this function to the PDN GW when the PDN connection is activated or when a new/target Serving GW is used for a PDN connection. This is indicated to the PDN GW by a "PDN Charging Pause Support Indication" in the Create Session Request during PDN activation/Attach and in the Modify Bearer Request in procedures with a change of Serving GW.
NOTE 2: It is assumed that Pause of PGW Charging is not invoked by SGW that is performing extended data buffering.
The PDN GW may indicate if the feature is to be enabled on a per PDN connection basis, if the current Serving GW supports the feature and the operator's policy is to enable the feature. This is indicated to the Serving GW by a "PDN Charging Pause Enabled" Indication in the Create Session Response during PDN activation/Attach and in the Modify Bearer Response in procedures with a change of Serving GW. This is an indication to the Serving GW that when the criteria for pause of PDN GW charging are met (as described further down in this clause) the PDN GW charging can be paused.
NOTE 3: PDNs where this function applies are based on an operator policy in the PDN GW. What enters into that policy is operator specific but may be based on for example if the PDN uses SDF based charging, UE is in home or visited network, APN employed, UE is configured for NAS signalling low priority, Charging Characteristics value etc.
The PDN GW shall stop any charging and usage monitoring actions for the PDN connection upon receiving a "PDN Charging Pause Start" Indication in a Modify Bearer Request. When the PDN GW receives a Modify Bearer Request for a PDN connection for which charging has been stopped previously and, if the Modify Bearer Request contains a "PDN Charging Pause Stop" Indication or does not contain a "PDN Charging Pause Start" Indication, then the PDN GW shall continue charging for the PDN connection.
NOTE 4: In addition to the Service Request Procedure, the PDN GW charging is also unpaused during mobility procedures involving the Serving GW based on Modify Bearer Request messages without "PDN Charging Pause Start" indication or during mobility procedures involving the Gn/Gp SGSN based on Update PDP Context Request messages.
NOTE 5: A Delete Bearer Command or Delete Bearer Request or Delete Bearer Response for a dedicated bearer does not unpause a previously paused PDN charging.
When bearers become suspended for a UE (see TS 23.272 [58]), the PDN GW charging is no longer paused and the PDN GW continues charging for the PDN connection after suspended bearers are resumed.
NOTE 6: The PDN GW discards packets received for a suspended UE as described in TS 23.272 [58].
While the PDN GW charging is currently paused and the UE is in ECM-IDLE (for ISR case the device is at same time in PMM-IDLE or STANDBY in UTRAN/GERAN accesses) the following applies:
- The PDN GW shall not perform charging and usage monitoring actions for downlink traffic on this PDN.
NOTE 7: The Serving GW charges anyway only for the amount of transmitted downlink traffic as described in clause 5.7A.
- Based on operator policy/configuration in the PDN GW, the PDN GW may limit the rate of downlink traffic sent to the Serving GW.
Based on operator policy/configuration in the Serving GW, the Serving GW may discard rather than buffer the downlink user plane packets for this PDN connection while the PDN GW charging is paused. This is to avoid delivery of user plane packets to the UE that were not counted in the PDN GW for charging and usage monitoring purposes. Regardless of operator policy/configuration, the downlink user plane packets received from PDN GW at the Serving GW shall trigger Downlink Data Notifications as described in clause 5.3.4.3.
When the Serving GW receives a Modify Bearer Request or Modify Access Bearers Request for a PDN connection triggering a Modify Bearer Request towards the PDN GW, the Serving GW shall consider the PDN charging as being unpaused if it has been paused previously.
Figure 5.3.6A: PDN GW Pause of charging procedure
1. The Serving GW receives downlink data packets for a UE known as not user plane connected (i.e. the Serving GW context data indicates no downlink user plane TEID for the eNodeB) as described in clause 5.3.4.3 step 1, i.e. the packets are buffered or discarded in Serving GW based on operator policy.
2. Based on operator policy/configuration the Serving GW triggers the procedure to pause PDN charging. Triggering criteria are based on Serving GW operator policy/configuration. Example of such policy may be:
a. Operator specified criteria/threshold (e.g. number/fraction of packets/bytes dropped at Serving GW in downlink since last time the UE was in ECM-CONNECTED state (or for ISR case PMM-CONNECTED state)).
b. Recent indication of "Abnormal Release of Radio Link" (see clause 5.3.5) or a recent Downlink Data Notification Reject (clause 5.3.4.3) without UE shortly re-entering ECM-CONNECTED state (or for ISR case without also re-entering PMM-CONNECTED state).
3. Serving GW sends a Modify Bearer Request (PDN Charging Pause Start) message to the PDN GW. PDN Charging Pause Start indicates that PDN GW charging shall be paused.
4. PDN GW confirms with a Modify Bearer Response message.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.7 GUTI Reallocation procedure
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The MME may initiate the GUTI Reallocation procedure to reallocate the GUTI and/or TAI list at any time when a signalling association is established between UE and MME. The GUTI Reallocation procedure allocates a new GUTI and/or a new TAI list and/or PLMN-assigned UE Radio Capability ID to the UE. The GUTI and/or the TAI list may also be reallocated by the Attach or the Tracking Area Update procedures.
When the UE supports RACS, and the MME needs to configure the UE with a UE Radio Capability ID, and the MME already has the UE radio capabilities for the UE, the MME may initiate the GUTI Reallocation procedure to provide the UE with the UE Radio Capability ID for the UE radio capabilities the UCMF returns to the MME for this UE. When the UE supports RACS, and the MME needs to delete any previously assigned PLMN-assigned UE Radio Capability ID(s) for the UE, the MME may initiate the GUTI Reallocation procedure to signal a PLMN-assigned UE Radio Capability ID deletion indication. If the UE receives PLMN-assigned UE Radio Capability ID deletion indication, the UE shall delete any PLMN-assigned UE Radio Capability ID(s) for this PLMN.
The GUTI Reallocation procedure is illustrated in Figure 5.3.7-1.
Figure 5.3.7-1: GUTI Reallocation Procedure
1. The MME sends GUTI Reallocation Command (GUTI, TAI list, PLMN-assigned UE Radio Capability ID, PLMN-assigned UE Radio Capability ID deletion indication) to the UE.
2. The UE returns GUTI Reallocation Complete message to the MME.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.8 Detach procedure
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.8.1 General
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The Detach procedure allows:
- the UE to inform the network that it does not want to access the EPS any longer, and
- the network to inform the UE that it does not have access to the EPS any longer.
The UE is detached either explicitly or implicitly:
- Explicit detach: The network or the UE explicitly requests detach and signal with each other.
- Implicit detach: The network detaches the UE, without notifying the UE. This is typically the case when the network presumes that it is not able to communicate with the UE, e.g. due to radio conditions.
Four detach procedures are provided when the UE accesses the EPS through E-UTRAN. The first detach procedure is UE-initiated detach procedure and other detach procedures are network-initiated detach procedure:
- UE-Initiated Detach Procedure. In the ISR activated case the UE initiated detach is split into two sub procedures, one for UE camping on E-UTRAN and one for UE camping on GERAN/UTRAN;
- MME-Initiated Detach Procedure;
- SGSN-Initiated Detach procedure with ISR activated;
- HSS-Initiated Detach Procedure.
NOTE 1: The MME and the UE may enter EMM-DEREGISTERED state without the above procedures.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.8.2 UE-initiated Detach procedure
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The Detach procedure when initiated by the UE is described in clauses 5.3.8.2.1 and 5.3.8.2.2.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.8.2.1 UE-initiated Detach procedure for E-UTRAN
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Figure 5.3.8.2-1 shows the case when UE camps on E-UTRAN and Detach Request is sent to MME.
Figure 5.3.8.2-1: UE-Initiated Detach Procedure - UE camping on E-UTRAN
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402 [2]. Steps 6, 7 and 8 concern GTP based S5/S8
1. The UE sends NAS message Detach Request (GUTI, Switch Off) to the MME. This NAS message is used to trigger the establishment of the S1 connection if the UE was in ECM-IDLE mode. Switch Off indicates whether detach is due to a switch off situation or not. The eNodeB forwards this NAS message to the MME along with the TAI+ECGI of the cell which the UE is using.
If the MME receives a Detach Request via a CSG cell with Switch Off parameter indicating that detach is not due to a switch off situation, and the CSG subscription for this CSG ID and associated PLMN is absent or expired, the MME shall trigger a MME-initiated Detach procedure as specified in clause 5.3.8.3.
If Dual Connectivity is active for the UE, the PSCell ID shall be included in the Uplink NAS Transport that carries the Detach Request message.
NOTE 2: Security procedures may be invoked if the NAS message is used to establish the S1 connection.
NOTE 3: For emergency attached or RLOS attached UEs that were not successfully authenticated, security procedures are not performed.
2. If the UE has no activated PDN connection, then steps 2 to 10 are not executed. If the PLMN has configured secondary RAT usage data reporting, the MME shall wait for step 11, if applicable, and shall perform step 12 before step 2 onwards. For any PDN connection to the SCEF, the MME indicates to the SCEF that the PDN connection for the UE is no longer available according to TS 23.682 [74] and steps 2 to 10 are not executed. For PDN connections to the P-GW, the active EPS Bearers in the Serving GW regarding this particular UE are deactivated by the MME sending Delete Session Request (LBI, User Location Information (ECGI), Secondary RAT usage data, PSCell ID) per PDN connection to the Serving GW. If ISR is activated, then the Serving GW shall not release the Control Plane TEID allocated for MME/SGSN until it receives the Delete Session Request message in step 5. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. If Secondary RAT usage data report was received from RAN, the MME includes this in the Delete Session Request message. If MME has received PSCell ID from eNodeB, the MME includes it in Delete Session Request.
3. When the S‑GW receives the first Delete Session Request message from the MME or SGSN in ISR activated state, the Serving GW deactivates ISR, releases the related EPS Bearer context information and responds with Delete Session Response (Cause).
When the S‑GW receives the Delete Session Request message from the MME or SGSN in ISR deactivated state, the Serving GW releases the related EPS Bearer context information and jumps to step 6 by sending a Delete Session Request (LBI) message per PDN connection to the PDN GW. After step 7 the Serving GW responds back to the MME/SGSN with the Delete Session Response (Cause and, optionally, APN Rate Control Status according to clause 4.7.7.3) message.
4. If ISR is activated, MME sends Detach Indication (Cause) message to the associated SGSN. The Cause indicates complete detach.
5. The active PDP contexts in the Serving GW regarding this particular UE are deactivated by the SGSN sending Delete Session Request (LBI, CGI/SAI) per PDN connection to the Serving GW. If the UE Time Zone has changed, the SGSN includes the UE Time Zone IE in this message.
6. If ISR is activated, Serving GW deactivates ISR. If ISR is not activated in the Serving GW, the Serving GW sends Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI), Secondary RAT usage data) per PDN connection to the PDN GW. If ISR is not activated, this step shall be triggered by step 2. This message indicates that all bearers belonging to that PDN connection shall be released. If the MME and/or SGSN sends UE's Location Information, and/or UE Time Zone Information, and/or Secondary RAT usage data in step 2 and/or step 5, the S‑GW includes the User Location Information, and/or UE Time Zone, and/or User CSG Information with the least age in this message and/or Secondary RAT usage data information.
7. The PDN GW acknowledges with Delete Session Response (Cause and, optionally, APN Rate Control Status according to clause 4.7.7.3).
8. The PDN GW employs a PCEF initiated IP‑CAN Session Termination Procedure as defined in TS 23.203 [6] with the PCRF to indicate to the PCRF that EPS Bearer is released if PCRF is applied in the network. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6].
9. The Serving GW acknowledges with Delete Session Response (Cause and, optionally, APN Rate Control Status).
10. The SGSN sends Detach Acknowledge message to the MME (optionally APN Rate Control Status). If received, the MME stores the APN Rate Control Status in the MM context.
11. If Switch Off indicates that detach is not due to a switch off situation, the MME sends a Detach Accept to the UE.
12. The MME releases the S1-MME signalling connection for the UE by sending S1 Release Command to the eNodeB with Cause set to Detach. The details of this step are covered in the "S1 Release Procedure", as described in clause 5.3.5.
NOTE 4: In the "S1 Release Procedure", if Dual Connectivity was active at the time of the release, the eNodeB includes the PSCell ID.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.8.2.2 UE-initiated Detach procedure for GERAN/UTRAN with ISR activated
|
Figure 5.3.8.2-2 shows the case when UE with ISR Activated camps on GERAN/UTRAN and Detach Request is sent to SGSN. Refer to clause 6.6.1 of TS 23.060 [7] for the UE-initiated Detach procedure when ISR is not activated.
Figure 5.3.8.2-2: UE-Initiated Detach Procedure - UE camping on GERAN/UTRAN, ISR activated
1. The UE sends NAS message Detach Request (Detach Type, P‑TMSI, P‑TMSI‑Signature, Switch Off) to the SGSN. Detach Type indicates which type of detach is to be performed, i.e. GPRS Detach only, IMSI Detach only or combined GPRS and IMSI Detach. Switch Off indicates whether detach is due to a switch off situation or not. The Detach Request message includes P‑TMSI and P‑TMSI Signature. P‑TMSI Signature is used to check the validity of the Detach Request message. If P‑TMSI Signature is not valid or is not included, the authentication procedure should be performed.
If the SGSN receives a Detach Request via a CSG cell with Switch Off parameter indicating that detach is not due to a switch off situation, and the CSG subscription for this CSG ID and associated PLMN is absent or expired, the SGSN shall trigger a SGSN-initiated Detach procedure as specified in clause 5.3.8.3A.
2. The active EPS Bearers in the Serving GW regarding this particular UE are deactivated by the SGSN sending Delete Session Request (LBI, User Location Information (CGI/SAI)) per PDN connection to the Serving GW. Because ISR is activated, then the Serving GW shall not release the Control Plan TEID allocated for MME/SGSN until it receives the Delete Session Request message in step 5. If the UE Time Zone has changed, the SGSN includes the UE Time Zone IE in this message.
3. Because the Serving GW receives this message in ISR activated state, the Serving GW deactivates ISR and acknowledges with Delete Session Response (Cause).
4. Because ISR is activated, the SGSN sends Detach Notification (Cause) message to the associated MME. Cause indicates complete detach.
5. The active PDP contexts in the Serving GW regarding this particular UE are deactivated by the MME sending Delete Session Request (LBI, ECGI) per PDN connection to the Serving GW. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message.
6. Serving GW deactivates ISR and sends Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI)) per PDN connection to the PDN GW. If ISR is not activated, this step shall be triggered by step 2. This message indicates that all bearers belonging to that PDN connection shall be released. If the MME and/or SGSN sends UE's Location Information and/or UE Time Zone Information in step 2 and/or step 5, the S‑GW includes the User Location Information and/or UE Time Zone with the least age in this message.
7. The PDN GW acknowledges with Delete Session Response (Cause).
8. The PDN GW employs a PCEF initiated IP CAN Session Termination Procedure as defined in TS 23.203 [6] with the PCRF to indicate to the PCRF that EPS Bearer is released if PCRF is applied in the network. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6].
9. The Serving GW acknowledges with Delete Session Response (Cause).
10. The MME sends Detach Acknowledge message to the SGSN.
11. If Switch Off indicates that detach is not due to a switch off situation, the SGSN sends a Detach Accept to the UE.
12. If the MS was GPRS detached, then the 3G SGSN releases the PS signalling connection.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.8.3 MME-initiated Detach procedure
|
The MME-Initiated Detach procedure when initiated by the MME is illustrated in Figure 5.3.8.3-1.
This procedure may be also used as part of the SIPTO function when the MME determines that GW relocation is desirable for all PDN connection(s) serving SIPTO-allowed APNs. The MME initiates the "explicit detach with reattach required" procedure and the UE should then re-establish those PDN connections for the same APN(s).
Figure 5.3.8.3-1: MME-Initiated Detach Procedure
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402 [2]. Steps 3, 4 and 5 concern GTP based S5/S8.
NOTE 2: Procedure steps (B) are used by the procedure steps (E) in clause 5.3.2.1.
1. The MME initiated detach procedure is either explicit (e.g. by O&M intervention) or implicit. The MME may implicitly detach a UE, if it has not had communication with UE for a long period of time. The MME does not send the Detach Request (Detach Type) message to the UE for implicit detach. The implicit detach is local to the MME, i.e. an SGSN registration will not be detached. If the UE is in ECM-CONNNECTED state the MME may explicitly detach the UE by sending a Detach Request message to the UE. The Detach Type may be set to re-attach in which case the UE should re-attach at the end of the detach process. If the UE is in ECM-IDLE state the MME pages the UE.
For emergency attached UEs, MME initiated implicit detach procedures are based on an inactivity timeout specific to emergency.
If this Detach procedure is due to the UE's Detach Request via a CSG cell which the UE is not allowed to access, i.e. the CSG subscription for this CSG ID and associated PLMN is absent or expired, the MME shall send a Detach Request to UE with an appropriate cause indicating the UE is not allowed to access this CSG.
In the case of satellite access for Cellular IoT, the MME initiates detach procedure if it detects that the UE's registered PLMN is not allowed to operate in the present UE location (see clause 4.13.4). In this case, the MME shall include in the Detach Request message a suitable cause value.
The MME may provide S&F Monitoring List to the UE (see clause 4.13.9.1).
2. If the UE has no activated PDN connection, then steps 2 to 10 are not executed. If the PLMN has configured secondary RAT usage reporting, the MME shall wait for step 11, if applicable, and perform step 12 before step 2 onwards. For any PDN connections to the SCEF, the MME indicates to the SCEF that the PDN connection for the UE is no longer available according to TS 23.682 [74] and steps 2 to 10 are not executed. For PDN connections to the P-GW, any EPS Bearer Context information in the Serving GW regarding this particular UE and related to the MME are deactivated by the MME sending Delete Session Request (LBI, User Location Information (ECGI), NAS Release Cause if available, Secondary RAT usage data, PSCell ID) message per PDN connection to the Serving GW. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. NAS Release Cause is only sent by the MME to the PDN GW if this is permitted according to MME operator's policy. If Secondary RAT usage data report was received from the RAN, the MME includes this in the Delete Session Request message. If MME has received PSCell ID from eNodeB, the MME includes it in Delete Session Request.
3. When the S‑GW receives the first Delete Session Request message from the MME or SGSN in ISR activated state, the Serving GW deactivates ISR, releases the related EPS Bearer context information and responds with Delete Session Response (Cause).
When the S‑GW receives the Delete Session Request message from the MME or SGSN in ISR deactivated state, the Serving GW releases the related EPS Bearer context information and jumps to step 6 by sending a Delete Session Request (LBI) message to the PDN GW. After step 7 the Serving GW responds back to the MME/SGSN with the Delete Session Response (Cause and, optionally, APN Rate Control Status according to clause 4.7.7.3) message.
4. If ISR is activated, MME sends Detach Notification (Cause) message to the associated SGSN. The cause indicates whether it is a local or complete detach.
5. If cause indicates complete detach then the SGSN sends a Delete Session Request (LBI, CGI/SAI) message per PDN connection to the Serving GW. If Cause indicates local detach then SGSN deactivates ISR and steps 5 to 9 shall be skipped. If the UE Time Zone has changed, the SGSN includes the UE Time Zone IE in this message.
6. If ISR is activated, Serving GW deactivates ISR.
If ISR is not activated and the Serving GW received one or several Delete Bearer Request message(s) from SGSN in step 2, the Serving GW sends a Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI), NAS Release Cause if available, Secondary RAT usage data) message for each associated PDN connection to the PDN GW. NAS Release Cause is the one received in the Delete Session Request from the MME. This message indicates that all bearers belonging to that PDN connection shall be released.
If the MME and/or SGSN send(s) UE's Location Information, and/or UE Time Zone and/or Secondary RAT usage data in step 2 and/or step 5, the S‑GW includes the User Location Information, and/or UE Time Zone Information with the least age in this message and/or Secondary RAT usage data.
7. The PDN GW acknowledges with Delete Session Response (Cause and, optionally, APN Rate Control Status according to clause 4.7.7.3) message.
8. The PDN GW employs an IP‑CAN Session Termination procedure as defined in TS 23.203 [6] with the PCRF to indicate to the PCRF that the EPS Bearer(s) are released if a PCRF is configured. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information and NAS Release Cause (if available) to the PCRF as defined in TS 23.203 [6].
9. The Serving GW acknowledges with Delete Session Response (Cause, APN Rate Control Status) message.
10. The SGSN sends Detach Acknowledge message to the MME (APN Rate Control Status). The MME stores the APN Rate Control Status in the MM context.
11. If the UE receives the Detach Request message from the MME in the step 1, the UE sends a Detach Accept message to the MME any time after step 1. The eNodeB forwards this NAS message to the MME along with the TAI+ECGI of the cell which the UE is using.
If Dual Connectivity is active for the UE, the PSCell ID shall be included in the Uplink NAS Transport that carries the Detach Accept message.
If the UE receives Detach Request from the MME via a CSG cell with the cause indicating the UE is not allowed to access this CSG, the UE shall remove this CSG ID and associated PLMN from its Allowed CSG list, if present.
12. After receiving the Detach Accept message, Delete Session Response and, if appropriate, Detach Acknowledge message, the MME releases the S1-MME signalling connection for the UE by sending an S1 Release Command (Cause) message to the eNodeB. The details of this step are covered in the "S1 Release Procedure", as described in clause 5.3.5 by step 4 to step 6. If the Detach Type requests the UE to make a new attach, the UE reattaches after the RRC Connection Release is completed.
NOTE 3: In the "S1 Release Procedure", if Dual Connectivity was active at the time of the release, the eNodeB includes the PSCell ID.
5.3.8.3A SGSN-initiated Detach procedure with ISR activated
The SGSN-Initiated Detach procedure with ISR activated is illustrated in Figure 5.3.8.3A-1. Refer to clause 6.6.2.1 of TS 23.060 [7] for the SGSN-initiated Detach procedure when ISR is not activated.
Figure 5.3.8.3A-1: SGSN-Initiated Detach Procedure with ISR activated
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402 [2]. Steps 3, 4 and 5 concern GTP based S5/S8.
1. The SGSN initiated detach procedure is either explicit (e.g. by O&M intervention) or implicit. The SGSN may implicitly detach a UE, if it has not had communication with UE for a long period of time. The SGSN does not send the Detach Request (Detach Type) message to the UE for implicit detach. The implicit detach is local to the SGSN, i.e. an MME registration will not be detached. If the UE is in PMM-CONNNECTED state the SGSN may explicitly detach the UE by sending a Detach Request message to the UE. The Detach Type may be set to re-attach in which case the UE should re-attach at the end of the detach process. If the UE is in PMM-IDLE state the SGSN pages the UE.
If this Detach procedure is due to the UE's Detach Request via a CSG cell which the UE is not allowed to access, i.e. the CSG subscription for this CSG ID and associated PLMN is absent or expired, the SGSN shall send a Detach Request to UE with an appropriate cause indicating the UE is not allowed to access this CSG.
2. Any EPS Bearer Context information in the Serving GW regarding this particular UE and related to the SGSN is deactivated by the SGSN sending Delete Session Request (LBI, User Location Information (ECGI)) message per PDN connection to the Serving GW. If the UE Time Zone has changed, the SGSN includes the UE Time Zone IE in this message.
3. Because the Serving GW receives this message in ISR activated state, the Serving GW deactivates ISR, releases the SGSN related EPS Bearer context information and acknowledges with Delete Session Response (Cause).
4. Because ISR is activated, the SGSN sends Detach Notification (Cause) message to the associated MME. The cause indicates whether it is a local or complete detach.
5. If cause indicates complete detach then the MME sends a Delete Session Request (LBI, User Location Information (ECGI)) message per PDN connection to the Serving GW. If Cause indicates local detach then MME deactivates ISR and steps 5 to 9 shall be skipped. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message.
6. The Serving GW sends a Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI)) message per PDN connection to the PDN GW. This message indicates that all bearers belonging to that PDN connection shall be released. If the MME and/or SGSN sends UE's Location Information and/or UE Time Zone in step 2 and/or step 5, the S‑GW includes the User Location Information and/or UE Time Zone Information with the least age in this message.
7. The PDN GW acknowledges with Delete Session Response (Cause) message.
8. The PDN GW employs an IP CAN Session Termination procedure as defined in TS 23.203 [6] with the PCRF to indicate to the PCRF that the EPS Bearer(s) are released if a PCRF is configured. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6].
9. The Serving GW acknowledges with Delete Session Response (Cause) message.
10. The MME sends Detach Acknowledge message to the SGSN.
11. If the UE receives the Detach Request message from the SGSN in the step 1, the UE sends a Detach Accept message to the SGSN any time after step 1.
If the UE receives Detach Request from the SGSN via a CSG cell with the cause indicating the UE is not allowed to access this CSG, the UE shall remove this CSG ID and associated PLMN from its Allowed CSG list, if present.
12. After receiving the Detach Accept message, if Detach Type did not request the UE to make a new attach, then the 3G SGSN releases the PS signalling connection.
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495b59b986f98d41912141cabbec196e
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23.401
|
5.3.8.4 HSS-initiated Detach procedure
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The HSS-Initiated Detach procedure is initiated by the HSS. The HSS uses this procedure for operator-determined purposes to request the removal of a subscriber's MM and EPS bearer at the MME and also at the SGSN if both an MME and an SGSN are registered in the HSS.
For UEs with emergency EPS bearers, the MME/SGSN shall not initiate detach procedure. Instead the MME/SGSN shall deactivate all the non-emergency PDN connection.
If the HSS-Initiated Detach procedure is initiated, and UE is RLOS attached, the MME shall not initiate detach procedure.
NOTE 1: HSS-initiated Detach can happen for a UE that camps on a cell in limited state due to UE moving to a forbidden area performs RLOS attach and the MME does not perform Purge procedure for the UE towards the HSS (as specified in clause 5.3.9.3).
For subscription change, e.g. RAT restrictions to disallow one of the RATs, the Insert Subscription Data procedure shall be used towards the MME, and also towards the SGSN if both an MME and an SGSN are registered in the HSS.
This procedure is not applied if a Cancel Location is sent to the MME or the SGSN with a cause other than Subscription Withdrawn.
The HSS-Initiated Detach Procedure is illustrated in Figure 5.3.8.4-1.
Figure 5.3.8.4-1: HSS-Initiated Detach Procedure
NOTE 2: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402 [2]. Steps 4, 5 and 6 concern GTP based S5/S8.
NOTE 3: Procedure steps (B) are used by the procedure steps (F) in clause 5.3.2.1.
NOTE 4: The steps below apply for an S4-SGSN. For Gn/Gp SGSN, the procedure specified in clause 6.6.2.2. of TS 23.060 [7] applies for the SGSN.
1. If the HSS wants to request the immediate deletion of a subscriber's MM contexts and EPS Bearers, the HSS shall send a Cancel Location (IMSI, Cancellation Type) message with Cancellation Type set to Subscription Withdrawn to the registered MME and also to the SGSN if an SGSN is also registered. When receiving the Cancel Location Message the MME/SGSN acknowledges with a Cancel Location ACK (IMSI) message to the HSS.
2. If Cancellation Type is Subscription Withdrawn, the MME/SGSN which has an active UE context informs the UE which is in ECM-CONNECTED state, that it has been detached, by sending Detach Request (Detach Type) message to the UE. If the Cancel Location message includes a flag to indicate re-attach is required, the MME/SGSN shall set the Detach Type to indicate that re-attach is required. If the UE is in ECM-IDLE state the MME pages the UE.
NOTE 5: The UE will receive only one Detach Request message in the RAT where it currently camps on.
3a. If the UE has no activated PDN connection, then steps 3 to 7 are not executed. If the PLMN has configured secondary RAT usage data reporting, the MME shall wait for Step 8a, if applicable, and perform step 10a before step 3a. If the MME has an active UE context, for any PDN connection to the SCEF, the MME indicates to the SCEF that the PDN connection for the UE is no longer available according to TS 23.682 [74] and steps 3 to 7 are not executed. For PDN connections to the P-GW, the MME sends a Delete Session Request (LBI, User Location Information (ECGI), NAS Release Cause if available, Secondary RAT usage data if available, PSCell ID if available) message per PDN connection to the Serving GW to deactivate the EPS Bearer Context information in the Serving GW. NAS Release Cause is only sent by the MME to the PDN GW if this is permitted according to MME operator's policy. If MME has received PSCell ID from eNodeB, the MME includes it in Delete Session Request.
3b. If the SGSN has an active UE context, the SGSN sends a Delete Session Request (LBI, User Location Information (CGI/SAI)) per PDN connection to the Serving GW to deactivate the EPS Bearer Context information in the Serving GW.
4. When the S‑GW receives the first Delete Session Request message from the MME or SGSN in ISR activated state, the Serving GW deactivates ISR, releases the related EPS Bearer context information and responds with Delete Session Response in step 7.
When the S‑GW receives one or several Delete Session Request message(s) from the MME or SGSN in ISR deactivated state, the Serving GW releases the related EPS Bearer context information and sends a Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI), NAS Release Cause if available, Secondary RAT usage data if PGW secondary RAT usage data reporting is active) message for each associated PDN connection to the PDN GW. NAS Release Cause is the one received in the Delete Session Request from the MME or SGSN. This message indicates that all bearers belonging to that PDN connection shall be released. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. If the MME and/or SGSN sends UE's Location Information and/or UE Time Zone Information in step 3a and/or step 3b, the S‑GW includes the User Location Information and/or UE Time Zone with the least age in this message.
5. The PDN GW acknowledges with Delete Session Response (Cause and, optionally, APN Rate Control Status according to clause 4.7.7.3) message.
6. The PDN GW employs a PCEF initiated IP‑CAN Session Termination procedure as defined in TS 23.203 [6] with the PCRF to indicate to the PCRF that the EPS bearer is released if a PCRF is configured. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information and NAS Release Cause (if available) to the PCRF as defined in TS 23.203 [6].
7. The Serving GW acknowledges with Delete Session Response (TEID and, optionally, APN Rate Control Status) message.
If received, the MME stores the APN Rate Control Status in the MM context.
8. If the UE receives the Detach Request message from the MME/SGSN, the UE sends a Detach Accept message to the MME/SGSN any time after step 2. The message is sent either in E-UTRAN or GERAN/UTRAN access depending on which access the UE received the Detach Request. For the Detach Accept message from UE to MME the eNodeB forwards this NAS message to the MME along with the TAI+ECGI of the cell which the UE is using.
If Dual Connectivity is active for the UE, the PSCell ID shall be included in the Uplink NAS Transport that carries the Detach Accept message.
9. Void.
10a. After receiving the Detach Accept message, the MME releases the S1-MME signalling connection for the UE by sending S1 Release Command (Cause) message to the eNodeB with Cause set to Detach. The details of this step are covered in the "S1 Release Procedure", as described in clause 5.3.5.
NOTE 6: In the "S1 Release Procedure", if Dual Connectivity was active at the time of the release, the eNodeB includes the PSCell ID.
10b. After receiving the Detach Accept message, if Detach Type did not request the UE to make a new attach, then the 3G SGSN releases the PS signalling connection.
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495b59b986f98d41912141cabbec196e
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23.401
|
5.3.9 HSS User Profile management function procedure
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.9.1 General
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The HSS user profile management function allows the HSS to update the HSS user profile stored in the MME. Whenever the HSS user profile is changed for a user in the HSS, and the changes affect the HSS user profile stored in the MME, the MME shall be informed about these changes by the means of the following procedure:
- Insert Subscriber Data procedure, used to add or modify the HSS user profile in the MME.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.9.2 Insert Subscriber Data procedure
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The Insert Subscriber Data procedure is illustrated in Figure 5.3.9.2-1.
Figure 5.3.9.2-1: Insert Subscriber Data procedure
1. The HSS sends an Insert Subscriber Data (IMSI, Subscription Data) message to the MME.
2. The MME updates the stored Subscription Data and acknowledges the Insert Subscriber Data message by returning an Insert Subscriber Data Ack (IMSI) message to the HSS. The update result should be contained in the Ack message.
The MME initiates appropriate action according to the changed subscriber data (e.g. MME initiates detach if the UE is not allowed to roam in this network). For received PDN subscription contexts that have no related active PDN connection in the MME, no further action is required except storage in the MME. Otherwise if the subscribed QoS Profile has been modified and the UE is in ECM‑CONNECTED state or in ECM-IDLE state when ISR is not activated but the UE is reachable by the MME, the HSS Initiated Subscribed QoS Modification procedure, as described in Figure 5.4.2.2-1, is invoked from step 2a. When ISR is not activated and the UE is in ECM IDLE state and is not reachable by the MME, e.g. when the UE is suspended, when the UE has entered into power saving mode or when the PPF is cleared in the MME, the HSS Initiated Subscribed QoS Modification procedure, as described in Figure 5.4.2.2-1, is invoked from step 2a at the next ECM IDLE to ECM CONNECTED transition. If the UE is in ECM‑IDLE state and the ISR is activated, this procedure is invoked at the next ECM‑IDLE to ECM‑CONNECTED transition. If the UE is in ECM‑IDLE state and the ISR is not activated and if the subscription change no longer allows the PDN connection, the MME initiated PDN disconnection procedure in clause 5.10.3 is used to delete the concerned PDN connection. If the MME receives RAT specific Subscribed Paging Time Window that is different from the one stored in the MME MM context, the MME updates RAT specific Subscribed Paging Time Window parameter in the MME MM context to the value received from the HSS.
If the UE is in ECM-CONNECTED state and connected via a CSG or hybrid cell, the MME shall check the received CSG subscription data. If the MME detects that the CSG membership to that cell has changed or expired, the MME initiates the procedure in clause 5.16.
If the MME received a changed Service Gap Time parameter in the updated subscription data, the MME shall provide the new Service Gap Time value to the UE in the next Tracking Area Update Accept message, or, if the UE does not send any Tracking Area Update Request within a certain time period that shall be longer than any PSM or eDRX interval used by the UE, the MME may initiate a detach with reattach required of the UE or an RRC connection release with release cause load balancing TAU required of the UE.
If supported by the MME and if the MME receives a modified Time Reference Information Distribution Indication in the updated subscription data while the UE is in ECM-CONNECTED, the MME shall provide the modified Time Reference Information Distribution Indication to the eNB. If supported by the MME and if the MME receives a modified Time Reference Information Distribution Indication in the updated subscription data while the UE's connection is suspended (see clause 5.3.4A), the MME shall provide the modified Time Reference Information Distribution Indication to the eNB after the UE has resumed the connection (see clause 5.3.5A).
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495b59b986f98d41912141cabbec196e
|
23.401
|
5.3.9.3 Purge function
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The Purge function allows an MME to inform the HSS that it has deleted the subscription data and MM context of a detached UE. The MME may, as an implementation option, delete the subscription data and MM context of an UE immediately after the implicit or explicit detach of the UE. Alternatively the MME may keep for some time the subscription data and the MM context of the detached UE, so that the data can be reused at a later attach without accessing the HSS.
Figure 5.3.9.3-1: Purge Procedure
1. After deleting the Subscription data and MM contexts of a detached UE, the MME sends Purge UE (IMSI) message to the HSS.
2. The HSS sets the UE Purged for E-UTRAN flag and acknowledges with a Purge UE Ack message.
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495b59b986f98d41912141cabbec196e
|
23.401
|
5.3.10 Security Function
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495b59b986f98d41912141cabbec196e
|
23.401
|
5.3.10.1 General
|
The security functions include:
- Guards against unauthorised EPS service usage (authentication of the UE by the network and service request validation).
- Provision of user identity confidentiality (temporary identification and ciphering).
- Provision of user data and signalling confidentiality (ciphering).
- Provision of origin authentication of signalling and user data (integrity protection).
- Authentication of the network by the UE.
Security-related network functions for EPS are described in TS 33.401 [41].
The aspects of user plane data integrity protection that involve interactions with the 5G Core are specified in TS 23.501 [83] and TS 23.502 [84].
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495b59b986f98d41912141cabbec196e
|
23.401
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5.3.10.2 Authentication and Key Agreement
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EPS AKA is the authentication and key agreement procedure that shall be used over E-UTRAN, between the UE and MME. EPS AKA is specified in TS 33.401 [41].
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.10.3 User Identity Confidentiality
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An M-TMSI identifies a user between the UE and the MME. The relationship between M-TMSI and IMSI is known only in the UE and in the MME.
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23.401
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5.3.10.4 User Data and Signalling Confidentiality
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.10.4.0 General
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There are two different levels of the security associations between the UE and the network.
i) RRC and UP security association is between the UE and E‑UTRAN. The RRC security associations protect the RRC signalling between the UE and E‑UTRAN (integrity protection and ciphering). The UP security association is between the UE and E‑UTRAN and can provide user plane encryption and integrity protection.
ii) NAS security association is between the UE and the MME. It provides integrity protection and encryption of NAS signalling and, when the Control Plane CIoT EPS Optimisation is used, user data.
Some earlier releases of the EPS specifications do not support User Plane Integrity Protection in EPS (EPS-UPIP). Hence UEs that support EPS-UPIP indicate this capability in the security algorithm octets of the UE Network Capability IE as defined in TS 24.301 [46] and use it as described in TS 33.401 [41]; and the MME copies this capability into S1-AP signalling sent to the E-UTRAN. The E-UTRAN can be locally configured with a policy (to be used when no explicit EPS UPIP policy is received from the MME), e.g. that the use of EPS-UPIP is "Preferred" for UE(s) that support User Plane Integrity Protection in EPS.
For EPC networks with no 5GC interworking, E-UTRAN can have a preconfigured policy for "preferred" User Plane Integrity Protection that can be used if MME does not provide a security policy for the bearers of an UE and if the E-UTRAN has received an indication that the UE supports User Plane Integrity Protection. This preconfigured policy applies to any bearer of any UE unless the MME provides a User Plane Integrity Protection security policy to the E-UTRAN, in which case the MME policy overwrites the preconfigured E-UTRAN policy.
Differentiated User plane integrity protection beyond preconfigured policy is only supported for PDN connections served by a SMF+PGW-C: to support PDN connections that "Require" the use of EPS-UPIP, the MME shall select a SMF+PGW-C.
NOTE 1: See TS 23.502 [84] for additional features for EPS-UPIP in case of interworking with 5GC.
NOTE 2: In this Release of the specifications, EPS UPIP can only be supported by UEs that support NR-PDCP.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.10.4.1 AS security mode command procedure
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The MME triggers the RRC level AS security mode command procedure by sending the needed security parameters to the eNodeB. This enables ciphering of the UP traffic and ciphering and integrity protection of the RRC signalling as described in TS 33.401 [41].
NOTE: The integrity protection of the UP traffic is enabled using RRC reconfiguration procedure as described in TS 33.401 [41].
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.10.4.2 NAS Security Mode Command procedure
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The MME uses the NAS Security Mode Command (SMC) procedure to establish a NAS security association between the UE and MME, in order to protect the further NAS signalling messages. This procedure is also used to make changes in the security association, e.g. to change the security algorithm.
Figure 5.3.10.4.2-1: NAS Security Mode Command Procedure
1. The MME sends NAS Security Mode Command (Selected NAS algorithms, eKSI, ME Identity request, UE Security Capability) message to the UE. ME identity request may be included when NAS SMC is combined with ME Identity retrieval (see clause 5.3.10.5).
2. The UE responds NAS with Security Mode Complete (NAS-MAC, ME Identity) message. The UE includes the ME Identity if it was requested in step 1.
NOTE: The NAS Security Mode Command procedure is typically executed as part of the Attach procedure (see clause 5.3.2.1) in advance of, or in combination with, executing the ME Identity Check procedure (see clause 5.3.10.5) and in the TAU procedure (see clauses 5.3.3.1 and 5.3.3.2).
More details of the procedure are described in TS 33.401 [41].
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.10.5 ME identity check procedure
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The Mobile Equipment Identity Check Procedure permits the operator(s) of the MME and/or the HSS and/or the PDN GW to check the Mobile Equipment's identity (e.g. to check that it has not been stolen, or, to verify that it does not have faults).
The ME Identity can be checked by the MME passing it to an Equipment Identity Register (EIR) and then the MME analysing the response from the EIR in order to determine its subsequent actions (e.g. sending an Attach Reject if the EIR indicates that the Mobile Equipment is prohibited).
The ME identity check procedure is illustrated in Figure 5.3.10.5-1.
Figure 5.3.10.5-1: Identity Check Procedure
1. The MME sends Identity Request (Identity Type) to the UE. The UE responds with Identity Response (Mobile Identity).
2. If the MME is configured to check the IMEI against the EIR, it sends ME Identity Check (ME Identity, IMSI) to EIR. The EIR responds with ME Identity Check Ack (Result).
NOTE: The Identity Check Procedure is typically executed as part of the Attach procedure (see clause 5.3.2.1).
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.11 UE Reachability procedures
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.11.1 General
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There are two procedures necessary for any service related entity that would need to be notified by the reachability of the UE at EPC NAS level:
- UE Reachability Notification Request procedure; and
- UE Activity Notification procedure.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.11.2 UE Reachability Notification Request procedure
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The UE Reachability Notification Request procedure is illustrated in Figure 5.3.11.2-1.
Figure 5.3.11.2-1: UE Reachability Notification Request Procedure
1) If a service-related entity requests the HSS to provide an indication regarding UE reachability on EPS, the HSS stores the service-related entity and sets the URRP-MME parameter to indicate that such request is received. If the value of URRP-MME parameter has changed from "not set" to "set", the HSS sends a UE-REACHABILITY-NOTIFICATION-REQUEST (URRP-MME) to the MME. If the MME has an MM context for that user, the MME sets URRP-MME to indicate the need to report to the HSS information regarding changes in UE reachability, e.g. when the next NAS activity with that UE is detected.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.11.3 UE Activity Notification procedure
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The UE Activity Notification procedure is illustrated in Figure 5.3.11.3-1.
Figure 5.3.11.3-1: UE Activity Procedure
1) The MME receives an indication regarding UE reachability, e.g. an Attach Request message from the UE or MME receive an indication from S‑GW that UE has handed over to non-3GPP coverage.
2) If the MME contains an MM context of the UE and if URRP-MME for that UE is configured to report once that the UE is reachable, the MME shall send a UE-Activity-Notification (IMSI, UE-Reachable) message to the HSS and clears the corresponding URRP-MME for that UE.
3) When the HSS receives the UE-Activity-Notification (IMSI, UE-Reachable) message or the Update Location message for an UE that has URRP-MME set, it triggers appropriate notifications to the entities that have subscribed to the HSS for this notification and clears the URRP-MME for that UE.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.12 Update CSG Location Procedure
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The Update CSG Location procedure takes place when the SGSN/MME needs to retrieve the CSG subscription information of the UE from the CSS.
Figure 5.3.12-1: Update CSG Location Procedure
1. The SGSN/MME sends Update CSG Location Request (MME Identity, IMSI, MSISDN) to the CSS. The MSIDSN is included if available.
2. The CSS acknowledges the Update CSG Location message by sending an Update CSG Location Ack (IMSI, CSG Subscription data) message to the SGSN/MME.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.13 CSS subscription data management function procedure
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.13.1 General
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The CSS subscription data management function allows the CSS to update the CSS subscription data stored in the MME.
The CSS subscription data is stored and managed in the MME independently from the Subscription Data received from the HSS.
Whenever the CSS subscription data is changed for a user in the CSS, and the changes affect the CSG subscription information stored in the MME, the MME shall be informed about these changes by the means of the following procedure:
- Insert CSG Subscriber Data procedure, used to add or modify the CSS subscription data in the MME.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.13.2 Insert CSG Subscriber Data procedure
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The Insert CSG Subscriber Data procedure is illustrated in Figure 5.3.13.2-1.
Figure 5.3.13.2-1: Insert CSG Subscriber Data procedure
1. The CSS sends an Insert CSG Subscriber Data (IMSI, CSG Subscription Data) message to the MME.
2. The MME updates the stored CSG Subscription Data and acknowledges the Insert CSG Subscriber Data message by returning an Insert CSG Subscriber Data Ack (IMSI) message to the CSS. The update result should be contained in the Ack message.
The MME initiates appropriate action according to the changed CSG subscriber data. If the UE is in ECM-CONNECTED state and connected via a CSG or hybrid cell, the MME shall check the received CSG subscriber data. If the MME detects that the CSG membership to that cell has changed or expired, the MME initiates the procedure in clause 5.16.
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495b59b986f98d41912141cabbec196e
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23.401
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5.3.14 UE Radio Capability Match Request
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If the MME, e.g. based on SRVCC capability in NAS, UE Usage Type or local policy, requires more information on the UE radio capabilities support to be able to set the IMS voice over PS Session Supported Indication (see clause 4.3.5.8), then the MME may send a UE Radio Capability Match Request message to the eNodeB. This procedure is typically used during the Initial Attach procedure, during Tracking Area Update procedure for the "first TAU following GERAN/UTRAN Attach" or for "UE radio capability update" or when MME has not received the Voice Support Match Indicator (as part of the MM Context).
Figure 5.3.14-1: UE Radio Capability Match Request
1 The MME indicates whether the MME wants to receive Voice support match indicator. The MME may include the UE Radio Capability information that it has previously received from the eNodeB via a S1-AP UE CAPABILITY INFO INDICATION as described in clause 5.11.2.
2. Upon receiving a UE Radio Capability Match Request from the MME, if the eNodeB has not already received the UE radio capabilities from the UE or from MME in step 1, the eNodeB requests the UE to upload the UE radio capability information by sending the RRC UE Capability Enquiry.
3. The UE provides the eNodeB with its UE radio capabilities sending the RRC UE Capability Information.
4. The eNodeB checks whether the UE radio capabilities are compatible with the network configuration for ensuring voice service continuity of voice calls initiated in IMS.
For determining the appropriate UE Radio Capability Match Response, the eNodeB is configured by the operator to check whether the UE supports certain capabilities required for Voice continuity of voice calls using IMS PS. In a shared network, the eNodeB keeps a configuration separately per PLMN.
NOTE 1: What checks to perform depends on network configuration, i.e. following are some examples of UE capabilities to be taken into account:
- the SRVCC, and UTRAN/E-UTRAN Voice over PS capabilities;
- the Radio capabilities for UTRAN/E-UTRAN FDD and/or TDD; and/or
- the support of UTRAN/E-UTRAN frequency bands.
NOTE 2: The network configuration considered in the decision for the Voice Support Match Indicator is homogenous within a certain area (e.g. MME Pool Area) in order to guarantee that the Voice Support Match Indicator from the eNodeB is valid within such area.
The eNodeB provides a Voice Support Match Indicator to the MME to indicate whether the UE capabilities and networks configuration are compatible for ensuring voice service continuity of voice calls initiated in IMS.
The MME stores the received Voice support match indicator in the MM Context and uses it as an input for setting the IMS voice over PS Session Supported Indication.
5. If eNodeB requested radio capabilities from UE in step 2 and 3, eNodeB also sends the UE radio capabilities to the MME using the S1-AP UE CAPABILITY INFO INDICATION. The MME stores the UE radio capabilities without interpreting them for further provision to the eNodeB in cases described in clause 5.11.2.
NOTE 3: Steps 4 and 5 may be received by the MME in any order.
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495b59b986f98d41912141cabbec196e
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23.401
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5.4 Session Management, QoS and interaction with PCC functionality
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.1 Dedicated bearer activation
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The dedicated bearer activation procedure for a GTP based S5/S8 is depicted in figure 5.4.1-1. This procedure shall not be used when the UE is accessing over NB-IoT (i.e. RAT Type = NB-IoT).
Figure 5.4.1-1: Dedicated Bearer Activation Procedure
NOTE 1: Steps 3-10 are common for architecture variants with GTP based S5/S8 and PMIP-based S5/S8. For an PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 1, 2, 11 and 12 concern GTP based S5/S8.
1. If dynamic PCC is deployed, the PCRF sends a PCC decision provision (QoS policy) message to the PDN GW. This corresponds to the initial steps of the PCRF-Initiated IP‑CAN Session Modification procedure or to the PCRF response in the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6], up to the point that the PDN GW requests IP‑CAN Bearer Signalling. The PCC decision provision message may indicate that User Location Information and/or UE Time Zone Information is to be provided to the PCRF as defined in TS 23.203 [6]. If dynamic PCC is not deployed, the PDN GW may apply local QoS policy.
2. The PDN GW uses this QoS policy to assign the EPS Bearer QoS, i.e., it assigns the values to the bearer level QoS parameters QCI, ARP, GBR and MBR; see clause 4.7.3. If this dedicated bearer is created as part of the handover procedure from non-3GPP access with GTP-based S2a/S2b, then the PDN GW applies the Charging Id already in use for the corresponding dedicated bearer while the UE was in non-3GPP access (i.e bearer with the same QCI and ARP as in non-3GPP access). Otherwise, the PDN GW generates a Charging Id for the dedicated bearer. The PDN GW sends a Create Bearer Request message (IMSI, PTI, EPS Bearer QoS, Maximum Packet Loss Rate (UL, DL), TFT, S5/S8 TEID, Charging Id, LBI, Protocol Configuration Options) to the Serving GW, the Linked EPS Bearer Identity (LBI) is the EPS Bearer Identity of the default bearer. The Procedure Transaction Id (PTI) parameter is only used when the procedure was initiated by a UE Requested Bearer Resource Modification Procedure - see clause 5.4.5. Protocol Configuration Options may be used to transfer application level parameters between the UE and the PDN GW (see TS 23.228 [52]), and are sent transparently through the MME and the Serving GW.
NOTE 2: The PCO is sent in the dedicated bearer activation procedure either in response to a PCO received from the UE, or without the need to send a response to a UE provided PCO e.g. when the network wants the bearer to be dedicated for IMS signalling.
For a QCI=1 bearer, the Maximum Packet Loss Rate (UL, DL) may be provided by the PDN GW as described in TS 23.203 [6].
3. The Serving GW sends the Create Bearer Request (IMSI, PTI, EPS Bearer QoS, Maximum Packet Loss Rate (UL, DL), TFT, S1-TEID, PDN GW TEID (GTP-based S5/S8), LBI, Protocol Configuration Options) message to the MME. If the UE is in ECM-IDLE state the MME will trigger the Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3). In that case the following steps 4-7 may be combined into Network Triggered Service Request procedure or be performed stand-alone. The MME checks if the UE can support the establishment of additional user plane radio bearer based on the maximum number of user plane radio bearers indicated by NB-IoT UE in the UE Network Capability IE as defined in clause 5.11.3 and for WB-E-UTRAN in clause 4.12.
If the UE is in ECM-IDLE state and extended idle mode DRX is enabled for the UE, the MME will trigger Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3), and start a timer which is configured to a value smaller than the GTP re-transmission timer. If the MME receives no response from the UE before the timer expires, the MME sends a Create Bearer Response with a rejection cause indicating that the UE is temporarily not reachable due to power saving and, if a Delay Tolerant Connection indication was set for the PDN connection, the MME sets the internal flag Pending Network Initiated PDN Connection Signalling. The rejection is forwarded by the Serving GW to the PDN GW. In this case, the steps 4-11 are skipped.
NOTE 3: If ISR is activated and the Serving GW does not have a downlink S1-U and the SGSN has notified the Serving GW that the UE has moved to PMM-IDLE or STANDBY state, the Serving GW sends Downlink Data Notification to trigger MME and SGSN to page the UE (as specified in clause 5.3.4.3) before sending the Create Bearer Request message.
4. The MME selects an EPS Bearer Identity, which has not yet been assigned to the UE. The MME then builds a Session Management Request including the PTI, TFT, EPS Bearer QoS parameters (excluding ARP), Protocol Configuration Options, the EPS Bearer Identity, the Linked EPS Bearer Identity (LBI) and a WLAN offloadability indication. If the UE has UTRAN or GERAN capabilities and the network supports mobility to UTRAN or GERAN, the MME uses the EPS bearer QoS parameters to derive the corresponding PDP context parameters QoS Negotiated (R99 QoS profile), Radio Priority, Packet Flow Id and TI and includes them in the Session Management Request. If the UE indicated in the UE Network Capability it does not support BSS packet flow procedures, then the MME shall not include the Packet Flow Id. The MME then signals the Bearer Setup Request (EPS Bearer Identity, EPS Bearer QoS, Maximum Packet Loss Rate (UL, DL), Session Management Request, S1-TEID) message to the eNodeB.
The MME may include an indication whether the traffic of this PDN Connection is allowed to be offloaded to WLAN as described in clause 4.3.23.
5. The eNodeB maps the EPS Bearer QoS to the Radio Bearer QoS. It then signals a RRC Connection Reconfiguration (Radio Bearer QoS, Session Management Request, EPS RB Identity) message to the UE. The UE shall store the QoS Negotiated, Radio Priority, Packet Flow Id and TI, which it received in the Session Management Request, for use when accessing via GERAN or UTRAN. The UE NAS stores the EPS Bearer Identity and links the dedicated bearer to the default bearer indicated by the Linked EPS Bearer Identity (LBI). The UE uses the uplink packet filter (UL TFT) to determine the mapping of traffic flows to the radio bearer. The UE may provide the EPS Bearer QoS parameters to the application handling the traffic flow. The application usage of the EPS Bearer QoS is implementation dependent. The UE shall not reject the RRC Connection Reconfiguration on the basis of the EPS Bearer QoS parameters contained in the Session Management Request.
NOTE 4: How the eNodeB uses the Maximum Packet Loss Rate (UL, DL) for handover threshold decision, if provided, is out of scope of 3GPP specifications.
NOTE 5: The details of the Radio Bearer QoS are specified in TS 36.300 [5].
6. The UE acknowledges the radio bearer activation to the eNodeB with a RRC Connection Reconfiguration Complete message.
7. The eNodeB acknowledges the bearer activation to the MME with a Bearer Setup Response (EPS Bearer Identity, S1-TEID, PSCell ID) message. The eNodeB indicates whether the requested EPS Bearer QoS could be allocated or not.
The MME shall be prepared to receive this message either before or after the Session Management Response message (sent in step 9).
The PSCell ID is included if Dual Connectivity is active for the UE in the RAN.
8. The UE NAS layer builds a Session Management Response including EPS Bearer Identity. The UE then sends a Direct Transfer (Session Management Response) message to the eNodeB.
9. The eNodeB sends an Uplink NAS Transport (Session Management Response) message to the MME.
10. Upon reception of the Bearer Setup Response message in step 7 and the Session Management Response message in step 9, the MME acknowledges the bearer activation to the Serving GW by sending a Create Bearer Response (EPS Bearer Identity, S1-TEID, User Location Information (ECGI), PSCell ID) message.
11. The Serving GW acknowledges the bearer activation to the PDN GW by sending a Create Bearer Response (EPS Bearer Identity, S5/S8-TEID, User Location Information (ECGI)) message.
12. If the dedicated bearer activation procedure was triggered by a PCC Decision Provision message from the PCRF, the PDN GW indicates to the PCRF whether the requested PCC decision (QoS policy) could be enforced or not, allowing the completion of the PCRF-Initiated IP‑CAN Session Modification procedure or the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6], after the completion of IP‑CAN bearer signalling. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6].
If the dedicated bearer activation is rejected with a cause indicating that the UE is temporarily not reachable due to power saving, then the PDN GW re-attempts the same procedure after it receives the indication that the is UE available for end to end signalling in the subsequent Modify Bearer Request message.
NOTE 6: The exact signalling of step 1 and 12 (e.g. for local break-out) is outside the scope of this specification. This signalling and its interaction with the dedicated bearer activation procedure are to be specified in TS 23.203 [6]. Steps 1 and 12 are included here only for completeness.
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.2 Bearer modification with bearer QoS update
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.2.1 PDN GW initiated bearer modification with bearer QoS update
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The PDN GW initiated bearer modification procedure (including EPS Bearer QoS update) for a GTP based S5/S8 is depicted in figure 5.4.2.1-1. This procedure is used in cases when one or several of the EPS Bearer QoS parameters QCI, GBR, MBR or ARP are modified (including the QCI or the ARP of the default EPS bearer e.g. due to the HSS Initiated Subscribed QoS Modification procedure, as described in clause 5.4.2.2) or to modify the APN-AMBR. Modification from a QCI of resource type non-GBR to a QCI of resource type GBR and vice versa is not supported by this procedure.
NOTE 1: The QCI of an existing dedicated bearer should only be modified if no additional bearer can be established with the desired QCI.
Figure 5.4.2.1-1: Bearer Modification Procedure with Bearer QoS Update
NOTE 2: Steps 3-10 are common for architecture variants with GTP based S5/S8 and PMIP-based S5/S8. For a PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 1, 2, 11 and 12 concern GTP based S5/S8.
1. If dynamic PCC is deployed, the PCRF sends a PCC decision provision (QoS policy) message to the PDN GW. This corresponds to the initial steps of the PCRF-Initiated IP‑CAN Session Modification procedure or to the PCRF response in the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6], up to the point that the PDN GW requests IP‑CAN Bearer Signalling. The PCC decision provision message may indicate that User Location Information and/or UE Time Zone Information is to be provided to the PCRF as defined in TS 23.203 [6]. If dynamic PCC is not deployed, the PDN GW may apply local QoS policy.
2. The PDN GW uses this QoS policy to determine that the authorized QoS of a service data flow has changed or that a service data flow shall be aggregated to or removed from an active bearer. The PDN GW generates the TFT and updates the EPS Bearer QoS to match the traffic flow aggregate. The PDN GW then sends the Update Bearer Request (PTI, EPS Bearer Identity, EPS Bearer QoS, APN-AMBR, TFT, Maximum Packet Loss Rate (UL, DL)) message to the Serving GW. The Procedure Transaction Id (PTI) parameter is used when the procedure was initiated by a UE Requested Bearer Resource Modification Procedure - see clause 5.4.5. For APN-AMBR, the EPS bearer identity must refer to a non-GBR bearer.
For a QCI=1 bearer, the Maximum Packet Loss Rate (UL, DL) may be provided by the PDN GW as described in TS 23.203 [6].
3. The Serving GW sends the Update Bearer Request (PTI, EPS Bearer Identity, EPS Bearer QoS, TFT, APN‑AMBR, Maximum Packet Loss Rate (UL, DL)) message to the MME. If the UE is in ECM‑IDLE state the MME will trigger the Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3). In that case the following steps 4‑7 may be combined into Network Triggered Service Request procedure or be performed stand-alone. If only the QoS parameter ARP is modified and if the UE is in ECM IDLE state the MME shall skip the Network Triggered Service Request. In that case the following steps 4-9 are also skipped and the MME sends an Update Bearer Response to the Serving GW.
If extended idle mode DRX is enabled for the UE, the MME will trigger Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3), and start a timer which is configured to a value smaller than the GTP re-transmission timer. If the MME receives no response from the UE before the timer expires, the MME sends an Update Bearer Response with a rejection cause indicating that the UE is temporarily not reachable due to power saving and, if a Delay Tolerant Connection indication was set for the PDN connection, the MME sets the internal flag Pending Network Initiated PDN Connection Signalling. The rejection is forwarded by the Serving GW to the PDN GW. In this case, the steps 4-11 are skipped.
NOTE 3: If ISR is activated and the Serving GW does not have a downlink S1-U and the SGSN has notified the Serving GW that the UE has moved to PMM-IDLE or STANDBY state, the Serving GW sends Downlink Data Notification to trigger MME and SGSN to page the UE (as specified in clause 5.3.4.3) before sending the Update Bearer Request message.
4. The MME builds a Session Management Request including the PTI, EPS Bearer QoS parameters (excluding ARP), TFT, APN‑AMBR, EPS Bearer Identity and a WLAN offloadability indication. If the UE has UTRAN or GERAN capabilities and the network supports mobility to UTRAN or GERAN, the MME uses the EPS Bearer QoS parameters to derive the corresponding PDP context parameters QoS Negotiated (R99 QoS profile), Radio Priority and Packet Flow Id and includes them in the Session Management Request. If the UE indicated in the UE Network Capability it does not support BSS packet flow procedures, then the MME shall not include the Packet Flow Id. If the APN‑AMBR has changed the MME may update the UE‑AMBR if appropriate. The MME then sends the Bearer Modify Request (EPS Bearer Identity, EPS Bearer QoS, Session Management Request, UE‑AMBR, Maximum Packet Loss Rate (UL, DL)) message to the eNodeB.
The MME may include an indication whether the traffic of this PDN Connection is allowed to be offloaded to WLAN as described in clause 4.3.23.
5. The eNodeB maps the modified EPS Bearer QoS to the Radio Bearer QoS. It then signals a RRC Connection Reconfiguration (Radio Bearer QoS, Session Management Request, EPS RB Identity) message to the UE. The UE shall store the QoS Negotiated, Radio Priority, Packet Flow Id, which it received in the Session Management Request, for use when accessing via GERAN or UTRAN. If the APN-AMBR has changed, the UE stores the modified APN-AMBR value and sets the MBR parameter of the corresponding non-GBR PDP contexts (of this PDN connection) to the new value. The UE uses the uplink packet filter (UL TFT) to determine the mapping of traffic flows to the radio bearer. The UE may provide EPS Bearer QoS parameters to the application handling the traffic flow(s). The application usage of the EPS Bearer QoS is implementation dependent. The UE shall not reject the Radio Bearer Modify Request on the basis of the EPS Bearer QoS parameters contained in the Session Management Request. The UE shall set its TIN to "GUTI" if the modified EPS bearer was established before ISR activation.
NOTE 4: The details of the Radio Bearer QoS are specified in TS 36.300 [5].
6. The UE acknowledges the radio bearer modification to the eNodeB with a RRC Connection Reconfiguration Complete message.
7. The eNodeB acknowledges the bearer modification to the MME with a Bearer Modify Response (EPS Bearer Identity, PSCell ID) message. With this message, the eNodeB indicates whether the requested EPS Bearer QoS could be allocated or not.
The MME shall be prepared to receive this message either before or after the Session Management Response message (sent in step 9).
The PSCell ID is included if Dual Connectivity is active for the UE in the RAN.
8. The UE NAS layer builds a Session Management Response including EPS Bearer Identity. The UE then sends a Direct Transfer (Session Management Response) message to the eNodeB.
9. The eNodeB sends an Uplink NAS Transport (Session Management Response) message to the MME.
10. Upon reception of the Bearer Modify Response message in step 7 and the Session Management Response message in step 9, the MME acknowledges the bearer modification to the Serving GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI), PSCell ID) message.
11. The Serving GW acknowledges the bearer modification to the PDN GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message.
12. If the Bearer modification procedure was triggered by a PCC Decision Provision message from the PCRF, the PDN GW indicates to the PCRF whether the requested PCC decision (QoS policy) could be enforced or not by sending a Provision Ack message allowing the completion of the PCRF-Initiated IP‑CAN Session Modification procedure or the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6], after the completion of IP‑CAN bearer signalling. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6].
If the Bearer modification is rejected with a cause indicating that the UE is temporarily not reachable due to power saving, then the PDN GW re-attempts the same procedure after it receives the indication that the is UE available for end to end signalling in the subsequent Modify Bearer Request message.
NOTE 5: The exact signalling of step 1 and 12 (e.g. for local break-out) is outside the scope of this specification. This signalling and its interaction with the bearer activation procedure are to be specified in TS 23.203 [6]. Steps 1 and 12 are included here only for completeness.
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.2.2 HSS Initiated Subscribed QoS Modification and MME initiated QoS modification
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The HSS Initiated Subscribed QoS Modification for a GTP-based S5/S8 is depicted in figure 5.4.2.2-1 where steps 1, 1a, are executed. The MME initiated QoS modification can happen, e.g. at Inter-PLMN mobility if there is a QoS Change upon Inter-PLMN mobility.
Figure 5.4.2.2-1: HSS Initiated Subscribed QoS Modification
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) and steps (B) are defined in TS 23.402 [2]. Steps 3, 4, 5, 7 and 8 concern GTP based S5/S8.
1. The HSS sends an Insert Subscriber Data (IMSI, Subscription Data) message to the MME. The Subscription Data includes EPS subscribed QoS (QCI, ARP) and the subscribed UE-AMBR and APN‑AMBR.
1a. The MME updates the stored Subscription Data and acknowledges the Insert Subscriber Data message by returning an Insert Subscriber Data Ack (IMSI) message to the HSS (see clause 5.3.9.2).
2a If only the subscribed UE-AMBR has been modified, the MME calculates a new UE-AMBR value as described in clause 4.7.3 and may then signal a modified UE-AMBR value to the eNodeB by using S1-AP UE Context Modification Procedure. The HSS Initiated Subscribed QoS Modification Procedure ends after completion of the UE Context Modification Procedure.
2b. If the QCI and/or ARP and/or subscribed APN-AMBR has been modified and there is related active PDN connection with the modified QoS Profile the MME sends the Modify Bearer Command (EPS Bearer Identity, EPS Bearer QoS, APN AMBR) message to the Serving GW. The EPS Bearer Identity identifies the default bearer of the affected PDN connection. The EPS Bearer QoS contains the EPS subscribed QoS profile to be updated.
3. The Serving GW sends the Modify Bearer Command (EPS Bearer Identity, EPS Bearer QoS, APN AMBR) message to the PDN GW.
4. If PCC infrastructure is deployed, the PDN GW informs the PCRF about the updated EPS Bearer QoS and APN-AMBR. The PCRF sends new updated PCC decision to the PDN GW. This corresponds to the PCEF-initiated IP‑CAN Session Modification procedure as defined in TS 23.203 [6].
The PCRF may modify the APN-AMBR and the QoS parameters (QCI and ARP) associated with the default bearer in the response to the PDN GW as defined in TS 23.203 [6].
5. The PDN GW modifies the default bearer of each PDN connection corresponding to the APN for which subscribed QoS has been modified. If the subscribed ARP parameter has been changed, the PDN GW shall also modify all dedicated EPS bearers having the previously subscribed ARP value unless superseded by PCRF decision. The PDN GW then sends the Update Bearer Request (EPS Bearer Identity, EPS Bearer QoS, TFT, APN‑AMBR) message to the Serving GW.
NOTE 2: As no PTI is included the MME use protocol specific details, as described in TS 29.274 [43], to determine if the Update Bearer Request was triggered by this procedure or not.
6. If the QCI and/or ARP parameter(s) have been modified, steps 3 to 10, as described in clause 5.4.2.1, Figure 5.4.2.1-1, are invoked. If neither the QCI nor the ARP have been modified, but instead only the APN-AMBR was updated, steps 3 to 8, as described in clause 5.4.3, Figure 5.4.3-1, are invoked.
7. The Serving GW acknowledges the bearer modification to the PDN GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message. If the bearer modification fails the PDN GW deletes the concerned EPS Bearer.
8. The PDN GW indicates to the PCRF whether the requested PCC decision was enforced or not by sending a Provision Ack message.
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495b59b986f98d41912141cabbec196e
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23.401
|
5.4.3 PDN GW initiated bearer modification without bearer QoS update
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The bearer modification procedure without bearer QoS update is used to update the TFT for an active default or dedicated bearer, to modify the APN-AMBR, to retrieve User Location from the MME, to inform PCO to UE or to instruct the MME (e.g. to activate/deactivate the location reporting).
The procedure for a GTP based S5/S8 is depicted in figure 5.4.3‑1. In this procedure there is no need to update the underlying radio bearer(s). This procedure may be triggered if the APN‑AMBR is changed by the PCRF/PDN GW.
Figure 5.4.3-1: Bearer Modification Procedure without Bearer QoS Update
NOTE 1: Steps 3-8 are common for architecture variants with GTP based S5/S8 and PMIP-based S5/S8. For an PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 1, 2, 9 and 10 concern GTP based S5/S8. Steps 3-8 may also be used within the HSS Initiated Subscribed QoS Modification.
1. If dynamic PCC is deployed, the PCRF sends a PCC decision provision (QoS policy) message to the PDN GW. This corresponds to the beginning of the PCRF-initiated IP-CAN Session Modification procedure or to the PCRF response in the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6], up to the point that the PDN GW requests IP-CAN Bearer Signalling. The PCC decision provision message may indicate that User Location Information and/or UE Time Zone Information is to be provided to the PCRF as defined in TS 23.203 [6]. If dynamic PCC is not deployed, the PDN GW may apply local QoS policy.
2. The PDN GW uses this QoS policy to determine that a service data flow shall be aggregated to or removed from an active bearer. The PDN GW generates the TFT and determines that no update of the EPS Bearer QoS is needed. The PDN GW then sends the Update Bearer Request (PTI, EPS Bearer Identity, APN-AMBR, TFT, Retrieve Location) message to the Serving GW. The Procedure Transaction Id (PTI) parameter is used when the procedure was initiated by a UE Requested Bearer Resource Modification procedure - see clause 5.4.5. "Retrieve Location" is indicated if requested by the PCRF. If the PDN GW initiated bearer modification procedure was triggered by a UE requested bearer resource modification procedure and if 3GPP PS Data Off UE Status was present in the Bearer Resource Command PCO, the PDN GW shall include the 3GPP PS Data Off Support Indication in the Update Bearer Request PCO.
3. The Serving GW sends the Update Bearer Request (PTI, EPS Bearer Identity, APN-AMBR, TFT, Retrieve Location) message to the MME. If the UE is in ECM-IDLE state (and extended idle mode DRX is not enabled) the MME will trigger the Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3). In that case the following steps 4-7 may be combined into Network Triggered Service Request procedure or be performed stand-alone. If both the PCO and the TFT are absent and the APN-AMBR has not been modified, the MME shall skip the following steps 4-7.
If the UE is in ECM-IDLE state and extended idle mode DRX is enabled for the UE, the MME will trigger Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3) and start a timer which is configured to a value smaller than the GTP re-transmission timer. If the MME receives no response from the UE before the timer expires, the MME sends an Update Bearer Response with a rejection cause indicating that UE is temporarily not reachable due to power saving and then sets the internal flag Pending Network Initiated PDN Connection Signalling. The rejection is forwarded by the Serving GW to the PDN GW. In this case, the steps 4-9 are skipped.
NOTE 2: If ISR is activated and the Serving GW does not have a downlink S1-U and the SGSN has notified the Serving GW that the UE has moved to PMM-IDLE or STANDBY state, the Serving GW sends Downlink Data Notification to trigger MME and SGSN to page the UE (as specified in clause 5.3.4.3) before sending the Update Bearer Request message.
NOTE 3: The PCO can be set by the PDN GW in accordance with the TS 23.380 [75].
4. The MME builds a Session Management Request message including the TFT, APN-AMBR, EPS Bearer Identity and a WLAN offloadability indication. The MME then sends a Downlink NAS Transport (Session Management Configuration) message to the eNodeB. If the APN AMBR has changed, the MME may also update the UE AMBR. And if the UE-AMBR is updated, the MME signal a modified UE-AMBR value to the eNodeB by using S1-AP UE Context Modification Procedure.
The MME may include an indication whether the traffic of this PDN Connection is allowed to be offloaded to WLAN as described in clause 4.3.23.
5. The eNodeB sends the Direct Transfer (Session Management Request) message to the UE. The UE uses the uplink packet filter (UL TFT) to determine the mapping of traffic flows to the radio bearer. The UE stores the modified APN-AMBR value and sets the MBR parameter of the corresponding non-GBR PDP contexts (of this PDN connection) to the new value. The UE shall set its TIN to "GUTI" if the modified EPS bearer was established before ISR activation.
6. The UE NAS layer builds a Session Management Response including EPS Bearer Identity. The UE then sends a Direct Transfer (Session Management Response) message to the eNodeB.
7. The eNodeB sends an Uplink NAS Transport (Session Management Response) message to the MME.
8. If the procedure is performed without steps 4-7 and location retrieval is requested and the UE is ECM_CONNECTED and unless the MME is configured not to retrieve ECGI from the eNodeB under this condition, the MME uses the Location Reporting Procedure described in clause 5.9.1 to retrieve the ECGI from the eNodeB. The MME acknowledges the bearer modification to the Serving GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message. The MME includes the last known User Location information.
NOTE 4: Based on operator policy and local regulation the MME may, instead of using the Location Reporting Procedure described in clause 5.9.1 to retrieve the ECGI from the eNodeB, use the last known User Location information obtained from e.g. attach procedure, tracking area update procedure, etc.
9. The Serving GW acknowledges the bearer modification to the PDN GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message.
10. If the bearer modification procedure was triggered by a PCC Decision Provision message from the PCRF, the PDN GW indicates to the PCRF whether the requested PCC decision (QoS policy) could be enforced or not by sending a Provision Ack message. This then allows the PCRF-Initiated IP‑CAN Session Modification procedure or the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6] to continue and eventually conclude, proceeding after the completion of IP‑CAN bearer signalling. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6].
If the bearer modification is rejected with a cause indicating that the UE is temporarily not reachable due to power saving, then the PDN GW re-attempts the same procedure after it receives the indication that the is UE available for end to end signalling in the subsequent Modify Bearer Request message.
NOTE 5: The exact signalling of step 1 and 10 (e.g. for local break-out) is outside the scope of this specification. This signalling and its interaction with the bearer activation procedure are to be specified in TS 23.203 [6]. Steps 1 and 10 are included here only for completeness.
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.4 Bearer deactivation
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.4.1 PDN GW initiated bearer deactivation
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The bearer deactivation procedure for a GTP based S5/S8 is depicted in figure 5.4.4.1-1. This procedure can be used to deactivate a dedicated bearer or deactivate all bearers belonging to a PDN address. If the default bearer belonging to a PDN connection is deactivated, the PDN GW deactivates all bearers belonging to the PDN connection.
When the last bearer belonging to the last PDN connection of a given APN is released, the PGW may forward to the MME the APN Rate Control Status for storing it in the MM context according to clause 4.7.7.3.
Figure 5.4.4.1-1: PDN GW Initiated Bearer Deactivation
NOTE 1: Steps 3-8 are common for architecture variants with GTP based S5/S8 and PMIP-based S5/S8. For an PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 1, 2, 9 and 10 concern GTP-based S5/S8.
1. If dynamic PCC is not deployed, the PDN GW is triggered to initiate the Bearer Deactivation procedure due either a QoS policy or on request from the MME (as outlined in clause 5.4.4.2) or on intra-node signalling request from the HeNB to release the LIPA PDN Connection. Optionally, the PCRF sends QoS policy to the PDN GW. This corresponds to the initial steps of the PCRF-initiated IP‑CAN Session Modification procedure or the response to the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6], up to the point that the PDN GW requests IP‑CAN Bearer Signalling. The PCC decision provision message may indicate that User Location Information and/or UE Time Zone Information is to be provided to the PCRF as defined in TS 23.203 [6]. If dynamic PCC is not deployed, the PDN GW may apply local QoS policy. The PDN GW initiated Bearer deactivation is also performed when handovers occur from 3GPP to non-3GPP, in which case, the default bearer and all the dedicated bearers associated with the PDN address are released, but the PDN address is kept in the PDN GW.
For an emergency PDN connection the PDN GW initiates the deactivation of all bearers of that emergency PDN connection when the PDN connection is inactive (i.e. not transferring any packets) for a configured period of time or when triggered by dynamic PCC.
For an PDN connection established towards the APN dedicated for Restricted Local Operator Services, the PDN GW initiates the deactivation of all bearers of the PDN connection per local operator policy e.g. when the duration of such PDN connection reaches a pre-configured period of time.
2. The PDN GW sends a Delete Bearer Request (PTI, EPS Bearer Identity, Causes and, optionally, APN Rate Control Status according to clause 4.7.7.3) message to the Serving GW. The Procedure Transaction Id (PTI) parameter in this step and in the following steps is only used when the procedure was initiated by a UE Requested Bearer Resource Modification Procedure - see clause 5.4.5. This message can include an indication that all bearers belonging to that PDN connection shall be released. The PDN GW includes 'Cause' IE in the Delete Bearer Request message and sets the IE to 'RAT changed from 3GPP to Non-3GPP' if the Delete Bearer Request message is caused by a handover from 3GPP to non-3GPP.
3a. The Serving GW sends the Delete Bearer Request (PTI, EPS Bearer Identity, Cause and, optionally, APN Rate Control Status) message to the MME. This message can include an indication that all bearers belonging to that PDN connection shall be released.
3b. If ISR is activated, the Serving GW sends the Delete Bearer Request (PTI, EPS Bearer Identity, Cause) message to the SGSN. This message can include an indication that all bearers belonging to that PDN connection shall be released, and the SGSN releases all bearer resources of the PDN connection.
NOTE 2: If all the bearers belonging to a UE are released due to a handover from 3GPP to non-3GPP, the SGSN changes the MM state of the UE to IDLE (GERAN network) or PMM-DETACHED (UTRAN network).
If ISR is activated, upon receiving Delete Bearer Request from SGW for the last PDN connection for a given UE, MME shall locally de-activate ISR.
NOTE 3: In this case, SGSN locally de-activates ISR as well (see TS 23.060 [7]).
If received, the MME stores the APN Rate Control Status in the MM context.
Steps 4 to 7 are not performed if at least one of the following three conditions is fulfilled:
(i) The UE is in ECM-IDLE and the last PDN connection of the UE is not being deleted and the Delete Bearer Request received from the Serving GW does not contain the cause "reactivation requested", which has been sent from the PDN GW;
(ii) UE is in ECM-IDLE and the last PDN connection is deleted due to ISR deactivation;
(iii) UE is in ECM-IDLE and the last PDN connection is deleted in 3GPP due to handover to non-3GPP access.
When steps 4 to 7 are not performed, the EPS bearer state is synchronized between the UE and the network at the next ECM-IDLE to ECM-CONNECTED transition (e.g. Service Request or TAU procedure).
4a. If the last PDN connection of a UE that does not support "Attach without PDN connectivity" is being released and the bearer deletion is neither due to ISR deactivation nor due to handover to non-3GPP accesses, the MME explicitly detaches the UE by sending a Detach Request message to the UE. If the UE is in ECM-IDLE state the MME initiates paging via Network Triggered Service Request procedure in clause 5.3.4.3 from step 3a onwards in order to inform UE of the request. Steps 4b to 7b are skipped in this case, and the procedure continues from step 7c.
4b. If the UE is in ECM-IDLE state and the reason for releasing PDN connection is "reactivation requested", the MME initiates paging via Network Triggered Service Request procedure in clause 5.3.4.3 from step 3a onwards in order to inform UE of the request and step 4c is performed after completion of the paging.
4c. If the release of the bearer in E‑UTRAN has already been signalled to the MME, steps 4c to 7 are omitted. Otherwise, if this is not the last PDN connection for the UE which is being released, the MME sends the S1-AP Deactivate Bearer Request (EPS Bearer Identity) message to the eNodeB. The MME builds a NAS Deactivate EPS Bearer Context Request message including the EPS Bearer Identity and a WLAN offloadability indication, and includes it in the S1-AP Deactivate Bearer Request message. When the bearer deactivation procedure was originally triggered by a UE request, the NAS Deactivate EPS Bearer Context Request message includes the PTI.
The MME may include an indication whether the traffic of this PDN Connection is allowed to be offloaded to WLAN as described in clause 4.3.23 if the PDN connection is not released.
5. The eNodeB sends the RRC Connection Reconfiguration message including the EPS Radio Bearer Identity to release and the NAS Deactivate EPS Bearer Context Request message to the UE.
6a. The UE RRC releases the radio bearers indicated in the RRC message in step 5, and indicates the radio bearer status to the UE NAS. Then the UE NAS removes the UL TFTs and EPS Bearer Identity according to the radio bearer status indication from the UE RRC. The UE responds to the RRC Connection Reconfiguration Complete message to the eNodeB.
6b. The eNodeB acknowledges the bearer deactivation to the MME with a Deactivate Bearer Response (EPS Bearer Identity, ECGI, TAI, PSCell ID, Secondary RAT usage data) message. If the PLMN has configured secondary RAT usage reporting and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included.
The PSCell ID is included if Dual Connectivity is active for the UE in the RAN.
The MME shall be prepared to receive this message either before or after the Session Management Response message sent in step 7b, and before or after, any Detach Request message sent in step 7c.
7a The UE NAS layer builds a Deactivate EPS Bearer Context Accept message including EPS Bearer Identity. The UE then sends a Direct Transfer (Deactivate EPS Bearer Context Accept) message to the eNodeB.
7b. The eNodeB sends an Uplink NAS Transport (Deactivate EPS Bearer Context Accept) message to the MME.
7c. If the UE receives the Detach Request message from the MME in the step 4a, the UE sends a Detach Accept message to the MME any time after step 4a. The eNodeB forwards this NAS message to the MME along with the TAI+ECGI of the cell which the UE is using.
NOTE 4: The UE may not be able to send this message, e.g. when the UE is out of coverage of E-UTRAN due to mobility to non-3GPP access.
7a,b,c If Dual Connectivity is active for the UE, the PSCell ID shall be included in the Uplink NAS Transport sent by the eNodeB.
8a. After reception of both the Deactivate Bearer Response message in step 6b and the Deactivate EPS Bearer Context Accept message in step 7b, the MME deletes the bearer context related to the deactivated EPS bearer and acknowledges the bearer deactivation to the Serving GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (ECGI), RAN/NAS Release Cause, Secondary RAT usage data, PSCell ID) message. If the MME received Secondary RAT usage data in step 6b, the MME shall include it in this message. If the MME received PSCell ID in step 6b, the MME shall include it in this message. If extended idle mode DRX is enabled, then the MME acknowledges the bearer deactivation to the Serving GW and at the same time the MME initiates the deactivation towards the UE. If the S1 connection had already been released by the eNodeB due to radio link failure and the MME receives a Delete Bearer Request while it is still deferring the sending of the S1 release (see clause 5.3.5), the MME shall include in the Delete Bearer Response the RAN/NAS Cause received in the S1 Release due to radio link failure procedure.
8b The SGSN deletes PDP Context related to the deactivated EPS bearer and acknowledges the bearer deactivation to the Serving GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (CGI/SAI)) message. If extended idle mode DRX is enabled, then the SGSN acknowledges the bearer deactivation to the Serving GW and at the same time the SGSN initiates the deactivation towards the UE.
9. If ISR is activated, after receiving the two Delete Bearer Response messages from the MME and the SGSN, or if ISR is not activated, after receiving the Delete Bearer Response messages from the MME, the Serving GW deletes the bearer context related to the deactivated EPS bearer acknowledges the bearer deactivation to the PDN GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (ECGI or CGI/SAI), Secondary RAT usage data) message. If the MME and/or SGSN sent UE's Location Information and/or UE Time Zone in step 8a and/or step 8b, the Serving GW includes the User Location Information and/or UE Time Zone Information with the least age in this message. The Serving GW includes the Secondary RAT usage data if it was received in step 8a and if PGW secondary RAT usage data reporting is active.
10. The PDN GW deletes the bearer context related to the deactivated EPS bearer. If the dedicated bearer deactivation procedure was triggered by receiving a PCC decision message from the PCRF, the PDN GW indicates to the PCRF whether the requested PCC decision was successfully enforced by completing the PCRF-initiated IP‑CAN Session Modification procedure or the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203 [6], proceeding after the completion of IP‑CAN bearer signalling. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6]. If available, the PDN GW shall send RAN/NAS Release Cause to the PCRF as defined in TS 23.203 [6].
11. If the UE is being explicitly detached, the MME releases the S1-MME signalling connection for the UE by sending an S1 Release Command (Cause) message to the eNodeB. The details of this step are covered in the "S1 Release Procedure", as described in clause 5.3.5 by step 4 to step 6.
NOTE 5: In the "S1 Release Procedure", if Dual Connectivity was active at the time of the release, the eNodeB includes the PSCell ID.
NOTE 6: The exact signalling of step 1 and 10 (e.g. for local break-out) is outside the scope of this specification. This signalling and its interaction with the dedicated bearer activation procedure are to be specified in TS 23.203 [6]. Steps 1 and 10 are included here only for completeness.
If all the bearers belonging to a UE that does not support "Attach without PDN connectivity" are released, the MME shall change the MM state of the UE to EMM-DEREGISTERED and the MME sends the S1 Release Command to the eNodeB, which initiates the release of the RRC connection for the given UE if it is not released yet, and returns an S1 Release Complete message to the MME.
If all bearers of an emergency attached or RLOS attached UE are deactivated the MME may initiate the explicit MME-Initiated Detach procedure. Regardless of the outcome of any explicit Detach procedure the MME changes the EMM state of the UE to EMM-DEREGISTERED and the MME sends the S1 Release Command to the eNodeB if it is not yet released.
If the default bearer belonging to a PDN connection is deactivated, the MME determines the Maximum APN Restriction for the remaining PDN connections and stores this new value for the Maximum APN Restriction. In addition if ISR is activated the SGSN determines the Maximum APN Restriction for the remaining bearer contexts and stores this new value for the Maximum APN Restriction.
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.4.2 MME Initiated Dedicated Bearer Deactivation
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MME initiated Dedicated Bearer Deactivation is depicted in Figure 5.4.4.2-1 below. This procedure deactivates dedicated bearers. Default bearers are not affected. To initiate the release of the full PDN connection including the default bearer, the MME uses the UE or MME requested PDN disconnection procedure defined in clause 5.10.3.
Figure 5.4.4.2-1: MME initiated Dedicated Bearer Deactivation
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) and steps (B) are defined in TS 23.402 [2]. Steps 3, 4, 5 and 9 concern GTP based S5/S8
0. Radio bearers for the UE in the ECM-CONNECTED state may be released due to local reasons (e.g. abnormal resource limitation or radio conditions do not allow the eNodeB to maintain all the allocated GBR bearers: it is not expected that non-GBR bearers are released by the eNodeB unless caused by error situations). The UE deletes the bearer contexts related to the released radio bearers.
1. When the eNodeB releases radio bearers in step 0, it sends an indication of bearer release to the MME. This indication may be e.g. the Bearer Release Request (EPS Bearer Identity) message to the MME, or alternatively Initial Context Setup Complete, Handover Request Ack and UE Context Response, Path Switch Request may also indicate the release of a bearer.
The eNodeB includes the ECGI and TAI in the indication sent to the MME. The eNodeB also includes the PSCell ID if Dual Connectivity is active for the UE in the RAN.
If the PLMN has configured secondary RAT reporting and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included.
2. The MME sends the Delete Bearer Command (EPS Bearer Identity, User Location Information, UE Time Zone, RAN/NAS Release Cause if available, Secondary RAT usage data, PSCell ID) message per PDN connection to the Serving GW to deactivate the selected dedicated bearer. RAN/NAS Release Cause indicates the RAN release cause and/or the NAS release cause. RAN/NAS Release Cause is only sent by the MME to the PDN GW if this is permitted according to MME operator's policy. If the MME received Secondary RAT usage data in step 1, the MME shall include it in this message. If MME received PSCell ID in step 1, the MME shall include it in this message.
3. The Serving GW sends the Delete Bearer Command (EPS Bearer Identity, User Location Information, UE Time Zone, RAN/NAS Release Cause, Secondary RAT usage data) message per PDN connection to the PDN GW. The Serving GW includes the Secondary RAT usage data it in this message if it was received in the previous message and if PGW secondary RAT usage data reporting is active.
4. If PCC infrastructure is deployed, the PDN GW informs the PCRF about the loss of resources by means of a PCEF-initiated IP‑CAN Session Modification procedure as defined in TS 23.203 [6] and provides the User Location Information, UE Time Zone and RAN/NAS Release cause (if available) received in the Delete Bearer Command from the S-GW if requested by the PCRF as defined in TS 23.203 [6]. The PCRF sends an updated PCC decision to the PDN GW.
NOTE 2: User Location Information and UE Time Zone might not be available if the MME or the Serving GW are of a previous release and did not provide this information.
5. The PDN GW sends a Delete Bearer Request (EPS Bearer Identity) message to the Serving GW.
6. The Serving GW sends the Delete Bearer Request (EPS Bearer Identity) message to the MME.
7. Steps between steps 4 and 7, as described in clause 5.4.4.1, are invoked. This is omitted if the bearer deactivation was triggered by the eNodeB in step 0 and step 1.
This is also omitted if the MME initiated bearer release due to failed bearer set up during handover, the UE and the MME deactivate the failed contexts locally without peer-to peer ESM signalling.
8. The MME deletes the bearer contexts related to the deactivated EPS bearer and acknowledges the bearer deactivation to the Serving GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (ECGI), Secondary RAT usage data) message. The MME includes the Secondary RAT usage data if it received this in step 7 from the eNodeB.
9. The Serving GW deletes the bearer context related to the deactivated EPS bearer and acknowledges the bearer deactivation to the PDN GW by sending a Delete Bearer Response (EPS Bearer Identity, Secondary RAT usage data) message. The Serving GW includes the Secondary RAT usage data if it was received in step 8 and if PGW secondary RAT usage data reporting is active.
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.5 UE requested bearer resource modification
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The UE requested bearer resource modification procedure for an E-UTRAN is depicted in figure 5.4.5-1. The procedure allows the UE to request for a modification of bearer resources (e.g. allocation or release of resources) for one traffic flow aggregate with a specific QoS demand. Alternatively, the procedure allows the UE to request for the modification of the packet filters used for an active traffic flow aggregate, without changing QoS. If accepted by the network, the request invokes either the Dedicated Bearer Activation Procedure, the Bearer Modification Procedure or a dedicated bearer is deactivated using the PDN GW Initiated Bearer Deactivation Procedure. The procedure is used by the UE when the UE already has a PDN connection with the PDN GW. A UE can send a subsequent Request Bearer Resource Modification Message before the previous procedure is completed. The UE requested bearer resource modification procedure is used to indicate the change of 3GPP PS Data Off UE Status to the PDN GW via the PCO, only if the UE has been previously informed that the PDN GW supports the 3GPP PS Data Off feature. When a UE supports only Control Plane CIoT EPS Optimisation as defined in clause 5.3.4B the UE need not support the UE requested bearer resource modification procedure in order to modify the traffic flow aggregate, as the UE does not support any DRBs. The UE may need to support UE requested bearer resource modification procedure for other purposes, e.g. header compression negotiation, see TS 24.301 [46].
The UE supporting 15 EPS bearers as defined in clause 4.12 shall not initiate a UE requested bearer resource modification procedure that would trigger the establishment of a new EPS bearer, if it has already 8 EPS bearers established and the UE has not received an Indication for support of 15 EPS bearers per UE or has received cause #65 "maximum number of EPS bearers reached".
In this procedure the UE signals a Traffic Aggregate Description (TAD) which is a partial TFT, together with a Procedure Transaction Identifier (PTI), and an EPS Bearer Identity (when the TAD operation is modify, delete or add to an existing packet filter). When the TAD operation is modify or delete, the packet filter identifiers of the TAD are the same as the TFT packet filter identifiers of the referenced EPS Bearer (as the concatenation of the TFT packet filter identifier and the EPS Bearer identifier represents a unique packet filter identifier within the PDN connection), for which resources are being modified. The TAD is released by the UE after it has received a TFT related to the current PTI from the network.
Figure 5.4.5-1: UE requested bearer resource modification
NOTE 1: Steps 1, 2, and 5 are common for architecture variants with GTP-based S5/S8 and PMIP-based S5/S8. The procedure steps marked (A) differ in the case that PMIP-based S5/S8 is employed and is defined in TS 23.402 [2].
If the bearer resource modification procedure is initiated for re-negotiation of header compression configuration for Control Plane CIoT EPS Optimisation, the MME shall not send Bearer Resource Command message to the Serving GW. In this case, the Bearer Modification Procedures (according to clause 5.4.3) is invoked and only the steps from 4 to 7 are performed.
1. The UE sends a Request Bearer Resource Modification (LBI, PTI, EPS Bearer Identity, QoS, TAD, Protocol Configuration Options) message to the MME. If the UE was in ECM-IDLE mode, this NAS message is preceded by the Service Request procedure.
The TAD indicates one requested operation (add, modify, or delete packet filters). If traffic flows are added, the TAD includes the packet filter(s) (consisting of the packet filter information including packet filter precedence, but without a packet filter identifier) to be added. The UE also sends the QCI requested and GBR, if applicable, for the added traffic flows. If the UE wants to link the new packet filter(s) to an existing packet filter to enable the usage of existing bearer resources for the new packet filter(s), the UE shall provide an existing packet filter identifier together with the new packet filter(s). If the new packet filter(s) are not linked to an existing packet filter the UE shall provide at least one UL packet filter in the TAD. If a downlink only traffic flow(s) is to be added the UE shall provide an UL packet filter that effectively disallows any useful packet flows (see clause 15.3.3.4 of TS 23.060 [7] for an example of such packet filter).
NOTE 2: Receiving at least one UL packet filter from the UE ensures that a valid state for the TFT settings of the PDN connection as defined in clause 15.3.0 of TS 23.060 [7] is maintained if the TAD add operation results in the establishment of a new dedicated EPS bearer.
If the UE wants to change the GBR in addition, the UE includes the GBR requirement of the EPS Bearer. The TAD is released when the procedure is completed.
When only requesting for a modification of GBR (i.e. decrease or increase), the TAD shall include the existing packet filter identifier(s) for which the GBR change request applies to. The UE includes the GBR requirement of the EPS Bearer. The TAD is released when the procedure is completed.
When requesting for a modification of packet filter(s) (e.g. change of port number), the TAD shall include packet filter identifier(s) for which the change request applies to together with the changed packet filter information.
If the UE requests for deletion of traffic flows, the TAD includes the packet filter identifier(s) to be deleted. If the packet filters to be deleted were mapped to a GBR Bearer, the UE includes the new GBR requirement of the EPS Bearer.
The UE sends the Linked Bearer Id (LBI) only when the requested operation is add, to indicate to which PDN connection the additional bearer resource is linked to. The EPS Bearer Identity is only sent when the requested operation is modify or delete. The Procedure Transaction Id is dynamically allocated by the UE for this procedure. The UE should ensure as far as possible that previously used PTI values are not immediately reused. The PTI is released when the procedure is completed. Protocol Configuration Options may be used to transfer application level parameters between the UE and the PDN GW (see TS 23.228 [52]), and are sent transparently through the MME and the Serving GW.
If the PDN GW indicated support for the 3GPP PS data off feature during PDN connection setup, the UE shall include in the PCO the 3GPP PS Data Off Support Indication, which indicates whether the user has activated or deactivated 3GPP PS Data Off.
2. The MME sends the Bearer Resource Command (IMSI, LBI, PTI, EPS Bearer Identity, QoS, TAD, Protocol Configuration Options) message to the selected Serving GW. The MME validates the request using the Linked Bearer Id. The same Serving GW address is used by the MME as for the EPS Bearer identified by the Linked Bearer Id received in the Request Bearer Resource Modification message.
3. The Serving GW sends the Bearer Resource Command (IMSI, LBI, PTI, EPS Bearer Identity, QoS, TAD, Protocol Configuration Options) message to the PDN GW. The Serving GW sends the message to the same PDN GW as for the EPS Bearer identified by the Linked Bearer Id.
4. The PDN GW may either apply a locally configured QoS policy, or it may interact with the PCRF to trigger the appropriate PCC decision, which may take into account subscription information. This corresponds to the beginning of a PCEF-initiated IP‑CAN Session Modification procedure as defined in TS 23.203 [6], up to the point that the PDN GW requests IP‑CAN Bearer Signalling. When interacting with PCRF, the PDN GW provides to the PCRF the content of the TAD and, if applicable, the GBR change (increase or decrease) associated with the packet filter information contained in the TAD. The GBR change is either calculated from the current Bearer QoS and the requested Bearer QoS from the UE, or set to the requested GBR if the TAD indicates an add operation and no EPS Bearer Identity was received. If the TAD indicates an add operation, the requested QCI is also provided to the PCRF unless an existing packet filter identifier is provided together with the new packet filter.
The PCC decision provision message may indicate that User Location Information and/or UE Time Zone information is to be provided to the PCRF as defined in TS 23.203 [6].
If the TAD operation is modify, delete, a request for changing the GBR, or add with a link to existing packet filter(s), then the PDN GW provides to the PCRF the SDF filter identifier(s), previously assigned on Gx, that correspond to the received packet filter identifiers of the EPS bearer indicated by the received EPS bearer identity.
NOTE 3: The ability of the PCRF to handle multiple PCC rules in the same request depends on operator policy. It is therefore recommended that the UE avoids providing references to multiple packet filters for different applications and services.
If the PDN GW detects that the 3GPP PS Data Off UE Status has changed, the PDN GW shall indicate this event to the charging system for offline and online charging.
If the 3GPP PS Data Off UE Status indicates that 3GPP PS Data Off is activated for the UE, the PDN GW shall enforce the PCC rules for downlink traffic to be applied when 3GPP PS Data Off is activated, as described in TS 23.203 [6].
5. If the request is accepted, either the Dedicated Bearer Activation Procedure (according to clause 5.4.1), the PDN GW Initiated Bearer Deactivation Procedure (according to clause 5.4.4.1) or one of the Bearer Modification Procedures (according to clause 5.4.2.1 or 5.4.3) is invoked. The PTI allocated by the UE is used as a parameter in the invoked Dedicated Bearer Activation Procedure, the PDN GW Initiated Bearer Deactivation Procedure or the Bearer Modification Procedure to correlate it to the UE Requested Bearer Resource Modification Procedure. This provides the UE with the necessary linkage to what EPS Bearer to be used for the new traffic flow aggregate. The PDN GW shall not modify the QoS parameters requested by the UE.
The PDN GW inserts, modifies or removes packet filter(s) corresponding to the TAD into the TFT for the EPS bearer. If PCC is in use, the PDN GW uses the service data flow filters as specified in the resulting PCC rule(s). The PDN GW validates the state of the TFT settings of the PDN connection as defined in clause 15.3.0 of TS 23.060 [7]. If after the execution of all TAD operations the TFT of the dedicated EPS bearer contains only packet filters for the downlink direction, the PDN GW shall add a packet filter which effectively disallows any useful packet flows in uplink direction (see clause 15.3.3.4 in TS 23.060 [7] for an example of such a packet filter) to the TFT.
NOTE 4: The PDN GW addition of an uplink packet filter allows the handling of pre-Release 11 UEs which may have provided only downlink packet filters in a TAD add operation without linking to an existing packet filter.
When a new packet filter is inserted into a TFT, the PDN GW assigns a new packet filter identifier which is unique within the TFT. The PDN GW maintains the relation between the SDF filter identifier in the PCC rule received from the PCRF and the packet filter identifier of the TFT of this EPS bearer. If all of the packet filter(s) for a dedicated EPS bearer have been removed from the TFT, the PDN GW performs the PDN GW Initiated Bearer Deactivation Procedure.
If the requested QoS is not granted (i.e. the requested QoS cannot be accepted or resources could not be allocated), or the resulting TFT settings of the PDN connection does not pass the validation, then the PDN GW sends a Bearer Resource Failure Indication (with a cause indicating the reason why the request failed or was rejected) message, which shall be delivered to the UE.
6. If the PDN GW interacted with the PCRF in step 4, the PDN GW indicates to the PCRF whether the PCC decision could be enforced or not. This corresponds to the completion of the PCEF-initiated IP‑CAN session modification procedure as defined in TS 23.203 [6], proceeding after the completion of IP‑CAN bearer signalling. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203 [6].
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.6 Void
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.7 E-UTRAN initiated E-RAB modification procedure
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When SCG bearer option is applied to support dual connectivity operation, this procedure is used to transfer bearer contexts to and from Secondary eNodeB (see TS 36.300 [5]) or Secondary gNodeB (see TS 37.340 [85]). During this procedure, both the MME and Serving GW are never relocated. The presence of IP connectivity between the Serving GW and the Master eNodeB (see TS 36.300 [5] or TS 37.340 [85] for Master eNodeB definition), as well as between the Serving GW and the Secondary RAN node is assumed.
NOTE: In E-UTRAN, eNodeB is not allowed to negotiate bearer-level QoS parameters as defined in clause 4.7.2.1.
Figure 5.4.7-1: E-UTRAN initiated E-RAB modification procedure
1. The Master eNodeB sends a E-RAB Modification Indication message (eNodeB address(es) and TEIDs for downlink user plane for all the EPS bearers, CSG Membership Information, Secondary RAT usage data) to the MME. The Master eNodeB indicates for each bearer whether it is modified or not. If the PLMN has configured secondary RAT usage reporting and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included. The eNodeB shall include the ECGI and, if Dual Connectivity is activated for the UE, the PSCell ID, in the E-RAB Modification Indication message.
If the Secondary eNodeB is a hybrid access eNodeB, the Master eNodeB includes the CSG Membership Information for the SCG bearer(s) in the E-RAB Modification Indication message. The MME determines the CSG membership based on the CSG Membership Information as specified in TS 36.300 [5], but does not update the User CSG Information in the Core Network. A failure of the CSG Membership Information verification does not impact the E-UTRAN initiated E-RAB modification procedure.
2. The MME sends a Modify Bearer Request (eNodeB address(es) and TEIDs for downlink user plane for all the EPS bearers, ISR Activated, User Location Information, PSCell ID, Secondary RAT usage data and indication to send it to PDN GW) message per PDN connection to the Serving GW, only for the affected PDN connections. If ISR was activated before this procedure, MME should maintain ISR. The UE is informed about the ISR status in the Tracking Area Update procedure. If the Serving GW supports Modify Access Bearers Request procedure and if there is no need for the SGW to send the signalling to the PDN GW, the MME may send a Modify Access Bearers Request (eNodeB address(es) and TEIDs for downlink user plane for all the EPS bearers, ISR Activated) to the Serving GW to optimise the signalling. If the MME received Secondary RAT usage data in step 1, the MME shall include it in this message. If the MME received PSCell ID in step 1, the MME shall include it in this message.
If Secondary RAT usage data was included and if PGW secondary RAT usage data reporting is active, the Serving GW shall send Modify Bearer Request (Secondary RAT usage data) message to the PDN GW for each PDN connection. The PDN GW responds with Modify Bearer Response message to the Serving GW.
3. The Serving GW returns a Modify Bearer Response (Serving GW address and TEID for uplink traffic) message to the MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message.
The Serving GW starts sending downlink packets to the eNodeB using the newly received address and TEID.
4. In order to assist the reordering function in the Master eNodeB and/or Secondary RAN nodes, for the bearers that are switched between Master eNodeB and Secondary RAN nodes, the Serving GW shall send one or more "end marker" packets on the old path immediately after switching the path as defined in TS 36.300 [5], clause 10.1.2.2.
5. The MME confirms the E-RAB modification with the E-RAB Modification Confirm (CSG Membership Status) message. The MME indicates for each bearer whether it was successfully modified, kept unmodified or already released by the EPC as defined in TS 36.413 [36]. For the EPS bearers that have not been switched successfully in the core network, it is the MME decision whether to maintain or release the corresponding EPS bearers. The eNodeB uses the CSG Membership Status to decide on further actions, as specified in TS 36.300 [5].
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495b59b986f98d41912141cabbec196e
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23.401
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5.4.8 E-UTRAN initiated UE Context Modification procedure
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When split bearer option is applied to support dual connectivity operation, this procedure is used is by the eNodeB to request the modifications on the established UE Context. In the current version of the specification, this procedure is only used for membership verification, as described in TS 36.300 [5].
Figure 5.4.7-1: E-UTRAN initiated UE context modification procedure
1. The addition of an hybrid HeNB as the SeNodeB is triggered, providing the CSG-ID and the CSG Membership Information to the MeNodeB.
2. The Master eNodeB sends UE Context Modification Indication message to the MME, which includes the CSG Membership Information of the SeNodeB.
3. The MME verifies the CSG membership based on the provided CSG Membership Information as specified in TS 36.300 [5], but does not update the User CSG Information in the Core Network. A failure of the CSG Membership Information verification does not impact the E-UTRAN UE Context Modification procedure.
4. The MME confirms the UE Context Modification Indication with the UE Context Modification Confirm (CSG Membership Status) message. If CSG Membership Information was not present in the UE Context Modification Indication message, the MME can not perform CSG Membership Information verification and does not provide CSG Membership Status in the UE Context Modification Confirm message.
5. If the CSG Membership Status returned by the MME is different from what was reported by the UE, the eNodeB may decide on further actions.
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495b59b986f98d41912141cabbec196e
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23.401
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5.5 Handover
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1 Intra-E-UTRAN handover
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1.1 X2-based handover
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1.1.1 General
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These procedures are used to hand over a UE from a source eNodeB to a target eNodeB using the X2 reference point. In these procedures the MME is unchanged. Two procedures are defined depending on whether the Serving GW is unchanged or is relocated. In addition to the X2 reference point between the source and target eNodeB, the procedures rely on the presence of S1-MME reference point between the MME and the source eNodeB as well as between the MME and the target eNodeB.
The handover preparation and execution phases are performed as specified in TS 36.300 [5]. If emergency bearer services are ongoing for the UE handover to the target eNodeB is performed independent of the Handover Restriction List. The MME checks, as part of the Tracking Area Update in the execution phase, if the handover is to a restricted area and if so MME releases the non-emergency bearers as specified in clause 5.10.3.
If the serving PLMN changes during X2-based handover, the source eNodeB shall indicate to the target eNodeB (in the Handover Restriction List) the PLMN selected to be the new Serving PLMN.
When the UE receives the handover command it will remove any EPS bearers for which it did not receive the corresponding EPS radio bearers in the target cell. As part of handover execution, downlink and optionally also uplink packets are forwarded from the source eNodeB to the target eNodeB. When the UE has arrived to the target eNodeB, downlink data forwarded from the source eNodeB can be sent to it. Uplink data from the UE can be delivered via the (source) Serving GW to the PDN GW or optionally forwarded from the source eNodeB to the target eNodeB. Only the handover completion phase is affected by a potential change of the Serving GW, the handover preparation and execution phases are identical.
If the MME receives a rejection to a NAS procedure (e.g. dedicated bearer establishment/modification/release; location reporting control; NAS message transfer; etc.) from the eNodeB with an indication that an X2 handover is in progress (see TS 36.300 [5]), the MME shall reattempt the same NAS procedure either when the handover is complete or the handover is deemed to have failed, except in the case of Serving GW relocation. The failure is known by expiry of the timer guarding the NAS procedure.
If the X2 handover includes the Serving GW relocation, and if the MME receives a rejection to a NAS message transfer for a Downlink NAS Transport or Downlink Generic NAS Transport message from the eNodeB with an indication that an X2 handover is in progress, the MME should resend the corresponding message to the target eNodeB when either the handover is complete or to the source eNodeB when the handover is deemed to have failed if the MME is still the serving MME.
If the MME receives a rejection to a NAS message transfer for a CS Service Notification or to a UE Context Modification Request message with a CS Fallback indicator from the eNodeB with an indication that an X2 handover is in progress, the MME shall resend the corresponding message to the target eNodeB when the handover is complete or to the source eNodeB when the handover is deemed to have failed.
If during the handover procedure the MME detects that the Serving GW needs be relocated, the MME shall reject any PDN GW initiated EPS bearer(s) request received since handover procedure started and shall include an indication that the request has been temporarily rejected due to handover procedure in progress. The rejection is forwarded by the Serving GW to the PDN GW, with the indication that the request has been temporarily rejected.
Upon reception of a rejection for an EPS bearer(s) PDN GW initiated procedure with an indication that the request has been temporarily rejected due to handover procedure in progress, the PDN GW start a locally configured guard timer. The PDN GW shall re-attempt, up to a pre-configured number of times, when either it detects that the handover is completed or has failed using message reception or at expiry of the guard timer.
For handover the following applies related to handling of radio capabilities:
- If the source eNodeB and target eNodeB support RACS as defined in clause 5.11.3a, the source eNodeB provides the UE's UE Radio Capability ID to the target eNodeB.
- If the source eNodeB has knowledge that the target eNodeB might not have a local copy of the Radio Capability corresponding to the UE Radio Capability ID (i.e. because the source eNodeB had itself to retrieve the UE's Radio Capability from the MME) then the source eNodeB may also send some (or all) of the UE's Radio Capability to the target eNodeB (the size limit based on local configuration) in X2 signalling as defined in TS 36.423 [76]. In the case of inter-PLMN handover, when the source and target eNodeB support RACS as defined in clause 5.11.3a and the source eNodeB determines based on local configuration that the target PLMN does not support the UE Radio Capability ID assigned by the source PLMN, then the source eNodeB shall provide the UE radio capabilities to the target eNodeB and shall not send the UE Radio Capability ID.
- If the target eNodeB does not have mapping between the specific UE Radio Capability ID and the UE radio capabilities and no UE radio capabilities are provided by source eNodeB, it shall use the procedure described in TS 36.413 [36] to retrieve the mapping from the Core Network.
- If, as permitted in TS 36.423 [76], the target eNodeB during the handover preparation received the UE radio capabilities but did not receive the UE Radio Capability ID the target eNodeB shall proceed with handover using the received UE radio capabilities.
- If the target eNodeB received both the UE radio capabilities and the UE Radio Capability ID, then the target eNodeB shall use any locally stored UE radio capability information corresponding to the UE Radio Capability ID.
- If none are stored locally, the target eNodeB may request the full UE radio capability information from the core network.
- If the full UE radio capability information is not promptly received from the core network, or the target eNodeB chooses not to request it, then the target eNodeB shall proceed with the UE radio capabilities sent by the source RAN node. The target eNodeB shall not use the UE radio capability information received from the source eNodeB for any other UE with the same UE Radio Capability ID.
- If the target eNodeB knows (e.g. by configuration) that the UE's E-UTRA radio capabilities applicable to the target eNB may be different to the E-UTRA radio capabilities stored in the source eNodeB (e.g. for handover to/from an E-UTRA eNodeB that supports the NTN enhancements as defined in TS 36.300 [5]), then the target eNodeB shall trigger retrieval of the radio capability information again from the UE.
NOTE: In order to support handover from an E-UTRA eNodeB that supports the NTN enhancements as defined in TS 36.300 [5] the target eNodeB needs to be upgraded to support the above behaviour.
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1.1.2 X2-based handover without Serving GW relocation
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This procedure is used to hand over a UE from a source eNodeB to a target eNodeB using X2 when the MME is unchanged and decides that the Serving GW is also unchanged. The presence of IP connectivity between the Serving GW and the source eNodeB, as well as between the Serving GW and the target eNodeB is assumed.
Figure 5.5.1.1.2-1: X2-based handover without Serving GW relocation
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402 [2].
1a. If the PLMN has configured secondary RAT usage reporting, the source eNodeB during the handover execution phase may provide RAN usage data Report (Secondary RAT usage data, handover flag) to the MME. The source eNodeB shall provide this only when the Target eNodeB has confirmed handover over X2 interface (see TS 36.300 [5] and the source eNodeB has sent a HO command to the UE). The handover flag indicates to the MME that it should buffer the usage data report before forwarding it to the Serving GW.
1b. The target eNodeB sends a Path Switch Request message to MME to inform that the UE has changed cell, including the TAI+ECGI of the target cell and the list of EPS bearers to be switched.
If Dual Connectivity is activated for the UE, the PSCell ID shall be included in the Path Switch Request message.
If the target cell is a CSG cell, the target eNodeB includes the CSG ID of the target cell in Path Switch Request message. If the target cell is in hybrid mode, it includes the CSG ID of the target cell and CSG Access Mode set to "hybrid" in the Path Switch Request message. Moreover, the Path Switch Request message contains the CSG Membership Status IE if the hybrid cell accessed by the UE has a different CSG from the source cell or the source cell does not have a CSG ID. The MME determines the CSG membership based on the CSG ID and the target PLMN id received from the target eNodeB.The MME updates the User CSG information based on the CSG ID and CSG Access Mode received from the target eNodeB and CSG membership if one of the parameters has changed.
For SIPTO at the Local Network with stand-alone GW architecture, the target eNodeB shall include the Local Home Network ID of the target cell in the Path Switch Request message.
The MME determines that the Serving GW can continue to serve the UE.
2. The MME sends a Modify Bearer Request (eNodeB address(es) and TEIDs for downlink user plane for the accepted EPS bearers, ISR Activated, Secondary RAT usage data, User Location Information, PSCell ID) message per PDN connection to the Serving GW for each PDN connection where the default bearer has been accepted by the target eNodeB. If the PDN GW requested location information change reporting, the MME also includes the User Location Information IE in this message if it is different compared to the previously sent information. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. If the Serving Network has changed, the MME includes the new Serving Network IE in this message. If ISR was activated before this procedure, MME should maintain ISR. The UE is informed about the ISR status in the Tracking Area Update procedure. If the Serving GW supports Modify Access Bearers Request procedure and if there is no need for the SGW to send the signalling to the PDN GW, the MME may send Modify Access Bearers Request (eNodeB address(es) and TEIDs for downlink user plane for the accepted EPS bearers, ISR Activated) per UE to the Serving GW to optimise the signalling. The MME includes the Secondary RAT usage data if the MME received it from the source eNodeB in step 1a. The MME includes the PSCell ID if the MME received it from the target eNodeB in step 1b.
If the PDN GW requested UE's User CSG information (determined from the UE context), the MME includes the User CSG Information IE in this message if the User CSG Information has changed.
The MME uses the list of EPS bearers to be switched, received in step 1, to determine whether any dedicated EPS bearers in the UE context have not been accepted by the target eNodeB. The MME releases the non-accepted dedicated bearers by triggering the bearer release procedure as specified in clause 5.4.4.2. If the Serving GW receives a DL packet for a non-accepted bearer, the Serving GW drops the DL packet and does not send a Downlink Data Notification to the MME.
If the default bearer of a PDN connection has not been accepted by the target eNodeB and there are multiple PDN connections active, the MME shall consider all bearers of that PDN connection as failed and release that PDN connection by triggering the MME requested PDN disconnection procedure specified in clause 5.10.3.
If none of the default EPS bearers have been accepted by the target eNodeB or there is a LIPA PDN connection that has not been released, the MME shall act as specified in step 6.
3. If the Serving GW has received the User Location Information IE and/or the UE Time Zone IE and/or the Serving Network IE and/or User CSG Information IE from the MME in step 2 the Serving GW informs the PDN GW(s) about this information that e.g. can be used for charging, by sending the message Modify Bearer Request (Serving GW Address and TEID, User Location Information IE and/or UE Time Zone IE and/or Serving Network IE and/or User CSG Information IE, Secondary RAT usage data) per PDN connection to the PDN GW(s) concerned. The Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic) message to the MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message. If the Serving GW cannot serve the MME Request in the Modify Access Bearers Request message without S5/S8 signalling or without corresponding Gxc signalling when PMIP is used over the S5/S8 interface, it shall respond to the MME with indicating that the modifications are not limited to S1-U bearers, and the MME shall repeat its request using Modify Bearer Request message per PDN connection. The Serving GW forwards the Secondary RAT usage data to the PDN GW, if the Serving GW received it in step 2 and if PGW secondary RAT usage data reporting is active.
4. The Serving GW starts sending downlink packets to the target eNodeB using the newly received address and TEIDs. A Modify Bearer Response message is sent back to the MME.
5. In order to assist the reordering function in the target eNodeB, the Serving GW shall send one or more "end marker" packets on the old path immediately after switching the path as defined in TS 36.300 [5], clause 10.1.2.2.
6. The MME confirms the Path Switch Request message with the Path Switch Request Ack message. If the UE‑AMBR is changed, e.g. all the EPS bearers which are associated to the same APN are rejected in the target eNodeB, the MME shall provide the updated value of UE‑AMBR to the target eNodeB in the Path Switch Request Ack message.
If the CSG membership status was included in the Path Switch Request message, the MME shall include its verified CSG membership status in the Path Switch Request Ack message.
If some EPS bearers have not been switched successfully in the core network, the MME shall indicate in the Path Switch Request Ack message which bearers failed to be established (see more detail in TS 36.413 [36]) and for dedicated bearers initiate the bearer release procedure as specified in clause 5.4.4.2 to release the core network resources of the failed dedicated EPS bearers. The target eNodeB shall delete the corresponding bearer contexts when it is informed that bearers have not been established in the core network.
If none of the default EPS bearers have been switched successfully in the core network or if they have not been accepted by the target eNodeB or the LIPA PDN connection has not been released, the MME shall send a Path Switch Request Failure message (see more detail in TS 36.413 [36]) to the target eNodeB. The MME performs explicit detach of the UE as described in the MME initiated detach procedure of clause 5.3.8.3.
If the MME supports RACS as defined in clause 5.11.3a and has UE Radio Capability ID stored in the UE's context it includes it in the Path Switch Request Ack message, if the target eNodeB supports RACS.
If supported by the MME and if the UE is subscribed to receive time reference information, then the MME includes the Time Reference Information Distribution Indication in the Path Switch Request Ack message.
7. By sending Release Resource the target eNodeB informs success of the handover to source eNodeB and triggers the release of resources. This step is specified in TS 36.300 [5].
8. The UE initiates a Tracking Area Update procedure when one of the conditions listed in clause "Triggers for tracking area update" applies. If ISR is activated for the UE when the MME receives the Tracking Area Update Request, the MME should maintain ISR by indicating ISR Activated in the Tracking Area Update Accept message.
NOTE 2: It is only a subset of the TA update procedure that is performed by the MME, since the UE is in ECM‑CONNECTED state and the MME is not changed.
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1.1.3 X2-based handover with Serving GW relocation
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This procedure is used to hand over a UE from a source eNodeB to a target eNodeB using X2 when the MME is unchanged and the MME decides that the Serving GW is to be relocated. The presence of IP connectivity between the source Serving GW and the source eNodeB, between the source Serving GW and the target eNodeB, and between the target Serving GW and target eNodeB is assumed. (If there is no IP connectivity between target eNodeB and source Serving GW, it is assumed that the S1-based handover procedure in clause 5.5.1.2 shall be used instead.)
Figure 5.5.1.1.3-1: X2-based handover with Serving GW relocation
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2].
1a. If the PLMN has configured Secondary RAT usage data reporting and the source eNodeB has Secondary RAT usage data to report, the eNodeB sends a RAN usage data Report (Secondary RAT usage data, handover flag) message to the MME. The eNodeB shall provide this only when it is to perform a Path Switch (i.e. the Target eNodeB has confirmed it is ready over X2 interface (see TS 36.300 [5] and the source eNodeB has sent a HO command to the UE). The handover flag indicates to the MME that it should buffer the report before forwarding the Secondary RAT usage charging data.
1b. The target eNodeB sends a Path Switch Request message to MME to inform that the UE has changed cell, including the ECGI of the target cell and the list of EPS bearers to be switched.
If Dual Connectivity is activated for the UE, the PSCell ID shall be included in the Path Switch Request message.
If the target cell is a CSG cell, the target eNodeB includes the CSG ID of the target cell in Path Switch Request message. If the target cell is in hybrid mode, it includes the CSG ID of the target cell and CSG Access Mode set to "hybrid" in the Path Switch Request message. Moreover, the Path Switch Request message contains the CSG Membership Status IE if the hybrid cell accessed by the UE has a different CSG from the source cell or the source cell does not have a CSG ID. The MME determines the CSG membership based on the CSG ID and the target PLMN id received from the target eNodeB. The MME updates the User CSG information based on the CSG ID and CSG Access Mode received from the target eNodeB and CSG membership if one of the parameters has changed.
For SIPTO at the Local Network with stand-alone GW architecture, the target eNodeB shall include the Local Home Network ID of the target cell in the Path Switch Request message.
The MME determines that the Serving GW is relocated and selects a new Serving GW according to clause 4.3.8.2 on "Serving GW Selection Function".
NOTE 2: The MME knows the S‑GW Service Area with a TA granularity.
2. The MME sends a Create Session Request (bearer context(s) with PDN GW addresses and TEIDs (for GTP-based S5/S8) or GRE keys (for PMIP-based S5/S8) at the PDN GW(s) for uplink traffic, eNodeB address(es) and TEIDs for downlink user plane for the accepted EPS bearers, the Protocol Type over S5/S8, Serving Network, UE Time Zone, Secondary RAT usage data, User Location Information, PSCell ID) message per PDN connection to the target Serving GW for each PDN connection where the default bearer has been accepted by the target eNodeB. The target Serving GW allocates the S‑GW addresses and TEIDs for the uplink traffic on S1_U reference point (one TEID per bearer). The Protocol Type over S5/S8 is provided to Serving GW which protocol should be used over S5/S8 interface. If the PDN GW requested location information change reporting, the MME also includes the User Location Information IE in this message if it is different compared to the previously sent information. If the PDN GW requested UE's User CSG information (determined from the UE context), the MME includes the User CSG Information IE in this message if the User CSG Information has changed.
The MME uses the list of EPS bearers to be switched, received in step 1, to determine whether any dedicated EPS bearers in the UE context have not been accepted by the target eNodeB. The MME releases the non-accepted dedicated bearers by triggering the bearer release procedure as specified in clause 5.4.4.2 via target Serving GW. If the Serving GW receives a DL packet for a non-accepted bearer, the Serving GW drops the DL packet and does not send a Downlink Data Notification to the MME.
If the default bearer of a PDN connection has not been accepted by the target eNodeB and there are multiple PDN connections active, the MME shall consider all bearers of that PDN connection as failed and release that PDN connection by triggering the MME requested PDN disconnection procedure specified in clause 5.10.3 via source Serving GW.
If none of the default EPS bearers have been accepted by the target eNodeB or there is a LIPA PDN connection that has not been released, the MME shall act as specified in step 5.
If the MME received it from the source eNodeB in step 1a and PDN GW Secondary RAT reporting is active, the MME includes the Secondary RAT usage data with a flag stating that the target SGW shall not process the information and only forward it to the PDN GW. If MME received PSCell ID in step 1b, the MME shall include it in Create Session Request.
3. The target Serving GW assigns addresses and TEIDs (one per bearer) for downlink traffic from the PDN GW. The Serving GW allocates DL TEIDs on S5/S8 even for non-accepted bearers. It sends a Modify Bearer Request (Serving GW addresses for user plane and TEID(s), Serving Network, PDN Charging Pause Support Indication, Secondary RAT usage data) message per PDN connection to the PDN GW(s). The S‑GW also includes User Location Information IE and/or UE Time Zone IE and/or User CSG Information IE if it is present in step 2. The PDN GW updates its context field and returns a Modify Bearer Response (Charging Id, MSISDN, PDN Charging Pause Enabled Indication (if PDN GW has chosen to enable the function), etc.) message to the Serving GW. The MSISDN is included if the PDN GW has it stored in its UE context. The PDN GW starts sending downlink packets to the target GW using the newly received address and TEIDs. These downlink packets will use the new downlink path via the target Serving GW to the target eNodeB. The Serving GW shall allocate TEIDs for the failed bearers and inform to the MME. The Serving GW forwards the Secondary RAT usage data to the PDN GW, if the Serving GW received it in step 2 and if PGW secondary RAT usage data reporting is active.
If the Serving GW is relocated, the PDN GW shall send one or more "end marker" packets on the old path immediately after switching the path in order to assist the reordering function in the target eNodeB. The source Serving GW shall forward the "end marker" packets to the source eNodeB.
4. The target Serving GW sends a Create Session Response (Serving GW addresses and uplink TEID(s) for user plane) message back to the target MME. The MME starts a timer, to be used in step 7.
5. The MME confirms the Path Switch Request message with the Path Switch Request Ack (Serving GW addresses and uplink TEID(s) for user plane) message. If the UE‑AMBR is changed, e.g. all the EPS bearers which are associated to the same APN are rejected in the target eNodeB, the MME shall provide the updated value of UE‑AMBR to the target eNodeB in the Path Switch Request Ack message. The target eNodeB starts using the new Serving GW address(es) and TEID(s) for forwarding subsequent uplink packets.
If the CSG membership status was included in the Path Switch Request message, the MME shall include its verified CSG membership status in the Path Switch Request Ack message.
If some EPS bearers have not been switched successfully in the core network, the MME shall indicate in the Path Switch Request Ack message which bearers failed to be established (see more detail in TS 36.413 [36]) and for dedicated bearers initiate the bearer release procedure as specified in clause 5.4.4.2 to release the core network resources of the failed dedicated EPS bearers. The target eNodeB shall delete the corresponding bearer contexts when it is informed that bearers have not been established in the core network.
If none of the default EPS bearers have been switched successfully in the core network or if they have not been accepted by the target eNodeB or the LIPA PDN connection has not been released, the MME shall send a Path Switch Request Failure message (see more detail in TS 36.413 [36]) to the target eNodeB. The MME performs explicit detach of the UE as described in the MME initiated detach procedure of clause 5.3.8.3.
If the MME supports RACS as defined in clause 5.11.3a and has UE Radio Capability ID stored in the UE's context it includes it in the Path Switch Request Ack message.
If supported by the MME and if the UE is subscribed to receive time reference information, then the MME includes the Time Reference Information Distribution Indication in the Path Switch Request Ack message.
6. By sending Release Resource the target eNodeB informs success of the handover to source eNodeB and triggers the release of resources. This step is specified in TS 36.300 [5].
7. When the timer has expired after step 4, the source MME releases the bearer(s) in the source Serving GW by sending a Delete Session Request message (Cause, Operation Indication, Secondary RAT usage data, User Location Information, PSCell ID). The operation Indication flag is not set, that indicates to the Source Serving GW that the Source Serving GW shall not initiate a delete procedure towards the PDN GW. If PSCell ID was received in step 1a, the MME includes it in Delete Session Request message. The Source Serving GW acknowledges with Delete Session Response messages. If ISR has been activated before this procedure, the cause indicates to the Source S‑GW that the Source S‑GW shall delete the bearer resources on the other old CN node by sending Delete Bearer Request message(s) to that CN node. The MME includes the Secondary RAT usage data in this message if it received it in step 1a.
8. The UE initiates a Tracking Area Update procedure when one of the conditions listed in clause "Triggers for tracking area update" applies.
NOTE 3: It is only a subset of the TA update procedure that is performed by the MME, since the UE is in ECM‑CONNECTED state. The UE is informed about the ISR status in the Tracking Area Update procedure.
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1.2 S1-based handover
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1.2.1 General
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The S1-based handover procedure is used when the X2-based handover cannot be used. The source eNodeB initiates a handover by sending Handover Required message over the S1-MME reference point. This procedure may relocate the MME and/or the Serving GW. The source MME selects the target MME. The MME should not be relocated during inter-eNodeB handover unless the UE leaves the MME Pool Area where the UE is served. The MME (target MME for MME relocation) determines if the Serving GW needs to be relocated. If the Serving GW needs to be relocated the MME selects the target Serving GW, as specified in clause 4.3.8.2 on Serving GW selection function.
The source eNodeB decides which of the EPS bearers are subject for forwarding of downlink and optionally also uplink data packets from the source eNodeB to the target eNodeB. The EPC does not change the decisions taken by the RAN node. Packet forwarding can take place either directly from the source eNodeB to the target eNodeB, or indirectly from the source eNodeB to the target eNodeB via the source and target Serving GWs (or if the Serving GW is not relocated, only the single Serving GW).
The availability of a direct forwarding path is determined in the source eNodeB and indicated to the source MME. If X2 connectivity is available between the source and target eNodeBs, a direct forwarding path is available.
If a direct forwarding path is not available, indirect forwarding may be used. The source MME uses the indication from the source eNodeB to determine whether to apply indirect forwarding. The source MME indicates to the target MME whether indirect forwarding should apply. Based on this indication, the target MME determines whether it applies indirect forwarding.
If both source eNodeB and source MME support DAPS the source eNodeB may decide that some of the E-RABs are subject for DAPS handover as defined in TS 36.300 [5]; in this case, the source eNodeB provides the DAPS information indicating the request concerns a DAPS handover for that E-RAB as part of the Source to Target eNodeB Transparent Container. If the Target eNodeB accepts that the request concerns of DAPS handover and both Target eNodeB and Target MME support DAPS, the S1-based DAPS handover will be performed and the target eNodeB provides DAPS response information as part of the Target to Source eNodeB Transparent Container.
If the MME receives a rejection to an S1 interface procedure (e.g. dedicated bearer establishment/modification/release; location reporting control; NAS message transfer; etc.) from the eNodeB with an indication that an S1 handover is in progress (see TS 36.300 [5]), the MME shall reattempt the same S1 interface procedure when either the handover is complete or is deemed to have failed if the MME is still the serving MME, except in the case of Serving GW relocation. If the S1 handover changes the serving MME, the source MME shall terminate any other ongoing S1 interface procedures except the handover procedure.
If the S1 handover includes the Serving GW relocation, and if the MME receives a rejection to a NAS message transfer for a Downlink NAS Transport or Downlink Generic NAS Transport message from the eNodeB with an indication that an S1 handover is in progress, the MME should resend the corresponding message to the target eNodeB when either the handover is complete or to the source eNodeB when the handover is deemed to have failed if the MME is still the serving MME.
If the MME receives a rejection to a NAS message transfer for a CS Service Notification or to a UE Context modification Request message with a CS Fallback indication from the eNodeB with an indication that an S1 handover is in progress, the MME shall resend the corresponding message to the target eNodeB when either the handover is complete or to the source eNodeB when the handover is deemed to have failed if the MME is still the serving MME.
In order to minimise the number of procedures rejected by the eNodeB, the MME should pause non-handover related S1 interface procedures (e.g. downlink NAS message transfer, E-RAB Setup/Modify/Release, etc.) while a handover is ongoing (i.e. from the time that a Handover Required has been received until either the Handover procedure has succeeded (Handover Notify) or failed (Handover Failure)) and continue them once the Handover procedure has completed if the MME is still the serving MME, except in the case of Serving GW relocation.
If during the handover procedure the MME detects that the Serving GW or/and the MME needs be relocated, the MME shall reject any PDN GW initiated EPS bearer(s) request received since handover procedure started and shall include an indication that the request has been temporarily rejected due to handover procedure in progress. The rejection is forwarded by the Serving GW to the PDN GW, with the indication that the request has been temporarily rejected.
Upon reception of a rejection for an EPS bearer(s) PDN GW initiated procedure with an indication that the request has been temporarily rejected due to handover procedure in progress, the PDN GW start a locally configured guard timer. The PDN GW shall re-attempt, up to a pre-configured number of times, when either it detects that the handover is completed or has failed using message reception or at expiry of the guard timer.
If emergency bearer services are ongoing for the UE, handover to the target eNodeB is performed independent of the Handover Restriction List. The MME checks, as part of the Tracking Area Update in the execution phase, if the handover is to a restricted area and if so MME releases the non-emergency bearers as specified in clause 5.10.3.
If emergency bearer services are ongoing for the UE, handover to the target CSG cell is performed independent of the UE's CSG subscription. If the handover is to a CSG cell that the UE is not subscribed, the target eNodeB only accepts the emergency bearers and the target MME releases the non-emergency PDN connections that were not accepted by the target eNodeB as specified in clause 5.10.3.
For inter-PLMN handover to a CSG cell, if the source MME has the CSG-ID list of the target PLMN, the source MME shall use it to validate the CSG membership of the UE in the target CSG cell. Otherwise, based on operator's configuration the source MME may allow the handover by validating the CSG membership of the UE in the target CSG cell using the CSG-ID list of the registered PLMN-ID. If neither the CSG-ID list of the target PLMN nor the operator's configuration permits the handover, the source MME shall reject the handover due to no CSG membership information of the target PLMN-ID.
As specified in clause 4.3.8.3, with regard to CIoT EPS Optimisations, the source MME attempts to perform handover to a target MME that can support the UE's Preferred Network Behaviour. For a UE that is using a Non-IP connection to a PDN Gateway, or a PDN connection to a SCEF, if these bearers cannot be supported by the target MME, the source MME does not attempt to handover those bearers, but instead releases them upon successful completion of the handover. If the MME does not have any bearer for the UE that can be transferred, then the MME sends an S1-AP Handover Preparation Failure message to the source eNodeB.
For PDN connection of Ethernet Type, if the target MME does not support Ethernet PDN Type, the source MME does not attempt to handover those bearers, but instead releases them upon successful completion of the handover.
NOTE 1: Inter-PLMN handover to a CSG cell in a PLMN which is not an equivalent PLMN for the UE is not supported.
For handover the following applies related to handling of radio capabilities:
- If the source eNodeB and target eNodeB support RACS as defined in clause 5.11.3a, the Source to Target transparent container need not carry the UE radio capabilities (instead the UE Radio Capability ID is supplied from the CN to the target eNodeB). However, if the source eNodeB has knowledge that the target eNodeB might not have a local copy of the Radio Capability corresponding to the UE Radio Capability ID (i.e. because the source eNodeB had itself to retrieve the UE's Radio Capability from the MME) then the source eNodeB may send some (or all) of the UE's Radio Capability to the target eNodeB (the size limit based on local configuration. In the case of inter-PLMN handover, when the source and target eNodeB support RACS as defined in clause 5.11.3a and the source eNodeB determines based on local configuration that the target PLMN does not support the UE Radio Capability ID assigned by the source PLMN, then the source eNodeB shall include the UE radio capabilities in the Source to Target transparent container. At such an inter-PLMN handover, the source CN node shall not provide the UE Radio Capability ID to the target CN node (or in intra-CN node case not to the target eNodeB). If the target eNodeB does not have a mapping between the UE Radio Capability ID received from the MME and the UE radio capabilities and no UE radio capability is provided in the Source to Target transparent container, it shall use the procedure described in TS 36.413 [36] to retrieve the mapping from the Core Network. If the target eNodeB received both the UE radio capabilities (in the Source to Target transparent container) and the UE Radio Capability ID (from the MME), then the target eNodeB shall use any locally stored UE radio capability information corresponding to the UE Radio Capability ID. If none are stored locally, the target eNodeB may request the full UE radio capability information from the core network. If the full UE radio capability information is not promptly received from the core network, or the target eNodeB chooses not to request it, then the target eNodeB shall proceed with the UE radio capabilities sent by the source RAN node. The target eNodeB shall not use the UE radio capability information received from the source RAN node for any other UE with the same UE Radio Capability ID.
- If the target eNodeB knows (e.g. by configuration) that the UE's E-UTRA radio capabilities applicable to the target eNB may be different to the E-UTRA radio capabilities stored in the source eNodeB (e.g. for handover to/from an E-UTRA eNodeB that supports the NTN enhancements as defined in TS 36.300 [5]), then the target eNodeB shall trigger retrieval of the radio capability information again from the UE.
NOTE 2: In order to support handover from an E-UTRA eNodeB that supports the NTN enhancements as defined in TS 36.300 [5] the target eNodeB needs to be upgraded to support the above behaviour.
The Inter eNodeB S1 based handover procedure specified in clause 5.5.1.2.2 may also be used for intra-eNodeB handover.
NOTE 3: One use case for intra-eNodeB handover to be performed by the Inter eNodeB S1 based handover procedure is when an eNodeB serves a satellite access system that covers more than one country. In such a situation, the UE might move from a "cell" in one country into a "cell" in another country, and the eNodeB may need to cause the MME to change to an MME serving the UE's new country.
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495b59b986f98d41912141cabbec196e
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23.401
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5.5.1.2.2 S1-based handover, normal
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This procedure describes the S1-based handover in the normal case, clause 5.5.1.2.3 describes it when the procedure is rejected by the target eNodeB or the target MME and clause 5.5.1.2.4 describes when the procedure is canceled by the source eNodeB.
Figure 5.5.1.2.2-1: S1-based handover
NOTE 1: For a PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402 [2]. Steps 16 and 16a concern GTP based S5/S8.
NOTE 2: If the Serving GW is not relocated, the box "Source Serving GW" in figure 5.5.1.2.2-1 is acting as the target Serving GW.
1. The source eNodeB decides to initiate an S1-based handover to the target eNodeB. This can be triggered e.g. by no X2 connectivity to the target eNodeB, or by an error indication from the target eNodeB after an unsuccessful X2-based handover, or by dynamic information learnt by the source eNodeB.
2. The source eNodeB sends Handover Required (Direct Forwarding Path Availability, Source to Target transparent container, target eNodeB Identity, CSG ID, CSG access mode, target TAI, S1AP Cause) to the source MME. The source eNodeB indicates which bearers are subject to data forwarding. Direct Forwarding Path Availability indicates whether direct forwarding is available from the source eNodeB to the target eNodeB. This indication from source eNodeB can be based on e.g. the presence of X2. The target TAI is sent to MME to facilitate the selection of a suitable target MME. When the target cell is a CSG cell or a hybrid cell, the source eNodeB shall include the CSG ID of the target cell. If the target cell is a hybrid cell, the CSG access mode shall be indicated.
3. The source MME selects the target MME as described in clause 4.3.8.3 on "MME Selection Function" and if it has determined to relocate the MME, it sends a Forward Relocation Request (MME UE context, Source to Target transparent container, RAN Cause, target eNodeB Identity, CSG ID, CSG Membership Indication, target TAI, MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone, Direct Forwarding Flag, Serving Network, Local Home Network ID, LTE-M UE Indication) message to the target MME. The target TAI is sent to the target MME to help it to determine whether S‑GW relocation is needed (and, if needed, aid SGW selection). The old Serving Network is sent to target MME to support the target MME to resolve if Serving Network is changed. In network sharing scenarios Serving Network denotes the serving core network.
The source MME shall perform access control by checking the UE's CSG subscription when CSG ID is provided by the source eNodeB. If there is no subscription data for this CSG ID or the CSG subscription is expired, and the target cell is a CSG cell, the source MME shall reject the handover with an appropriate cause unless the UE has emergency bearer services.
The MME UE context includes IMSI, MSISDN, ME Identity, UE security context, UE Network Capability, AMBR, Selected CN operator ID, APN restriction, Serving GW address and TEID for control signalling, and EPS Bearer context(s), UE Radio Capability ID, Time Reference Information Distribution Indication.
The MME UE context received from the source MME contains the MSISDN if the MSISDN was available at the source MME.
An EPS Bearer context includes the PDN GW addresses and TEIDs (for GTP-based S5/S8) or GRE keys (for PMIP-based S5/S8) at the PDN GW(s) for uplink traffic, APN, Serving GW addresses and TEIDs for uplink traffic, and TI.
Based on the CIoT EPS Optimisation capabilities of the target MME (determined according to the target MME selection procedure of clause 4.3.8.3) the source MME only includes the EPS Bearer Context(s) that the target MME can support. If none of the UE's EPS Bearers can be supported by the selected target MME, the source MME rejects the S1 handover attempt by sending a Handover Preparation Failure (Cause) message to the Source eNodeB. If the target MME supports CIoT EPS Optimisation and the use of header compression has been negotiated between the UE and the source MME, the source MME also includes in the Forward Relocation Request the previously negotiated Header Compression Configuration that includes the information necessary for the ROHC channel setup but not the RoHC context itself.
If the source MME includes EPS Bearer Context, in addition to the Serving GW IP address and TEID for S1-U use plane, the source MME also includes Serving GW IP address and TEID for S11-U, if available.
NOTE 3: If the handover is successful, the source MME will signal to the SGW and/or SCEF to release any non-included EPS Bearers after step 14. The non-included bearers are locally released by the UE following the Bearer Context Status synchronisation that occurs during the Tracking Area Update at step 18.
If SIPTO at the Local Network is active for a PDN connection in the architecture with stand-alone GW the source MME shall include the Local Home Network ID of the source cell in the EPS Bearer context corresponding to the SIPTO at the Local Network PDN connection.
RAN Cause indicates the S1AP Cause as received from source eNodeB.
The source MME includes the CSG ID in the Forward Relocation Request when the target cell is a CSG or hybrid cell. When the target cell is a hybrid cell, or if there are one or several emergency bearers and the target cell is a CSG cell, the CSG Membership Indication indicating whether the UE is a CSG member shall be included in the Forward Relocation Request message.
The Direct Forwarding Flag indicates if direct forwarding is applied, or if indirect forwarding is going to be set up by the source side.
The target MME shall determine the Maximum APN restriction based on the APN Restriction of each bearer context in the Forward Relocation Request, and shall subsequently store the new Maximum APN restriction value.
If the UE receives only emergency services and the UE is UICCless, IMSI can not be included in the MME UE context in Forward Relocation Request message. For emergency attached UEs, if the IMSI cannot be authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available.
If a UE is RLOS attached, the old MME includes an RLOS indication to the new MME. If the RLOS attached UE in the old MME does not have a USIM, IMSI can not be included in the Forward Relocation Request message. If the RLOS attached UE has USIM but the IMSI cannot be successfully authenticated, then the IMSI shall be marked as unauthenticated. Also, in this case, security parameters are included only if available.
If the Old MME is aware the UE is a LTE-M UE, it provides the LTE-M UE Indication to the new MME.
4. If the MME has been relocated, the target MME verifies whether the source Serving GW can continue to serve the UE. If not, it selects a new Serving GW as described in clause 4.3.8.2 on "Serving GW Selection Function". If the MME has not been relocated, the source MME decides on this Serving GW re-selection.
If the source Serving GW continues to serve the UE, no message is sent in this step. In this case, the target Serving GW is identical to the source Serving GW.
If a new Serving GW is selected, the target MME sends a Create Session Request (bearer context(s) with PDN GW addresses and TEIDs (for GTP-based S5/S8) or GRE keys (for PMIP-based S5/S8) at the PDN GW(s) for uplink traffic, Serving Network, UE Time Zone) message per PDN connection to the target Serving GW. The target Serving GW allocates the S‑GW addresses and TEIDs for the uplink traffic on S1_U reference point (one TEID per bearer). The target Serving GW sends a Create Session Response (Serving GW addresses and uplink TEID(s) for user plane) message back to the target MME.
5. The Target MME sends Handover Request (EPS Bearers to Setup, AMBR, S1AP Cause, Source to Target transparent container, CSG ID, CSG Membership Indication, Handover Restriction List, UE Radio Capability ID) message to the target eNodeB. This message creates the UE context in the target eNodeB, including information about the bearers, and the security context. For each EPS Bearer, the Bearers to Setup includes Serving GW address and uplink TEID for user plane, and EPS Bearer QoS. If the direct forwarding flag indicates unavailability of direct forwarding and the target MME knows that there is no indirect data forwarding connectivity between source and target, the Bearers to Setup shall include "Data forwarding not possible" indication for each EPS bearer. Handover Restriction List is sent if available in the Target MME; it is described in clause 4.3.5.7 "Mobility Restrictions".
S1AP Cause indicates the RAN Cause as received from source MME.
The Target MME shall include the CSG ID and CSG Membership Indication when provided by the source MME in the Forward Relocation Request message.
The target eNodeB sends a Handover Request Acknowledge (EPS Bearer Setup list, EPS Bearers failed to setup list Target to Source transparent container) message to the target MME. The EPS Bearer Setup list includes a list of addresses and TEIDs allocated at the target eNodeB for downlink traffic on S1‑U reference point (one TEID per bearer) and addresses and TEIDs for receiving forwarded data if necessary. If the UE‑AMBR is changed, e.g. all the EPS bearers which are associated to the same APN are rejected in the target eNodeB, the MME shall recalculate the new UE-AMBR and signal the modified UE‑AMBR value to the target eNodeB.
If none of the default EPS bearers have been accepted by the target eNodeB, the target MME shall reject the handover as specified in clause 5.5.1.2.3.
If the target cell is a CSG cell, the target eNodeB shall verify the CSG ID provided by the target MME, and reject the handover with an appropriate cause if it does not match the CSG ID for the target cell. If the target eNodeB is in hybrid mode, it may use the CSG Membership Indication to perform differentiated treatment for CSG and non-CSG members. If the target cell is a CSG cell, and if the CSG Membership Indication is "non member", the target eNodeB only accepts the emergency bearers.
If the MME supports RACS as defined in clause 5.11.3a and has UE Radio Capability ID stored in the UE's context it includes it in the Handover Request message, if target eNodeB supports RACS.
If supported by the MME and if the UE is subscribed to receive time reference information, then the MME includes the Time Reference Information Distribution Indication in the Handover Request message.
6. If indirect forwarding applies and the Serving GW is relocated, the target MME sets up forwarding parameters by sending Create Indirect Data Forwarding Tunnel Request (target eNodeB addresses and TEIDs for forwarding) to the Serving GW. The Serving GW sends a Create Indirect Data Forwarding Tunnel Response (target Serving GW addresses and TEIDs for forwarding) to the target MME. If the Serving GW is not relocated, indirect forwarding may be set up in step 8 below.
Indirect forwarding may be performed via a Serving GW which is different from the Serving GW used as the anchor point for the UE.
7. If the MME has been relocated, the target MME sends a Forward Relocation Response (Cause, Target to Source transparent container, Serving GW change indication, EPS Bearer Setup List, Addresses and TEIDs) message to the source MME. For indirect forwarding, this message includes Serving GW Address and TEIDs for indirect forwarding (source or target). Serving GW change indication indicates a new Serving GW has been selected.
8. If indirect forwarding applies, the source MME sends Create Indirect Data Forwarding Tunnel Request (addresses and TEIDs for forwarding) to the Serving GW. If the Serving GW is relocated it includes the tunnel identifier to the target serving GW.
The Serving GW responds with a Create Indirect Data Forwarding Tunnel Response (Serving GW addresses and TEIDs for forwarding) message to the source MME.
Indirect forwarding may be performed via a Serving GW which is different from the Serving GW used as the anchor point for the UE.
9. The source MME sends a Handover Command (Target to Source transparent container, Bearers subject to forwarding, Bearers to Release) message to the source eNodeB. The Bearers subject to forwarding includes list of addresses and TEIDs allocated for forwarding. The Bearers to Release includes the list of bearers to be released.
9a. The Handover Command is constructed using the Target to Source transparent container and is sent to the UE. Upon reception of this message the UE will remove any EPS bearers for which it did not receive the corresponding EPS radio bearers in the target cell.
9b. If the PLMN has configured Secondary RAT usage data reporting and the source eNodeB has Secondary RAT usage data to report, the eNodeB sends a RAN Usage data Report (Secondary RAT usage data, handover flag) message to the source MME. The handover flag indicates to the MME that it should buffer the report before forwarding the Secondary RAT usage data.
10. The source eNodeB sends the eNodeB Status Transfer message to the target eNodeB via the MME(s) to convey the PDCP and HFN status of the E-RABs for which PDCP status preservation applies, as specified in TS 36.300 [5]. The source eNodeB may omit sending this message if none of the E-RABs of the UE shall be treated with PDCP status preservation.
If there is an MME relocation the source MME sends this information to the target MME via the Forward Access Context Notification message which the target MME acknowledges. The source MME or, if the MME is relocated, the target MME, sends the information to the target eNodeB via the MME Status Transfer message.
11. The source eNodeB should start forwarding of downlink data from the source eNodeB towards the target eNodeB for bearers subject to data forwarding. This may be either direct (step 11a) or indirect forwarding (step 11b).
12. After the UE has successfully synchronized to the target cell, it sends a Handover Confirm message to the target eNodeB. Downlink packets forwarded from the source eNodeB can be sent to the UE. Also, uplink packets can be sent from the UE, which are forwarded to the target Serving GW and on to the PDN GW.
13. The target eNodeB sends a Handover Notify (TAI+ECGI, Local Home Network ID) message to the target MME. If Dual Connectivity is activated for the UE, the PSCell ID shall be included in the Handover Notify message.
For SIPTO at the Local Network with stand-alone GW architecture, the target eNodeB shall include the Local Home Network ID of the target cell in the Handover Notify message.
14. If the MME has been relocated, the target MME sends a Forward Relocation Complete Notification message to the source MME. The source MME in response sends a Forward Relocation Complete Acknowledge (Secondary RAT usage data) message to the target MME. The source MME includes Secondary RAT usage data in this message if it received this in step 9b. Regardless if MME has been relocated or not, a timer in source MME is started to supervise when resources in Source eNodeB and if the Serving GW is relocated, also resources in Source Serving GW shall be released.
Upon receipt of the Forward Relocation Complete Acknowledge message the target MME starts a timer if the target MME allocated S‑GW resources for indirect forwarding.
For all bearers that were not included in the Forward Relocation Request message sent in step 3, the MME now releases them by sending a Delete Bearer Command to the SGW, or, the appropriate message to the SCEF.
15. The MME sends a Modify Bearer Request (eNodeB address and TEID allocated at the target eNodeB for downlink traffic on S1‑U for the accepted EPS bearers, ISR Activated, Secondary RAT usage data if PGW secondary RAT usage data reporting is active, User Location Information, PSCell ID) message to the target Serving GW for each PDN connection, including the PDN connections that need to be released. If the PDN GW requested location information change reporting and/or User CSG information (determined from the UE context), the MME also includes the User Location Information IE (if it is different compared to the previously sent information) and/or User CSG Information IE in this message. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. If Serving GW is not relocated but the Serving Network has changed or if the MME has not received any old Serving Network information from the old MME, the MME includes the Serving Network IE in this message. For the case that neither MME nor S-GW changed, if ISR was activated before this procedure MME should maintain ISR. The UE is informed about the ISR status in the Tracking Area Update procedure. If the Serving GW supports Modify Access Bearers Request procedure and if there is no need for the SGW to send the signalling to the PDN GW, the MME may send Modify Access Bearers Request (eNodeB address and TEID allocated at the target eNodeB for downlink traffic on S1 U for the accepted EPS bearers, ISR Activated) per UE to the Serving GW to optimise the signalling. If Serving GW is not relocated and if Secondary RAT usage data was received in step 9a, the MME includes the Secondary RAT usage data in the message. If the Serving GW has been relocated and if PGW Secondary RAT reporting is active, the MME includes the Secondary RAT usage data and also includes a flag stating that the Serving GW should not process the information and only forward it to the PDN GW. If PSCell ID is received in step 13, the MME includes it in Modify Bearer Request message.
The MME releases the non-accepted dedicated bearers by triggering the bearer release procedure as specified in clause 5.4.4.2. If the Serving GW receives a DL packet for a non-accepted bearer, the Serving GW drops the DL packet and does not send a Downlink Data Notification to the MME.
If the default bearer of a PDN connection has not been accepted by the target eNodeB and there are other PDN connections active, the MME shall handle it in the same way as if all bearers of a PDN connection have not been accepted. The MME releases these PDN connections by triggering the MME requested PDN disconnection procedure specified in clause 5.10.3.
When the Modify Bearer Request does not indicate ISR Activated the Serving GW deletes any ISR resources by sending a Delete Bearer Request to the other CN node that has bearer resources on the Serving GW reserved.
16. If the Serving GW is relocated, the target Serving GW assigns addresses and TEIDs (one per bearer) for downlink traffic from the PDN GW. It sends a Modify Bearer Request (Serving GW addresses for user plane and TEID(s), Serving Network, PDN Charging Pause Support Indication, Secondary RAT usage data) message per PDN connection to the PDN GW(s). The S‑GW also includes User Location Information IE and/or UE Time Zone IE and/or User CSG Information IE if they are present in step 15. The Serving GW also includes Serving Network IE if it is present in step 4 or step 15. The Serving GW allocates DL TEIDs on S5/S8 even for non-accepted bearers. The PDN GW updates its context field and returns a Modify Bearer Response (Charging Id, MSISDN, PDN Charging Pause Enabled Indication (if PDN GW has chosen to enable the function), etc.) message to the target Serving GW. The MSISDN is included if the PDN GW has it stored in its UE context. The PDN GW starts sending downlink packets to the target GW using the newly received address and TEIDs. These downlink packets will use the new downlink path via the target Serving GW to the target eNodeB. The Secondary RAT usage data is included if it was received in step 15 and if PGW secondary RAT usage data reporting is active.
If the Serving GW is not relocated, but has received the User Location Information IE and/or UE Time Zone IE and/or User CSG Information IE and/or Serving Network IE from the MME in step 15, the Serving GW shall inform the PDN GW(s) about these information that e.g. can be used for charging, by sending the message Modify Bearer Request (User Location Information IE, UE Time Zone IE, User CSG Information IE, Serving Network IE) to the PDN GW(s) concerned. A Modify Bearer Response message is sent back to the Serving GW.
If the Serving GW is not relocated and it has not received User Location Information IE nor UE Time Zone IE nor User CSG Information IE nor Serving Network IE from the MME in step 15, no message is sent in this step and downlink packets from the Serving‑GW are immediately sent on to the target eNodeB.
If the Serving GW is relocated, the PDN GW shall send one or more "end marker" packets on the old path immediately after switching the path in order to assist the reordering function in the target eNodeB. The source Serving GW shall forward the "end marker" packets to the source eNodeB. If data forwarding -direct or indirect) occurs, the source eNodeB shall forward the "end marker" packets to the target eNodeB via the forwarding tunnel.
17. The Serving GW shall return a Modify Bearer Response (Serving GW address and TEID for uplink traffic) message to the MME as a response to a Modify Bearer Request message, or a Modify Access Bearers Response (Serving GW address and TEID for uplink traffic) as a response to a Modify Access Bearers Request message. If the Serving GW cannot serve the MME Request in the Modify Access Bearers Request message without S5/S8 signalling other than to unpause charging in the PDN GW or without corresponding Gxc signalling when PMIP is used over the S5/S8 interface, it shall respond to the MME with indicating that the modifications are not limited to S1-U bearers, and the MME shall repeat its request using Modify Bearer Request message per PDN connection.
If the Serving GW does not change, the Serving GW shall send one or more "end marker" packets on the old path immediately after switching the path in order to assist the reordering function in the target eNodeB. If data forwarding -direct or indirect) occurs, the source eNodeB shall forward the "end marker" packets to the target eNodeB via the forwarding tunnel.18. The UE initiates a Tracking Area Update procedure when one of the conditions listed in clause "Triggers for tracking area update" applies.
For a UE supporting CIoT EPS Optimisations, the EPS bearer status information shall be included in the TAU Request. The MME shall then indicate the EPS bearer status to the UE in the TAU Accept and the UE shall locally release any non-transferred bearer.
The target MME knows that it is a Handover procedure that has been performed for this UE as it received the bearer context(s) by handover messages and therefore the target MME performs only a subset of the TA update procedure, specifically it excludes the context transfer procedures between source MME and target MME. In this case, the target MME shall set the Header Compression Context Status for each EPS Bearer in the TAU Accept message based on information obtained in step 3.
19. When the timer started in step 14 expires the source MME sends a UE Context Release Command () message to the source eNodeB. The source eNodeB releases its resources related to the UE and responds with a UE Context Release Complete () message. When the timer started in step 14 expires and if the source MME received the Serving GW change indication in the Forward Relocation Response message, it deletes the EPS bearer resources by sending Delete Session Request (Cause, LBI, Operation Indication, Secondary RAT usage data, User Location Information, PSCell ID) messages to the Source Serving GW. The operation Indication flag is not set, that indicates to the Source Serving GW that the Source Serving GW shall not initiate a delete procedure towards the PDN GW. Secondary RAT usage data is included if it was received in step 9b. PSCell ID is included if it was received in step 9b. The Source Serving GW acknowledges with Delete Session Response () messages. If ISR has been activated before this procedure, the cause indicates to the Source S‑GW that the Source S‑GW shall delete the bearer resources on the other old CN node by sending Delete Bearer Request message(s) to that CN node.
20. If indirect forwarding was used then the expiry of the timer at source MME started at step 14 triggers the source MME to send a Delete Indirect Data Forwarding Tunnel Request message to the S‑GW to release the temporary resources used for indirect forwarding that were allocated at step 8.
21. If indirect forwarding was used and the Serving GW is relocated, then the expiry of the timer at target MME started at step 14 triggers the target MME to send a Delete Indirect Data Forwarding Tunnel Request message to the target S‑GW to release temporary resources used for indirect forwarding that were allocated at step 6.
5.5.1.2.2a S1-based DAPS handover, normal
This procedure describes the S1-based DAPS handover in the normal case.
Figure 5.5.1.2.2a-1: S1-based DAPS handover
1. Step 1 to step 9b are performed as described in clause 5.5.1.2.2 with the following changes:
The Source to Target Transparent Container which is included in Handover Required message in step 2 in clause 5.5.1.2.2 will contain the DAPS Information if DAPS HO is supported by source eNodeB and source MME and DAPS HO is requested for one or more DRBs as described in TS 36.300 [5].
If DAPS HO is supported by the target eNodeB and target MME and the DAPS Information is received for one or more DRBs in the Source to Target transparent container, the target eNodeB provides the DAPS Response Information in the Target to Source transparent container in Handover Request Acknowledge message in step 5a in clause 5.5.1.2.2.
2. The source eNodeB sends the eNodeB Early Status Transfer message to the target eNodeB via the MME(s) to convey the PDCP and HFN status of the E-RABs for which PDCP status preservation applies, as specified in TS 36.300 [5]. For the DRBs not subject to DAPS, step 10 to step 10c in clause 5.5.1.2.2 may be performed.
If there is an MME relocation the source MME sends this information to the target MME via the Forward Access Context Notification message which the target MME acknowledges. The source MME or, if the MME is relocated, the target MME, sends the information to the target eNodeB via the MME Early Status Transfer message.
3. This step is the same as step 11 in clause 5.5.1.2.2.
4. This step is the same as step 12 in clause 5.5.1.2.2.
5. This step is the same as step 13 in clause 5.5.1.2.2 with the difference that the Notify Source eNodeB IE is included in the Handover Notify message.
6. This step is the same as step 14 in clause 5.5.1.2.2 with following changes:
If there is an MME relocation and the target MME receives this Notify Source eNodeB information from the target eNodeB, the target MME provides the Notify Source eNodeB information via the Forward Relocation Complete Notification message.
7. If the Notify Source eNodeB IE is provided in either step 5 or step 6, the source MME sends the Handover Success message to source eNodeB to inform the source eNodeB that the UE has successfully accessed the target eNodeB.
8. The Source eNodeB initiates the eNodeB Status Transfer message for the DRB(s) subject to DAPS. This step is the same as step 10 in clause 5.5.1.2.2.
9. Steps 15 to 21b in clause 5.5.1.2.2 are performed.
|
495b59b986f98d41912141cabbec196e
|
23.401
|
5.5.1.2.3 S1-based handover, Reject
|
The Target eNodeB rejects the use of the Handover procedure if none of the requested bearers in the Handover Request message could be established. In this case no UE context is established in the target MME/eNodeB and no resources are allocated. Further, the Target MME rejects the handover request and clears all resource in Target eNodeB and Target MME if the Target eNodeB accepts the handover request but none of the default EPS bearers gets resources allocated. In both cases, the UE remains in the Source eNodeB/MME.
Figure 5.5.1.2.3-1: S1-based handover, Reject
NOTE 1: Steps 3, 4, 7 and 8 are performed if the MME is relocated.
NOTE 2: If the MME is not relocated Steps 5 and 6 are performed by the source MME and, in the description below, the source MME acts as the target MME.
1-5. Steps 1 to 5 in the flow are identical to steps 1-5 in clause 5.5.1.2.2.
6a. If the Target eNodeB fails to allocate any resources for any of the requested EPS bearers it sends a Handover Failure (Cause) message to the Target MME. The Target MME clears any reserved resources for this UE in the target MME.
6b. If the Target MME receives a Handover Request Acknowledge message from the Target eNodeB but none of the default EPS bearers are in the EPS Bearer Setup list IE, the Target MME clears any reserved resources for this UE in both the Target MME and the Target eNodeB.
7. This step is only performed for Serving GW relocation, i.e. if steps 4/4a have been performed. The Target MME deletes the EPS bearer resources by sending Delete Session Request (Cause) messages to the Target Serving GW. The Target Serving GW acknowledges with Delete Session Response (Cause) messages.
8. The Target MME sends the Forward Relocation Response (Cause) message to the Source MME.
9. When the Source MME receives the Forward Relocation Response message, it sends a Handover Preparation Failure (Cause) message to the Source eNodeB.
|
495b59b986f98d41912141cabbec196e
|
23.401
|
5.5.1.2.4 S1-based handover, Cancel
|
Instead of completing the handover procedure, the source eNodeB may at any time during the handover procedure, up to the time when a handover command message is sent to the UE cancel the handover.
The MME shall cancel the handover resources as defined in clause 5.5.2.5.1 for case the source RAN is eNodeB.
|
495b59b986f98d41912141cabbec196e
|
23.401
|
5.5.2 Inter RAT handover
| |
495b59b986f98d41912141cabbec196e
|
23.401
|
5.5.2.0 General
|
During Inter RAT handover indirect forwarding may apply for the downlink data forwarding performed as part of the handover. From its configuration data the MME knows whether indirect forwarding applies and it allocates a downlink data forwarding path on a Serving GWs for indirect forwarding. From its configuration data the S4 SGSN knows whether indirect forwarding applies and it allocates downlink data forwarding paths on Serving GWs for indirect forwarding. It is configured on MME and S4 SGSN whether indirect downlink data forwarding does not apply, applies always or applies only for inter PLMN inter RAT handovers.
During the handover procedure, the source MME shall reject any PDN GW initiated EPS bearer(s) request received since handover procedure started and shall include an indication that the request has been temporarily rejected due to handover procedure in progress. The rejection is forwarded by the Serving GW to the PDN GW, with the indication that the request has been temporarily rejected.
Upon reception of a rejection for an EPS bearer(s) PDN GW initiated procedure with an indication that the request has been temporarily rejected due to handover procedure in progress, the PDN GW behaves as specified in clause 5.5.1.2.1.
For inter-PLMN handover to a CSG cell, if the source MME/S4-SGSN has the CSG-ID list of the target PLMN, the source MME/S4-SGSN shall use it to validate the CSG membership of the UE in the target CSG cell. Otherwise, based on operator's configuration the source MME/S4-SGSN may allow the handover by validating the CSG membership of the UE in the target CSG cell using the CSG-ID list of the registered PLMN-ID. If neither the CSG-ID list of the target PLMN nor the operator's configuration permits the handover, the source MME/S4-SGSN shall reject the handover due to no CSG membership information of the target PLMN-ID
NOTE 1: Inter-PLMN handover to a CSG cell in a PLMN which is not an equivalent PLMN for the UE is not supported.
NOTE 2: Inter-PLMN handover to a CSG cell of an equivalent PLMN is only supported if the CSG-ID of the cell is in the CSG-ID list of both equivalent PLMNs.
NOTE 3: Upon bearer loss or UE-detected bearer QoS degradation during inter-RAT 3GPP handover, after receiving the Handover Command the UE can adopt an implementation dependent mechanism to trigger the handover of one or more PDN connections or mobility of one or more IP flows to WLAN (e.g. taking into account policies obtained from ANDSF).
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