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7.3.2.14 Media distribution response
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Table 7.3.2.14-1 describes the information flow media distribution response from an MC Service server (5G MBS session control role) that has a desired 5G MBS session to the MC service server.
Table 7.3.2.14-1: Media distribution response
Information element
Status
Description
MBS session ID
M
MBS session identifier
Bandwidth
M
Maximum bandwidth required
SDP information
M
SDP with media and floor control information applicable to groups that can use this session (e.g. codec, protocol id)
5QI
O
Actual 5QI
Media stream identifier
O
This element identifies the media stream of the SDP used for the group call
Media distribution indicator
O
Indicates to the MC service server whether the media in the ongoing group communication should be sent or not
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7.3.2.15 Media distribution release
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Information flow for Media distribution release is reused without modification as specified in clause 10.7.2.10 of 3GPP TS 23.280 [3].
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7.3.2.16 MBS session announcement acknowledgement
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Table 7.3.2.16-1 describes the information flow of an MBS session announcement acknowledgement message sent from the MC service clients to the MBS service server, to acknowledge the reception of the MBS session announcement.
Table 7.3.2.16-1: MBS session announcement acknowledgement.
Information element
Status
Description
MC service ID
M
The MC service identity of the MC service client.
MBS session ID(s)
M
The identity of the MBS session(s) whose announcement information is received.
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7.3.3 Procedures for usage of 5G MBS
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7.3.3.1 MBS session creation and MBS session announcement
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7.3.3.1.1 General
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The procedures in this clause describe how MBS session creation and MBS session announcement can be used for the transmission of MC service group communication data over either broadcast or multicast MBS sessions. The MBS session can either be created with or without dynamic PCC rule, where the latter requires less interaction done by the MC service server towards the 5GC (either directly or via NEF).
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7.3.3.1.2 Procedure for pre-created MBS session and MBS session announcement
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Pre-conditions:
- The MC service server has decided to use an MBS session for MC service group communications associated to a certain MC service group based on transport only mode.
- The MC service server has performed MB-SMF discovery and selection either directly or indirectly, via NEF/MBSF, unless the corresponding information is locally configured.
- MC service clients 1 to n are attached to the 5GS, registered and affiliated to the same MC service group X.
- The MC service server is aware whether to request the creation of the MBS service server with or without dynamic PCC rule.
Figure 7.3.3.1.2-1: Use of pre-created MBS session.
1. The MC service server initiates an MBS session creation procedure towards the 5GC as described in 3GPP TS 23.247 [15]. The procedure starts once the MC service server initiates a TMGI allocation request (either directly to MB-SMF or indirectly via NEF). Upon the reception of the TMGI allocation response, the MC service server sends an MBS session creation request, including further information related to the MBS session, e.g., MBS session ID, MBS session mode and the QoS requirements if dynamic PCC rule is not considered. However, if dynamic PCC rule is considered, the MC service server defines these requirements at a later step, namely it sends an MBS authorization/policy create request towards PCF (either directly or to the NEF) indicating the QoS requirements.
In the case of an untrusted MC service server, when the requested MBS service area crosses several MB-SMF service areas, the TMGI allocation request is rejected by the NEF/MBSF and it guides the MC service server by dividing the requested MBS service area into groups as described in 3GPP TS 23.247 [15]. Hence, the MC service server initiates a new TMGI allocation request for each grouped MBS service area. If during MBS session creation request the 5GS discovers that requested MBS service area crosses several MB-SMF service areas, the request is rejected, and the NEF/MBSF guides the MC service server as described earlier. Hence, the MC service server initiates a new MBS session creation procedure for each grouped MBS service area. The MC service server may utilize a unicast session if any MBS service area is not supported by any MB-SMF.
NOTE 1: In case of LTE eMBMS and 5G MBS co-existence, the MC service server may trigger the establishment of eMBMS bearers as described in 3GPP TS 23.280 [3] (or it may establish a unicast bearer) based on the RAT capabilities supported by the affiliated members in the MC service group X. If MBSF and BM-SC are co-located, TMGI used by 4G eMBMS can be the same as the MBS session ID.
NOTE 2: For the case of multi carrier support for broadcast MBS sessions, the MC service server may indicate the frequencies within a broadcast MBS service area by providing the MBS frequency selection area ID(s) (MBS FSA ID(s)) to the MB-SMF, or indirectly, via NEF.
2. The MC service server provides the MC service clients affiliated to MC service group X with the information related to the created MBS session via the MBS session announcement. As described in table 7.3.2.1-1, the MBS session announcement includes information such as the MBS session ID, MBS session mode (broadcast or multicast service type) and SDP information related to the MBS session under consideration.
NOTE 3: The MC service server may send an MBS session announcement at an earlier step during the MBS session creation procedure towards the MC service clients once the MC group associated to the MBS session is known.
Optionally, the MC service server includes the information elements related to the established eMBMS bearer once the MC service server has determined the need, as indicated in table 7.3.2.1-1. The MC service clients which camp on LTE will subsequently react to the information elements related to the eMBMS bearer as described in 3GPP TS 23.280 [3].
3. MC service clients store and process the received MBS session information.
4. MC service clients may provide an MBS session announcement acknowledgment to the MC service server to indicate the reception of the corresponding MBS session announcement.
5. Based on the MBS session mode (either multicast or broadcast), the following actions take place:
5a. For multicast MBS sessions, MC service clients initiate a UE session join request towards the 5GC using the information provided via the MBS session announcement. Hence, upon the first successful UE session join request, the multicast is then established, and the radio resources are reserved, if the session is in an active state. The established session can either be in active or inactive state as indicated in 3GPP TS 23.247 [15]. The MC service clients sends a UE session join notification towards the server. If indicated in the MBS session announcement information, MC service clients report the monitoring state (i.e., the reception quality of the MBS session) back to the MC service server; or
5b. For broadcast MBS sessions, if the MC service client is accessing over 5G, the session is established as part of the session creation procedures as described in 3GPP TS 23.247 [15], and the network resources are reserved both in 5GC and NG-RAN. The MC service clients start monitoring the reception quality of the broadcast MBS session. If indicated in the MBS session announcement information, MC service clients report the monitoring state (i.e., the reception quality of the MBS session) back to the MC service server.
NOTE 4: It is implementation specific whether the MBS session reception quality level is determined per MBS session, per media stream or per MBS QoS flow level via e.g., measurements of radio level signals, such as the reference signals from the NG-RAN node(s), or packet loss.
6. The MC service clients provide a listening status notification related to the announced session (multicast or broadcast session) in the form of an MBS listening status report.
7. An MC service group communication setup takes place as specified in 3GPP TS 23.379 [6], 3GPP TS 23.281 [4], or 3GPP TS 23.282 [5]. The MC service server determines to use the pre-created MBS session for this group communication.
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7.3.3.1.3 Procedure for dynamic MBS sessions
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In this scenario, the group communication is already taken place and a unicast PDU session is utilized for MC DL transmission. When the MC service server decides to use an MBS session for the transmission under consideration, the MC service server interacts with 5GC to reserve the necessary network resources.
NOTE 1: The MC service server logic for determining when to create a dynamic MBS session is implementation specific.
The procedure in figure 7.3.3.1.3-1 shows one MC service client receiving the DL media. There might also be MC service clients in the same MC group communication session that receive the communication on an MBS session.
Pre-conditions:
- MC service client is attached to the 5GS, registered and affiliated to a certain MC service group X.
- The MC service server is aware whether to request the creation of the MBS service server with or without dynamic PCC rule.
- The MC service server has performed MB-SMF discovery and selection either directly or indirectly, via NEF/MBSF, unless the corresponding information is locally configured.
- No MBS session exists, or the existing multicast MBS session fails to satisfy the QoS requirements.
Figure 7.3.3.1.3-1: Use of dynamic MBS session.
1. An MC service group communication session is established as specified in 3GPP TS 23.379 [6], 3GPP TS 23.281 [4], or 3GPP TS 23.282 [5].
2. The MC service server decides to create an MBS session. The MBS session creation procedure takes place as described in step 1 of clause 7.3.3.1.2.
NOTE 2: In case of LTE eMBMS and 5G MBS co-existence, the MC service server may trigger the establishment of eMBMS bearers as described in 3GPP TS 23.280 [3] (or it may establish a unicast bearer) based on the RAT capabilities supported by the affiliated members in the MC service group X. If MBSF and BM-SC are co-located, TMGI used by 4G eMBMS can be the same as the MBS session ID.
NOTE 3: For the case of multi carrier support for broadcast MBS sessions, the MC service server may indicate the frequencies within a broadcast MBS service area by providing the MBS frequency selection area ID(s) (MBS FSA ID(s)) to the MB-SMF, or indirectly, via NEF.
3. The MC service server provides the MC service client with the information related to the created MBS session via an MBS session announcement. As described in table 7.3.2.1-1, the session announcement includes information such as the MBS session ID, MBS session mode (broadcast or multicast service type), and SDP information related to the MBS session.
Optionally, the MC service server includes the information elements related to the established eMBMS bearer once the MC service server has determined the need, as indicated in table 7.3.2.1-1. The MC service clients which camp on LTE will subsequently react to the information elements related to the eMBMS bearer as described in 3GPP TS 23.280 [3].
4. The MC service client stores the MBS session ID and other associated information.
5. The MC service client may send an MBS session announcement ack back to the MC service server.
6. Based on the MBS session mode (either multicast or broadcast), the following actions take place:
6a. For multicast MBS sessions, MC service client initiates a UE session join request towards the 5GC using the information provided via the MBS session announcement. Hence, upon the first successful UE session join request, the multicast is then established, and the radio resources are reserved, if the session is in active state. The established session can either be in active or inactive state as indicated in 3GPP TS 23.247 [15]. The MC service client sends a UE session join notification towards the server. If indicated in the MBS session announcement information, MC service clients report the monitoring state (i.e., the reception quality of the MBS session) back to the MC service server; or
6b. For broadcast MBS sessions, if the MC service client is accessing over 5G, the session is established as part of the session creation procedures as described in 3GPP TS 23.247 [15], and the network resources are reserved both in 5GC and NG-RAN. The MC service clients start monitoring the reception quality of the broadcast MBS session. If indicated in the MBS session announcement information, MC service clients report the monitoring state (i.e., the reception quality of the MBS session) back to the MC service server.
NOTE 4: It is implementation specific whether the MBS session reception quality level is determined per MBS session, per media stream or per MBS QoS flow level via e.g., measurements of radio level signalling such as the reference signals from the NG-RAN node(s), packet loss.
7. The MC service clients provide a listening status notification related to the announced session (multicast or broadcast session) in the form of an MBS listening status report.
8. An MC service group communication via dynamic MBS session is established.
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7.3.3.2 Request for updating MBS resources for group communications
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7.3.3.2.1 General
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The MC service server can create one or several MBS sessions based on certain service requirements (e.g., QoS profile), a certain service area, or the activity status of multicast MBS sessions. However, during the life cycle of the MBS sessions, the MC service server may need to update the sessions to meet emerging needs, including the service requirements, service area related parameters, etc…, as defined in 3GPP TS 23.247 [15].
In case of dynamic PCC rule, the MC service server needs to determine what aspects are needed to be updated (either service area related aspects/ multicast activation status, service requirements aspects, or both as described in 3GPP TS 23.247 [15]) in order to interact with the required entity in the 5GC either directly, (in case the MC service server is in trusted domain), or indirectly via NEF/MBSF.
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7.3.3.2.2 Procedure for updating MBS resources without dynamic PCC rule
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The procedure shown in figure 7.3.3.2.2-1 presents an MBS session update procedure triggered by the MC service server (either directly to the MB-SMF, or indirectly via NEF/MBSF). Within the update request, either the service requirements, MBS service area, activity status of multicast MBS session, or all three are done, as indicated in 3GPP TS 23.247 [15].
Pre-conditions:
- The MC service clients 1 to n are attached to the 5GS, registered and affiliated to the same active MC service group.
- The MC service server has obtained the required information related to the MB-SMF, either locally configured or during initial session configuration.
- The MBS session is created with certain service requirements and optionally with a certain broadcast/multicast service area. The MBS session is announced to be associated with the MC service group for group communication purposes.
Figure 7.3.3.2.2-1: MBS session update without dynamic PCC.
1. An MBS session is established as described in in 3GPP TS 23.247 [15] (either a multicast or a broadcast session), and associated with a certain active MC group for group communication purposes. In the case of a multicast MBS session, the MC service clients have already joined the session.
2. The MC service server invokes an MBS session update request towards the 5GC (either directly to the MB-SMF or indirectly via NEF/MBSF) once the need has emerged to modify some aspects for the given MBS session under consideration. Hence, the MC service server sends the MBS session update request as described in 3GPP TS 23.247 [15] and either directly to the MB-SMF or indirectly via NEF/MBSF, indicating the MBS session ID to be updated. Along with the update request, the updated aspects are sent, which are either service requirements (required QoS), service area, or both. In case of multicast MBS sessions, the MC service server may as well update the status (active or inactive) of the multicast MBS session once needed within the update request.
NOTE 1: The updated service area information is required for local MBS and for broadcast MBS services.
3. Based on the needed requirements, the corresponding MBS session is accordingly modified, as indicated in 3GPP TS 23.247 [15]. The update may lead to QoS Flow(s) addition, modification, or removal.
4. The MC service server receives an MBS session update response as described in 3GPP TS 23.247 [15], once the requested modifications are performed, and the indicated MBS session is updated accordingly.
In case the of untrusted MC service server, if the MBS service area is partially accepted by the 5GC, the reduced MBS service area information is grouped and provided by the NEF/MBSF in the response. Hence, the MC service server should send a new MBS session creation request (as described in clause 7.3.3.1.3) for each grouped MC service area. The MC service server may utilize a unicast session if any MBS service area is not supported by any MB-SMF.
5. The MC service server may initiate a session announcement towards the MC service clients associated with the ongoing session in order to announce the updated information, if required, e.g., the updated service area or SDP information.
NOTE 2: The updated service area information is required for local MBS and for broadcast MBS services.
6. The MC service server sends an MapGroupToSessionStream over the configured MBS session providing the required information to receive the media related to the established MC service group communication.
7. The MC service clients process the received information over the MapGroupToSessionStream in order to receive the associated MC media over the specific MBS session stream.
8. MC service client 1 sends media to the MC service server over unicast to be distributed for the established group communication.
9. The MC service server distributes the MC media to the MC services clients 2 to n over the indicated streams.
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7.3.3.2.3 Procedure for updating MBS resources with dynamic PCC rule
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The procedure shown in figure 7.3.3.2.3-1 presents an MBS session update procedure triggered by the MC service server to the 5GC, either directly or via NEF/MBSF. Based on the required updates to be done, the MC service server needs to interact with the MB-SMF to update the MBS service area and multicast activity status, with the PCF to update the required QoS requirements, or sequentially both to update all the above, as indicated in 3GPP TS 23.247 [15].
Pre-conditions:
- The MC service clients 1 to n are attached to the 5GS, registered and affiliated to the same active MC service group.
- The MC service server has obtained the required information related to the MB-SMF, either locally configured or during initial session configuration.
- The MBS session is created with certain service requirements and optionally with a certain broadcast/multicast service area. The MBS session is announced to be associated with the MC service group for group communication purposes.
Figure 7.3.3.2.3-1: MBS session update with dynamic PCC.
1. An MBS session is established as described in 3GPP TS 23.247 [15] (either a multicast or a broadcast MBS session), and associated with a certain active MC group for group communication purposes. In the case of a multicast MBS session, the MC service clients have already joined the MBS session.
2. The MC service server, based on the update requirements (i.e., MBS service area and/or the multicast MBS session activity status as well as the service requirements), perform the MBS session update with PCC procedure towards the 5GS as described in 3GPP TS 23.247 [15] and/or the MBS session activate/deactivate procedure as described in clause 7.3.3.4.
In case the of untrusted MC service server, if the MBS service area is partially accepted by the 5GC, the reduced MBS service area information is grouped and provided by the NEF/MBSF in the response. Hence, the MC service server should send a new MBS session creation request (as described in clause 7.3.3.1.3) per grouped MC service area. The MC service server may utilize a unicast session if any MBS service area is not supported by any MB-SMF.
NOTE 1: The updated service area information is required for local MBS and for broadcast MBS services.
3. The MC service server may initiate an MBS session announcement towards the MC service clients associated with the ongoing MBS session in order to announce the updated information if required, e.g., the updated service area or SDP information.
NOTE 2: The updated service area information is required for local MBS and for broadcast MBS services.
4. The MC service server sends an MapGroupToSessionStream over the MBS session providing the required information to receive the media related to the established MC service group communication.
5. The MC service clients process the received information over the MapGroupToSessionStream in order to receive the associated MC media over the specific MBS session stream.
6. MC service client 1 sends media to the MC service server over unicast to be distributed for the established group communication.
7. The MC service server distributes the MC media to the MC services clients 2 to n over the indicated streams.
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7.3.3.3 MBS session deletion request
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7.3.3.3.1 General
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The MC service server can decide to release a certain MBS session once it is no longer further utilized for the associated MC service group communication, e.g., the MC service group is no longer active, the MC media transmission is over and no further MC media to be delivered, group communication is terminated. The MBS session deletion procedure leads to releasing the network resources associated to that MBS session.
NOTE: It is up to implementation of MC service server to decide whether to release the MBS session or re-use it for subsequent group operations.
To delete the MBS session, the MC service server sends an MBS session deletion request to the 5GS providing the corresponding MBS session ID. The MBS session deletion request is sent to the MB-SMF (directly or via NEF/MBSF) when PCC is not used. However, if dynamic PCC rule is utilized, a policy authorization deletion request is initially sent to the PCF. Further details are provided in 3GPP TS 23.247 [15].
MC service server further informs the MC service client with the MBS session de-announcement, so that the MC client UE stops monitoring the broadcast MBS session or leaves the multicast MBS session. This procedure is applied for both broadcast MBS session and multicast MBS session.
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7.3.3.3.2 Procedure
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The procedure in figure 7.3.3.3.2-1 describes the MBS session deletion aspects for group communication.
Pre-conditions:
- MC service clients 1 to n are attached to the 5GS, registered and affiliated to the same active MC service group.
- An MBS session is configured to address the corresponding MC service group with certain service requirements and optionally with a certain broadcast/multicast service area. The session is announced and established for group communication purposes for the MC service group.
Figure 7.3.3.3.2-1: MBS session deletion procedure.
1. The MC service server decides to delete the MBS session for the associated MC group communication, either multicast or broadcast session.
2. The MC service server sends an MBS session de-announcement message with the MBS session ID towards the MC service client(s). Upon receiving the MBS session de-announcement message, either 3a or 3b is performed.
3a. If the MBS session identified by MBS session ID is a broadcast MBS session, the MC service client(s) stops monitoring the broadcast MBS session and removes the broadcast MBS session related information.
3b. If the MBS session identified by MBS session ID is a multicast MBS session, the joined MC service client(s) initiate an MBS session leave procedure to leave the indicated MBS session in order to release the respective network resources, as defined in 3GPP TS 23.247 [15].
4. Subsequently, the MC service clients may send an MBS session de-announcement acknowledgement message to the MC service server indicating the status of MBS session.
5. The MC service server initiates the MBS session deletion procedure with the 5GC (either directly or through NEF/MBSF) in order to stop using the configured MBS session and release the corresponding network resources. The MC service server indicates within the MBS session release request the corresponding MBS session ID. The MBS session deletion procedure can either be with or without a dynamic PCC rule, as indicated in 3GPP TS 23.247 [15].
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7.3.3.4 Request to activate / de-activate multicast MBS sessions
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7.3.3.4.1 General
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In case of multicast MBS sessions, the members affiliated to a certain MC group need to initiate a UE session join request towards the 5GC in order to receive the MC media sent via the associated MBS session. The UE session join request enables the reservation of NG-RAN resources for the members of the MC group. However, it is not necessary that the MC media is delivered over the whole time the multicast MBS session is associated to the group under consideration. Therefore, the MC service server is able to efficiently utilize and control the reservation of radio resources based on the availability of MC data to be delivered via the activation and de-activation procedure. This presents more flexibility and efficient use of resources different from LTE.
The most suitable scenario to activate/de-activate a certain multicast MBS session is based on whether there is an MC group call, e.g., MCPTT group call, taking place over that associated MBS session to the MC group. In this manner, the MC service server can activate the associated multicast session once an MC group call takes place, then deactivate it once the MC group call is over. Whether the multicast session is activated (i.e., in an active state), or de-activated (in an inactive state), the MC group is associated to the multicast session and its members are within a UE session join.
The MBS session update request with the requested MBS session status is triggered by the MC service server either directly towards the MB-SMF or indirectly via NEF/MBSF.
NOTE: The activation of de-activation procedure may also be triggered by MB-SMF based on receiving notification from MB-UPF based on the availability of MC data to be transmitted.
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7.3.3.4.2 Multicast MBS session activation procedure
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The procedure shown in figure 7.3.3.4.2-1 presents the multicast MBS session activation procedure triggered by the MC service server.
Pre-conditions:
- MC service clients are attached to the 5GS, registered and affiliated to the same MC service group X.
- The MC service server has directly performed (or via NEF/MBSF) an MB-SMF discovery and selection, unless the corresponding information is locally configured.
- The MC service server has decided to use a multicast MBS session for MC service group communications associated to MC service group X.
- The MBS session is created and announced to address MC group communication related to the associated MC service group X with certain service requirements and optionally with a certain service area.
Figure 7.3.3.4.2-1: Multicast MBS session activation procedure.
1. The multicast MBS session is established as the first UE session join request, which is initiated by the first MC service UE towards 5GC, is granted. At this stage, the multicast MBS session is established with an inactive state.
2. The MC service server decides to activate the multicast MBS session as MC data is needed to be transmitted over the MBS session to the MC group X, as an MC group communication (e.g., MCPTT group call) is to take place over the associated MBS session.
3. The MC service sends an MBS session update request towards the 5GC, either directly to the MB-SMF or via NEF/MBSF, indicating the MBS session ID to be activated as described in 3GPP TS 23.247 [15].
4. The 5GC changes the MBS session status to "active" and finds the list of joined MC service UEs associated with the MBS session and activates the NG- RAN resources for MC data delivery as described in 3GPP TS 23.247 [15].
5. The 5GC may send an MBS session update response to the MC service server indicating that the requested multicast MBS session has been activated as described in 3GPP TS 23.247 [15].
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7.3.3.4.3 Multicast MBS session de-activation procedure
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The procedure shown in figure 7.3.3.4.3-1 presents the multicast MBS session activation procedure triggered by the MC service server.
Pre-conditions:
- MC service clients are attached to the 5GS, registered and affiliated to the same MC service group X.
- The MC service server has directly performed (or via NEF/MBSF) an MB-SMF discovery and selection, unless the corresponding information is locally configured.
- A multicast MBS session is created and announced to address the corresponding MC service group with certain service requirements and optionally with a certain multicast service area.
- The MC service clients have already joined the multicast MBS session and are able to receive the MC data over the associated MBS session.
Figure 7.3.3.4.3-1: Multicast MBS session deactivation procedure.
1. The group communication associated with MC service group X takes place, and the corresponding MC data is delivered over the associated multicast MBS session, hence the MBS session has an active state.
2. The MC service server decides to deactivate the multicast MBS session, as no further MC data to be delivered to the associated group, as the MC group call is over, and no further MC media is to be delivered.
3. The MC service server sends an MBS session update request towards the 5GC, either directly to the MB‑SMF or via NEF/MBSF, indicating the MBS session ID to be deactivated as described in 3GPP TS 23.247 [15].
4. The 5GC changes the MBS session state to "inactive" and deactivates the radio resources associated with the joined MC service UEs as described in 3GPP TS 23.247 [15].
5. The 5GC may send an MBS session update response to the server indicating that the requested multicast MBS session has been inactivated as described in 3GPP TS 23.247 [15].
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7.3.3.5 MC service group media transmissions over 5G MBS sessions
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7.3.3.5.1 General
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The MC service server can decide to configure an MBS session per MC service group to transmit the media related to the corresponding MC service group communications. Such group communications can comprise different service requirements. For that, multicast and broadcast MBS sessions need to be configured with multiple MBS QoS flows to address different service requirements, e.g., different required QoS, provided by the MC service server. For instance, application-level control messages or media associated to a group communication can comprise different QoS requirements. Also, different type of group communications can comprise different QoS requirements, e.g., emergency group calls should be handled with a higher priority than normal group calls.
The configuration of multiple MBS QoS flows to address different service requirements is associated to the assignment of different streams (e.g., different ports) within an MBS session.
The established multicast MBS session can either be in active or inactive state, where the former indicates the activation of radio resources hence transmitting the MC media to the associated MC service group, and the latter indicates their deactivation as no MC media is being transmitted. The MC service server may trigger the activation of multicast MBS sessions once the MC service group is established and active, as well as once the MC media is available for transmission. For this purpose, the MC service server sends a multicast MBS session activation request towards the 5GC indicating the MBS session ID to be activated.
Similar to the use of eMBMS, the MC service server shall provide the associated information between a specific group communication and the stream to be used within an MBS session. This information could be sent in advance in an MBS session announcement or could be provided on demand in an additional signalling message for the MBS session, e.g., MapGroupToSessionStream (similar to the MapGroupToBearer in eMBMS).
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7.3.3.5.2 Procedure
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The procedure in figure 7.3.3.5.2-1 describes how media related to a specific group communication can be distributed over a configured MBS session which consist of multiple QoS flows, i.e. addressing different service requirements. The procedure is applicable for both the pre-created MBS session case as described in clause 7.3.3.1.2 and the dynamic MBS session case as described in clause 7.3.3.1.3. For simplicity, the figure 7.3.3.5.2-1 shows that the MBS session is pre-created prior to the group communication establishment.
Pre-conditions:
- MC service clients 1 to n are attached to the 5GS, registered and affiliated to the same MC service group X.
- The MC service server has decided to use an MBS session for MC service group communications associated to MC service group X.
Figure 7.3.3.5.2-1: MC service group media transmission over MBS sessions
1. The MC service server creates a multicast or a broadcast MBS session targeting group communications associated to MC service group X, as being specified in 3GPP TS 23.247 [15]. Therefore, the MC service server can provide default service requirements to be addressed by the MBS session, e.g. associated to MC 5QIs and specific allocation and retention priority (ARP) to transmit the media associated to MC service group communications.
The MBS session is announced and received by MC service client 2 to n. The MC service server has identified that MC service clients 2 to n can receive media over the MBS sessions, e.g. based on a notification from the MC service clients indicating the successful join of the multicast MBS session or a monitoring report of the broadcast MBS session (similar to the listening status report used for eMBMS).
2. A new MC service group communication is established for the MC service group X consisting of a specific required QoS, e.g. an MC service emergency group communication. The group communication setup can be done over unicast.
2a. For broadcast MBS sessions, the session is established upon sending a session start request as part of the MBS session creation procedure, which is described in 3GPP TS 23.247 [15].
2b. For multicast MBS session, the session is established upon the acceptance of the first UE session join request initiated from the MC service UE towards the 5GS, as described in 3GPP TS 23.247 [15]. The multicast session can then have either an active or an inactive state.
3. The MC service server may send a multicast MBS session activation request towards the 5GC in order to activate the multicast MBS session in case the session has an inactive state. For this purpose, the MC service server indicates the MBS session ID to be activated.
4. Considering that the established group communication requires a specific QoS, e.g. an MC service emergency group communication which requires higher priority (i.e. better ARP), the MC service server requests an MBS session update to the 5GS to provide the new required QoS, if not done during the MBS session creation in step 1. The MBS session should then be updated and an additional QoS flow may be configured.
5. The MC service server sends a MapGroupToSessionStream to MC service clients 2 to n over the configured MBS session providing the required stream information to receive the media related to the specific established MC service group communication within the MBS session.
6. MC service clients process the MapGroupToSessionStream information to receive the related media over the specific MBS session stream.
7. MC service client 1 sends media to the MC service server over unicast to be distributed for the established group communication.
8. The MC service server distributes the media to MC service clients 2 to n over the indicated stream within the established MBS session.
NOTE: The MC service server can stop the unicast delivery (if ongoing) towards the MC service clients considering the UE session join notification or the MBS listening status report.
9. The MC service server may send a multicast MBS session deactivation request towards the 5GC in order to deactivate the multicast MBS session. For this purpose, the MC service server indicates the MBS session ID to be deactivated.
10. The MC service server may further trigger the UE to leave multicast MBS session.
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7.3.3.6 Aplication level control signalling over 5G MBS sessions
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7.3.3.6.1 Description
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The MC service server may use an 5G MBS session for application level control signalling. An 5G bearer for application level control signalling is typically used for the purposes beyond the benefit for using 5G for resource efficiency, e.g. for improved MC service performance (KPIs), handling of high load scenarios.
Similar to the usage of eMBMS, both broadcast and multicast 5MBS session for application level control signalling may be used to transmit the following messages,
- Transmission control (e.g. call setup and floor control)
- MBS session announcement for media sessions
- Group application paging
- Group dynamic data (e.g. status of the group)
- Group state (e.g. emergency alerts)
Similar to the usage of eMBMS bearer in 3GPP TS 23.280 [3], 5G MBS session for application level control signalling is created in a service area that is larger than the estimated service for media MBS session. The service area for the media sessions is mainly based on counting of group members in each defined service area. The MBS session for application level control signalling is also created with a QoS that is better than MBS media session since the packet loss requirements are much stricter.
The MC service client shall not send responses to group-addressed application level control signalling unless instructed or configured to respond.
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7.3.3.6.2 Procedure
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The procedure in figure 7.3.3.6.2-1 shows only one of the receiving MC service clients using an 5G MBS session.
Figure 7.3.3.6.2-1: Use of 5G MBS for application-level control signalling
1. The MC service server determines to create MBS session for application-level control signalling, The creation of the 5G MBS session is done according to 3GPP TS 23.247 [15].
2. The MC service server passes the 5G MBS session info for the service description associated with the 5G MBS session to the MC service client. The MC service client obtains the MBS session ID, from the service description.
NOTE: For 5G MBS and 4G eMBMS co-existence, the eMBMS bearers activation and MBS session announcement are performed as specified in the procedure for pre-created MBS session and session announcement.
3. The MC service client stores the information associated with the MBS session ID. The MC service client uses the MBS session ID and other 5G MBS session related information to enable monitoring of the 5G MBS session by the MC service UE. In the case of multicast, UE may execute network layer multicast MBS joining as defined in 3GPP TS 23.247 [15].
4. Steps 4 to 6 defined in clause 7.3.3.1.2 are performed.
5. The MC service server transmits MC application control messages over the MBS session.
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7.3.3.7 Multi-server MBS session coordination
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7.3.3.7.1 General
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The motivation and principle of supporting Multi-server MBS session coordination is exactly similar to Multi-server eMBMS bearer coordination as described in 3GPP TS 23.280 [3].
NOTE: The procedures in clause 7.3.3.7.2 are only used when MBS session sharing between multiple MC service servers is required. It is implementation specific whether MBS session is shared amongst multiple MC service servers.
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7.3.3.7.2 Procedures
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7.3.3.7.2.1 MBS Session coordination independent of media
The procedure in this sub clause applies to both multicast and broadcast MBS session. The principle and pre-condition are similar with eMBMS bearer coordination as defined in 3GPP TS 23.280 [3].
This procedure is used when two or more MC service servers are serving users in the same area and are configured to share 5G MBS sessions for that specific area. The MC service servers may be of the same kind or different kind. The MC service servers are not participating in the same group call, which means that each MC service server transmit media independently of each other.
Pre-conditions:
- All MC service servers are configured with the contact information of those MC service servers that are configured to take the MBS session control role.
Figure 7.3.3.7.2.1-1: Multiple server MBS procedure independent of media.
1. The MC service server 1 evaluates whether MBS transmission is desired for each service area in which MC service group members are located, based upon the locations, affiliation status and other factors.
2. The MC service server 1 determines whether another MC service server has already established an MBS session with coverage for the MBS service area where MBS transmissions are desired. To do this, the MC service server 1 consults a pre-configured list of MC service servers and sends them a discover MBS session request. This request may be sent to several MC service servers.
NOTE: MC service servers of the same type can be configured to discover MBS sessions from a single server. The single server then becomes a centralized entity for MBS session control for the MC service. Similarly, all MC service servers of all types can be configured to discover MBS sessions from a single server. The single server then becomes a centralized MBS session controller for all MC services.
3. The MC service server 2 (MBS session control role) responds with a discover MBS session response indicating whether there is an MBS session available in the specific MBS service area with the requested bandwidth. The discover MBS session response message includes the MBS session ID of the MBS session that is shared between the MC service servers. If the MBS session of interest has insufficient bandwidth, the polling MC service server 1 may resort to unicast, or may allocate another MBS session for the congested area. If a duplicate MBS session is allocated for the same area, the MBS session should not be shared with other servers and may be torn down as soon as the congestion on the original MBS session clears up, in order to conserve resources.
For any MBS service areas not covered by another MC service server, the MC service server 1 prepares to distribute media to those MBS service areas by setting up an MBS session. The MBS session set up by the MC service server 1 may then become available for other MC service servers (controlling role) for other MC service groups.
4. 4a.The MC service server 1 performs the MBS session announcement towards MC client 1, as well as MBS notification handling, according to the relevant procedures specified in this specification. In case of multicast MBS sessions, the MC service UE subsequently initiates a UE session join towards 5GC, and may send a UE session join notification to MC service server 1 indicating it has successfully joined the multicast MBS session under consideration.
4.b If the MC service server 2 is authorized to receive MBS related location information from the users utilizing the services from MC service server 1, the MC service server 2 may optionally do the MBS session announcement and handling of the notifications on behalf of MC service server 1. The notifications shall in this case be sent to both MC service server 1 and MC service server 2. In case of multicast MBS sessions, the MC service UE subsequently initiates a UE session join towards 5GC, and may send a UE session join notification to MC service server 2.
5. The MC service server 1 sends a media distribution request to the MC service server 2 (MBS session control role). The media distribution request is sent to reserve the specified capacity in the MBS session.
6. MC service server 2 (MBS session control role) sends a media distribution response to the MC service server 1 indicating whether the request can be supported and supplies details about the MBS session.
7. The MC service server 1 establishes a group communication session via the MBS session, informing MBS session connected MC service clients 1 and 2 that a group communication session is about to start on the MBS session. This step is equivalent to MapGroupToSessionStream.
8. MC service client 2 sends media on the uplink to the MC service server 1.
9. The MC service server 1 forwards the media to MC service server 2 (MBS session control role).
10. The MC service server 2 (MBS session control role) distributes the media to MC service client 1 with MBS capabilities over the MBS session.
11. The MC service server 1 sends a media distribution release request, informing the MC service server 2 (MBS session control role) to request the MC service server 2 (MBS session control role) to release the capacity that was reserved in step 5.
12. The MC service server 2 (MBS session control role) responds to the request by sending a media distribution release response.
7.3.3.7.2.2 MBS session coordination within one group call
The procedure in this subclause applies to both multicast MBS session and broadcast MBS session.
The principle is similar to eMBMS bearer coordination within one group call as the following:
- It may be used when two MC service servers are serving users in the same area and are configured to share MBS sessions for that specific area. The MC service servers are of the same kind, and the MC service servers may participate in the same group call, and by that have a need to deliver the same content.
Pre-conditions:
- All MC service servers are configured with the contact information of those MC service servers that are configured to take the MBS session control role.
Figure 7.3.3.7.2.2-1: Multiple server MBS procedure within one group call
1. The MC service server 1 evaluates whether MBS based transmission is desired for each service area in which MC service group members are located, based upon the locations, affiliation status and other factors.
2. The MC service server 1 determines whether another MC service server has already established an MBS session with coverage for the MBS service area where MBS based transmission is desired. To do this, the MC service server 1 consults a pre-configured list of MC service servers and sends them a discover MBS session request. This request may be sent to several MC service servers.
NOTE 1: MC service servers of the same type can be configured to discover MBS sessions from a single server. The single server then becomes a centralized entity for MBS session control for the MC service. Similarly, all MC service servers of all types can be configured to discover MBS sessions from a single server. The single server then becomes a centralized MBS session controller for all MC services.
3. The MC service server 2 (MBS session control role) responds with a discover MBS session response indicating whether there is an MBS session available in the specific MBS service area with the requested bandwidth. The discover MBS session response message includes the ID of the MBS session that is shared between the MC service servers. If the MBS session of interest has insufficient bandwidth, the polling MC service server 1 may resort to unicast, or may allocate another MBS session for the congested area. If a duplicate MBS session is allocated for the same area, the MBS session should not be shared with other servers and may be torn down as soon as the congestion on the original MBS session clears up, in order to conserve resources.
For any MBS service areas not covered by another MC service server, the MC service server 1 prepares to distribute media to those MBS service areas by setting up an MBS session. The MBS session created by the MC service server 1 may then become available for other MC service servers (controlling role) for other MC service groups.
4a. The MC service server 1 performs the MBS session announcement as well as the MBS listening reporting according to the relevant procedures specified in this specification. In case of multicast MBS sessions, the MC service UE(s) subsequently initiate a UE session join towards 5GC, and may send a UE session join notification to MC service server 1 indicating it has successfully joined the multicast MBS session under consideration.
4b. If the MC service server 2 is authorized to receive MBS related location information from the users utilizing the services from MC service server 1, the MC service server 2 may optionally do the MBS session announcement and handling the listening reports on behalf of MC service server 1. Listening reports shall in this case be sent to both MC service server 1 and MC service server 2. In case of multicast MBS sessions, the MC service UE(s) subsequently initiate a UE session join towards 5GC, and may send a UE session join notification to MC service server 2.
NOTE 2: Steps 1-4 are also performed by MC service server 3, but is not shown in the procedure to make it easier to read.
5. The MC service client 2 initiates a group call that is subject for MBS transmission. In this scenario there are more than one MC service server (i.e., MC service server 1 and MC service server 3) that serve MC service clients that are affiliated to the group, and by that should receive the media in the group call.
6a. The MC service server 1 sends a media distribution request to the MC service server 2 (MBS session control role). The media distribution request includes the MC group identifier. This indicates that the media distribution request is used for this specific group call.
6b. The MC service server 3 sends a media distribution request to the MC service server 2 (MBS session control role). The media distribution request includes the MC group identifier. This indicates that the media distribution request is used for this specific group call.
7a. The MC service server 2 (MBS session control role) sends a media distribution response to the MC service server 1 indicating whether the request can be supported and supplies details about the MBS session. This also includes details on which media stream should be used for transmitting the media on the MBS session. This information is used in the MapGroupToSessionStream message sent by the MC service server when setting up the group call.
7b. The MC service server 2 (MBS session control role) sends a media distribution response to the MC service server 3 indicating that the group call is already transmitted on the MBS session by another MC service server. Based on the information, the MC service server 3 could decide to not transmit media if media is already transmitted.
8a. The media is sent from the MC service client 2 to MC service server 1, which is the participating server for the MC service group of the group call.
8b. The media is forwarded to all MC service servers that are serving users that take part in the group call.
NOTE 3: The figure above does not visualize the participating server for the MC service group and controlling server for the MC service group. The media is sent to all participating servers for the MC service group which are the servers that decide on unicast or MBS transmission.
9. The MC service server 1 forwards the media to MC service server 2 (MBS session control role).
10. The MC service server 2 (MBS session control role) distributes the media to MC service client 1 with MBS capabilities via MBS session.
11. The MC service server 1 sends a media distribution release request, to request the MC service server 2 (MBS session control role) to release the capacity that was reserved in step 5. The media distribution release request shall only be sent when the group call is terminated.
12. The MC service server 2 (MBS session control role) responds to the request by sending a media distribution release response.
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7.3.3.8 Service continuity between 5G MBS delivery and unicast delivery
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7.3.3.8.1 General
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This clause addresses the issue of MC service media delivery over MBS session, specifically, to maintain the service continuity when switching between 5G MBS delivery and unicast delivery.
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7.3.3.8.2 Service continuity for broadcast MBS session
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7.3.3.8.2.1 General
The MC service client reports the broadcast reception quality to the MC service server which is used to make the decision whether to use the unicast delivery to the MC service UE(s) which are suffering bad broadcast reception quality due to e.g., move out of the broadcast service area.
An MC service client monitors the broadcast MBS session to receive MC service media. Based on the received quality (e.g., radio level quality, RTP packet loss), the MC service client needs to inform the MC service server that the MC service client is able to receive the MC service media on the broadcast MBS session with sufficient quality or not.
This estimation of the broadcast reception quality may be dependent on, for example, the modulation and coding scheme (MCS) and measurements from the reference signals from the NG-RAN node(s), RTP packet loss, BLER of the received media.
7.3.3.8.2.2 Procedures
7.3.3.8.2.2.1 Service continuity from broadcast to unicast
The procedure in figure 7.3.3.8.2.2.1-1 illustrates the UE which is receiving media via broadcast MBS session is switched to unicast delivery because the UE suffers from bad broadcast reception quality due to e.g., moving out of the broadcast service area. It shows only one of the receiving MC service clients receiving the broadcast MBS session.
Pre-conditions:
1. The MC group communication is ongoing and the MC service media (e.g., DL media, application layer control signalling) is transmitted via broadcast MBS session.
2. The MC service client is receiving the MC service media (e.g., DL media, application layer control signalling) via the broadcast MBS session.
3. The MC service client(s) already have the associated information (e.g., SDP) to receive the unicast delivery during the group communication establishment phase.
Figure 7.3.3.8.2.2.1-1: Service continuity from broadcast to unicast
1. An MC service group communication session is ongoing and the DL media is transmitted over broadcast MBS session.
2. The MC service client detects that it suffers bad broadcast reception due to e.g., moving out of the broadcast service area of the announced MBS session ID (i.e., TMGI). The MC service client may determine the broadcast reception quality by using the BLER of the received media. When no media is received, the quality estimation can consider the reference signals and the modulation and coding scheme (MCS).
3. The MC service client sends MBS listening status report which indicates the broadcast reception quality associated with the MBS session ID is not sufficient to receive media. The MC service client may also map the determined broadcast reception quality to a broadcast reception quality level. The broadcast reception quality level indicates at which specific broadcast reception quality level the MC service media has been received.
NOTE 1: It is implementation that the broadcast reception quality level can be determined per MBS session, per media stream or per MBS QoS flow level via e.g., measurements of radio level signalling such as the reference signals from the NG-RAN node(s), packet loss.
NOTE 2: The set of MBS reception quality levels and the mapping of the determined broadcast reception quality to those levels are implementation.
NOTE 3: The frequency of MC service UE sending listening reports can be limited to prevent signalling congestion. E.g., the MC service UE can stop monitoring the broadcast reception quality and send the MBS listening status report only once when it moves outside of the broadcast service area.
4. The MC service server based on the report from the participant, determines that the UE is not able to receive the media or the QoS requirements is not satisfied. The MC service server determines to send the MC service media (e.g., DL media, application layer control signalling) via the unicast delivery to the reported MC service client.
5. If the unicast QoS flow is not satisfied, the MC service server interacts with the 5GC to update the QoS requirements.
6. The MC service server sends the MC service media via the unicast delivery towards the MC service client which suffers bad broadcast reception quality.
7. The MC service client then receives the DL MC service via both broadcast MBS session and unicast delivery.
7.3.3.8.2.2.2 Service continuity from unicast to broadcast
The procedure in figure 7.3.3.8.2.2.2-1 illustrates the UE receiving media via unicast delivery being switched to broadcast MBS session as the UE enters the broadcast service area where the NG-RAN is broadcasting the MC service media of the ongoing group communication. The MC service client now is able to receive the broadcast media. Only one of the receiving MC service clients receiving the broadcast MBS session is shown.
Pre-conditions:
1. The MC group communication is ongoing and the MC service media (e.g., DL media, application layer control signalling) is transmitted via broadcast MBS session in the broadcast service areas.
2. The MC service client is receiving the MC service media (e.g., DL media, application layer control signalling) via the unicast delivery.
3. The MC service client has already received the broadcast MBS session announcement, MapGroupToSessionStream information and enters the broadcast service area.
Figure 7.3.3.8.2.2.2-1: Service continuity from unicast to broadcast.
1. An MC service group communication session is ongoing and the broadcast MBS session is used to deliver the MC service media of the group communication. The MC service client is receiving the MC service media via the unicast delivery.
2. The MC service client detects that it is able to receive the broadcast media due to e.g., moving into the broadcast service area of the announced MBS session ID. The MC service client may determine the broadcast reception quality by using the BLER of the received media. When no media is received, the quality estimation can consider the reference signals and the modulation and coding scheme (MCS).
3. The MC service client sends MBS listening status report which indicates the broadcast reception quality associated with the MBS session ID is sufficient to receive media. The MC service client may also map the determined broadcast reception quality to a broadcast reception quality level. The broadcast reception quality level indicates at which specific broadcast reception quality level the MC service media has been received.
NOTE 1: The set of MBS reception quality levels and the mapping of the determined broadcast reception quality to those levels are implementation.
NOTE 2: It is implementation that the broadcast reception quality level can be determined per MBS session, per media stream or per MBS QoS flow level via e.g., measurements of radio level signals, such as the reference signals from the NG-RAN node(s), or packet loss.
4. Based on the MapGroupToSessionStream received before, the MC service client receives the DL MC service via both the broadcast MBS session and the unicast delivery.
NOTE 3: If any information about the broadcast MBS session stream has changed, the MC service server provides the MapGroupToSessionStream again.
5. The MC service server, based on the report from the participant, determines to stop sending the MC service media (e.g., DL media, application layer control signalling) via the unicast delivery to the reporting MC service client. After then, the MC service client receives the MC service media only via the broadcast MBS session.
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7.3.3.8.3 Service continuity for multicast MBS session
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7.3.3.8.3.1 General
The MC service server may also switch between multicast and unicast by utilizing application layer mechanisms similar to switching between broadcast and unicast as specified in clause 7.3.3.8.2. If indicated in the MBS session announcement information, the MC service client reports the monitoring state (i.e., the reception quality of the MBS session) back to the MC service server.
NOTE: Once the MC service UE has successfully joined the multicast MBS session and started to receive the MC service media via the multicast MBS session, then the network mechanism specified in TS 23.247 [15] will deliver the media from the MC service server via the 5GC Individual MBS traffic delivery method or the 5GC Shared MBS traffic delivery method towards the MC service UE(s). The usage of 5GC Individual MBS traffic delivery method or the 5GC Shared MBS traffic delivery method is transparent to the MC service server.
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7.3.3.8.4 Path switch between MBS session and 5G ProSe UE-to-network relay
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7.3.3.8.4.1 General
The MC service communications over 5G ProSe UE-to-network relay is supported for unicast delivery.
NOTE: In this release of the specification, service continuity is supported for unicast PDU session over 5G ProSe UE-to-network relay, however it is not yet supported for multicast/broadcast MBS sessions for MC service communications.
The path switch procedures for MC service communications between MBS session and 5G ProSe UE-to-network relay is specified in this clause.
The architecture of MC service utilizing IMS service continuity is specified in Annex B.
7.3.3.8.4.2 Path switch procedure from MBS session to a 5G ProSe UE-to-network relay
This clause describes the procedures for path switch from MBS session to a 5G ProSe UE-to-network relay.
Figure 7.3.3.8.4.2-1 illustrates the path switch procedure from MBS session to a 5G ProSe UE-to-network relay.
Figure 7.3.3.8.4.2-1: Path switch from MBS session to a 5G ProSe UE-to-network relay.
1. The DL media is transmitted over an MBS session to a (remote) MC service client.
2. The MC service client sends an MBS listening status report indicating that the MBS reception quality associated with the MBS session ID is not sufficient to receive media. The MC service client may also map the determined MBS reception quality to an MBS reception quality level. The MBS reception quality level indicates at which specific MBS reception quality level the MC service media has been received.
3. The MC service server based on the report from the MC service client determines that the (remote) MC service UE is unable to receive the media or the QoS requirements are not satisfied. The MC service server determines to send the MC service communications (e.g., DL media, application layer control signalling) via the unicast delivery to the reported MC service client.
4. The MC service server sends the DL media to the (remote) MC service UE over a unicast PDU session.
NOTE 1: Steps 2 to 4 may occur after step 6 if the MBS listening status report towards the MC service server has failed due to connection lost.
5. The remote MC service UE discovers and utilizes a 5G ProSe UE-to-network relay UE in its proximity once it has detected being out of the network coverage. This step applies to both 5G ProSe Layer-3 and Layer-2 UE-to-network relay.
NOTE 2: An NG-RAN based measurement report triggers the remote MC service UE to perform a 5G Prose UE-to-Network relay discovery over PC5, as indicated in 3GPP TS 38.331 [19]. The remote MC service UE establishes a secure point-to-point link with the relay UE in its proximity over PC5. As part of this process the remote MC service UE is mutually authenticated at PC5 layer with either the relay or with the network as specified in 3GPP TS 23.304 [17].
6. For the case of 5G ProSe Layer-3 UE-to-network relay without the support of N3IWF, as described in 3GPP TS 23.304 [17], the remote MC service client performs SIP re-registration over the relay UE due to the change in IP address of the remote MC service UE and initiates IMS service continuity procedures as described in Annex B.
NOTE 3: For the case of 5G ProSe Layer-3 UE-to-Network relay with the support of N3IWF, the relay UE performs registration and authentication procedures towards the 5GC to support the remote MC service UE with an end-to-end confidentiality and IP address reservation requirements, as described in 3GPP TS 23.304 [17].
NOTE 4: For the case of 5G ProSe Layer-2 UE-to-network relay, the 5GC can provide the service continuity for the remote MC service UE with the UE's original IP address, as described in 3GPP TS 23.304 [17].
7. The MC service server sends the MC service communications using the unicast delivery via the 5G ProSe MC service UE-to-Network relay UE towards the remote MC service client. The MC service client then receives the DL MC service communication via the relay UE.
7.3.3.8.4.3 Path switch from a 5G ProSe UE-to-network relay to MBS session
This clause describes the procedure for path switch from a 5G ProSe UE-to-network relay to MBS session.
Figure 7.3.3.8.4.3-1 illustrates path switch from a 5G ProSe UE-to-network relay to MBS session.
Figure 7.3.3.8.4.3-1 Path switch from a 5G ProSe UE-to-network relay to MBS session.
1. The remote MC service client is receiving the MC service media using the unicast delivery via a 5G ProSe UE-to-Network relay UE. This step applies to both 5G ProSe Layer 3 and Layer 2 UE-to-network relay.
2. Based on the (remote) MC service UE`s path selection policies described in 3GPP TS 23.304 [17], and once the NG-RAN based measurement report discussed in 3GPP TS 38.331 [19] is triggered due to network coverage detection, the (remote) MC service UE connects to the network via the Uu-interface.
NOTE 1: The path selection policies may be pre-configured in the MC service UE or provided by the PCF, as defined in 3GPP TS 23.304 [17].
3. For the case of 5G ProSe Layer-3 UE-to-network relay without the support of N3IWF, the (remote) MC service client performs SIP re-registration over Uu and initiates the IMS service continuity procedures as described in Annex B. Further, the MC service server sends MC service communications using unicast delivery which traverses over Uu to the remote MC service client.
NOTE 2: For the case of 5G ProSe Layer-3 UE-to-network relay via the support of N3IWF, the (remote) MC service UE performs registration procedures towards the 5GS to establish the necessary resources over the Uu-interface.
NOTE 3: For the case of 5G ProSe Layer-2 UE-to-network relay, the 5GC can provide the service continuity for the (remote) MC service UE with the UE's original IP address, as described in 3GPP TS 23.304 [17].
4. The MC service client receives the MC service communication over a unicast PDU session.
5. Optionally, the MC service server may send the MBS session announcement to the (remote) MC service client with the information of the MBS session.
NOTE 4: The information of the MBS session can be available at the (remote) MC service client due to a previous MC service signalling via the relay UE.
6a. If a multicast MBS session has been announced, the MC service UE performs a UE session join towards the 5GC using the MBS session information, and the MC service client may send a UE session join notification towards the server.
6b. If a broadcast MBS session has been announced, the MC service client start monitoring the reception quality of the broadcast MBS session.
7. The MC service client sends an MBS listening status report which indicates the MBS reception quality associated with the MBS session ID is sufficient to receive media.
NOTE 5: It is implementation specific whether the MBS session reception quality level is determined per MBS session, per media stream or per MBS QoS flow level via e.g., measurements of radio level signalling such as the reference signals from the NG-RAN node(s), packet loss.
8. Based on the report received from MC service client in step 7, the MC service server determines to stop sending the MC service communications (e.g., DL media, application layer control signalling) using the unicast delivery. Further, the MC server sends the MC service communications via the MBS session.
9. The MC service client receives the MC service communications from the MC service server via the MBS session.
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7.3.3.9 MC service inter-system switching between 5G and LTE
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7.3.3.9.1 General
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When working in transport only mode, the MC service server guides the MC service clients throughout the MC media transmission for switching between the LTE and 5G systems. For this purpose, the location management client sends location related information to the location management server, similar to the one defined in 3GPP TS 23.280 [3], which is triggered due to its location change – in this case due to Radio Access Technology (RAT) change, to inform the server hence the latter provides guidance related to how to receive the MC services after the location update.
The procedures cover both the deployment scenarios with/without MBSF/MBSTF. The procedures specify four inter-system switching related scenarios as follows:
1. Inter-system switching from 5G MBS session to LTE eMBMS bearer, as described in clause 7.3.3.9.2
2. Inter-system switching from 5G MBS session to LTE unicast bearer, as described in clause 7.3.3.9.3
3. Inter-system switching from LTE eMBMS to 5G MBS session, as described in clause 7.3.3.9.4
4. Inter-system switching from LTE eMBMS to 5G unicast PDU session, as described in clause 7.3.3.9.5
In all the inter-system switching related scenarios described in clauses 7.3.3.9.2, 7.3.3.9.3, 7.3.3.9.4 and 7.3.3.9.5, the functional entity that resides in 5GS may be NEF, or MBSF, or MB-SMF for session creation and together with PCF or PCC related interaction.
NOTE: There will be a service interrupt when the MC service server performs path switch between 5G and LTE bearers or sessions.
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7.3.3.9.2 Inter-system switching from 5G MBS session to LTE eMBMS bearer
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The procedure provided in figure 7.3.3.9.2-1 describes how the MC service server handles inter-system switching when the MC service UE switches from 5G to LTE network, where the MC service server is able to provide the MC services to the clients over eMBMS bearer(s).
Pre-conditions:
- MC service clients are attached to the 5GS, registered and affiliated to the same MC service group X.
- The MC services can be provided via both 5GS and EPS.
- The MC service client(s) is within the eMBMS service area.
- It is assumed that the MC service client(s) has not received the eMBMS bearer announcement while camping in 5GS.
Figure 7.3.3.9.2-1: Inter-system switching from 5G MBS session to LTE eMBMS bearer.
1. An MC service group communication takes place, and the MC media is delivered over 5G MBS session (either broadcast or multicast session mode), which is associated to the MC service group X.
2. The MC service UE performs handover to EPS.
3. Location information handling can be based on location reports provided by the MC service client, where the MC service UE`s location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the MC service server.
Also, location information handling can be based on notifications provided from the network to the MC service server related to 5GS supporting EPS interworking, as specified in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9] and described in clause 7.4.3. For that, the MC service server can subscribe to receive notifications of specific events from the network. For instance, the MC service server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g., access network information notification and change of access type. Also, when SCEF+NEF is deployed, the MC service server can subscribe to SCEF+NEF related notifications for specific events, e.g., core network (CN) type change.
4. The MC service server analyses the location information and decides how to serve the client. If the MC service server decides to serve the client via eMBMS bearer, it may send an eMBMS bearer announcement as described in 3GPP TS 23.280 [3]. This step is optional as the bearer announcement related information could be sent in advance (implementation specific).
5. If not already available, the MC service client stores the announced TMGI(s), service area, and any relevant information to the eMBMS, which is delivered via the bearer announcement. As a result, the MC service client starts monitoring the bearer.
6. The MC service client sends an eMBMS listening status report to inform the server of its ability of receiving MC media over the specified bearer.
7. The MC server sends the necessary information related to receiving the MC media in the form of the MapGroupToBearer.
8. The MC service group communication takes place over EPS, and the MC media is transmitted over an eMBMS bearer.
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7.3.3.9.3 Inter-system switching from 5G MBS session to LTE unicast bearer
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The procedure provided in figure 7.3.3.9.3-1 describes how the MC service server handles inter-system switching when the MC service UE switches from 5G to LTE network, where the MC service server is unable to provide the MC services to the client over eMBMS bearer.
Pre-conditions:
- MC service clients are attached to the 5GS, registered and affiliated to the same MC service group X.
- The MC services can be provided via both 5GS and EPS.
Figure 7.3.3.9.3-1: Inter-system switching from 5G MBS session to LTE unicast bearer.
1. An MC service group communication takes place, and the MC media is delivered over 5G MBS session (either broadcast or multicast session mode), which is associated to the MC service group X.
2. The MC service UE performs handover to EPS.
3. Location information handling can be based on location reports provided by the MC service client, where the MC service UE`s location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the MC service server.
Also, location information handling can be based on notifications provided from the network to the MC service server related to 5GS supporting EPS interworking, as specified in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9] and described in clause 7.4.3. For that, the MC service server can subscribe to receive notifications of specific events from the network. For instance, the MC service server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g. access network information notification and change of access type. Also, when SCEF+NEF is deployed, the MC service server can subscribe to SCEF+NEF related notifications for specific events, e.g. core network (CN) type change.
4. The MC service server may interact with the EPC for providing the required media resources over the unicast bearer, if not already allocated.
5. The MC service group communication takes place over EPS, and the MC media is transmitted over a unicast bearer.
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7.3.3.9.4 Inter-system switching from LTE eMBMS to 5G MBS session
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The procedure provided in figure 7.3.3.9.4-1 describes how the MC service server handles inter-system switching when the MC service UE switches from LTE network to 5G, where the MC service server is able to provide the MC services to the client over 5G MBS sessions (either broadcast or multicast).
Pre-conditions:
- MC service clients are attached to the EPC and affiliated to the same MC service group X.
- The MC services can be provided via both 5GS and EPS.
- The MC service client(s) is within the service area (if the session is limited to an area), where the MBS session is configured.
- It is assumed that the MC service client(s) has not received the 5G MBS session announcement while camping in EPS.
Figure 7.3.3.9.4-1: Inter-system switching from LTE eMBMS bearer to 5G MBS sessions (either broadcast or multicast).
1. An MC service group communication takes place, and the MC media is delivered over eMBMS bearer, which is associated to the MC service group X.
2. The MC service UE performs handover to 5GS.
3. Location information handling can be based on location reports provided by the MC service client, where the MC service UE`s location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the MC service server.
Also, location information handling can be based on notifications provided from the network to the MC service server related to 5GS supporting EPS interworking, as specified in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9] and described in clause 7.4.3. For that, the MC service server can subscribe to receive notifications of specific events from the network. For instance, the MC service server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g., access network information notification and change of access type. Also, when SCEF+NEF is deployed, the MC service server can subscribe to SCEF+NEF related notifications for specific events, e.g., core network (CN) type change.
4. The MC service server analyses the location information and decides how to serve the client. If the MC service server decides to serve the client via 5G MBS session, it may send an MBS session announcement indicating information among others the session mode to serve the MC service client and the corresponding MBS session ID. This step is optional as the session announcement related information could be sent in advance (implementation specific).
5. The MC service UE acts according to the MBS session mode provided to receive the DL media.
5a. In case of multicast MBS sessions, the MC service UE performs a UE session join towards the 5GC indicating the MBS session ID to join. It may as well send a UE session join acknowledgement to the MC service server.
5b. In case of broadcast MBS sessions, the MC service UE starts monitoring the broadcast MBS session.
6. The MC service client sends an MBS listening status report to the server indicating its ability to receive media over the indicated MBS session.
7. The MC service server sends a MapGroupToSessionStream over the MBS session providing the required stream information to receive the media related to the group communication.
8. The MC service client processes the received information related to the MC media over the MBS session.
9. The MC service group communication takes place over 5GS, and the MC media is delivered over the broadcast or multicast MBS session.
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7.3.3.9.5 Inter-system switching from LTE eMBMS to 5G unicast PDU session
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The procedure provided in figure 7.3.3.9.5-1 describes how the MC service server handles inter-system switching when the MC service UE switches from LTE network to 5G, where the MC service server is able to provide the MC services to the client over 5G MBS sessions (either broadcast or multicast).
Pre-conditions:
- MC service clients are attached to the EPC and affiliated to the same MC service group X.
- The MC services can be provided via both 5GS and EPS.
Figure 7.3.3.9.5-1: Inter-system switching from LTE eMBMS bearer to 5G unicast PDU session.
1. An MC service group communication takes place, and the MC media is delivered over eMBMS bearer, which is associated to the MC service group X.
2. The MC service UE performs handover to 5GS.
3. Location information handling can be based on location reports provided by the MC service client, where the MC service UE`s location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the MC service server.
Also, location information handling can be based on notifications provided from the network to the MC service server related to 5GS supporting EPS interworking, as specified in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9] and described in clause 7.4.3. For that, the MC service server can subscribe to receive notifications of specific events from the network. For instance, the MC service server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g. access network information notification and change of access type. Also, when SCEF+NEF is deployed, the MC service server can subscribe to SCEF+NEF related notifications for specific events, e.g. core network (CN) type change.
4. The MC service server may interact with the 5GC to request media resources (if not already allocated) with specific requirements over unicast PDU session, as it is able to serve the MC service client via unicast PDU session, as described in clause 7.2.
5. The MC service group communication takes place over 5GS, and the MC media is delivered over unicast PDU session.
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7.3.3.10 MBS transmission in MCPTT
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7.3.3.10.1 General
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MCPTT server can determine to use 5G MBS for the transmission of downlink media for different types of MCPTT group calls.
The application layer signalling such as the floor control messages, application layer paging messages may be transmitted along with the MC media over the same MBS session however with different QoS requirements, or over other means such as unicast downlink or a different MBS session.
When using the procedures for pre-configured or dynamic MBS session establishment for MCPTT, the MCPTT server performs the procedure of call connect and disconnect over MBS session at the group communication session establishment phase.
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7.3.3.10.2 Call connect and disconnect over MBS session procedures
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7.3.3.10.2.1 General
MBS session can be used for MCPTT group calls. One MBS session may be not permanently associated to one specific group or group call.
NOTE: It is implementation-specific that one MBS session can be re-assigned to different groups, or is associated to only one group.
The procedure in clause 7.3.3.10.2 requires that the group session is setup before the media transmission starts. This eliminates the need for the receiving clients to continuously use a unicast session. Prior to this, the MBS session is activated and announced to the MCPTT clients.
7.3.3.10.2.2 Procedure
7.3.3.10.2.2.1 Group call connect over MBS session
Pre-conditions:
- The MCPTT clients 1 to n are attached to the 5GS, registered and affiliated to the same MCPTT group X.
- The MCPTT server has directly performed (or via NEF/MBSF) an MB-SMF discovery and selection, unless the corresponding information is locally configured.
- The MCPTT server has decided to use an MBS session for the MCPTT service group call associated with to the MCPTT group X.
Figure 7.3.3.10.2.2.1-1: Group call connect over broadcast and multicast MBS sessions.
1. An MBS session is configured with the required QoS requirements announced and established.
NOTE: In case of broadcast MBS sessions, the session is established as part of session configuration procedures as described in 3GPP TS 23.247 [15]. In case of multicast MBS sessions, the session is established as specified in step 2.
2. In the case of multicast MBS sessions, the MCPTT UE initiates a UE session join towards the 5GS, based on the session information provided to the MCPTT UE during the session announcement step. This step is essential in order to receive the corresponding MC media. The multicast MBS session is hence established once the first initiated UE session join is accepted as indicated in 3GPP TS 23.247 [15].
3. MCPTT client 1 initiates a group call by sending an initial floor request over a unicast PDU session towards the MCPTT server.
4. The MCPTT server sends a MapGroupToSessionStream including the necessary stream information for the MCPTT clients 2 to n to receive the MC media related to the group call which is taken place within the associated MBS session.
5. The MCPTT clients 2 to n process the MapGroupToSessionStream information and may send a MapGroupToSessionStream Ack back to the MCPTT server if required.
6. The MCPTT server grants MCPTT client 1 the right to transmit media over the associated MBS session and sends a floor granted message to client 1 over a unicast PDU session.
7. A floor taken message is sent from the MCPTT server to MCPTT clients 2 to n indicating the MCPTT ID of the transmitting client, i.e., MCPTT client 1 and the associated MCPTT group ID. The floor taken message is transmitted over the associated MBS session.
8. MCPTT client 1 sends the MC media over uplink unicast PDU session towards the MCPTT server.
9. The MCPTT server sends the MC media over the indicated stream within the associated MBS session to the MCPTT clients 2 to n.
7.3.3.10.2.2.2 Group call disconnect from MBS session
Figure 7.3.3.10.2.2.2-1 presents the procedure for a group communication call disconnect over broadcast and multicast MBS sessions.
Figure 7.3.3.10.2.2.2-1: Group call disconnect over broadcast and multicast MBS sessions.
1. The MC group communication is taking place over the associated MBS session. MCPTT client 1 is sending the MC media over a unicast PDU session to the MCPTT server.
2. The MCPTT server sends the MC media over the associated MBS session to MCPTT clients 2 to n.
3. After the MC media transmission is over, i.e., no further media to be sent over the group communication, the MCPTT server sends an UnMapGroupFromSessionStream to de-associate the group call from the MBS session.
4. The MCPTT server may release the MBS session as described in clause 7.3.3.3.2.
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7.3.3.10.3 Enhanced MCPTT group call setup procedure with 5MBS
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Enhanced MCPTT group call setup procedure with eMBMS bearer is specified in clause 10.10.6 of 3GPP TS 23.379 [6]. When using mission critical services over 5G MBS, the application paging message transported over 5G MBS session should also be supported.
The related procedures and information flow are as specified in 3GPP TS 23.379 [6], with only difference of using of 5G MBS session for the transmission of application paging message.
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7.3.3.10.4 Downlink media transmission with 5MBS
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The MCPTT service shall support the procedure for using pre-created MBS session, or dynamic MBS session as specified clause 7.3.3.1.
MCPTT may use MBS session for the different types of MCPTT group calls. Both pre-arranged group calls and chat group calls can use the pre-created 5G MBS session for distributing the media.
Both the media packets as well as the floor control messages to the receiving users are sent on the 5G MBS session. Optionally a separate 5G MBS session could be used for the floor control messages.
7.3.3.10.5 Switching between 5G MBS session, 5G unicast PDU session, LTE eMBMS bearer, and LTE unicast bearer for MCPTT
The MCPTT service shall support the procedure for switching between 5G MBS session, 5G unicast PDU session, LTE eMBMS bearer and LTE unicast bearer as specified in clause 7.3.3.8 and clause 7.3.3.9 with the following clarifications:
- The MC service client is the MCPTT client;
- The MC service server is the MCPTT server; and
- The MC service ID is the MCPTT ID.
The MCPTT service shall use the MCPTT-1, MCPTT-4, MCPTT‑7, MCPTT-8 and MCPTT‑9 reference points for this procedure.
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7.3.3.11 MBS transmission in MCVideo
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7.3.3.11.1 General
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MCVideo server can determine to use 5G MBS for the transmission of DL link media for different types of MCVideo group calls.
The application layer signalling such as the transmit media request and transmit media granted messages, may be transmitted along with the MC media over the same MBS session however with different QoS requirements, or over other means such as unicast downlink or a different MBS session.
When using the procedures for pre-configured or dynamic MBS session establishment for MCVideo, the MCVideo server perform the procedure of call connect and disconnect over MBS session.
The MCVideo service shall support the procedure for using MBS sessions as specified clause 7.3.3.1 with the following clarifications:
- The MC service client is the MCVideo client;
- The MC service server is the MCVideo server; and
- The MC service ID is the MCVideo ID.
The MCVideo service shall use the MCVideo-1, MCVideo‑8 and MCVideo-9 reference points for this procedure.
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7.3.3.11.2 Call connect and disconnect over MBS session procedures
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7.3.3.11.2.1 General
MBS session can be used for MCVideo group calls. One MBS session may not be permanently associated to one specific group or group call.
NOTE: It is implementation-specific that one MBS session can be re-assigned to different groups, or is associated to only one group.
The procedure in clause 7.3.3.11.2.2 requires that the group session is setup before the media transmission start. This eliminates the need for the receiving clients to continuously use a unicast session. Prior to this the MBS session is activated and announced to the MCVideo clients.
7.3.3.11.2.2 Procedure
7.3.3.11.2.2.1 Group call connect over MBS session
Figure 7.3.3.11.2.2.1-1 presents the procedure for a group communication, in specific, video call connects over either broadcast or multicast MBS sessions.
Pre-conditions:
- The MCVideo clients 1 to n are attached to the 5GS, registered and affiliated to the same MCVideo group X.
- The MCVideo server has directly performed (or via NEF/MBSF) an MB-SMF discovery and selection, unless the corresponding information is locally configured.
- The MCVideo server has decided to use an MBS session for the MCVideo services associated to the MCVideo group X.
Figure 7.3.3.11.2.2.1-1: Group call connect on MBS session
1. An MBS session is configured with the required QoS requirements, announced and established.
NOTE: In case of broadcast MBS sessions, the session is established as part of session configuration procedures as described in 3GPP TS 23.247 [15]. In case of multicast MBS sessions, the session is established as specified in step 2.
2. In the case of multicast MBS sessions, the MCVideo UEs initiate a UE session join towards the 5GC based on the session information provided to the MCVideo UE during the session announcement step. This step is essential in order to receive the corresponding MC media. The multicast MBS session is hence established once the request of the first initiated UE session join is accepted as indicated in 3GPP TS 23.247 [15].
3. MCVideo client 1 initiates a MCVideo group communication, namely a video group call, by sending an initial transmit media request over a unicast PDU session towards the MCVideo server.
4. The MCVideo server sends a MapGroupToSessionStream including the necessary stream information for the MCVideo clients 2 to n to receive the MC media related to the group call which is taken place within the associated MBS session.
5. The MCVideo clients 2 to n process the MapGroupToSessionStream information and may send a MapGroupToSessionStream Ack back to the MCVideo server if required.
6. The MCVideo server grants MCVideo client 1 the right to transmit media over the associated MBS session and sends a transmit media grated message to client 1 over a unicast PDU session.
7. A media transmission notification message is sent from the MCVideo server to the MC clients 2 to n over the associated MBS session. It indicates the MCVideo ID of the transmitting client, i.e., MCVideo ID of service client 1 and the associated MC group ID.
8. MCVideo clients 2 to n process the notification message and get informed about the necessary information of the video group call.
9. The MCVideo clients 2 to n may send a receive media request to the MCVideo server, to indicate the reception of media over the associated MBS session. As a result, the MCVideo server sends a corresponding response message.
10. MCVideo client 1 sends the MC media over a unicast PDU session towards the MCVideo server.
11. The MCVideo server sends the MC media over the indicated stream within the associated MBS session to the MCVideo clients 2 to n.
7.3.3.11.2.2.2 Group call disconnect from MBS session
Figure 7.3.3.11.2.2.2-1 presents the procedure for a group call disconnect over broadcast and multicast MBS sessions.
Figure 7.3.3.11.2.2.2-1: Group call disconnect from MBS session
1. The MC group call is taking place over the associated MBS session. MCVideo client 1 is sending the MC media over a unicast PDU session to the MCVideo server.
2. The MCVideo delivers the MC media over the associated broadcast or multicast MBS session to MCVideo clients 2 to n.
3. After the MC media transmission is over, i.e., no further media to be sent over the group communication, the MCVideo server sends an UnMapGroupFromSessionStream to MCVideo clients 2 to n to indicate the de-association of the group call from the corresponding MBS session stream.
4. The MCVideo server may release the MBS session as described in clause 7.3.3.3.2.
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7.3.3.11.3 Switching between 5G MBS session, 5G unicast PDU session, LTE eMBMS bearer, and LTE unicast bearer for MCVideo
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The MCVideo service shall support the procedure for switching between 5G MBS session, 5G unicast PDU session, LTE eMBMS bearer and LTE unicast bearer as specified in clause 7.3.3.8 and clause 7.3.3.9 with the following clarifications:
- The MC service client is the MCVideo client;
- The MC service server is the MCVideo server; and
- The MC service ID is the MCVideo ID.
The MCVideo service shall use the MCVideo-1, MCVideo-4, MCVideo‑7, MCVideo-8 and MCVideo‑9 reference points for this procedure.
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7.3.3.11.4 DL media transmission with 5MBS for MCVideo
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The MCViedo service shall support the procedure for using pre-created MBS session, or dynamic MBS session as specified clause 7.3.3.1.
MCVideo may use pre-created MBS session for the different types of MCVideo group calls. Both pre-arranged group calls and chat group calls can use the pre-created MBS session for distributing the media. The MBS session can be used by any group.
When using the pre-created MBS session for MCVideo, the MCVideo server may perform the procedure of call connect and disconnect over MBS as defined in clause 7.3.3.11.2 for the group communication session establishment step, or send map group communication to MBS session as defined in clause 7.3.2.4 after group communication session establishment.
MCVideo may also use dynamic MBS session for the different types of MCVideo group calls. Both pre-arranged group calls and chat group calls can use the dynamic MBS session for distributing the media.
When using the procedures for dynamic MBS session establishment for MCVideo, the MCVideo server perform the procedure of triggering MBS session configuration as defined in clause 7.3.3.1 and mapping group communication to MBS session as defined in defined in clause 7.3.2.4 at the group communication session establishment step.
Both the media packets as well as the transmission control messages to the receiving MCVideo clients are sent on the MBS session. Optionally a separate MBS session could be used for the transmission control messages.
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7.3.3.12 MBS transmission in MCData
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7.3.3.12.1 General
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The procedures and information flows for Short data service and file distribution of MC Data group are defined in 3GPP TS 23.282 [5].
When using 5G MBS, MCData server can determine to use either pre-created MBS session or dynamic MBS session as defined in clause 7.3.3.1 for the transmission of DL link media for different types of MCData service capabilities.
MCData may use the 5G MBS session for the MCData features short data service and file distribution for MCData group communication. The 5G MBS session can be used by any MCData group.
Both the media packets as well as application level control signalling (e.g. transmission control) to the receiving users may be sent on the MBS session. Optionally, a separate MBS Session could be used for the application level control signalling (e.g. transmission control).
When MBSF/MBSTF are deployed in 5GS, MCData server could also determine to use File distribution capabilities provided by MBSF/MBSTF for file distribution.
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7.3.3.12.2 Usage of MBS session for MCData
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The MCData service shall support the procedure for using pre-created MBS session or dynamic MBS session as specified in Clause 7.3.3.1 with the following clarifications:
- The MC service client is the MCData client;
- The MC service server is the MCData server; and
- The MC service ID is the MCData ID.
When using the procedures for pre-created or dynamic MBS session establishment for MCData, the MCData server performs the procedure of group communication connect and disconnect over MBS session at the group communication session establishment phase.
The MCData service shall use the MCData-SDS-1, MCData-SDS-3, MCData-FD-1, MCData-FD-3, MCData-DS-1 and MCData-DS-3 reference points for this procedure.
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7.3.3.12.3 Switching between 5G MBS session, 5G unicast PDU session, LTE eMBMS bearer, and LTE unicast bearer for MCData
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The MCData service shall support the procedure for switching between 5G MBS session, 5G unicast PDU session, LTE eMBMS bearer, and LTE unicast bearer or eMBMS bearer as specified in clause 7.3.3.8 and clause 7.3.3.9 with the following clarifications:
- The MC service client is the MCData client;
- The MC service server is the MCData server; and
- The MC service ID is the MCData ID.
The MCData service shall use the MCData-SDS-1, MCData-SDS-2, MCData-SDS-3, MCData-FD-1, MCData FD-2, MCData‑FD-3, MCData-DS-1, MCData-DS-2 and MCData‑DS-3 reference points for this procedure.
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7.3.3.12.4 Group communication connect and disconnect over MBS session procedures
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7.3.3.12.4.1 General
MBS session can be used for MCData group communication. One MBS session may be not permanently associated to one specific group or group communication.
NOTE: It is implementation-specific that one MBS session can be re-assigned to different groups, or is associated to only one group.
The procedure in clause 7.3.3.12.4 requires that the group session is setup before the data transmission starts. This eliminates the need for the receiving clients to continuously use a unicast session. Prior to group session setup, the MBS session is activated and announced to the MCData clients.
7.3.3.12.4.2 Procedure
The procedure specified in this clause is applicable (for the group communication establishment) for Group standalone short data service using media plane as described in clause 7.4.2.6 in 3GPP TS 23.282 [5] and for Group short data service session as described in clause 7.4.2.7 in 3GPP TS 23.282 [5].
7.3.3.12.4.2.1 Group communication connect over MBS session
Pre-conditions:
- The MCData clients 1 to n are attached to the 5GS, registered and affiliated to the same MCData group X.
- The MCData server has directly performed (or via NEF/MBSF) an MB-SMF discovery and selection, unless the corresponding information is locally configured.
- The MCData server has decided to use an MBS session for the MCData service group communication associated with to the MCData group X.
Figure 7.3.3.12.4.2.1-1: Group communication connect over broadcast and multicast MBS sessions.
1. An MBS session is configured with the required QoS requirements announced and established.
NOTE 1: In case of broadcast MBS sessions, the session is established as part of session configuration procedures as described in 3GPP TS 23.247 [15]. In case of multicast MBS sessions, the session is established as specified in step 2.
2. In the case of multicast MBS sessions, the MCData UE initiates a UE session join towards the 5GS based on the session information provided to the MCData UE during the session announcement step. This step 2 is essential in order to receive the corresponding MC media. The multicast MBS session is hence established once the first initiated UE session join is accepted as indicated in 3GPP TS 23.247 [15].
3. The MCData client 1 initiates a group communication by sending a MCData group data request over a unicast PDU session towards the MCData server.
4. MCData server initiates the MCData group data request towards each MCData clients 2 to n.
5. The receiving MCData clients 2 to n optionally notify the user about the incoming MCData session data request.
6. The receiving MCData client 2 to n accept or reject the MCData group data request and the corresponding result is in the MCData group data response towards MCData server.
7. The MCData server sends a MapGroupToSessionStream including the necessary stream information for the MCData clients 2 to n to receive the MC data related to the group communication which is taken place within the associated MBS session.
8. The MCData clients 2 to n process the MapGroupToSessionStream information and may send a MapGroupToSessionStream Ack back to the MCData server if required.
9. MCData server forwards the MCData group data response received from MCData client 2 to n to the MCData user initiating the MCData session data request.
NOTE 2: The steps 4 to 6 and steps 7 to 8 can occur in any order, and prior to step 10 depending on the conditions to proceed with the data transmission.
10. MCData client 1 sends the MC data over uplink unicast PDU session towards the MCData server.
11. The MCData server sends the MC data over the indicated stream within the associated MBS session to the MCData clients 2 to n.
7.3.3.12.4.2.2 Group communication disconnect from MBS session
Figure 7.3.3.12.4.2.2-1 presents the procedure for a group communication disconnect over broadcast and multicast MBS sessions.
Figure 7.3.3.12.4.2.2-1: Group communication disconnect over broadcast and multicast MBS sessions.
1. The MC group communication is taking place over the associated MBS session. MCData client 1 is sending the MC data over a unicast PDU session to the MCData server.
2. The MCData server sends the MC data over the associated MBS session to MCData clients 2 to n.
3. After the MC data transmission is over, i.e., no further data to be sent over the group communication, the MCData server sends an UnMapGroupFromSessionStream to de-associate the group communication from the MBS session.
4. The MCData server may release the MBS session as described in clause 7.3.3.3.2.
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7.3.3.12.5 Downlink media transmission with 5MBS
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The MCData service shall support the procedure for using pre-established MBS session, or dynamic MBS session as specified in clause 7.3.3.1.
MCData may use MBS session for the different types of sub-services. Both SDS and FD can use the pre-established MBS session or dynamic MBS session for distributing the data.
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7.3.3.13 Use of FEC to protect 5G MBS transmissions
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7.3.3.13.1 General
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Application layer FEC can be used to recover the packet losses when delivering a MC service over 5G MBS, to reach its required level of QoS.
The support of FEC is optional for the MC service servers and MC service clients. FEC can be optionally applied by the MBSTF, if required by the MC service server (as specified in clause 7.3.3.13.2), or directly by the MC service server (as defined in 3GPP TS 23.280 [3]).
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7.3.3.13.2 FEC encoding by the MBSTF
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In this procedure, depicted in figure 7.3.3.13.2-1, the MC service server asks the MBSF/MBSTF to apply FEC to a set of media, transported by a 5G MBS session, using the Setup FEC request.
This procedure can be applied when using pre-created MBS session and session announcement (as specified in clause 7.3.3.1.2) or using MBS session and session announcement (as specified in clause 7.3.3.1.3).
Pre-condition:
1. The MC service server has already configured and activated a 5G MBS session.
Figure 7.3.3.13.2-1: Application of FEC by the MBSF-MBSTF
1. The MC service server decides to set up FEC for a set of MC service media flows. It will send the FEC request to MBSF/MBSTF.
It includes the following elements: the MBS session ID of the MBS session transporting those media, the media descriptions (codecs, transport protocols, bitrates, destination IP addresses and ports), the identification of the FEC repair packet flow (IP destination and port), and an upper bound to the additional latency resulting due to FEC application. The MC Service server may perform this request several times to protect separately different sets of media transported within the same 5G MBS session.
2. If the MBSF can satisfy the request, the Setup FEC response includes a modified list of media information and FEC information. The response also includes an identifier of the corresponding FEC process instance, which can be used to release the application of FEC for these media flows.
NOTE 1: Source media packets may be modified by the application of FEC (e.g., addition of a footer or header), leading to a modification of the delivery protocol to be announced within the media information.
NOTE 2: The Release FEC request is not shown in the figure.
3. The MC service server announces the 5G MBS session to the MC service client with the MBS session announcement procedure, including the modified list of media information and FEC information within the SDP information.
4. When the MC service server decides to transmit the MC service media flow for a group communication, the MC service server sends to the group a message identifying the MC service media flow and the MBS session ID, such as the MapGroupToSessionStream message for MCPTT or MCVideo.
5. The MC service server sends the downlink media to the MBSTF over Nmb8.
6. The MBSTF performs FEC encoding of the downlink media in accordance with the announced FEC algorithm and parameters and delivers it over 5G MBS.
7. The MC service client performs FEC decoding of the encoded media flows in accordance with the announced FEC information and delivers the decoded flows to the media player.
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7.3.4 Support of Multicast MBS session reception in RRC_INACTIVE state
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7.3.4.1 General
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Multicast MBS reception in RRC_INACTIVE mode enables a higher number of UEs in a cell to participate in public safety group calls using MBS sessions. The MC service server may indicate to the 3GPP core network that a UE is preferred to be kept in RRC_Connected when the related MBS session which the UE joined is active via provisioning the MBS assistance information as described in 3GPP TS 23.247 [15].
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7.3.4.2 Provisioning of the MBS assistance information
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After the MC service server has obtained the MBS Session ID of a multicast MBS Session via the TMGI allocation or the MBS session creation procedure, and the MBS session is mapped to a certain MC group, the MC service server may provision the MBS assistance information of a UE to the 5GC as described in 3GPP TS 23.247 [15].
Such provisioning may be performed and updated until the MBS session is deleted. If the MC service server decides to allow to keep an MC service UE(s) in the RRC_CONNECTED state based on certain information (such as MC service user’s role in the group or certain operational situations, e.g., group leader, floor request frequency), the MC service server may provision the UE’s MBS assistance information to the 3GPP core network, as described in 3GPP TS 23.247 [15]
NOTE: In case of congestion, the MC service UEs, which are provisioned as part of the MBS session assistance information, are kept the last in the RRC_Connected state. However, it is up to NG-RAN to release them based on the congestion situation if required.
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7.4 MC services over 5GS supporting EPS interworking
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7.4.1 General
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MC services over a 5G system supporting EPS interworking are provided to 5GS/EPS capable MC service UEs as defined in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9].
This clause describes procedures related to the support of MC services over a 5G system with EPS interworking.
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7.4.2 Inter-system mobility
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As specified in 3GPP TS 23.501 [7], a dedicated user plane anchor point, i.e. UPF + PGW-U function, is defined for interworking between 5GS and EPS. This enables that the network can directly handle PDU sessions (in 5GS) and PDN connections (in EPS) associated to MC service sessions of an MC service UE during inter-system change.
The inter-system change of an MC service UE will be transparent to the MC service server. The MC service server will continue interacting with the same control plane functions, e.g. PCF, and user plane function, e.g. UPF + PGW-U.
NOTE 1: For the case that seamless session continuity is required for MC services, e.g. for MCPTT services, EPS interworking with N26 (interface between AMF in 5GC and MME in EPC) is required for inter-system change, as described in 3GPP TS 23.501 [7].
The procedure in figure 7.4.2-1 describes in a high level inter-system mobility of 5GS/EPS capable MC service UEs with associated MC service sessions.
Pre-conditions:
- MC service UE is a 5GS/EPS capable UE.
- MC service UE is registered to a 5GS supporting EPS interworking for the support of MC services.
Figure 7.4.2-1: MC services over 5GS with EPS interworking – Inter-system mobility
1. MC service UE is registered to the MC service server over the 5GS. MC service UE has established a PDU session(s) associated to MC service sessions.
2. The 5GS supporting EPS interworking decides that the MC service UE should be handed over to EPS, e.g. due to radio conditions. 5GS handles associated PDU sessions of the MC service UE to establish corresponding PDN connections in EPS, i.e. required default and dedicated EPS bearers associated to MC service sessions.
NOTE 2: The interworking procedures with EPS are described in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9].
3. MC service UE is registered on EPS. MC services continue being provided to the MC service UE over EPS via the established PDN connections (default and dedicated bearers associated to corresponding MC service sessions) in step 2.
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7.4.3 Network notifications of EPS interworking related events
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In the case of MC services provided over a 5GS supporting EPS interworking, the MC service server may not be able to identify whether an MC service UE is registered on 5GS or EPS. Therefore, the MC service server can subscribe/unsubscribe to receive notifications of specific events from the network. These notifications can be related to PDU sessions/PDN connections to which MC service sessions are bounded or related to a specific MC service UE or group of MC service UEs.
Such notifications can be provided from the PCF (via N5 or Rx) for specific events, e.g. access network information notification and change of access type. If SCEF+NEF is deployed, notifications can also be provided from SCEF+NEF for specific events, e.g. core network (CN) type change. These event procedures are described in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9].
The procedure in figure 7.4.3-1 describes a high level subscription/notification procedure between the MC service server and the network.
Pre-conditions:
- MC service UE is a 5GS/EPS capable UE.
- MC service UE is registered to a 5GS supporting EPS interworking for the support of MC services.
Figure 7.4.3-1: Network notifications of EPS interworking related events
1. MC service UE is registered to the MC service server over the 5GS. MC service UE has established a PDU session(s) associated to MC service sessions.
2. MC service server subscribes to receive notifications from the network associated to MC service UE related to EPS interworking events. For instance, the MC service server may subscribe to notifications of events from the PCF associated to the MC service UE, e.g. access network information notification and change of access type, as specified in 3GPP TS 23.503 [9].
If SCEF+NEF is deployed, the MC service server may also subscribe to notifications of events from SCEF+NEF associated to the MC service UE, e.g. CN type change, as specified in 3GPP TS 23.501 [7] and 3GPP TS 23.502 [10].
3. The 5GS supporting EPS interworking decides that the MC service UE should be handed over to EPS, e.g. due to radio conditions. 5GS handles associated PDU sessions of the MC service UE to establish corresponding PDN connections in EPS, i.e. required default and dedicated EPS bearers associated to MC service sessions.
NOTE 1: The interworking procedures with EPS are described in 3GPP TS 23.501 [7], 3GPP TS 23.502 [10], and 3GPP TS 23.503 [9].
4. MC service UE is registered on EPS. MC services continue being provided to the MC service UE over EPS via the established PDN connections (default and dedicated bearers associated to corresponding MC service sessions) in step 2.
5. The network provides notifications to the MC service server of subscribed events associated to the MC service UE.
NOTE 2: Step 5 can occur before or in parallel to step 4.
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7.5 Enhancements for Location management over 5GS
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7.5.1 General
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In addition to the location management functions defined in 3GPP TS 23.280 [3], the location management system over 5GS shall support the following enhancement:
- Inter-system RAT changes event triggering and report as described in clause 7.3.3.9.1.
- Serving and neighbouring 5G NR Cell Global Identifiers (NCGI) as optional Location Information elements in the information flows of 3GPP TS 23.280 [3] clause 10.9.2.
- The MC service server can subscribe to the PCF related notification to obtain the MC service UE location information as described in 3GPP TS 23.503 [9].
- The reference point between the location management server and the 5GS to obtain location information from the PLMN operator can either be the Le reference point or the N33 reference point indirectly via the NEF, as described in 3GPP TS 23.273 [26].
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7.5.2 Information flows for location information
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7.5.2.1 General
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In this clause, only those information flows which requires enhancement to 3GPP TS 23.280 [3] for MC services over 5G specific are included.
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7.5.2.2 Location reporting configuration
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Table 7.5.2.2-1 describes the information flow from the location management server to the location management client for the location reporting configuration.
Compared to that is defined in 3GPP TS 23.280 [3], the following changes are made:
- Allowing the location management server to configure location reporting by including inter-RAT trigger information.
- Adding a new NOTE 3 to clarify the usage of triggering event for inter-RAT changes
Table 7.5.2.2-1: Location reporting configuration
Information element
Status
Description
MC service ID
M
Identity of the MC service user to which the location reporting configuration is targeted.
Requested non-emergency location information
O
(see NOTE 1)
Identifies what location information is requested, except for emergency or imminent peril calls or emergency alerts
Requested emergency location information
O
(see NOTE 1)
Identifies what location information is requested, for emergency or imminent peril calls or emergency alerts
Triggering criteria in non- emergency cases
O
(see NOTE 1 and NOTE 3
Identifies when the location management client will send the location report in non-emergency cases
Handling criteria in not reporting location information cases
O
Identifies when the location management client will store location information (e.g. never, off-network, IOPS)
Triggering criteria in not reporting location information cases
O
(see NOTE 2)
Identifies the causes when the location management client will generate location information
Minimum time between consecutive reports
O
(see NOTE 1)
Defaults to 0 if absent and 0 for emergency calls, imminent peril calls and emergency alerts
Triggering criteria in emergency cases
O
(see NOTE 1)
Identifies when the location management client will send the location report in emergency cases
NOTE 1: If none of the information elements is present, this represents a cancellation for location reporting based on Triggering criteria in emergency and non-emergency cases, if configured.
NOTE 2: If not present, location information is generated based on Triggering criteria in emergency and non-emergency cases, if configured.
NOTE 3: Triggering criteria can contain the inter-RAT trigger information if the inter-system RAT changes information is expected from the LMC in case of LTE eMBMS and 5G MBS co-existence.
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7.5.2.3 Location information report
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Table 7.5.2.3-1 describes the information flow from the location management client to the location management server for the location information reporting.
Compared to that is defined in 3GPP TS 23.280 [3], the following changes are made:
- Allowing the location management client to report the the inter-RAT information in the location information report;
- Adding a new NOTE 5 to clarify the usage of triggering event for inter-RAT changes
Table 7.5.2.3-1: Location information report (LMC – LMS)
Information element
Status
Description
Set of MC service IDs
M
Set of identities of the reporting MC service user on the MC service UE (e.g. MCPTT ID, MCVideo ID, MCData ID)
MC service ID
(see NOTE 4)
O
Identity of the requesting MC service user.
Functional alias(es)
(see NOTE 1)
O
Functional alias that corresponds to the reporting MC service ID.
MC service UE label
O
Generic name of the reporting MC service UE
Triggering event
(see NOTE 3 and NOTE 5)
M
Identity of the event that triggered the sending of the report
Location Information (see NOTE 2 and NOTE 5)
M
Location information of the individual MC service user
NOTE 1: Each functional alias corresponds to an individual MC service ID.
NOTE 2: This may contain multiple sets of elements for the MC service user. The following elements shall accompany the location information elements: time of measurement and optional accuracy. The following location information elements shall be optional (configurable) present: longitude, latitude, speed, bearing, altitude, ECGI, eMBMS SAIs, MBS FSA ID(s), with at least one provided.
NOTE 3: An on-demand request may be the triggering event.
NOTE 4: In case of an on-demand request of an MC service user the MC service ID shall be provided. In case of an MC service server request or an event-triggered report, no MC service ID is provided.
NOTE 5: Triggering event can contain the inter-RAT information if the inter-RAT changes information is expected from the LMC in case of LTE eMBMS and 5G MBS co-existence.
Table 7.5.2.3-2 describes the information flow from the location management server to the MC service server for location information reporting.
Compared to that is defined in 3GPP TS 23.280 [3], the following changes are made:
- Adding a new NOTE 4 to clarify the usage of triggering event for inter-RAT changes
Table 7.5.2.3-2: Location information report (LMS – MC service server)
Information element
Status
Description
Set of MC service IDs
M
Set of identities of the reporting MC service user on the MC service UE (e.g. MCPTT ID, MCVideo ID, MCData ID)
Functional alias(es) (see NOTE 1)
O
Functional alias that corresponds to the MC service ID.
Triggering event (see NOTE 3 and NOTE 4)
M
Identity of the event that triggered the sending of the report
Location Information (see NOTE 2 and NOTE 4)
M
Location information of the individual MC service user
NOTE 1: Each functional alias corresponds to an individual MC service ID.
NOTE 2: This may contain multiple sets of elements for the MC service user. The following elements shall accompany the location information elements: time of measurement and optional accuracy. The following location information elements shall be optional (configurable) present: longitude, latitude, speed, bearing, altitude, ECGI, MBMS SAIs, MB FSA ID(s), with at least one provided.
NOTE 3: An on-demand request may be the triggering event.
NOTE 4: Triggering event can contain the inter-RAT information if the inter-RAT information is expected from the LMC in case of LTE eMBMS and 5G MBS co-existence.
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7.5.3 Procedure
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7.5.3.1 General
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In this clause, only the procedure which requires enhancement to 3GPP TS 23.280 [3] for MC services over 5G specific are included.
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7.5.3.2 Event-triggered location reporting procedure
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NOTE 1: This procedure is valid for single MC system operation only.
The location management server provides location reporting configuration to the location management clients, indicating what information the location management server expects and what events will trigger the sending of this information to the location management server. For eMBMS and MBS co-existing, the MC service server needs to obtain the inter-RAT information. If the inter-RAT information report from the MC service UE is expected, the MC service server may obtain the inter-RAT information from the location management server, and the location management server then performs the procedure as described clause 10.9.3.1 in 3GPP TS 23.280 [3], clause 7.5.2.2 and 7.5.2.3. In addition to those trigger criteria defined in 3GPP TS 23.280 [3], the new inter-RAT triggers may include, the change of MBS FSA ID, inter-system RAT type changes. The location information report contains the inter- RAT information.
NOTE 2: How the location management client can identify or obtain information about the case that an inter-RAT change has occurred is implementation specific or out of the scope of this specification.
Similar to the usage of eMBMS bearer for transmitting of location reporting configuration defined in TS 23.280, the location reporting configuration message can also be sent over 5G MBS Session.
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7.6 MC service over 5G ProSe
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7.6.1 Off network group communication for MC service
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The procedures and information flows used in 3GPP TS 23.280 [3], 3GPP TS 23.379 [6], 3GPP TS 23.281 [4], and 3GPP TS 23.282 [5] are reused for Off network group communication for MC service over 5G ProSe with following differences:
- Discovery Group ID is replaced by Application Layer Group ID, as specified in 3GPP TS 23.304 [17].
- The ProSe Layer-2 Group ID of the target MC service group may be used by the ProSe layer as the target group info;
- The Groupcast mode 5G ProSe Direct Communication procedure in clause 6.4.2 of 3GPP TS 23.304 [17] is utilized for the establishment of off-network group communication and the following media plane traffic exchanges.
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7.6.2 Off-network private communication
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The procedures and information flows used in 3GPP TS 23.280 [3], 3GPP TS 23.379 [6], 3GPP TS 23.281 [4], and 3GPP TS 23.282 [5] are reused for off‑network private communication for MC service over 5G ProSe with following differences:
- PPPP (ProSe Per-Packet Priority) is replaced with PQI, as specified in 3GPP TS 23.304 [17].
- The ProSe discovery group ID is replaced with Application layer group ID which identifies a discovery group as specified in 3GPP TS 23.304 [17]. The Application layer group ID and the user info ID of the target MC service user are provisioned to the MC service client in the MC service user profile. The MC service client enables the ProSe layer to determine the IP address for the communication with the target MC service user by providing the Application layer group ID and user info ID of the target MC service user.
- Group Member Discovery procedure in 3GPP TS 23.304 [17] is utilized to enable for the call initiator to determine whether the called MC service user is in the proximity of the calling user prior to the establishment of an off-network private communication.
- The Unicast mode 5G ProSe Direct Communication procedure in 3GPP TS 23.304 [17] is utilized for the establishment of off-network private communication and the following media plane traffic exchanges.
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7.6.3 Use of 5G ProSe UE-to-network relay
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7.6.3.1 5G ProSe UE-to-network relay service authorization
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The MC service shall support the capability for 5G ProSe UE-to-network relay to restrict the relayed group communication on a per group basis by using the relay service codes corresponding to the group.
5G ProSe (as specified in 3GPP TS 23.304 [17]) supports layer 2 UE-to-network relay and layer 3 UE-to-network relay. The procedure defined in clause 10.5 of 3GPP TS 23.280 [3] applies with the following differences:
- 5G ProSe UE-to-network relay is provisioned that each relay service code is offering layer 2 or layer 3 UE-to-Network Relay service.
- 5G ProSe remote UE is provisioned that each relay service code is offering layer 2 or layer 3 UE-to-Network Relay service.
- 5G ProSe Layer-3 UE-to-network relay is provisioned with suitable relay service codes to support access to N3IWF for the case of 5G ProSe Layer-3 UE-to-network relay with the support of N3IWF.
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7.6.3.2 UE-to-network relay MC service
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The 5G ProSe UE-to-network relay provides a layer 2 or layer 3 routing service (as specified in 3GPP TS 23.304 [17]) for a 5G ProSe remote UE, when the MC service user on the 5G ProSe remote UE requires to access the MC service via a 5G ProSe UE-to-network relay.
The application layer signalling for the MC service user on a 5G ProSe remote UE using a 5G ProSe UE-to-network relay are identical to the application layer signalling for the MC service user on an on-network UE.
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7.7 MCVideo enhancement with ECN marking for L4S
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23.289
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7.7.1 General
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These clauses specify the procedure for the MCVideo communication (e.g., video pull from server) enhancement with ECN marking for L4S (L4S is defined in IETF RFC 9330 [24]).
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7.7.2 Information flows
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7.7.2.1 L4S feedback report
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Table 7.7.2.1-1 defines the L4S feedback report from MCVideo client to MCVideo server to provide DL L4S feedback information, and from the MCVideo server to the MCVideo client to provide UL L4S feedback information.
Table 7.7.2.1-1: L4S ECN feedback report
Information element
Status
Description
MCVideo ID
M
Identity of the MCVideo user
Media identifier
O
Identifies the communication, e.g. by identifying the media flow within a media multiplex, present only if media multiplexing
L4S information
M
The L4S ECN information reported related to DL congestion if it is sent from the MCVideo client to the MCVideo server, or related to the UL congestion if it is sent from the MCVideo server to the MCVideo client
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7.7.3 Procedures
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7.7.3.1 One-from-server video pull enhancement
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Procedure in figure 7.7.3.1-1 is the common signalling control plane procedures for the MCVideo communication enhancement with ECN marking for L4S capability.
Pre-condition:
1. The MCVideo server has already obtained the L4S handling capability from the MCVideo client 1.
Figure 7.7.3.1-1: One-from-server video pull enhancement with ECN marking for L4S capability
1-5. Same as step 1 to step 5 in clause 7.3.2.4.2 of 3GPP TS 23.281 [4].
6a. The MCVideo server may determine to utilize the 5GS L4S capabilities to obtain the congestion information to improve the downlink stream transmission control. The MCVideo server interacts with the 5GS to request the ECN marking for L4S as specified in 3GPP TS 23.502 [10].
6b. The 5GS starts to perform the ECN marking as specified in 3GPP TS 23.501 [7]. The MCVideo UE receives the DL media stream with ECN marking in the IP header which reflects the DL network congestion status.
6c. The MCVideo client, based on the DL ECN marking in the IP header, generates and sends the L4S feedback report towards the MCVideo server as described in IETF RFC 9330 [24].
7. The MCVideo server, based on step 6b performs the DL media stream control, e.g., adjust the DL media packet sending rate.
NOTE: How the DL media packet sending rate is adapted is outside the scope of the present document.
8.-9. Step 8 and step 9 are same as step 6 and step 7 of clause 7.3.2.4.2 of 3GPP TS 23.281 [4], respectively.
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7.7.3.2 One-to-server- video push enhancement
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Figure 7.7.3.2-1 describes a common signalling control plane procedure for MC video client initiating the establishment of video push where the push feature is enhanced via ECN marking for L4S capability. Precondition: - The MCVideo server has already obtained the L4S handling capability from the MCVideo client 1. Figure 7.7.3.2-1: One-to-server video push with ECN marking for L4S capability 1.-5. Same as steps 1 to step 5 of 3GPP TS 23.281 [4] clause 7.4.2.4.2. 6. The MCVideo server may determine to utilize the 5GS L4S capability to obtain the congestion information to improve the UL stream transmission control. For this purpose, the MCVideo server interacts with the 5GS to request the ECN marking for L4S as specified in 3GPP TS 23.502 [10]. 7. The 5GS starts to perform the ECN marking as specified in 3GPP TS 23.501 [7]. The 5GS receives the UL media stream with ECN marking in the IP header which reflects the UL network congestion status. The 5GS exposes the congestion information to the MCVideo server as specified in 3GPP TS 23.501 [7]. 8. Based on the UL ECN marking in the IP header, the MCVideo server generates and sends the L4S feedback report towards the MCVideo client as described in IETF RFC 9330 [24]. 9. Based on the L4S feedback report, the MCVideo performs UL stream control, e.g., adjust the UL media packet sending rate. NOTE: How the UL media packet sending rate is adapted is outside the scope of the present document. 10.-11. Step 10 and step 11 are same as step 6 and step 7 f clause 7.4.7.4.2 of 3GPP TS 23.281 [4], respectively. Annex A (normative): Configuration data for MC services using 5GS A.1 General This Annex provides information about the static data needed for configuration of MC services encompassing the following category: - Initial MC service UE configuration data (see subclause A.2). - MC service user profile configuration data (see subclause A.3). - MC service group configuration data (see subclause A.4). - MC service configuration data (see subclause A.5). - Location user profile configuration data (see subclause A.6) - Initial recording admin UE and/ or replay UE configuration data (see subclause A.7). - ACM client user profile configuration data (see subclause A.8). Each parameter that can be configured online shall only be configured through one online reference point. Each parameter that can be configured offline shall only be configured through one offline reference point. The most recent configuration data made available to the MC service UE shall always overwrite previous configuration data, irrespective of whether the configuration data was provided via the online or offline mechanism. A.2 Initial MC service UE configuration data The configuration data defined in 3GPP TS 23.280 [3] in Annex A.6 apply, with the following exceptions: - DNN and the corresponding DN credentials instead of the PDN credentials shall be used, along with the S-NSSAI to be used for each MC service; - The Default Configured slice(s) information may be pre-configured at the MC service UE and be utilized as defined in 3GPP TS 23.501 [7]; NOTE: It is up to UE implementation, whether an S-NSSAI value is included in the Requested NSSAI. If not included, the corresponding MC traffic could be handled according to the URSP rule with the "match all" Traffic descriptor. - Additional MC network slice identification information may be provided for each S-NSSAI, e.g., the corresponding network slice credentials. A.3 MC service user profile configuration data The configuration data defined in 3GPP TS 23.379 [6] in Annex A.3, apply, with the following exceptions: - "MCPTT group ID" instead of the "ProSe discovery group ID" shall be used; The configuration data defined in 3GPP TS 23.281 [4] in Annex A.3, apply, with the following exceptions: - "MCVideo group ID" instead of the "ProSe discovery group ID" shall be used; The configuration data defined in 3GPP TS 23.282 [5] in Annex A.3, apply, with the following exceptions: - "MCData group ID" instead of the "Discovery group ID" shall be used; A.4 MC service group configuration data The configuration data defined in 3GPP TS 23.379 [6] in Annex A.4, 3GPP TS 23.281 [4] in Annex A.4, 3GPP TS 23.282 [5] in Annex A.4, apply, with the following exceptions: - " Default PQI (as specified in 3GPP TS 23.304 [17]) values" instead of "Default ProSe Per-Packet priority (as specified in 3GPP TS 23.303 [7]) values" shall be used; A.5 MC service configuration data The configuration data defined in 3GPP TS 23.379 [6] in Annex A.5, 3GPP TS 23.281 [4] in Annex A.5, 3GPP TS 23.282 [5] in Annex A.5, apply, with the following exceptions: - "Default PQI (as specified in 3GPP TS 23.304 [17]) values" instead of "Default ProSe Per-Packet priority (as specified in 3GPP TS 23.303 [7]) values" shall be used; A.6 Location user profile configuration data The location user profile configuration data defined in A.8 of 3GPP TS 23.280 [3] applies. A.7 Initial recording admin UE and/or replay UE configuration data The initial recording admin and replay UE configuration data defined in A.10 of 3GPP TS 23.280 [6] is applicable with the following exceptions: - DNN and the corresponding PDU access credentials shall be used instead of APN and PDN access credentials for configurations related to 3GPP connectivity information. - The default configured slice(s) information may be pre-configured at the MC service UE and be utilized as defined in 3GPP TS 23.501 [7]. A.8 ACM client user profile configuration data The ACM client user profile configuration data defined in 3GPP TS 23.280 [6] clause A.9 is applicable. Annex B (informative): Service continuity for MC service B.1 Service continuity between on-network MC service and UE-to-network relay MC service This annex describes how 3GPP TS 23.237 [18] mechanisms for IMS service continuity can be used to provide service continuity between on-network MC service and UE-to-network relay MC service. Figure B.1-1: Service continuity from on-network to UE-to-network relay The details of MBS interfaces are specified in clause 4.7. The interaction between SIP core and 5GC is specified in 3GPP TS 23.228 [2]. The procedure for service continuity from on-network MCPTT service to UE-to-network relay MCPTT service is described in Annex B of 3GPP TS 23.280 [3]. As illustrated in figure B.1-1: - Initially UE-1 has a direct connection to the network via 5GS (on-network MCPTT service). It is registered with the SIP core and is engaged in a SIP session with the MCPTT Application Server (solid lines SIP-1 and MC[service]-1 in figure B.1-1). - When UE-1 realises that it is losing connection to the network, or after the connection to the network has been lost, UE-1 discovers a UE-to-network relay (UE-R) and establishes a PC5 connection with UE-R. UE-1 registers with the SIP core over the target access leg and enters UE-to-network relay MC service by transferring the media streams over the target leg (dashed lines SIP-1 and MC[service]-1 in figure B.1-1). - The SIP session is anchored at a Service Centralisation and Continuity Application Server (SCC AS) before and after the handover, as described in 3GPP TS 23.237 [18]. Annex C (informative): Change history Change history Date Meeting TDoc CR Rev Cat Subject/Comment New version 2020-10 SA6#39-BIS-e Initial version. 0.0.0 2020-10 Implemented the following pCRs approved in SA6#39-BIS-e: S6-201792, S6-201981. 0.1.0 2020-11 SA6#40-e Implemented the following pCRs approved in SA6#40-e: S6-202308, S6-202309. 0.2.0 2021-01 SA6#41-e Implemented the following pCRs approved in SA6#41-e: S6-210197, S6-210199, S6-210214,S6-210216, S6-210217, S6-210218, S6-210219, S6-210333 0.3.0 2021-03 SA6#42-e Implemented the following pCRs approved in SA6#42-e: S6-210553, S6-210650, S6-210686 0.4.0 2021-03 SA#91-e SP-210176 Presentation for information at SA#91-e 1.0.0 2021-04 SA6#42-BIS-e Implemented the following pCRs approved in SA6#42-BIS-e: S6-210953, S6-210954 1.1.0 2021-05 Editorial corrections 1.1.1 2021-06 SA6#43-e Implemented the following pCRs approved in SA6#43-e: S6-211405, S6-211407, S6-211408, S6-211409, S6-211410 1.2.0 2021-06 SA#92-e SP-210473 Presentation for approval at SA#92-e 2.0.0 2021-06 SA#92-e SP-210473 MCC Editorial update for publication after TSG SA approval (SA#92) 17.0.0 2021-12 SA#94-e SP-211526 0013 1 F Corrections on network slicing 17.1.0 2021-12 SA#94-e SP-211530 0004 2 B MBS session release 18.0.0 2021-12 SA#94-e SP-211530 0007 2 B MC service media distribution over 5G MBS 18.0.0 2021-12 SA#94-e SP-211530 0008 1 B Call connect and disconnect over 5G MBS in MCPTT context 18.0.0 2021-12 SA#94-e SP-211530 0009 1 B Call connect and disconnect over 5G MBS in MCVideo context 18.0.0 2021-12 SA#94-e SP-211530 0010 1 B Service continuity between 5G MBS delivery and unicast delivery 18.0.0 2021-12 SA#94-e SP-211530 0011 2 B Architecture for MC/5MBS 18.0.0 2021-12 SA#94-e SP-211530 0012 3 B MBS architecture and functionalities 18.0.0 2021-12 SA#94-e SP-211530 0014 1 B Request for creation of MBS resources for group communications 18.0.0 2021-12 SA#94-e SP-211530 0016 B Request for updating MBS resources for group communications 18.0.0 2021-12 SA#94-e SP-211530 0017 1 B Request to activate or de-activate multicast MBS sessions 18.0.0 2021-12 SA#94-e SP-211530 0020 1 B MC service control signalling over 5G MBS 18.0.0 2021-12 SA#94-e SP-211530 0021 2 B Multi-server MBS session coordination 18.0.0 2021-12 SA#94-e SP-211530 0022 2 B Procedure for inter-system switching between eMBMS and 5G MBS 18.0.0 2022-03 SA#95-e SP-220107 0023 1 C Alignment of section 4.7 of 23.289 with latest version of 23.247 (v 17.1.0) 18.1.0 2022-03 SA#95-e SP-220107 0024 1 F Updating aspects related to the MBS resources update 18.1.0 2022-03 SA#95-e SP-220107 0025 1 F Alignment of some information flows within TS 23.289 18.1.0 2022-03 SA#95-e SP-220108 0026 1 B Use of 5G ProSe UE-to-network relay service for MC services 18.1.0 2022-03 SA#95-e SP-220107 0027 1 F Updating aspects and terminology related to MBS session creation and MC traffic transmission 18.1.0 2022-03 SA#95-e SP-220107 0028 1 F Updating the MBS session release related terminology and aspects 18.1.0 2022-03 SA#95-e SP-220107 0029 1 F Minor corrections to the procedures related to MBS session creation 18.1.0 2022-03 SA#95-e SP-220107 0030 B EPS interworking requirements 18.1.0 2022-03 SA#95-e SP-220107 0031 B MC services over 5GS supporting EPS interworking 18.1.0 2022-03 SA#95-e SP-220107 0032 B Network notifications for EPS interworking related events 18.1.0 2022-03 SA#95-e SP-220107 0033 C Update to inter-system switching between 5G MBS and eMBMS procedures 18.1.0 2022-03 SA#95-e SP-220107 0034 2 C Clean up of EPS-5GMBS interworking 18.1.0 2022-03 SA#95-e SP-220107 0035 2 C Clean up of switching between unicast and 5G MBS, between LTE eMBMS and 5G MBS 18.1.0 2022-03 SA#95-e SP-220107 0036 1 C Enhanced MCPTT group call setup procedure with 5MBS session 18.1.0 2022-03 SA#95-e SP-220107 0037 1 C Information flows for media distribution over 5MBS 18.1.0 2022-03 SA#95-e SP-220107 0038 1 C Description of 5G MBS usage for MCData 18.1.0 2022-03 SA#95-e SP-220107 0039 1 C Updates to usage of 5MBS for MCVideo 18.1.0 2022-03 SA#95-e SP-220107 0040 1 F Corrections to align with SA2 5G MBS specification 18.1.0 2022-03 SA#95-e SP-220107 0041 1 C Usage of FEC capabilities 18.1.0 2022-03 SA#95-e SP-220108 0042 1 B Architectural model over 5G ProSe 18.1.0 2022-03 SA#95-e SP-220108 0043 1 B Off-network functional model over 5G ProSe 18.1.0 2022-03 SA#95-e SP-220108 0044 B Off network group communication for MC service 18.1.0 2022-03 SA#95-e SP-220108 0045 1 B Off network private communication for MC service 18.1.0 2022-03 SA#95-e SP-220108 0046 1 B 5G ProSe UE-to-network relay for MC service 18.1.0 2022-03 SA#95-e SP-220108 0047 2 B Service continuity with a 5G ProSe UE-to-network relay for MBMS 18.1.0 2022-06 SA#96 SP-220480 0048 1 C Clarifications related to multi carrier support for MBS session creation and announcement 18.2.0 2022-06 SA#96 SP-220480 0049 1 B Clarifications related to multi carrier support for MBS session update 18.2.0 2022-06 SA#96 SP-220479 0050 1 C Update to service continuity procedure from an MBS session to 5G ProSe UE-to-network relay 18.2.0 2022-06 SA#96 SP-220479 0051 1 C Update to service continuity procedure from 5G ProSe UE-to-network relay to an MBS session 18.2.0 2022-06 SA#96 SP-220479 0052 1 B Requirements related to 5G ProSe Layer-3 relaying via N3IWF 18.2.0 2022-06 SA#96 SP-220476 0053 F Corrections to the use of MC service system 18.2.0 2022-06 SA#96 SP-220480 0054 F Corrections in MBS UE session join notification 18.2.0 2022-06 SA#96 SP-220480 0055 D Small editorial corrections 18.2.0 2022-06 SA#96 SP-220480 0056 1 B Update to 5G MBS service announcement 18.2.0 2022-06 SA#96 SP-220480 0057 1 F Update to broadcast MBS sessions monitoring and the reception quality of the MBS session 18.2.0 2022-06 SA#96 SP-220480 0058 F Resolve the EN about architecture and reference alignment in clause 4.7.1 18.2.0 2022-06 SA#96 SP-220480 0059 1 C Resolve the EN in clause 5.2 18.2.0 2022-06 SA#96 SP-220480 0060 1 C Resolve the EN on SA4 aspect 18.2.0 2022-06 SA#96 SP-220480 0064 3 F Architectural and functional model for 5G MBS mission critical UE 18.2.0 2022-06 SA#96 SP-220480 0067 1 F Rename "MBS service announcement" to "MBS session announcement" for self consistency in the spec 18.2.0 2022-06 SA#96 SP-220480 0068 2 B Group communication connect and disconnect over 5G MBS for MCData 18.2.0 2022-06 SA#96 SP-220475 0069 1 A Updating network slicing requirements for MC services 18.2.0 2022-06 SA#96 SP-220480 0071 1 C Including MBS FSA ID into the location information report 18.2.0 2022-06 SA#96 SP-220480 0073 C Removing unicast bearer status from eMBMS bearer information 18.2.0 2022-06 SA#96 SP-220480 0074 F Add MBS service announcement acknowledge 18.2.0 2022-06 SA#96 SP-220480 0075 1 F Clarification on GC1 in clause 4.7 18.2.0 2022-06 SA#96 SP-220480 0076 1 F Format corrections to clause 7.3.2.9 18.2.0 2022-06 SA#96 SP-220480 0077 1 F UE session join notification message name alignment 18.2.0 2022-06 SA#96 SP-220480 0078 1 F Update to de-announcement 18.2.0 2022-09 SA#97-e SP-220929 0079 F Various textual fixes in 23.289 v 18.2.0 18.3.0 2022-09 SA#97-e SP-220929 0080 1 C Updating the general architecture of MBS system 18.3.0 2022-09 SA#97-e SP-220929 0081 1 F Clarification on MBS capable RAT usage 18.3.0 2022-09 SA#97-e SP-220929 0082 1 F Adding SCEF+NEF deployment option 18.3.0 2022-09 SA#97-e SP-220929 0083 2 F Clarification on MBS QoS 18.3.0 2022-09 SA#97-e SP-220929 0084 2 F Corrections to inter-RAT change report via LMC and LMS 18.3.0 2022-09 SA#97-e SP-220929 0086 1 F Message name corrections to clause 7.3.3.6.2 18.3.0 2022-09 SA#97-e SP-220929 0087 F Configurations for MC over 5G Prose 18.3.0 2022-09 SA#97-e SP-220929 0088 1 F Clarifications on UE´s MBMS/MBS capabilities 18.3.0 2022-09 SA#97-e SP-220929 0089 1 F Adding references to 3GPP TS 26.502 18.3.0 2022-09 SA#97-e SP-220929 0090 1 C Correcting MBS session ID types 18.3.0 2022-09 SA#97-e SP-220929 0091 1 F Update the scope clause with reference to 5G network architecture specs 18.3.0 2022-12 SA#98-e SP-221248 0092 1 F N5 descriptions update for MBS 18.4.0 2022-12 SA#98-e SP-221248 0093 1 F Added additional subclause for switching from MBS session to unicast bearer for MCPTT 18.4.0 2022-12 SA#98-e SP-221248 0094 F Corrections to reference point usage in switching from MBS session to unicast bearer for MCData 18.4.0 2022-12 SA#98-e SP-221248 0095 F Title correction and use of group communication connect & disconnect clarification in MCData 18.4.0 2023-03 SA#99 SP-230291 0096 1 F MBS session identity corrections 18.5.0 2023-03 SA#99 SP-230291 0097 2 F Clarification on MBS service area in pre-conditions 18.5.0 2023-03 SA#99 SP-230291 0098 2 F Clarification on the unicast delivery stop after MBS delivery 18.5.0 2023-03 SA#99 SP-230291 0100 1 F Correction for usage of term MCX to MC service 18.5.0 2023-06 SA#100 SP-230703 0101 1 C Add 5G NR Cell Global Identifier (NCGI) to Location Information Element 18.6.0 2023-09 SA#101 SP-231006 0104 F Add 5G NR Cell Global Identifier (NCGI) to Location Information Element 18.7.0 2023-09 SA#101 SP-231006 0105 2 F Resolve the ENs about NPN utilization 18.7.0 2023-09 SA#101 SP-231006 0107 2 F Support of multicast MBS data reception in RRC inactive state 18.7.0 2023-12 SA#102 SP-231554 0108 1 F Update resources management procedures 19.0.0 2023-12 SA#102 SP-231554 0109 1 F Including clarification related to the IE of resource management 19.0.0 2024-03 SA#103 SP-231554 0117 A Alignments of 23.289 Rel-19 with other specs 19.1.0 2024-06 SA#104 SP-240759 0119 1 A Including NID in the MBS session announcement 19.2.0 2024-06 SA#104 SP-240767 0120 2 B UE to UE single hop relay 19.2.0 2024-06 SA#104 SP-240768 0121 F Add the FRMCS requirements reference 19.2.0 2024-06 SA#104 SP-240767 0122 1 F Correction of the reference in the scope clause 19.2.0 2024-06 SA#104 SP-240767 0123 B 5G MC interworking with legacy system 19.2.0 2024-06 SA#104 SP-240767 0124 1 D Corrections of the NOTE number 19.2.0 2024-09 SA#105 SP-241223 0125 1 B Support of exposing network congestion information for MC services 19.3.0 2024-09 SA#105 SP-241223 0127 1 B Enhancement to MCVideo with 5G network capabilities 19.3.0 2024-12 SA#106 SP-241722 0126 3 B Location reporting information obtained from the PLMN operator (5G) 19.4.0 2024-12 SA#106 SP-241708 0129 3 A MBS service area handling 19.4.0 2024-12 SA#106 SP-241722 0130 2 F Corrections in clauses related to ECN marking for L4S 19.4.0 2024-12 SA#106 SP-241722 0131 1 B MCVideo push enhancement via ECN marking for L4S 19.4.0 2024-12 SA#106 SP-241723 0132 B Support of MCGWUE over 5GS 19.4.0 2024-12 SA#106 SP-241717 0133 1 B Support of MC services over NTN 19.4.0 2024-12 SA#106 SP-241717 0134 1 B Business agreements related to NTN 19.4.0 2024-12 SA#106 SP-241722 0136 1 B Include the support of MC recording and replay and ACM for 5GS 19.4.0 2024-12 SA#106 SP-241708 0138 A Correction of reference points in 23.289 Rel-19 19.4.0 2024-12 SA#106 SP-241707 0140 2 A Correction of a reference in clause 7.3.3.1.3 19.4.0 2024-12 SA#106 SP-241707 0141 2 C Support of provisioning MBS assistance information to the 5GC 19.4.0 2025-03 SA#107 SP-250211 0144 1 F Some corrections to 23.289 19.5.0 2025-03 SA#107 SP-250205 0145 F Minor correction in clause 4.12.1 19.5.0
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23.304
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1 Scope
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The present document specifies the Stage 2 of the Proximity based Services (ProSe) features in 5GS. 5G ProSe features consist of: 5G ProSe Direct Discovery, 5G ProSe Direct Communication, 5G ProSe UE-to-Network Relay, 5G ProSe UE-to-UE Relay and 5G ProSe Intermediate UE-to-Network Relay.
5G ProSe Direct Discovery identifies that 5G ProSe-enabled UEs are in proximity using NR.
5G ProSe Direct Communication enables establishment of communication paths between two or more 5G ProSe-enabled UEs that are in direct communication range using NR.
5G ProSe UE-to-Network Relay enables indirect Layer-2 and Layer-3 single-hop communication and Layer-3 multi-hop communication between the 5G network and 5G ProSe-enabled UEs (e.g. for 5G ProSe-enabled UEs that are out of coverage of the network).
Editor's note: Support for Multi-hop Layer-2 UE-to-Network relaying will be aligned with RAN WGs' progress/decision.
5G ProSe UE-to-UE Relay enables indirect Layer-2 and Layer-3 single-hop communication and Layer-3 multi-hop communication between two 5G ProSe End UEs.
5G ProSe Intermediate UE-to-Network Relay enables Layer-3 multi-hop communication between a 5G Remote UE and a 5G ProSe UE-to-Network Relay.
Security aspects of ProSe in 5GS are defined in TS 33.503 [29].
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a8d70e48ab373cc561a495222059d495
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23.304
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2 References
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The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or non‑specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 23.287: "Architecture enhancements for 5G System (5GS) to support Vehicle-to-Everything (V2X) services".
[3] 3GPP TS 23.303: "Proximity-based services (ProSe); Stage 2".
[4] 3GPP TS 23.501: "System Architecture for the 5G System; Stage 2".
[5] 3GPP TS 23.502: "Procedures for the 5G System (5GS); Stage 2".
[6] 3GPP TS 22.261: "Service requirements for next generation new services and markets; Stage 1".
[7] 3GPP TS 22.278: "Service requirements for the Evolved Packet System (EPS)".
[8] 3GPP TS 23.288: "Architecture enhancements for 5G System (5GS) to support network data analytics services".
[9] 3GPP TS 23.503: "Policy and Charging Control Framework for the 5G System".
[10] Void.
[11] 3GPP TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2".
[12] 3GPP TS 38.300: "NR; NR and NG-RAN Overall Description; Stage 2".
[13] 3GPP TS 38.304: "NR; User Equipment (UE) procedures in idle mode".
[14] 3GPP TS 23.122: "Non-Access-Stratum (NAS) functions related to Mobile Station in idle mode".
[15] 3GPP TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification".
[16] 3GPP TS 38.331: "NR; Radio Resource Control (RRC); Protocol Specification".
[17] IETF RFC 4862: "IPv6 Stateless Address Autoconfiguration".
[18] IETF RFC 3927: "Dynamic Configuration of IPv4 Link-Local Addresses".
[19] IETF RFC 826: "An Ethernet Address Resolution Protocol".
[20] Void.
[21] 3GPP TR 23.752: "Study on system enhancement for Proximity based Services (ProSe) in the 5G System (5GS)".
[22] 3GPP TS 32.277: "Proximity-based Services (ProSe) charging".
[23] 3GPP TS 24.554: "Proximity-services (ProSe) in 5G System (5GS) protocol aspects; Stage 3".
[24] IETF RFC 2131: "Dynamic Host Configuration Protocol".
[25] IETF RFC 4039: "Rapid Commit Option for the Dynamic Host Configuration Protocol version 4 (DHCPv4)".
[26] Void.
[27] Void.
[28] 3GPP TS 38.351: "NR; Sidelink Adaptation Layer Protocol".
[29] 3GPP TS 33.503: "Security Aspects of Proximity based Services (ProSe) in the 5G System (5GS)".
[30] 3GPP TS 29.500: "5G System; Technical Realization of Service Based Architecture; Stage 3".
[31] 3GPP TS 23.167: "3rd Generation Partnership Project; Technical Specification Group Services and Systems Aspects; IP Multimedia Subsystem (IMS) emergency sessions".
[32] 3GPP TS 23.041: "Technical realization of Cell Broadcast Service (CBS)".
[33] 3GPP TS 22.268: "Public Warning System (PWS) requirements".
[34] 3GPP TS 38.413: "NG-RAN; NG Application Protocol (NGAP)".
[35] IETF RFC 7181: "The Optimized Link State Routing Protocol Version 2 (OLSRv2)".
[36] IETF RFC 6130: "Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP)".
[37] IETF RFC 5444: "Generalized Mobile Ad Hoc Network (MANET) Packet/Message Format".
[38] 3GPP TS 24.501: "Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3".
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3 Definitions of terms and abbreviations
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3.1 Terms
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For the purposes of the present document, the terms given in TR 21.905 [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].
5G ProSe-enabled UE: A UE that supports 5G ProSe requirements and associated procedures.
5G ProSe Direct Discovery: A procedure employed by a 5G ProSe-enabled UE to discover other 5G ProSe-enabled UEs in its vicinity based on direct radio transmissions between the two UEs with NR technology.
5G ProSe Direct Communication: A communication between two or more UEs in proximity that are 5G ProSe-enabled, by means of user plane transmission using NR technology via a path not traversing any network node.
5G ProSe UE-to-Network Relay: A 5G ProSe-enabled UE that provides functionality to support connectivity to the network for 5G ProSe Remote UE(s).
5G ProSe Intermediate UE-to-Network Relay: A 5G ProSe-enabled UE that provides functionality to support connectivity to the network for 5G ProSe Remote UE(s) by using the PC5 reference point with other 5G ProSe-enabled UEs. The 5G ProSe Intermediate UE-to-Network Relay is located on the path between 5G ProSe Remote UE and 5G ProSe UE-to-Network Relay.
Editor's note: Aspects on Multi-hop Layer-2 UE-to-Network relaying (e.g. terms, functionalities, etc.) will be aligned with RAN WGs' progress/decision.
5G ProSe Remote UE: A 5G ProSe-enabled UE that communicates with a DN via zero or more 5G ProSe Intermediate UE-to-Network Relay(s) and a 5G ProSe UE-to-Network Relay.
5G ProSe UE-to-UE Relay: A 5G ProSe-enabled UE that provides functionality to support connectivity between 5G ProSe End UEs.
5G ProSe End UE: A 5G ProSe-enabled UE that connects with another 5G ProSe-enabled UE(s) via one or more 5G ProSe UE-to-UE Relay(s).
Application Layer ID: An identifier identifying a 5G ProSe-enabled UE within the context of a specific application. The format of this identifier is outside the scope of 3GPP.
Direct Network Communication: One mode of network communication, where there is no 5G ProSe UE-to-Network Relay between a UE and the 5G network.
Indirect Network Communication: One mode of network communication, where there is a 5G ProSe UE-to-Network Relay between a UE and the 5G network.
Member ID: An identifier uniquely identifying a member in the Application Layer managed group and that is managed by the ProSe application layer.
Mode of communication: Mode of communication to be used by the 5G ProSe-enabled UE over PC5 reference point, i.e. broadcast mode, groupcast mode or unicast mode.
Open ProSe Discovery: ProSe Direct Discovery without explicit permission from the 5G ProSe-enabled UE being discovered, according to TS 22.278 [7].
ProSe identifier: A globally unique identifier used to identify the ProSe Application associated with the ProSe operation in 5G ProSe Direct Discovery and 5G ProSe Direct Communication. In this Release, the "Application ID" defined in TS 23.303 [3] can be used as the ProSe identifier in 5G ProSe Direct Discovery and in a consequent 5G ProSe Direct Communication.
Restricted ProSe Discovery: ProSe Direct Discovery that only takes place with explicit permission from the 5G ProSe-enabled UE being discovered, according to TS 22.278 [7].
Relay Service Code: A Relay Service Code is used for the case of UE-to-Network Relay as well as for the case of UE-to-UE Relay. The definition for the case of UE-to-Network Relay is in TS 23.303 [3]. For the case of UE-to-UE Relay, the Relay Service Code is used to identify a connectivity service the 5G ProSe UE-to-UE Relay provides and the authorized users the 5G ProSe UE-to-UE Relay would offer service to. The definition of values of Relay Service Code for the case of UE-to-UE Relay is out of scope of this specification.
User Info ID: The User Info ID is configured for Model A or Model B Group Member Discovery, 5G ProSe UE-to-Network Relay Discovery and 5G ProSe UE-to-UE Relay Discovery, either for public safety or commercial applications based on the policy of the HPLMN or via the ProSe application server that allocates it. The definition of values of User Info ID is out of scope of this specification.
For the purposes of the present document, the following term and definition given in TS 23.303 [3] apply:
Application Layer Group ID
Destination Layer-2 ID
Discovery Entry ID
Discovery Filter
Discovery Query Filter
Discovery Response Filter
Geographical Area
Local PLMN
Model A
Model B
Metadata Index Mask
ProSe Application ID
ProSe Application Code
ProSe Application Mask
ProSe Query Code
ProSe Response Code
ProSe Restricted Code
ProSe Restricted Code Prefix
ProSe Restricted Code Suffix
ProSe Discovery UE ID
ProSe Layer-2 Group ID
Restricted ProSe Application User ID
Source Layer-2 ID
For the purposes of the present document, the following term and definition given in TS 23.287 [2] apply:
NR Tx Profile
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3.2 Abbreviations
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For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905 [1].
5G DDNMF 5G Direct Discovery Name Management Function
AS layer Access Stratum layer
NCGI NR Cell Global ID
PDUID ProSe Discovery UE ID
PFI PC5 QoS Flow Identifier
PQI PC5 5QI
ProSe Proximity based Services
RPAUID Restricted ProSe Application User ID
RSC Relay Service Code
RSD Rule Selection Descriptor
TAI Tracking Area Identity
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4 Architecture model and concepts
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4.1 General concept
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Proximity based Services (ProSe) are services that can be provided by the 5GS based on UEs being in proximity to each other.
The 5GS enablers for ProSe include the following functions:
- 5G ProSe Direct Discovery;
- 5G ProSe Direct Communication;
- 5G ProSe UE-to-Network Relay;
- 5G ProSe Intermediate UE-to-Network Relay;
- 5G ProSe UE-to-UE Relay.
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4.2 Architectural reference model
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4.2.1 Non-roaming reference architecture
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Figure 4.2.1-1 shows the high-level view of the non-roaming 5G System architecture for Proximity-based Services (ProSe) with service-based interfaces within the Control Plane. In this figure, UE A and UE B use a subscription of the same PLMN.
Figure 4.2.1-1: Non-roaming 5G System architecture for Proximity-based Services
Figure 4.2.1-2 shows the high-level view of the non-roaming 5G System architecture for Proximity-based Services (ProSe) in reference point representation. In this figure, UE A and UE B use a subscription of the same PLMN.
Figure 4.2.1-2: Non-roaming 5G System architecture for Proximity-based Services in reference point representation
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4.2.2 Roaming reference architecture
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Figure 4.2.2-1 shows the high-level view of the roaming 5G System architecture for Proximity-based Services (ProSe) with service-based interfaces within the Control Plane. In the figure, UE A uses a subscription of HPLMN.
Figure 4.2.2-1: Roaming 5G System architecture for Proximity-based Services
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4.2.3 Inter-PLMN reference architecture
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The following figure 4.2.3-1 shows the high level view of the non-roaming inter-PLMN architecture with service-based interfaces within the Control Plane. In this figure, PLMN A is the HPLMN of UE A and PLMN B is the HPLMN of UE B.
Figure 4.2.3-1: Non-roaming Inter-PLMN 5G System architecture for Proximity-based Services
Figure 4.2.3-2 shows the high level view of the roaming architecture with service-based interfaces within the Control Plane. In this figure, UE A uses a subscription of PLMN A and UE B uses a subscription of PLMN B; UE A is roaming in PLMN C while UE B is not roaming.
Figure 4.2.3-2: Roaming Inter-PLMN 5G System architecture for Proximity-based Services
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4.2.4 AF-based service parameter provisioning
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The 5G System provides NEF services to enable communication between NFs in the PLMN and a ProSe Application Server. Figure 4.2.4-1 shows the high level view of AF-based service parameter provisioning for 5G ProSe communications. The ProSe Application Server may provide ProSe service parameters to the PLMN via NEF. The NEF stores the ProSe service parameters in the UDR.
Figure 4.2.4-1: 5G System architecture for AF-based service parameter provisioning for 5G ProSe communications
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4.2.5 Reference points
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PC1: The reference point between the ProSe application in the UE and in the ProSe Application Server. It is used to define application level signalling requirements. This reference point is not specified in this release of the specification.
PC3a: The reference point between the UE and the 5G DDNMF. PC3a relies on 5GC user plane for transport (i.e. an "over IP" reference point). It is used to authorise 5G ProSe Direct Discovery request and perform allocation of ProSe Application Codes / ProSe Restricted Codes corresponding to ProSe Application Identities used for 5G ProSe Direct Discovery.
PC5: The reference point between ProSe-enabled UEs used for control and user plane for 5G ProSe Direct Discovery, 5G ProSe Direct Communication, 5G ProSe UE-to-Network Relay, 5G ProSe Intermediate UE-to-Network Relay and 5G ProSe UE-to-UE Relay.
PC8: The reference point between the UE and the 5G ProSe Key Management Function (5G PKMF). The details are defined in TS 33.503 [29].
Npc2: The reference point between the ProSe Application Server and the 5G DDNMF. It is used to define the interaction between ProSe Application Server and 5G DDNMF for 5G ProSe Direct Discovery.
Npc4: The reference point between the UDM and 5G DDNMF. It is used to provide subscription information in order to authorise 5G ProSe Direct Discovery request.
Npc6: The reference point between the 5G DDNMF in the HPLMN and the 5G DDNMF in a Local PLMN (5G ProSe Direct Discovery). This reference point is used for HPLMN control of ProSe service authorization.
Npc7: The reference point between the 5G DDNMF in the HPLMN and the 5G DDNMF in the VPLMN. It is used for HPLMN control of ProSe service authorization.
Npc8: The reference point between the PCF and the 5G DDNMF. It is used to define the interactions between the 5G DDNMF and the PCF to e.g. get a PDUID from the PCF.
Npc9: The reference point between the 5G PKMF of the 5G ProSe Remote UE and the 5G PKMF of the 5G ProSe UE-to-Network Relay and between the 5G PKMF of the 5G ProSe End UE and the 5G PKMF of the 5G ProSe UE-to-UE Relay. The details are defined in TS 33.503 [29].
Npc10: The reference point between the 5G PKMF and UDM. The details are specified in TS 33.503 [29].
Npc11: The reference point between the AUSF and Prose Anchor Function (PAnF). The details are specified in TS 33.503 [29].
Npc12: The reference point between the PAnF and UDM. The details are specified in TS 33.503 [29].
Npc13: The reference point between the SMF and PKMF. The details are specified in TS 33.503 [29].
Npc14: The reference point between the SMF and PAnF. The details are specified in TS 33.503 [29].
NOTE: Npc2, Npc4, Npc6, Npc7, Npc8, Npc9, Npc10, Npc11, Npc12, Npc13 and Npc14 show the interactions that exist between the NF services in the NFs. These reference points are realised by corresponding NF service-based interfaces and by specifying the identified consumer and producer NF service as well as their interaction in order to realize a particular system procedure.
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