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4.5.1 General
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The UAV is associated with the following identifiers in the 3GPP system.
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4.5.2 CAA-Level UAV Identity
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A UAV is assigned a CAA-level UAV Identity by functions in the aviation domain (e.g. USS). This assigned identity is used for Remote Identification and Tracking and to identify the UAV.
The UAV provides the CAA-level UAV Identity to the 3GPP system during UUAA procedures.
The CAA-level UAV Identity is used by the UAV as UAV identity in Remote Identification.
The aviation domain may allocate a new CAA-level UAV Identity for the UAV at any time. The new CAA-level UAV Identity may be provided to the UAV and 3GPP system during UAS related procedures.
NOTE: It is assumed that mechanisms are available to ensure privacy and protection (e.g. anti-spoofing) of the CAA-assigned UAV Identity when it is used for Remote Identification. Security solutions to provide such privacy are outside the scope of this specification.
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4.5.3 3GPP UAV ID
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A 3GPP UAV ID is associated to the UAV by the 3GPP system in the subscription information and is used by the 3GPP system to identify the UAV. GPSI in the format of External Identifier is used as the 3GPP UAV ID.
The USS stores the association of the CAA-level UAV ID (provided by the UAV or a new one allocated by the aviation domain) to the 3GPP UAV ID (which is provided during the UUAA procedure).
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5 Functional description and information flows
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5.1 Void
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5.2 UAV Authentication and Authorization
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5.2.1 UUAA Model
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The following applies for UUAA for a UAV:
- UUAA-MM is optional and performed at 5GS registration based on operator's policy. If required by the operator, UUAA-MM is performed if the UAV has an aerial UE subscription in the Access and Mobility Subscription Data and provides the CAA-Level UAV ID in the Registration Request message.
- UUAA-SM in 5GS is performed at PDU session establishment to a subscribed DNN applicable for UAS services if the UAV provides the CAA-Level UAV ID in the PDU Session Establishment Request message. Whether the DNN is applicable for UAS services is determined by the aerial service indication being set for the DNN in the Session Management Subscription Data.
- UUAA-SM in EPS is performed at PDN Connection Establishment when activating a PDN Connection to a subscribed APN applicable for UAS service if the UAV provides the CAA-Level UAV ID in the ESM container. Whether the APN is applicable for UAS services is determined by the aerial service indication being set for the corresponding DNN in the Session Management Subscription Data (fetched from UDM triggered by CAA-Level UAV ID being provided in request).
- UUAA-SM may be performed to re-authenticate the UAV or to reauthorize at PDU session modification or EPS bearer modification (e.g. in case of C2 authorization or flight plan authorization change) if the UE includes CAA-Level UAV ID and a UUAA Aviation Payload.
NOTE: If the network is configured to perform UUAA at registration, UAV has not provided CAA-Level UAV ID and the UE has aerial subscription, then the AMF can allow the UAV to register as a normal UE. If the network is configured to perform UUAA at PDU Session Establishment, the UE has not provided CAA-Level UAV ID and the SM subscription data indicates that UUAA-SM to be performed, the SMF rejects the PDU Session Establishment request.
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5.2.2 UUAA at Registration in 5GS (UUAA-MM)
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5.2.2.1 General
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The UUAA-MM procedure is optional and triggered for a UE that requires UAV authentication and authorization by a USS when registering with 5GS. The UUAA-MM procedure is triggered by the AMF. UUAA-MM is triggered during the UE Registration based on the local network policy, if the UE has an Aerial UE subscription with the 5GS and if the UE has provided the CAA-Level UAV ID of the UAV in the Registration Request, or when the USS that authenticated the UAV triggers a re-authentication.
The UE is authenticated and authorized by USS using a CAA-Level UAV ID and credentials associated to the CAA-Level UAV ID, different from the 3GPP subscription credentials (e.g. SUPI and credentials used for PLMN access). During UUAA-MM procedure, the AMF communicates with the USS via a UAS NF and forwards authentication messages transparently between the UE and UAS NF.
UAS NF stores the UAV UEs UUAA context after successful UUAA procedure. The UUAA context may be stored in the UDSF or may be stored locally in the UAS NF depending on deployments. The UAS NF shall also create an implicit subscription for notification towards the AMF after the successful UUAA procedure. This notification is used by the UAS NF to trigger re-authentication, update authorization data or revoke authorization of the UAV, upon receipt of such request from the USS.
Figure 5.2.2.1-1: UUAA in the context of the Registration procedure (UUAA-MM)
1. The UE sends a Registration request message and, if configured with one, it shall provide a CAA-level UAV ID of the UAV and optionally a USS address when registering for UAS services.
2. If primary authentication is required (e.g. if this is an initial Registration), AMF invokes it as described in step 9 in Figure 4.2.2.2.2-1 of TS 23.502 [3]. Subsequently AMF retrieves UE subscription data from UDM as described in step 14 in Figure 4.2.2.2.2-1 of TS 23.502 [3] - (not shown in the figure).
3. AMF shall determine whether UUAA-MM is required for the UAV. The AMF decides that UUAA is required if:
a) the UE has a valid Aerial UE subscription information;
b) UUAA is to be performed during Registration according to local operator policy;
c) there is no successful UUAA result from a previous UUAA-MM procedure;
d) the UE has provided a CAA-Level UAV ID.
AMF shall not perform UUAA-MM for non-3GPP access and shall ensure that the UE is not allowed to access any aerial services in non-3GPP access by rejecting PDU session establishment requests for aerial services (identified by DNN/S-NSSAI).
4. If AMF determines in step 3 that a UUAA-MM is to be performed, AMF shall include a pending UUAA-MM indication in the Registration Accept message. The AMF stores in the UE context that a UUAA is pending. The UE shall wait for completion of the UUAA-MM procedure without attempting to register for UAS services or to establish user plane connectivity to USS or UAV-C.
If AMF determines that UUAA is not to be performed during this Registration procedure, UUAA may be triggered during PDU Session Establishment later on.
If UUAA is configured in the AMF to be performed during 5GS registration and the UE has provided a CAA-Level UAV ID in the registration request in step 1, but the UE does not have an aerial subscription in the UE subscription data retrieved from the UDM in step 2, then the AMF rejects the registration with an indication informing no aerial subscription. This information indicates to the UAV of the reason for the rejection for aerial services and ensures that the UE is not allowed to access any aerial service.
If UAS services become enabled or disabled (e.g. because the aerial subscription becomes a part of the UE subscription data retrieved from UDM as described in clause 5.2.3.3.1 of TS 23.502 [3]) then AMF may trigger a UE Configuration Update procedure as described in clauses 4.5.1 and 4.2.4.2 of TS 23.502 [3] to notify the UE. The UE may initiate a mobility registration update procedure to get the UAS services after completion of the UE Configuration Update procedure.
If UUAA is configured in the AMF to be performed during 5GS registration, the UE did not provide a CAA-Level UAV ID in the registration request in step 1, but UE has aerial subscription in the UE subscription data retrieved from UDM in step 2, then the AMF accepts the registration and ensures that the UE is not allowed to access any aerial service by storing in the UE context that 'UUAA-MM has FAILED' and further rejecting PDU session establishment requests for aerial services (identified by DNN/S-NSSAI). At a later point in time, if the UE wants to use the aerial services by providing the CAA Level UAV ID later on via UUAA-MM procedure, then the UE shall first perform Mobility Registration Update as explained in clause 4.2.2.2.2 of TS 23.502 [3].
5. If UE indicates its support for Network Slice-Specific Authentication and Authorization (NSSAA) procedure in the UE MM Core Network Capability and if the UE includes Requested S-NSSAI in Registration Request which is subject to NSSAA, however, the Requested S-NSSAI has not been successfully authenticated, the NSSAA procedure is executed as described in clause 4.2.2.2.2 of TS 23.502 [3].
6. If required based on step 3 determination and if the S-NSSAI that is associated with the UAS services is part of the Allowed NSSAI, UUAA-MM procedure (see clause 5.2.2.2) is executed at this step. Once the UUAA-MM procedure is successfully completed for the UAV, the AMF stores a successful UUAA result and updates the UE context indicating that UUAA is no longer pending and the authorized CAA-Level UAV ID if provided by the USS. The USS may provide a new CAA-Level UAV ID as the authorized CAA-Level UAV ID. The AMF shall trigger a UE Configuration Update procedure (see TS 23.502 [3], clause 4.2.4.2) to deliver the UUAA result, the UUAA Authorization Payload containing UAV configuration and the authorized CAA-Level UAV ID if received from the USS to the UE.
NOTE 1: The UAV configuration is application layer information outside the scope of 3GPP.
If UUAA fails, based on local network policy, the AMF may decide to de-register the UE with an appropriate cause value in the De-Registration Request message, or keep the UE-registered with a failure UUAA result in UE context as described in step 7 of clause 5.2.2.2 and ensures that the UE is not allowed to access any aerial service based on the DNN/S-NSSAI value. If the UE is de-registered, the UE may re-attempt to re-register without including the CAA-level UAV ID.
NOTE 2: The security aspects for this procedure is defined in TS 33.256 [10].
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5.2.2.2 UUAA-MM Procedure
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Figure 5.2.2.2-1: UUAA-MM procedure
1. For a UE that requires UUAA or when triggered by re-authentication by USS, the AMF triggers a UUAA-MM procedure. If the UE does not have an Aerial subscription in the UE subscription data retrieved from the UDM, the AMF shall not trigger a UUAA-MM procedure.
2. AMF to UAS NF/NEF: The AMF invokes Nnef_Authentication_AuthenticateAuthorize Request message. For initial authentication, this shall include the GPSI and the CAA-Level UAV ID and may include USS address (e.g. FQDN), UUAA Aviation Payload if it was provided by the UE. For re-authentication triggered by AMF, this may not include the CAA-Level UAV ID. UAS NF resolves the USS address based on CAA-Level UAV ID or considers the pre-configured USS addresses per serving area based on the current location of the UAV or uses the provided USS address, as described in clause 4.4.2. In addition, the AMF may also include the User Location Information (e.g. Cell ID). The UAS NF should store the serving AMF ID.
The AMF identifies the UAS NF/NEF based on local configuration or by NF discovery procedure using DNN/S-NSSAI and/or UE provided identity e.g. USS address.
The AMF also provides a Notification Endpoint to the UAS NF/NEF, so that UAS NF/NEF can include this Notification Endpoint together with UUAA updated parameters, as shown in clause 5.2.4. By providing the Notification Endpoint, the AMF is implicitly subscribed to be notified of re-authentication, update authorization data or revocation of UAV from UAS NF/NEF, if the UUAA result is successful in step 5.
NOTE 1: The security aspects for this procedure is defined in TS 33.256 [10].
3. UAS NF/NEF to USS: Naf_Authentication_AuthenticateAuthorize Request message, shall include the GPSI and CAA-Level UAV ID and optionally UAV location obtained from AMF in step 2 e.g. to support geo-caging functionality. UAS NF/NEF may translate the Cell ID received as UAV location from AMF in step 2 into a corresponding geographic area and/or may further obtain the UE location information using Location Service Procedures as defined in TS 23.273 [8].
The UAS NF/NEF also provides a Notification Endpoint to the USS, so that USS can include this Notification Endpoint together with UUAA updated parameters, as shown in clause 5.2.4. By providing the Notification Endpoint, the UAS NF/NEF is implicitly subscribed to be notified of re-authentication, update authorization data or revocation of UAV from USS, if the UUAA result is successful in step 5.
4. [Conditional] Multiple round-trip messages as required by the authentication method used by USS. Naf_Authentication_AuthenticateAuthorize Response messages from USS shall include GPSI and shall include an authentication message based on authentication method used that is forwarded transparently to UE over NAS MM transport messages. The authentication message in step 4d may contain UUAA Aviation Payload required by the USS if it was not provided by the UE before.
5. USS to UAS NF/NEF: (final) Naf_Authentication_AuthenticateAuthorize Response message, shall include: GPSI, a UUAA result (success/failure) for the UAV and the UAS NF, may include an authorized/new CAA-Level UAV ID for the UAV and a UUAA Authorization Payload to the UAV (e.g. security info to be used to secure communications with USS) and a final authentication message (e.g. indicating success or failure and if the UUAA is for re-authentication, indicating whether the UAS service related network resource can be released in case of UUAA failure) based on authentication method used that is forwarded transparently to UE over NAS MM transport messages. The USS may send in the Naf_Authentication_AuthenticateAuthorize Response message the information about relevant USSs (i.e. a list of USS addresses, information about geographical area each of the USSs serve); the USS includes that information also inside the UUAA Authorization Payload for the UAV consumption.
6. UAS NF/NEF to AMF: (final) Nnef_Authentication_AuthenticateAuthorize Response message, forwards information received from USS in step 5. If UUAA for re-authentication failed and UAS NF/NEF received indication that the UAS service related network resource can be released in step 5, the UAS NF/NEF includes an indication that the PDU sessions associated with the "DNN(s) subject to aerial services" can be released.
7a. [Conditional] UAS NF/NEF to AMF: If UUAA-MM succeeded and UAS NF/NEF has not subscribed to AMF for the access and mobility information events before, UAS NF/NEF subscribes to AMF for the mobility event notification by sending Namf_EventExposure_Subscribe request with the mobility events as described in TS 23.502 [3], Table 5.2.2.3.1-1 with Event ID = Reachability Filter.
7b. [Conditional] UAS NF/NEF to AMF: If UUAA-MM failed and UAS NF/NEF has subscribed to AMF for the access and mobility information events earlier, UAS NF/NEF unsubscribes to AMF for the mobility event notification by sending Namf_EventExposure_Unsubscribe request with Subscription Correlation ID.
8a. [Conditional] AMF to UAS NF/NEF: The AMF acknowledges the subscription request from 7a by sending Namf_EventExposure_Subscribe response with Subscription Correlation ID.
8b. [Conditional] AMF to UAS NF/NEF: The AMF acknowledges the un-subscription request from 7b by sending Namf_EventExposure_Unsubscribe response.
9. AMF to UE: (final) NAS MM transport message forwarding authentication message from USS including authentication/authorization result (success/failure) and the UUAA Authorization Payload.
10. [Conditional] if UUAA-MM succeeded, AMF triggers a UE Configuration Update procedure to deliver to the UAV authorization information from USS, as described in clause 5.2.2.1.
11. [Conditional] If UUAA-MM fails during a Re-authentication and Re-authorization and there are PDU session(s) established using UAS services and the USS has indicated that the network resources can be released, AMF may trigger these PDU Sessions release. AMF identifies the relevant PDU session(s) for UAS services based on the DNN/S-NSSAI value of the PDU session.
NOTE 2: When the UUAA-MM fails during a Re-authentication and the USS has not indicated that the network resources can be released, the USS can initiate UUAA revocation as described in clause 5.2.7.
[Conditional] if UUAA-MM fails, based on network policy the AMF may trigger Network-initiated Deregistration procedure described (as specified in clause 4.2.2.3.3 of TS 23.502 [3]) and it shall include in the explicit De-Registration Request the appropriate rejection cause value.
If there is an AMF relocation for the UAV, the new serving AMF shall notify the UAS NF about the new AMF ID and the related CAA-level UAV ID using the existing AMF event notification service.
At any time after the initial registration, the USS (via UAS NF/NEF) or the AMF may initiate Re-authentication procedure for the UAV. For AMF initiated case the Re-authentication procedure shall start from step 2. USS initiated re-authentication procedure is described in clause 5.2.4.
If the UE is deregistered as per clause 4.2.2.3 of TS 23.502 [3], then the AMF shall unsubscribe to UAS NF and then UAS NF/NEF may clear the UUAA-MM context and update USS.
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5.2.3 UUAA At PDN Connection/PDU Session Establishment (UUAA-SM)
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5.2.3.1 General
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NOTE 1: The security aspects for this procedure is defined in TS 33.256 [10].
An UAV uses PDU Sessions or PDN Connections in the UE for connectivity with the USS and for connectivity with a networked UAV-C.
A networked UAV-C is a UE which uses existing procedures for establishing PDU Session or PDN Connection for communication with the USS/UTM and the procedures described in this clause do not apply to a networked UAV-C.
This clause describes procedure that applies both for 5GS and EPS, where PDU Session refers to 5GS and PDN Connection refers to EPS.
PDU Session(s)/PDN Connection(s) for UAS services shall only be established after a UAV has been authenticated and authorized by the USS. This may happen during UUAA-SM as described in this clause.
A UAV may use either a common or separate PDU Session/PDN connection for connectivity with the USS and a UAV-C.
When the UAV requests establishment of a PDU session/PDN connection, the PDU session/PDN Connection may require UUAA authorization of the UAV, subject to operator policy and regulatory requirements.
If the UAV uses the PDU session/PDN connection for C2 the PDU session is subject to C2 authorization as described in clause 5.2.5.
The PDU Session/PDN Connection is identified by the SMF/SMF+PGW-C as being for USS/C2 communication based on the aerial service indication set in the Session Management Subscription data for the DNN or DNN and S-NSSAI combination.
To subscribe to the PDU Session/PDN Connection Status Event, UAS NF/NEF determines the APN/DNN or DNN and S-NSSAI combination as below:
- The UAS NF/NEF may receive APN/DNN or DNN and S-NSSAI combination from the USS as specified in clause 4.15.3.2.3 of TS 23.502 [3];
- The UAS NF/NEF may map the AF-Identifier from the USS into APN/DNN or DNN and S-NSSAI combination based on local configuration as specified in clause 4.15.3.2.3 of TS 23.502 [3]; or
- The UAS NF/NEF may map the External Application Identifier from the USS into the APN/DNN or DNN and S-NSSAI combination based on local configuration.
NOTE 2: If the PDU session/PDN connection for C2 communication and the PDU session/PDN connection for USS communication are separate, different AF-Identifiers or External Application Identifiers can be used.
During the establishment or modification procedure of the PDU Session/PDN connection for C2 communication, the USS shall provide the 3GPP system with following information for enabling basic C2 communication between UAV and UAV-C:
- Traffic filters;
- QoS requirements.
The USS can enable/disable C2 communication between UAV and UAV-C necessary for services used during the flight operation at any point in time as described in clause 5.2.9.
UAS NF stores the UAV UEs UUAA context after successful UUAA-SM procedure. The UUAA context may be stored in the UDSF or may be stored locally in the UAS NF depending on deployments. The SMF shall subscribe for notifications from UAS NF which may be used to trigger re-authentication, update authorization data or revoke authorization of the UAV, upon receipt of such request from the USS.
Clause 5.2.3.2 defines the USS UAV Authorization/Authentication (UUAA) procedures at PDU Session Establishment in 5GS and clauses 5.2.3.3 and 5.2.3.4 are for the PDN Connection Establishment for EPS using the interworking functionality.
When the C2 authorization is revoked by the USS, the SMF or SMF+PGW-C shall release the PDU Session/PDN connection for C2 communication (in case separate PDU Sessions/PDN Connections are used), or disable C2 communication for the PDU Session/PDN connection (in case common PDU Session/PDN Connection is used), e.g. by removing the traffic filters for C2 communications and the QoS flow for C2 communication and informs the UE with a PDU session modification/bearer modification request.
When the UUAA is revoked by the USS, all UAV related PDU Session/PDN connections shall be released.
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5.2.3.2 USS UAV Authorization/Authentication (UUAA) during the PDU Session Establishment
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The USS UAV Authorization/Authentication (UUAA) is triggered by the SMF during the PDU Session Establishment, specified in TS 23.502 [3], clause 4.3.2.2 and additionally based on the SM subscription data obtained from UDM and the Service Level Device Identity provided by the UE in the PDU Session establishment request.
Figure 5.2.3.2 -1: UUAA during PDU Session Establishment
The procedure assumes that the UE/UAV has already registered on the AMF.
0. Steps 1 - 5 as in TS 23.502 [3] figure 4.3.2.2.1-1.
The UAV includes the Service Level Device Identity (e.g. the CAA-Level UAV ID of the UVA) and may include the Authentication Server Address (i.e. the USS address or the USS address for the corresponding geographical area based on the UAV current location) and optionally Authentication Data (i.e. the UUAA Aviation Payload) in the PDU Session Establishment request.
The SMF determines that it needs to invoke UAS NF/NEF service operation for UUAA Authentication/Authorization of the PDU session establishment request based on that the provided DNN/S-NSSAI combination is dedicated for aerial services (have aerial service indicator set) and that the Service Level Device Identity (CAA-Level-UAV ID) is included in the request. If the provided APN/DNN is dedicated for aerial services but Service Level Device Identity (CAA-Level UAV ID) is not provided, the SMF shall reject the establishment of the PDU Session and steps 1 - 9 are not performed.
The SMF identifies the UAS NF/NEF based on local configuration or by NF discovery procedure using DNN/S-NSSAI and/or UE provided identity e.g. USS address.
1. The SMF invokes Nnef_Authentication_AuthenticateAuthorize service operation, including the Service Level Device Identity (that contains the CAA-Level UAV ID of the UAV), DNN, S-NSSAI and may include the Authentication Server Address (i.e. the USS address) and the UUAA Aviation Payload if it was provided by the UE, GPSI, optionally UAV location, PEI if available and the UE IP Address if available. The UAV location is the User Location Information provided by the AMF (e.g. Cell ID). The UAS NF/NEF selects a USS based on either the Service Level Device Identity (i.e. CAA-Level UAV ID of the UAV) or the pre-configured USS addresses per serving area based on the current location of the UAV or the Authentication Server address (i.e. USS address) as described in clause 4.4.2.
SMF also provides a Notification Endpoint to the UAS NF/NEF, so that UAS NF/NEF can include this Notification Endpoint together with UUAA updated parameters, as shown in clause 5.2.4. By providing the Notification Endpoint, the SMF is implicitly subscribed to be notified of re-authentication, update authorization data or revocation of UAV from UAS NF/NEF, if the UUAA result is successful in step 4.
2. From UAS NF/NEF to USS: Naf_Authentication_AuthenticateAuthorize service operation forwarding the authentication request received information from the SMF. UAS NF may translate the Cell ID received as part of UAV location in the Nnef_Authentication_AuthenticateAuthorize request at step 1 into a corresponding geographic area and/or may further obtain the UE location information using Location Service Procedures as defined in TS 23.273 [8] and include them in the Naf_Authentication_AuthenticateAuthorize message towards the USS e.g. to support geo-caging functionality.
UAS NF/NEF also provides a Notification Endpoint to the USS, so that USS can include this Notification Endpoint together with UUAA updated parameters, as shown in clause 5.2.4. By providing the Notification Endpoint, the UAS NF/NEF is implicitly subscribed to be notified of re-authentication, update authorization data or revocation of UAV from USS, if the UUAA result is successful in step 4.
3. [Conditional] Multiple round-trip messages as required by the authentication method used by USS. This step is performed if the Naf_Authentication_AuthenticateAuthorize response messages from USS in step 3a does not contain a UUAA result (SUCCESS/FAILURE). Naf_Authentication_AuthenticateAuthorize response messages from USS shall include GPSI and shall include an authentication message based on authentication method used that is forwarded transparently to UE over NAS MM transport messages. The authentication message in step3e may contain UUAA Aviation Payload required by the USS if it was not provided by the UE before.
4. From USS to UAS NF/NEF: Naf_Authentication_AuthenticateAuthorize response.
The USS sends Naf_Authentication_AuthenticateAuthorize response to the UAS NF/NEF with the Authentication/Authorization result containing the UUAA result (SUCCESS/FAILURE) for the UAS NF and indication whether the UAS service related network resource can be released in the case of UUAA failure for re-authentication or re-authorization, optionally a Service Level Device Identity containing the authorized CAA-Level UAV ID, requested policy information and the UUAA Authorization Payload. The requested policy information from USS may contain a DN Authorization Profile Index and/or a DN authorized Session AMBR. The USS may include a new CAA-Level UAV ID as authorized CAA-Level UAV ID. The USS may send in the Naf_Authentication_AuthenticateAuthorize response the information about relevant USSs (i.e. a list of USS addresses and information about a geographical area each of the USSs serve); the USS includes that information also inside the UUAA Authorization Payload for the UAV consumption.
NOTE 1: The USS stores a mapping between CAA-Level UAV ID and the External Identifier (i.e. GPSI as defined in clause 4.5.3). The External Identifier (GPSI) and/or UAV IP Address can be used at a later point by the USS for accessing various services exposed by 3GPP network e.g. location information retrieval, monitoring event configuration, requesting dedicated policies for e.g. C2, etc.
5. The UAS NF/NEF confirms the successful Authentication/Authorization of the PDU Session. The UAS NF/NEF stores the UUAA result together with the GPSI. UAS NF/NEF forwards the Authentication/Authorization result, a Service Level Device Identity containing the authorized CAA-Level UAV ID and the Authorization Data (i.e. the UUAA Authorization Payload), if received from the USS, to the SMF.
6. [Conditional] If the authentication/authorization is successful, the USS shall subscribe to the PDU Session Status Event as described in steps 1-5 in Figure 4.15.3.2.3-1 of TS 23.502 [3]. This step can be executed in parallel to step 4. The UAS NF/NEF determines the DNN, S-NSSAI to subscribe to the PDU Session Status Event notification as specified in clause 5.2.3.1.
7. The PDU Session establishment continues with steps 7 to 21 in Figure 4.3.2.2.1-1 of TS 23.502 [3] and completes. In the step 7b in Figure 4.3.2.2.1-1of TS 23.502 [3], if the SMF receives the DN Authorization Profile Index from the UAS NF/NEF, it sends the DN Authorization Profile Index to retrieve the PDU Session related policy information (described in clause 6.4 of TS 23.503 [9]) and the PCC rule(s) (described in clause 6.3 of TS 23.503 [9]) from the PCF. If the SMF receives the DN authorized Session AMBR in from the UAS NF/NEF, it sends the DN authorized Session AMBR within the Session AMBR to the PCF to retrieve the authorized Session AMBR (described in clause 6.4 of TS 23.503 [9]).
The SMF transfers the Authentication/Authorization result, the Service Level Device Identity containing the authorized CAA-Level UAV ID and the Authorization Data (i.e. the UUAA Authorization Payload) to the UAV if received from the UAS NF, as in steps 11, 12 and 13 in Figure 4.3.2.2.1-1 of TS 23.502 [3].
If the authentication/ authorization result is a failure, the SMF rejects the PDU session establishment with a proper cause value.
8. [Conditional] If the USS in step 6 subscribed to the PDU Session Status Event the SMF will, as described in steps 6-7 in Figure 4.15.3.2.3-1 of TS 23.502 [3], detect when the PDU Session is established and send the PDU Session Establishment event report to the UAS NF/NEF by means of Nsmf_EventExposure_Notify message, including GPSI and the UE IP Address. Then, the UAS-NF/NEF forwards the event message to the USS.
If UUAA-SM fails during a Re-authentication and Re-authorization and the USS has indicated that the network resources can be released, SMF may trigger PDU Session release for UAS services with a proper cause value.
NOTE 2: When the UUAA-SM fails during a Re-authentication and the USS has not indicated that the network resources can be released, the USS can initiate UUAA revocation as described in clause 5.2.7.
NOTE 3: If C2 information reference is available from USS during the initial PDU Session Establishment procedure the SMF can interact with the PCF to set up a predefined PCC rule(s) profile for the C2 communication.
If the PDU session is released as per clause 4.3.4 of TS 23.502 [3] then the SMF shall notify the UAS NF/NEF about the PDU Session Status event (as specified in clause 4.15.3.2.3 of TS 23.502 [3]). Then the UAS NF/NEF may clear the UUAA-SM context and notify the USS about the PDU session release.
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5.2.3.3 USS UAV Authorization/Authentication (UUAA) during default PDN connection at Attach
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In the figure 5.2.3.3-1 the execution of the UUAA is specified for the scenario where UUAA-SM is performed at Attach.
Figure 5.2.3.3-1: UUAA during PDN connection establishment at Attach procedure in EPS
0. Steps 1 - 13 in TS 23.401 [6] figure 5.3.2.1-1 and steps 1 - 2 in TS 23.502 [3] figure 4.11.1.5.2-1 or clause 4.11.2.4.1 in TS 23.502 [3].
UE sends Attach Request including the Service Level Device Identity (i.e. the CAA-Level UAV ID of the UAV) and may include the Authentication Server Address (i.e. the USS address or the USS address for the corresponding geographical area based on UAV current location location) and optionally Authentication Data (i.e. the UUAA Aviation Payload), etc. in the PCO to the SMF+PGW-C.
Based on that the Service Level Device Identity (CAA-Level UAV ID) is provided with the request, the SMF+PGW-C retrieves the Session Management Subscription Data from the UDM+HSS using the Nudm_SDM_Get service operation and based on that the provided APN/DNN is dedicated for aerial services (have aerial service indicator set), it determines to invoke UAS NF/NEF service operation for UUAA Authentication/Authorization. If the provided APN/DNN is dedicated for aerial services but Service Level Device Identity (CAA-Level UAV ID) is not provided, the SMF+PGW-C shall reject the establishment of the PDU Session and steps 1 -9 are not performed.
NOTE 1: The definition of the PCO field is for stage 3 to specify.
1. SMF+PGW-C configures an Access Control List (ACL) in UPF+PGW-U to stop any traffic over the default PDN Connection until the UUAA has been done and successful.
2. Steps 14 - 22 in figure 5.3.2.1-1 of TS 23.401 [6] and steps 3 - 6 in figure 4.11.1.5.2-1 of TS 23.502 [3] or clause 4.11.2.4.1 of TS 23.502 [3].
During the Attach procedure, at step 15 of Figure 5.3.2.1-1 in TS 23.401, the SMF+PGW-C includes, in PCO, an Indication to the UE that "UpLink Data NOT ALLOWED" on the PDN connection. The UE shall not send Uplink data to the network, until it receives an indication further from the network that "UpLink Data ALLOWED".
3. UUAA is invoked as described in steps 1 and 2 of figure 5.2.3.2-1.
4. [Conditional] Multiple round-trip messages as required by the authentication method used by USS. This step is performed if the Naf_Authentication_AuthenticateAuthorize response messages from USS in step 4a does not contain a SUCCESS/FAILURE indication. The PCO including the authentication message from the USS is transferred to the UE by the SMF+PGW-C in Update Bearer Request and Downlink NAS Transport (steps 4b - 4d). The response from the UE is transferred to the SMF+PGW-C in an Uplink NAS Transport and Update Bearer Response (steps 4e - 4g).
5. UUAA procedure continues as described in steps 4 & 5 of figure 5.2.3.2-1.
6. If the authentication/authorization is successful, the USS shall subscribe to the PDN Connection Status Event as described in steps 1-5 in figure 4.15.3.2.3-1 of TS 23.502 [3]. This step can be executed in parallel to step 5. The UAS NF/NEF determines the APN/DNN to subscribe to the PDN Connection Status Event notification as specified in clause 5.2.3.1.
7. If the UUAA is successful, the SMF+PGW-C contacts the PCF to update the PDN Connection. Then the SMF+PGW-C updates the Access Control List (ACL) and policies in the UPF+PGW-U to allow traffic over the default PDN Connection. If a DN Authorization Profile Index was received from the UAS NF/NEF SMF+PGW-C in previous step, the SMF+PGW C includes that when retrieving the ACL from the PCF. If the SMF receives the DN authorized Session AMBR in from the UAS NF/NEF, it sends the DN authorized Session AMBR within the Session AMBR to the PCF to retrieve the authorized Session AMBR (described in clause 6.4 of TS 23.503 [9]).
8. The SMF+PGW-C updates the UE by invoking the PDN GW initiated bearer modification without QoS update procedure (figure 5.4.3-1 of TS 23.401 [6]) initiated by sending an Update Bearer Request message to the SGW. The PCO includes an indication that "UpLink Data ALLOWED", the UUAA Aviation Payload i.e. the Authentication/Authorization result and the Authorization Data. The UE (for the UAV) confirms the update (see clause 5.4.3 of TS 23.401 [6]).
9. If the USS in step 6 subscribed to the PDN Connection Status Event the SMF+PGW-C will, as described in steps 6-7 in Figure 4.15.3.2.3-1 of TS 23.502 [3], detect when the PDN Connection is established and send the PDN Connection Establishment event report to the UAS NF/NEF by means of Nsmf_EventExposure_Notify message, including GPSI and the UE IP Address. Then, the UAS NF/NEF forwards the event message to the USS.
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5.2.3.4 USS UAV Authorization/Authentication (UUAA) using UE requested PDN connectivity procedure
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In the figure 5.2.3.4-1, the execution of UUAA during the UE requested PDN connectivity procedure is specified for the scenario where UUAA-SM is not performed at Attach.
Figure 5.2.3.4-1: UUAA during the UE requested PDN connectivity procedure in EPS
0. Steps 1-2 in figure 4.11.1.5.4.1-1 of TS 23.502 [3] and steps 1-4 in figure 5.10.2-1 of TS 23.401 [6].
UE sends a PDN connectivity request including the Service Level Device Identity (i.e. the CAA-Level UAV ID of the UAV) and may include the Authentication Server Address (i.e. the USS address or the USS address for the corresponding geographical area based on UAV current location) and optionally Authentication Data (i.e. the UUAA Aviation Payload), etc. in the PCO to the SMF+PGW-C.
Based on that the Service Level Device Identity (CAA-Level UAV ID) is provided with the request, the SMF+PGW-C retrieves the Session Management Subscription Data from the UDM+HSS using the Nudm_SDM_Get service operation and based on that the provided APN/DNN is dedicated for aerial services (have aerial service indicator set), it determines to invoke UAS NF/NEF service operation for UUAA Authentication/Authorization. If the provided APN/DNN is dedicated for aerial services but Service Level Device Identity (CAA-Level UAV ID) is not provided, the SMF+PGW-C shall reject the establishment of the PDU Session and steps 1-9 in this clause are not performed.
NOTE: The definition of the PCO field is for stage 3 to specify.
1. SMF+PGW-C configures an Access Control List (ACL) in UPF+PGW-U to stop any traffic over the default PDN Connection until the UUAA has been done and successful.
2. Steps 3-6 in figure 4.11.1.5.4.1-1 of TS 23.502 [3] and steps 5-12 in figure 5.10.2-1 of TS 23.401 [6].
During the UE requested PDN connectivity procedure, at step 5 of figure 5.10.2-1 of TS 23.401 [6], the SMF+PGW-C includes, in PCO, an indication to the UE that "Uplink Data NOT ALLOWED" on the PDN connection. The UE shall not send uplink data to the network, until it receives an indication further from the network that "Uplink Data ALLOWED".
3. Steps 3-9 of Figure 5.2.3.3-1 in clause 5.2.3.3.
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5.2.4 UUAA Re-authentication and Re-authorization by USS/UTM
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5.2.4.1 UAV Re-authentication procedure in 5GS
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Figure 5.2.4.1-1: UAV Re-authentication procedure in 5GS
UAS NF stores the UE UUAA context after successful UUAA procedure as explained in clause 5.2.2.2 for UUAA-MM and in clause 5.2.3 for UUAA-SM procedure. The UUAA context may be stored in the UDSF or may be stored locally in the UAS NF depending on deployments.
1. The USS sends a Naf_Authentication_Notification request to UAS NF for re-authentication of the UAV. The USS includes GPSI, CAA-Level UAV ID, PDU Session IP address if available in the re-authentication request and an authentication message to be transparently delivered to the UAV.
2. UAS NF retrieves the stored UUAA context for the UE. From the stored UUAA context the UAS NF determines the target AMF or SMF for sending the notification.
3a or 3b. The UAS NF sends Nnef_Authentication_Notification request to notify the target NF, i.e. either the AMF or the SMF, to initiate re-authentication of the UAV.
4. The UAS NF responds back to the USS indicating that re-authentication request has been successfully initiated
5. If UE is in CM_Idle state, the target NF (i.e. either the AMF or the SMF) initiates the Network Triggered Service Request procedures as described in clause 4.2.3.3 of TS 23.502 [3].
6a. If UUAA-MM was performed, the AMF initiates re-authentication of the UAV as described in steps 4c to 10 of UUAA-MM procedure, clause 5.2.2.2.
6b. If UUAA-SM was performed, the SMF then initiates re-authentication of the UAV as described in steps 3c to 7 of the UUAA-SM procedure, clause 5.2.3.2.
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5.2.4.2 UAV Re-authentication procedure in EPS
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Figure 5.2.4.2-1: UAV Re-authentication procedure in EPS
UAS NF stores the UE UUAA context after successful UUAA-SM procedure as explained in clause 5.2.3. The UUAA context may be stored in the UDSF or may be stored locally in the UAS NF depending on deployments.
1. The USS sends a Naf_Authentication_Notification request to UAS NF for re-authentication of the UAV. The USS includes GPSI, CAA-Level UAV ID, UE IP address in the re-authentication request and an authentication message to be transparently delivered to the UAV.
2. UAS NF retrieves the UE stored UUAA context. From the stored UUAA context the UAS NF determines the target SMF+PGW-C for sending the notification.
3. The UAS NF sends Nnef_Authentication_Notification request to notify the SMF+PGW-C, to initiate re-authentication of the UAV.
4. The UAS NF responds back to the USS indicating that re-authentication request has been successfully initiated
5. The SMF+PGW-C then initiates re-authentication of the UAV as in steps 5b to 8 in Figure 5.2.3.3-1: UUAA during PDN connection establishment at Attach procedure in EPS.
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5.2.4.3 USS initiated UAV Re-authorization procedure in 5GS
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Figure 5.2.4.3-1: UAV Re-authorization procedure in 5GS
UAS NF stores the UE UUAA context after successful UUAA procedure as explained in clause 5.2.2.2 for UUAA-MM and in clause 5.2.3 for UUAA-SM procedure. The UUAA context may be stored in the UDSF or may be stored locally in the UAS NF depending on deployments.
1. The USS sends a Naf_Authentication_Notification request to UAS NF for re-authorization of the UAV. The USS includes GPSI, CAA-Level UAV ID, Notification Correlation Information, an authorization message to be transparently delivered to the UAV. The CAA-Level UAV ID may be a new CAA-Level UAV ID. The authorization message may e.g. include a UUAA Authorization Payload, a C2 Authorization Result and a C2 Authorization Payload (e.g. containing C2 pairing information and C2 security information).
2. Based on the received GPSI and Notification Correlation Information from the USS, the UAS NF/NEF determines the corresponding Notification Correlation Information for Nnef_Authentication_Notification request.
3a For UUAA-MM re-authorization, the UAS-NF/NEF sends a Nnef_Authentication_Notification request including the CAA-Level UAV ID and the authorization message to the serving AMF.
3b For UUAA-SM re-authorization or C2 re-authorization, the UAS-NF/NEF sends a Nnef_Authentication_Notification request to the SMF serving the UUAA or C2 for the UE which includes the corresponding PDU session identity, CAA-Level UAV ID and the authorization message.
4. The UAS NF responds back to the USS indicating that re-authorization request has been successfully initiated.
5a. In the case of UUAA-MM:
If the UE is in CM_Idle state, the AMF initiates the Network Triggered Service Request procedures as described in clause 4.2.3.3 of TS 23.502 [3].
The AMF delivers the CAA-Level UAV ID and the authorization message to the UE using NAS MM Transport.
5b In the case of UUAA-SM or C2 re-authorization:
The SMF identifies, based on the received information, the PDU Session that is serving the UUAA-SM or C2 re-authorization and invokes the Network Requested PDU Session Modification procedure (figure 4.3.3.2-1 of TS 23.502 [3] triggering event SMF Requested modification) by sending Namf_Communication_N1N2MessageTransfer, including the CAA-Level UAV ID and the authorization message in the N1_SM_Container (step 3b in figure 4.3.3.2-1 of TS 23.502 [3]) .
The Network Triggered service request procedure is invoked by AMF to forward the CAA-Level UAV ID and the authorization message included in the N1_SM_container to the UE (from step 3a in figure 4.2.3.3-1 of TS 23.502 [3]).
6. The UE receives the CAA-Level UAV ID and the authorization message, which may e.g. include a UUAA Authorization Payload, a C2 Authorization Result and a C2 Authorization Payload (e.g. containing C2 pairing information and C2 security information). The UE acts on it accordingly (outside the scope of 3GPP).
NOTE: The UAV-C replacement procedure is described in clause 5.2.8. The C2 connectivity revocation procedure is described in clause 5.2.9.
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5.2.4.4 USS initiated UAV Re-authorization procedure in EPS
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Figure 5.2.4.4-1: UAV Re-authorization procedure in EPS
UAS NF/NEF stores the UE UUAA context after successful UUAA procedure as in clause 5.2.3 for UUAA-SM procedure. The UUAA context may be stored in the UDSF or may be stored locally in the UAS NF/NEF depending on deployments.
1. The USS sends a request to UAS NF/NEF for re-authorization of the UAV. The USS includes GPSI, Service Level Device Identity (e.g. CAA-Level UAV ID), Notification Correlation Information and authorization message to be transparently delivered to the UAV. The Service Level Device Identity (e.g. CAA-Level UAV ID) may be a new Service Level Device Identity (e.g. CAA-Level UAV ID). The authorization message may e.g. include a UUAA Authorization Payload, a C2 authorization result and a C2 Authorization Payload (e.g. containing, C2 pairing information and C2 security information).
2. Based on the received GPSI and Notification Correlation Information from the USS, the UAS NF/NEF determines the corresponding Notification Correlation Information for Nnef_Authentication_Notification request.
NOTE 1: In EPS the UUAA context is always UUAA-SM.
3. The UAS NF/NEF sends a Nnef_Authentication_Notification request to the SMF+PGW-C serving the UUAA or C2 which includes the corresponding PDN Connection identity, Service Level Device Identity (e.g. CAA-Level UAV ID) and the authorization message.
4. The UAS NF/NEF responds back to the USS indicating that re-authorization request has been successfully initiated.
5. The SMF+PGW-C identifies, based on the received information, the PDN Connection that is serving the UUAA-SM and invokes the PDN GW initiated bearer modification without QoS update procedure (figure 5.4.3-1 of TS 23.401 [6]) by sending Update Bearer Request message, including the Service Level Device Identity (e.g. CAA-Level UAV ID) and the authorization message in the PCO.
The Update Bearer Request message including the Service Level Device Identity (e.g. CAA-Level UAV ID) and the authorization message is forwarded by MME as Downlink NAS Transport to the UE (steps 4 and 5 in figure 5.4.3-1 of TS 23.401 [6]).
6. The UE receives the Service Level Device Identity (e.g. CAA-Level UAV ID) and the authorization message (which may e.g. include a UUAA Authorization Payload, a C2 authorization result and a C2 Authorization Payload (e.g. containing C2 pairing information and C2 security information). The UE acts on it accordingly (outside scope of 3GPP).
NOTE 2: The UAV-C replacement procedure is described in clause 5.2.8. The C2 connectivity revocation procedure is described in clause 5.2.9.
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5.2.5 Authorization for C2 over Uu
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5.2.5.1 General
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Authorization for C2 is required when a UAV establishes a user plane connection for C2 operations, i.e. to deliver messages with information of command and control for UAV operations from a UAV-C or USS to a UAV or to report telemetry data from a UAV to its UAV-C. Two sides of C2 communication, i.e. UAV and UAV-C, belong to the same UAS.
A UAV shall be authorized by the USS to use a PDU Session/PDN connection for C2. Authorization for C2 includes the following:
- UAV to UAV-C pairing authorization: Authorization for pairing with a networked UAV-C or a UAV-C that connects to the UAV via Internet connectivity, before the UAV and the UAV-C can exchange C2 communication. One UAV can be paired with only one UAV-C at the any time. One UAV-C may be paired with one or more UAVs at the same time.
- Flight Authorization: Authorization for flight when UAV also provides Flight Authorization information.
C2 authorization may be carried out:
- During the UUAA procedure (if UUAA is carried out at PDU session/PDN connection establishment) as described in clause 5.2.3 when the UAV requests establishment of PDU Session/PDN connection for connectivity.
- During PDU Session Modification/ UE requested bearer resource modification when the UAV requires to use an existing PDU session/PDN connection to exchange C2 communication related messages.
- During a new PDU Session/PDN connection establishment, if the UAV requires to use a separate PDU Session/PDN connection for C2 communication.
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5.2.5.2 Procedure for C2 authorization in 5GS
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5.2.5.2.1 C2 Authorization request during UUAA-SM procedure in 5GS
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If C2 authorization is requested during the UUAA-SM procedure the procedure described in clause 5.2.3.2 takes place with the following additions:
- In Step 0, the UE includes pairing information (if available) in a C2 Aviation Payload. which is forwarded further to the USS;
- In step 4, the USS performs C2 authorization taking into account the included pairing information, the Service Level Device Identity/CAA-Level UAV ID and 3GPP UAV ID/GPSI. The USS includes the resulting C2 Authorization result and optionally a C2 authorization payload in the Naf_Authentication_AuthenticateAuthorize response returned to the UAS-NF/NEF and the UAS NF/NEF forwards to the UAV/UE in step 7.
- The USS shall:
- in step 4 include a DN Authorization profile Index specifying a predefined set of PCC-rules in the PCF with initial restriction on the type of traffic allowed to pass on the PDU-session. For example, only traffic exchanged with the USS might be allowed to pass.
Once the authentication is complete, after step 4, the USS subscribes to PDU Session Status Events for the PDU session used for C2 communication, applicable for the GPSI received in step 2.
- when the USS in step 8 receives a PDU Session State Event Report indicating session start and including the PDU Session IP address the USS invokes the USS initiated pairing policy configuration procedure (see figure 5.2.5.4.1-1) with the received PDU Session IP address and authorized paired UAV-C IP-address as input to request corresponding traffic to be allowed on the PDU session in the UPF.
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5.2.5.2.2 UE initiated PDU Session Modification for C2 Communication
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C2 authorization is requested at PDU session Modification:
- After UUAA-SM is performed and a common PDU session is used for connectivity to USS and C2 communication to a UAV-C (as configured in the UAV); or
- If the UE has already established a PDU session for C2 communication to a UAV-C.
Figure 5.2.5.2.2-1: PDU Session modification for C2 communication (common PDU session for UAS services)
1. The UE establishes a PDU Session for USS communication as described in clause 5.2.3.
2-3. When the UAV needs to establish C2 communication the UAV determines that an existing PDU session can be used and initiates a PDU Session Modification procedure. The UE shall include in the request a CAA-Level UAV ID and shall include a C2 Aviation Payload within a UAS container that includes C2 authorization information. The USS may also use its locally configured pairing information for UAV - UAV-C pairing authorization which takes precedence over UAV provided pairing information. The pairing information includes the CAA-level UAV ID of the requesting UE and also includes identification information of UAV-C to pair if available. The UAV may also include other information such as Flight Authorization information.
NOTE: How the pairing information is configured in the UAV is outside the scope of 3GPP specifications.
4. The SMF determines that authorization is required based on that the DNN/S-NSSAI of the PDU session is dedicated for aerial services (have aerial service indicator set) and that the Service Level Device Identity (CAA-Level UAV ID) is included in the request and Then sends a Nnef_Authentication_AuthenticateAuthorize request to the UAS-NF including the UAS container provided by the UAV in step 2 (including the C2 Aviation Payload), the CAA-Level UAV ID, GPSI, PDU Session IP address and optionally the UAV location (e.g. Cell ID) provided by the AMF.
5. The UAS-NF forwards the received authorization request as a Naf_Authentication_AuthenticateAuthorize request to the USS.
6. Triggered by step 5, the USS performs C2 authorization based on the received information and invokes, in order to forward the C2 authorization result to the UAV/UE, the UAV Re-authorization procedure (see figure 5.2.4.3-1) including GPSI, CAA-Level UAV-ID (potentially new) and included in the authorization message, the C2 Authorization Result and the C2 Authorization Payload (e.g. containing C2 pairing information and C2 security information).
7. PDU Session Modification procedure forwards the C2 authorization result to the UAV/UE and completes as in figure 4.3.3.2-1 of TS 23.502 [3].
8. The USS invokes, with the received PDU Session IP address and the IP address of the authorized paired UAV-C as input, the USS initiated pairing policy configuration procedure (see figure 5.2.5.2.4-1) to request corresponding traffic to be allowed on the PDU session in the UPF.
Unless a dedicated QoS is requested for the C2 flows, this procedure does not invoke any interaction with the UE, AMF or RAN.
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5.2.5.2.3 UE initiated PDU Session Establishment for C2 Communication
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If C2 authorization is requested during PDU session establishment to a PDU session used specifically for C2 communication to UAV-C the UAV requests C2 authorization as follows.
Figure 5.2.5.2.3-1: PDU Session establishment for C2 communication (separate PDU Sessions for UAS services)
0. The UAV has performed a successful UUAA with the USS (UUAA-SM or UUAA-MM) and the USS has for the corresponding GPSI subscribed for PDU Session Status Event from the NEF.
1. When the UAV needs to establish C2 communication the UAV determines that a new dedicated PDU session is required for connectivity to UAV-C. The UE initiates PDU Session establishment procedure for a DNN/S-NSSAI dedicated for connectivity to UAV-C. In the PDU Session establishment request CAA-Level UAV ID and a C2 Aviation Payload to be used for C2 authorization shall be included and forwarded to the SMF. The pairing information includes the CAA-Level UAV IDs of the requesting UAV and identification information for the UAV-C to pair may be included in C2 Aviation Payload. The UAV may also include other information such as Flight Authorization information. The USS may also use its locally configured pairing information for UAV - UAV-C pairing authorization which then takes precedence over UAV provided pairing information.
2. The SMF determines that authorization is required based on that the requested DNN/S-NSSAI combination dedicated for aerial services (have aerial service indicator set) and that the Service Level Device Identity (CAA-Level UAV ID) is included in the request. The SMF then sends a Nnef_Authentication_AuthenticateAuthorize request, which is used to request authorization to pair the UAV with UAV-C, to the UAS NF/NEF that includes the GPSI, CAA-Level UAV ID and C2 Aviation Payload and optionally the UAV location (e.g. Cell ID) if provided by the AMF and the DNN and S-NSSAI of the PDU session.
If the requested DNN/S-NSSAI is dedicated for aerial services but no Service Level Device ID (CAA-Level UAV ID) has been provided with the request, the SMF rejects the PDU session establishment with a cause indicating that USS authorization is required.
The SMF also provides a Notification Endpoint to the UAS NF/NEF. By providing the Notification Endpoint, the SMF is implicitly subscribed to be notified of re-authorization, update authorization data or revocation of C2 connectivity from UAS NF/NEF, if the C2 authorization result is successful in step 5.
3. The UAS NF/NEF checks that a valid UUAA is stored for the GPSI and forwards the received authorization request as a Naf_Authentication_AuthenticateAuthorize request to the USS. If not, the request is not forwarded to the USS and the PDU session is rejected.
The UAS NF/NEF also provides a Notification Endpoint to the USS. By providing the Notification Endpoint, the UAS NF/NEF is implicitly subscribed to be notified of re-authorization, update authorization data or revocation of C2 connectivity from USS, if the UUAA result is successful in step 5.
NOTE: The USS may trigger a UAV re-authentication/re-authorization in response to the query from the UAS NF/NEF.
4. The USS performs C2 authorization based on the received information and sends the Naf_Authentication_AuthenticateAuthorize response to the UAS NF/NEF including the Service Level Device Identity (e.g. the CAA-Level UAV-ID) (potentially new), the C2 Authorization Result and the C2 Authorization Payload (e.g. C2 pairing information and C2 security information).
5. The UAS-NF/NEF forwards the information received from the USS in the Nnef_Authentication_AuthenticateAuthorize response sent to the SMF.
6. To inform the UE about the C2 Authorization Result the SMF includes the authorization result and, optionally, a new CAA-Level UAV ID if received from the USS, in the PDU Session Accept sent to the UE and let the PDU session establishment procedure continue until finalized.
If a failed C2 Authorization Result is received from the USS, the SMF instead rejects the PDU establishment and include a reason code indicating not authorized.
7. [Conditional] If the C2 authorization is successful the USS subscribes via the UAS-NF to a PDU Session Status event for the PDU session used for C2 including in the request the GPSI of the UAV. The UAS NF determines DNN, S-NSSAI corresponding to the PDU session used for C2 communication and uses this DNN, S-NSSAI to subscribe to SMF for PDU Session Status event. The SMF detects, as described in step 6-7 of figure 4.15.3.2.3-1 in TS 23.502 [3], when the PDU Session is established and send the PDU Session Status event report to the UAS NF/NEF by means of Nsmf_EventExposure_Notify message, including GPSI and UE IP Address. The UAS NF/NEF then forwards the event message to the USS.
8. [Conditional] The USS stores the received UE IP address and invokes, with the received PDU Session IP address and the IP-address of the authorized paired UAV-C as input, the USS initiated pairing policy configuration procedure (see figure 5.2.5.2.4-1) to request corresponding traffic to be allowed on the PDU session by the UPF.
Unless a dedicated QoS is requested for the C2 flows, this procedure does not invoke any interaction with the UE, AMF or RAN.
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5.2.5.3 Procedure for C2 authorization in EPS
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5.2.5.3.0 C2 Authorization request during UUAA-SM procedure in EPS
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If C2 authorization is requested during the UUAA-SM procedure the procedure described in clause 5.2.3.3 takes place with the following additions:
- In step 0, the UE includes pairing information (if available) in a C2 Aviation Payload, which is forwarded further to the USS.
- Initially in step 5, the USS performs C2 authorization taking into account the included pairing information, the Service Level Device Identity/CAA-Level UAV ID and 3GPP UAV ID/GPSI. The USS includes the resulting C2 Authorization result in the Naf_Authentication_AuthenticateAuthorize response returned to the UAS-NF/NEF and UAS NF/NEF forwards to the UAV/UE in step 8.
- The USS shall:
- in step 5 include a DN Authorization profile Index specifying a predefined set of PCC-rules in the PCF with initial restriction on the type of traffic allowed to pass on the PDN Connection. For example, only traffic exchanged with the USS might be allowed to pass.
Once the authentication is complete, after step 5, the USS subscribes to PDN Connectivity Status Events for the PDN Connection used for C2 communication, applicable for the GPSI received in step 2.
- when the USS in step 9 receives a PDN Connectivity Status Event Report indicating session start and including the PDN Connection IP address, the USS invokes the USS initiated pairing policy configuration procedure (see figure 5.2.5.4.2-1) with the received PDN Connection IP address and authorized paired UAV-C IP-address as input to request corresponding traffic to be allowed on the PDN Connection in the PGW-U.
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5.2.5.3.1 UE requested PDN connectivity for C2 authorization
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When the UAV requests to establish connectivity to an additional PDN over E-UTRAN for C2, the procedure described in clause 5.10.2 of TS 23.401 [6] takes place with the following modifications:
Figure 5.2.5.3.1-1: UE requested PDN Connectivity for C2 authorization
0. The UAV has performed a successful UUAA with the USS (UUAA-SM) and the USS has for the corresponding GPSI subscribed for PDN Connectivity Status Event reports from the NEF.
1. Steps 1 - 3 performed as in Figure 5.10.2-1 of TS 23.401 [6].
When the UAV needs to establish C2 communication, the UAV determines that a new PDN Connection is required for connectivity to UAV-C. The UE initiates a UE Requested PDN Connectivity procedure for connectivity to UAV-C. In the PCO in the PDN Connectivity Request, the Service Level Device Identity (e.g. the CAA-Level UAV ID) and a C2 Aviation Payload to be used for C2 authorization shall be included and forwarded to the MME. The pairing information includes the Service Level Device Identity (e.g. CAA-Level UAV IDs) of the requesting UAV and identification information for the UAV-C to pair may be included in C2 Aviation Payload. The UAV may also include other information such as Flight Authorization information. The USS may also use its locally configured pairing information for UAV - UAV-C pairing authorization which then takes precedence over UAV provided pairing information.
If Service Level Device Identity (CAA-Level UAV ID) is provided with the request, the SMF+PGW-C retrieves (if not already available) the Session Management Subscription Data for the UE from the UDM+HSS using the Nudm_SDM_Get service operation.
2. The SMF+PGW-C determines that authorization is required based on that the requested APN/DNN is dedicated for aerial services (have aerial service indicator set) and that the Service Level Device Identity (CAA-Level UAV ID) is included in the request. The SMF+PGW-C then sends a Nnef_Authentication_AuthenticateAuthorize request, which is used to request authorization to pair the UAV with UAV-C, to the UAS NF/NEF that includes the GPSI, Service Level Device Identity (e.g. the CAA-Level UAV ID) and C2 Aviation Payload and optionally the UAV location (e.g. Cell ID) if provided by the MME and the APN/DNN of the PDN Connection.
If the SMF+PGW-C determines that the authorization procedure with the USS is required, but the UAV has not provided the Service Level Device Identity (e.g. the CAA-Level UAV ID), the SMF+PGW-C rejects the PDN Connectivity Request with a cause indicating that USS authorization is required.
3. The UAS NF/NEF checks that a valid UUAA is stored for the GPSI and forwards the received authorization request as a Naf_Authentication_AuthenticateAuthorize request to the USS. If not, the request is not forwarded to the USS and the PDN connection is rejected.
4. The USS performs C2 authorization based on the received information and sends the Naf_Authentication_AuthenticateAuthorize response to the UAS NF/NEF including the Service Level Device Identity (e.g. the CAA-Level UAV-ID) (potentially new), the C2 Authorization Result and the C2 Authorization Payload (e.g. C2 pairing information and C2 security information).
5. The UAS NF/NEF forwards the information received from the USS in the Nnef_Authentication_AuthenticateAuthorize response sent to the SMF+PGW C.
6. To inform the UE about the C2 authorization result the SMF+PGW-C includes the C2 Authorization Result and optionally, the Authorization Payload (e.g. C2 pairing information and C2 security information) and a new Service Level Device Identity (e.g. CAA-Level UAV ID) if received from the USS, in the PCO in the PDN Connectivity Accept sent to the UE and let the PDN Connectivity Request procedure continue until finalized.
If a failed C2 authorization result is received from the USS, the SMF+PGW-C instead rejects the PDN Connectivity Request and includes a cause code indicating not authorized.
7. If the C2 authorization is successful the USS subscribes via the UAS NF/NEF to a PDN Connection Status Event report for the PDN Connection used for C2 including in the request the GPSI of the UAV. The UAS NF/NEF determines the APN/DNN and uses this APN/DNN to subscribe to SMF+PGW-C for PDN Connection Status Event. The SMF+PGW-C detects, as described in step 6-7 of figure 4.15.3.2.3-1 in TS 23.502 [3], when the PDN Connection is established and sends the PDN Connection Status Event report to the UAS NF/NEF by means of Nsmf_EventExposure_Notify message, including GPSI and UE IP Address. The UAS NF/NEF then forwards the event message to the USS.
8. The USS stores the received UE IP address and invokes, with the received PDN Connection IP address and the IP-address of the authorized paired UAV-C as input, the USS initiated C2 pairing policy configuration in EPS procedure (see figure 5.2.5.4.2-1) to request corresponding traffic to be allowed on the PDN Connection by the PGW-U.
Unless a dedicated QoS is requested for the C2 flows, this procedure does not invoke any interaction with the UE, MME or RAN.
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5.2.5.3.2 UE requested bearer resource modification of an existing PDN connection for C2 authorization
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C2 authorization is requested at UE requested bearer resource modification (see clause 5.4.5 of TS 23.401 [6]):
- After UUAA-SM is performed and a common PDN Connection is used for connectivity to USS and C2 communication to a UAV-C (as configured in the UAV); or
- If the UE has already established a PDN Connection for C2 communication to a UAV-C.
Figure 5.2.5.3.2-1: UE requested bearer resource modification of an existing PDN connection for C2 authorization
0. The UE establishes a PDN Connection for USS communication as described in clause 5.2.3.
1. When the UAV needs to establish C2 communication, the UAV determines that an existing PDN Connection can be used and initiates a UE requested bearer resource modification procedure as Steps 1 - 3 in Figure 5.4.5-1 of TS 23.401 [6]. In the PCO in the request, the UE includes a Service Level Device Identity (e.g. CAA-Level UAV ID) and shall include a C2 Aviation Payload that includes C2 authorization information. The USS may also use its locally configured pairing information for UAV - UAV-C pairing authorization which takes precedence over UAV provided pairing information. The pairing information includes the Service Level Device Identity (e.g. CAA-level UAV ID) of the requesting UE and also includes identification information of UAV-C to pair if available. The UAV may also include other information such as Flight Authorization information.
NOTE: How the pairing information is configured in the UAV is outside the scope of 3GPP specifications.
2. The SMF+PGW-C determines that authorization is required based on that the APN/DNN of the PDN Connection is dedicated for aerial services (have aerial service indicator set) and that the Service Level Device Identity (CAA-Level UAV ID) is included in the request and then sends a Nnef_Authentication_AuthenticateAuthorize request to the UAS-NF including the UAS information provided by the UAV in step 1 (including the C2 Aviation Payload), the Service Level Device Identity (e.g. CAA-Level UAV ID), GPSI, PDN Connection IP address and optionally the UAV location (e.g. Cell ID) provided by the MME.
The UAS-NF forwards the received authorization request as a Naf_Authentication_AuthenticateAuthorize request to the USS.
3. The UE requested bearer resource modification procedure completes as in clause 5.4.5-1 of TS 23.401 [6].
4. Triggered by step 5, the USS performs C2 authorization based on the received information and invokes, in order to forward the C2 authorization result to the UAV/UE, the UAV Re-authorization procedure (see figure 5.2.4.4-1) including GPSI, Service Level Device Identity (e.g. CAA-Level UAV-ID) (potentially new) and, included in the authorization message, the C2 Authorization Result and the C2 Authorization Payload (e.g. containing C2 pairing information and C2 security information).
5. The USS invokes, with the received PDN Connection IP address and the IP address of the authorized paired UAV-C as input, the USS initiated pairing policy configuration procedure (see figure 5.2.5.4.2-1) to request corresponding traffic to be allowed on the PDN Connection in the UPF/PGW-U.
Unless a dedicated QoS is requested for the C2 flows, this procedure does not invoke any interaction with the UE, MME or RAN.
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5.2.5.4 USS initiated C2 pairing policy configuration
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5.2.5.4.1 USS initiated C2 pairing policy configuration in 5GS
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The USS initiated C2 pairing policy configuration Figure 5.2.5.4.1-1.
Figure 5.2.5.4.1-1: USS initiated C2 pairing policy configuration in 5GS
0. The UAV is registered in the network and a PDU session is established as specified in clause 5.2.3.2.
1. The USS initiates the PDU Session modification by invoking the Nnef_AFSessionWithQoS_Create request including USS Identity/AF Identifier, UAV-UAVC Pairing info/Flow description(s), QoS reference. The UAV-UAVC Pairing info/Flow description(s) includes the UAV-C IP address. See step 1 in clause 4.15.6.6 of TS 23.502 [3]: Setting up an AF session with required QoS.
2. UAS NF/NEF authorizes the request from the USS followed by interacting with PCF triggering a Npcf_PolicyAuthorization_Create request and provides relevant parameters to the PCF.
PCF determines whether the request is authorized and if the requested QoS is allowed. PCF informs UAS NF/NEF if the request is accepted by invoking Npcf_PolicyAuthorization_Create response. See steps 2 - 4 in figure 4.15.6.6.6-1 of TS 23.502 [3].
3. UAS NF/NEF sends a Nnef_AFsessionWithQoS_Create response message (Transaction Reference ID, Result) to the USS. Result indicates whether the request is granted or not. See step 5 in figure 4.15.6.6.6-1 of TS 23.502 [3].
NOTE: Use of Nnef_AFSessionWithQoS_Create can be further evaluated with stage 3 work.
4. If the PCF determines that the SMF needs updated policy information, the PCF issues a Npcf_SMPolicyControl_UpdateNotify request with updated policy information. The updated policy information includes the UAV-C IP address. See steps 3 - 5 in figure 4.16.5.2-1 of TS 23.502 [3].
5. The PDU Session Modification continues and completes as in steps 2a - 13 in figure 4.3.3.2-1 of TS 23.502 [3], UE or network requested PDU Session Modification (for non-roaming and roaming with local breakout). Based on the updated policy information received, the SMF determines and provides N4 rules to enable communication between UAV and UAV-C, e.g. Packet Detection Rules, Forwarding Action Rules.
6-7. [Optional] The PCF sends Npcf_PolicyAuthorization_Notify message to the UAS NF/NEF when the modification of the transmission resources corresponding to the QoS update succeeded or failed. The UAS NF/NEF transfers this information to the USS by sending Nnef_AFSessionWithQoS_Notify message. See steps 6 and 7 in figure 4.15.6.6-1 of TS 23.502 [3].
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5.2.5.4.2 USS initiated C2 pairing policy configuration in EPS
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The USS initiated C2 pairing policy configuration in EPS figure 5.2.5.4.2-1.
Figure 5.2.5.4.2-1: USS initiated C2 pairing policy configuration in EPS
0. The UAV is registered in the network and a PDN Connection is established as specified in clause 5.2.3.3.
1. The USS initiates the PDN Connection modification by invoking the Nnef_AFSessionWithQoS_Create request including USS Identity/AF Identifier, Transaction Reference ID, UAV-UAVC Pairing info/Flow description(s), QoS reference. The UAV-UAVC Pairing info/Flow description(s) includes the UAV-C IP address. See step 1 in clause 4.15.6.6 of TS 23.502 [3]: Setting up an AF session with required QoS.
2. UAS NF/NEF authorizes the request from the USS followed by interacting with PCF triggering a Npcf_PolicyAuthorization_Create request and provides relevant parameters to the PCF.
PCF determines whether the request is authorized and if the requested QoS is allowed. PCF informs UAS NF/NEF if the request is accepted by invoking Npcf_PolicyAuthorization_Create response. See steps 2 - 4 in figure 4.15.6.6.6-1 of TS 23.502 [3].
3. UAS NF/NEF sends a Nnef_AFsessionWithQoS_Create response message (Transaction Reference ID, Result) to the USS. Result indicates whether the request is granted or not. See step 5 in figure 4.15.6.6.6-1 of TS 23.502 [3].
NOTE: Use of Nnef_AFSessionWithQoS_Create can be further evaluated with stage 3 work.
4. If the PCF determines that the SMF+PGW-C needs updated policy information, the PCF issues a Npcf_SMPolicyControl_UpdateNotify request with updated policy information. The updated policy information includes the UAV-C IP address. See steps 3 - 5 in figure 4.16.5.2-1 of TS 23.502 [3].
5. Based on the updated policy information received, the SMF+PGW-C determines and provides N4 rules to enable communication between UAV and UAV-C, e.g. Packet Detection Rules, Forwarding Action Rules.
6. [Conditional] If QoS needs to be updated: Based on the updated policy information received, the SMF+PGW-C determines N4 rules for QoS update and provides to the PGW-U.
Based on the updated policy information received, the SMF+PGW-C invokes the PDN GW initiated bearer modification with bearer QoS update procedure (clause 5.4.2.1 in TS 23.401 [6]) by sending Update Bearer Request message to the SGW. Steps 2 - 11 in clause 5.4.2.1-1 of TS 23.401 [6] are executed to update QoS in the UE and the RAN.
7-8. [Optional] The PCF sends Npcf_PolicyAuthorization_Notify message to the UAS NF/NEF when the modification of the transmission resources corresponding to the QoS update succeeded or failed. The UAS NF/NEF transfers this information to the USS by sending Nnef_AFSessionWithQoS_Notify message. See steps 6 and 7 in figure 4.15.6.6-1 of TS 23.502 [3].
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5.2.6 Void
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5.2.7 UUAA Revocation by USS/UTM
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Figure 5.2.7.1-1: Procedure for UAV authorization revocation by USS
UAS NF stores the UAV UE's UUAA context after successful UUAA procedure as explained in clause 5.2.2.2 for UUAA-MM and in clause 5.2.3.2 for UUAA-SM procedure.
1. The USS sends Naf_Authentication_Notification to UAS NF for authorization revocation. The USS includes GPSI, CAA-Level UAV ID, cause of revocation, PDU Session IP address if available in the authorization revocation request.
2. UAS NF retrieves the UAV UE's stored UUAA context. From the stored UUAA context the UAS NF determines the target AMF or SMF for sending the notification.
3a or 3b. The UAS NF sends Nnef_Authentication_Notification request to notify the target NF, i.e. either the AMF or the SMF that the UAV is not authorized anymore, indicating the cause is revocation. The target NF shall remove the successful UUAA result and respond to the UAS NF.
4. The UAS NF shall remove the UAV UE's UUAA context. The UAS NF responds back to the USS indicating that authorization revocation request has been successfully initiated.
5a. If UAS NF has subscribed to AMF for the Mobility Event Exposure with Event ID = Reachability Filter before, UAS NF unsubscribes to AMF for the mobility event notification by sending Namf_EventExposure_Unsubscribe request with Subscription Correlation ID.
5b. The AMF acknowledges the un-subscription request from 5a by sending Namf_EventExposure_Unsubscribe response.
6. If UE is in CM_Idle state, the target NF (i.e. either the AMF or the SMF) initiates the Network Triggered Service Request procedures as described in clause 4.2.3.3 of TS 23.502 [3].
7a. If the target NF is AMF, the AMF shall initiate UE Configuration Update procedure as described in clause 4.2.4.2 of TS 23.502 [3] to inform the UE that UUAA is revoked. The AMF shall also initiate the release of PDU Sessions related to UAS services.
7b. If the target NF is AMF, based on network policy the AMF may start network initiated de-registration process as described in clause 4.2.2.3.3 of TS 23.502 [3].
7c. If the target NF is SMF, the SMF starts network initiated PDU session release process as described in clause 4.3.4 of TS 23.502 [3] to release the associated PDU session.
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5.2.8 UAV Controller Replacement
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5.2.8.1 UAV controller replacement in 5GS
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If USS determines that UAV controller replacement is required the USS invokes an Nnef_AFsessionWithQoS_Update service operation to the UAS NF including in the request authorization information (i.e. new pairing information). NEF authorizes the request from the USS followed by interacting with PCF triggering a Npcf_PolicyAuthorization_Update request and provides relevant parameters to the PCF. The PCF uses the information provided by the NEF to derive new PCC rules to allow C2 communication between the UAV and the new UAV controller.
The procedure for UAV-C replacement is as follows:
Figure 5.2.8-1: UAV-C replacement procedure
0. A UAV has already established user plane connectivity for C2 operation. The USS determines that the UAV-C controlling the UAV needs to be replaced (e.g. if the UAV is misbehaving).
1. The USS initiates the UAV-C replacement by invoking the Nnef_AFSessionWithQoS_Update request including Transaction Reference ID, UAV-UAVC Pairing info/Flow description(s), QoS reference. See step 1 in TS 23.502 [3] clause 4.15.6.6a, AF session with required QoS update procedure.
2. NEF authorizes the request from the USS followed by interacting with PCF triggering a Npcf_PolicyAuthorization_Update request and provides relevant parameters to the PCF. PCF determines whether the request is authorized and if the requested QoS is allowed. PCF informs NEF if the request is accepted by invoking Npcf_PolicyAuthorization_Update Response. See Steps 2 - 4 in TS 23.502 [3] figure 4.15.6.6.6a-1.
3. NEF sends a Nnef_AFsessionWithQoS_Update response message (Transaction Reference ID, Result) to the USS. Result indicates whether the request is granted or not. See step 5 in TS 23.502 [3] figure 4.15.6.6.6a-1.
4. Steps 4 - 7 in Figure 5.2.5.4.1-1.
5. USS invokes the UAV Re-authorization procedure in Figure 5.2.4.3-1 to deliver the new pairing information to the UE. The USS includes the 3GPP UAV ID, the IP address of the PDU session and included in the authorization message the C2 Authorization Result and the C2 Authorization Payload (containing the C2 pairing information containing the new UAV-C identifier and C2 security information) which is further forwarded to the UE.
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5.2.8.2 UAV controller replacement in EPS
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The procedure for UAV-C replacement in EPS is as follows:
Figure 5.2.8.2-1: UAV controller replacement in EPS
0. UAV is attached to EPC with a PDN connection established
1. The USS determines that the UAV-C controlling the UAV needs to be replaced (e.g. if the UAV is misbehaving).
2. USS initiates the Nnef_AFSessionWithQoS_Update request including USS Identity/AF Identifier, Transaction Reference ID, UAV-UAVC Pairing info/Flow description(s), QoS reference. Steps 1-3 as in Figure 5.2.7.1-1 takes place.
3. The PCF determines updated policy information and configures the resources and routing information as in steps 2 - 4 in Figure 5.2.5.4.2-1.
4. The USS is informed whether the UAV-C replacement and authorization has succeeded or failed as in steps 6- 7 in Figure 5.2.5.4.1-1.
5. The USS invokes the UAV re-authorization procedure in EPS as in Figure 5.2.4.4-1. The USS includes the 3GPP UAV ID, the IP address of the PDU session and included in the authorization message, the C2 Authorization Result and the C2 Authorization Payload (e.g. containing the C2 pairing information containing the new UAV-C identifier and C2 security information) which is further forwarded to the UE.
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5.2.9 Revocation of C2 Connectivity
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5.2.9.1 Revocation of C2 connectivity in 5GS
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When the USS decides to revoke an existing C2 connection between the UAV and UAV-C the USS invokes an Nnef_AFsessionWithQoS_Revoke request to NEF in order to revoke the AF request as described in Figure 5.2.9.1-1.
Figure 5.2.9.1-1: Revocation of C2 connectivity in 5GS
0. USS decides to revoke C2 connectivity.
1. USS identifies the AF session corresponding to the C2 connectivity and invokes an Nnef_AFSessionWithQoS_Revoke Request including USS identity/AF identifier, Transaction Reference ID.
2. UAS NF/NEF indicates to the PCF to delete the context of application level session information by invoking an Npcf_PolicyAuthorization_Delete request.
3. The PCF initiates a network requested PDU session modification procedures as in steps 1b-13 in Figure 4.3.3.2-1 of TS 23.502 [3] removing the corresponding PCC rules installed at the SMF to support the AF session or may trigger a network requested PDU session release as in Steps 1b-13 Figure 4.3.4.2-1 of TS 23.502 [3].
4. The PCF acknowledge the request by sending an Npcf_PolicyAuthorization_Delete response.
NOTE: Steps 3 and 4 can be carried out in parallel.
5. The UAS NF/NEF acknowledge the USS request by sending an Nnef_AFSessionWithQoS_Revoke response.
6. USS may invoke the UAV Re-authorization procedure in Figure 5.2.4.3-1 to deliver a C2 authorization payload indicating that C2 authorization has been revoked.
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5.2.9.2 Revocation of C2 connectivity in EPS
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The procedure is as follows:
Figure 5.2.9.2-1: Revocation of C2 connectivity in EPS
0. USS decides to revoke C2 connectivity.
1. Steps 1 - 2 as described in Figure 5.2.9.1-1 are performed.
2. The PCF deletes policy information associated with the AF session and configures the resources and routing information as in steps 5 - 6 in Figure 5.2.5.4.2-1.
3. Steps 4-5 as described in Figure 5.2.9.1-1 are performed.
NOTE: Step 2 in Figure 5.2.9.2-1 and step 4 in Figure 5.2.9.1-1 can be carried out in parallel.
4. The USS may invoke the UAV re-authorization procedure in EPS as in Figure 5.2.4.4-1 to deliver a C2 authorization payload indicating that C2 connectivity is revoked.
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5.3 UAV Tracking
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5.3.1 UAV Tracking Model
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3GPP network supports the functionality of UAV Tracking via the service exposure support towards USS. The USS invokes 3GPP network service through a UAS-NF for UAV tracking. The UAS-NF acts as an NEF/SCEF and interacts with other network functions (e.g. GMLC and AMF/MME) to support UAV tracking. The USS shall use 3GPP UAV ID (e.g. GPSI) for identifying an individual target UAV. When USS/TPAE initiates UAV tracking via USA NF, it should include an indication of reliable UE location information required in the request. For further details on the architecture reference model, see clause 4.2.
Three UAV tracking modes are supported:
- UAV location reporting mode;
- UAV presence monitoring mode; and
- List of Aerial UEs in a geographic area..
USS/TPAE could at any time choose a UAV tracking mode and provide the corresponding request to UAS NF. The USS/TPAE logic on its choice of UAV Tracking Model is out of scope of 3GPP.
The 3GPP network may also provide the UAV location to the USS during the UUAA procedures, as described in clause 5.2.2 and clause 5.2.3.
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5.3.1.1 UAV Location Reporting Mode
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For UAV location reporting mode, the USS/TPAE that wants to be reported on the UAV location subscribes to the UAS NF with the target 3GPP UAV ID. The USS/TPAE could indicate the required location accuracy, reliable UE location information required and whether it's for immediate reporting or deferred reporting (e.g. periodic reporting). With the request received from USS/TPAE, UAS NF identifies the related NF, i.e. GMLC and trigger existing procedures to retrieve the location report. Then UAS NF reports back the UAV's location together with the 3GPP UAV ID to the USS/TPAE.
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5.3.1.2 UAV Presence Monitoring Mode
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For UAV presence monitoring mode, the USS/TPAE may subscribe for the event report of UAV moving in or out of the geographic area (e.g. longitude/latitude, zip code, etc). The request includes target 3GPP UAV ID, indication of reliable UE location information required and geographic area info.
If the requested geographic area info can be mapped to 3GPP defined area, such as a list of Tracking Areas or a list of cells as currently supported by 3GPP network as the Area Of Interest, UAS NF subscribes to AMF/MME for reporting the presence of the UAV in Area Of Interest using existing AMF/MME procedures, otherwise UAS NF subscribes to GMLC for configuring the presence monitoring. Upon receiving the report from AMF/MME or GMLC, the UAS NF notifies USS/TPAE for the UAV presence in the geographic area.
The USS may provide policies or rules to UAS NF based on the received event notification. If the traffic routing policies or rules were provided to UAS NF, when the location of UAV or the UAV presence in the monitoring area matches a policy, UAS NF based on the policy indicates SMF to take the appropriate network layer actions, e.g. revoke the connectivity between UAV and UAV controller. UAS NF considers those policies as active and ongoing instructions from USS without constant or repeated triggers/requests from USS. The traffic routing policy includes 3GPP UAV ID(s) (i.e. GPSI(s)) to identify the UAV(s) and the corresponding network layer actions e.g. revoke the resources of the related C2 communications.
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5.3.1.3 List of Aerial UEs in a geographic area
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In this mode, the USS/TPAE requests UAS NF for a list of the UAVs in the geographic area and served by the PLMN (i.e. no 3GPP UAV ID provided by the USS/TPAE). The request includes geographic area info, indication of reliable UE location information required and indication of one-time reporting by setting "maximumNumberOfReports" to 1. If the geographic area info can be mapped to 3GPP defined area such as a list of Tracking Areas or a list of cells, UAS NF triggers existing AMF/MME procedures to get the UE list within the TAI(s) or Cell Id(s). The UAS NF may include Aerial UE indication as an event filter in the request, that is used by the AMF/MME to separate out the UEs that are actual UAVs based UEs with aerial subscriptions. If the geographic area info cannot be mapped to 3GPP defined area such as a list of Tracking Areas or a list of cells, UAS NF provides a list of Tracking Areas which is larger than the geographic area to AMF/MME to retrieve the UE list within the list of Tracking Areas. Then UAS NF identifies UAVs from the UE list and obtains the location for each identified UAV via LCS procedure toward GMLC. The UAS NF compares the UAV location with the geographic area to identify the UAVs in the geographic area and provides feedback to USS/TPAE. For the UAV list received from the AMF/MME or the UAV list identified with GMLC provided location, the UAS NF performs the filtering by checking for each 3GPP UAV ID reported whether there is match for the corresponding UAV context. The UAS NF may also verify whether the requesting USS is authorized to obtain the location info of the UAV.
In the above UAV tracking modes, UAS NF may need to map the 3GPP UAV ID to 3GPP internal IDs and vice versa. The CAA Level UAV ID may be optionally provided by the UAS NF, if available, to the USS/TPAE during tracking and location reporting of UAV.
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5.3.2 Procedure for UAV location reporting
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The following procedures describe the 5GC UAV's location reporting service to USS.
Figure 5.3.2-1: UAV Location Reporting
1. USS to UAS NF/NEF: The USS sends Nnef_EventExposure_Subscribe request to the UAS NF/NEF as described in step 1b-1 from clause 6.1.2 of TS 23.273 [8] for immediate location reporting (i.e. 5GC-MT-LR) and step 1b-1 from clause 6.3.1 of TS 23.273 [8] for periodic, triggered and UE available location reporting (i.e. deferred 5GC-MT-LR). USS should include an indication of reliable UE location information required in the request.
2. UAS NF/NEF determines the relevant NF, i.e. GMLC for location reporting based on the UAV's capability or network capability, location accuracy etc.
3. UAS NF sends request to GMLC with the GPSI (i.e. 3GPP UAV ID) provided by USS to retrieve the UE location via the current location services supported by GMLC. The UAS NF/NEF performs 5GC-MT-LR Procedure as described in clause 6.1.2 of TS 23.273 [8] or deferred 5GC-MT-LR procedure as described in clause 6.3.1 (up to step 21b-1) of TS 23.273 [8] depending on whether the request received in step 1 was for immediate location reporting or deferred location reporting respectively. In this step, the location service exposure described in clause 5.5 of TS 23.273 [8] may also include the velocity of the UE.
4. UAS/NEF NF to USS: UAS NF/NEF provides the UAV location which may contain velocity of the UE to USS/TPAE in Nnef_EventExposure_Notify operation as described in step 24b-2 of Figure 6.1.2-1, if the request in step 1 was for immediate location reporting. The UAS NF/NEF includes the GPSI in the location reporting message to USS/TPAE as well as the UAV's location information (in the form of geo co-ordinates) which is understood by USS/TPAE (not assuming the knowledge of TA and Cell Id).
If the request in step 1 was for deferred 5GC-MT-LR, the UAS NF/NEF sends Nnef_EventExposure_Notify indicating whether or not the periodic or triggered location was successfully activated in the target UE, as described in step 21b-2 of Figure 6.3.1-1.
5. For deferred 5GC-MT-LR with periodic or triggered location request steps 22 to 30b-2 of Figure 6.3.1-1 are executed and the UAS NF/NEF provides the location report to USS/TPAE in Nnef_EventExposure_Notify operation.
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5.3.3 Procedure for UAV presence monitoring
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The following procedures describe the 3GPP UAV presence monitoring mode operation.
Figure 5.3.3-1: UAV Presence Monitoring
1. USS to UAS NF/NEF: The USS initiates the UAV presence monitoring request via the Nnef_EventExposure_Subscribe service operation to UAS NF/NEF to subscribe to the target UAV presence events from 3GPP network (e.g. moving in or out of the monitoring area). In addition to providing a GPSI corresponding to the target UAV for the presence monitoring, the request also includes the geographic area info (e.g. longitude/latitude, zip code, etc.), an indication of reliable UE location information required. Optionally, it includes a policy or rule indicating the 3GPP network to take the corresponding action when the Area of Interest (AOI) event report is detected. The policy or rule contains a moving in or moving out event associated with an indication of revoking the connectivity between UAV and UAV controller.
2. UAS NF/NEF maps the geographical area into an area of interest that is represented by a list of Cell IDs, gNB IDs or TAIs and determines the relevant NF (s), i.e. AMF or GMLC for location reporting based on the UAV's capability or network capability, the geographic area info etc.
3a. If the requested geographic area info can be mapped to 3GPP defined area and the relevant NF is determined as AMF in step 2, then the UAS NF/NEF maps the GPSI provided by USS to SUPI and provides the SUPI and the mapped 3GPP defined area to the AMF to obtain the UE presence status by reusing the Area of Interest mechanism.
3a. If the requested geographic area info cannot be mapped to 3GPP defined area and the relevant NF is determined as GMLC in step 2, then the UAS NF/NEF uses GMLC based procedure for configuring the presence monitoring. It is preferrable for UAS NF/NEF to use GMLC based procedure if presence monitoring is needed in a granularity finer than the Cell Id. The UAS NF/NEF invokes an Ngmlc_Location_ProvideLocation Request service operation towards the GMLC including the geographical area of interest for presence monitoring. The UAS NF/NEF may first use AMF based procedure for UE presence monitoring as described in step 3a before invoking GMLC service.
4. UAS NF/NEF receives the UAV presence monitoring report from AMF or GMLC.
5a. UAS NF/NEF reports the UAV presence in the geographic area to USS by including its GPSI in the report. The CAA Level UAV ID, if available with the UAS NF/NEF, may be optionally provided in the report.
5b-5c. [Optional] If policies have been provided to UAS NF/NEF in step1 from USS, when the UAV presence in the monitoring area matches a policy, UAS NF/NEF based on the policy indicates SMF (via PCF) to take the appropriate network layer actions, e.g. revoke the connectivity between UAV and UAV controller, etc. The UAS NF/NEF uses the Npcf_PolicyAuthorization_Update service operation as described in clause 4.15.6.6.6a of TS 23.502 [3] and provides relevant parameters to the PCF. UAS NF/NEF considers those policies as active and ongoing instructions from USS without constant or repeated triggers/requests from USS. The PCF issues a Npcf_SMPolicyControl_UpdateNotify request with updated policy information received from the UAS NF/NEF about the PDU Session as described in the PCF initiated SM Policy Association Modification procedure in clause 4.16.5.2.
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5.3.4 Procedure for obtaining list of Aerial UEs in a geographic area
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This procedure may be used by USS/TPAE to obtain a list of the UAVs in a geographic area and served by the PLMN. The USS/TPAE provides the geographic area information to the UAS-NF. Based on the received information, the UAS NF may either trigger the AMF/MME monitoring event configuration procedure with event ID "Number of UEs present in a geographical area" or the GMLC based location reporting procedure. The AMF/MME may filter the list of UAVs before sending it to the UAS NF (e.g. may filter only based on UE having Aerial subscription), if Aerial UE indication was included as an event filter in the monitoring event configuration request from the UAS NF. The UAS NF performs the filtering on the received list from AMF or MME before responding back to the USS/TPAE. The UAS-NF includes the 3GPP UAV ID and may include the CAA Level UAV ID, if available, for each of the UAVs in the tracking and location response to the USS/TPAE.
Figure 5.3.4-1: List of Aerial UEs in a geographic area
1. USS to UAS NF: The USS/TPAE sends the UAV list request to UAS NF to request UAV identity (e.g. 3GPP UAV ID, CAA Level UAV ID). The USS/TPAE includes geographic area info, an indication of reliable UE location information required and indication for immediate reporting in the request message to the UAV-NF.
2. UAS NF to AMF/MME: UAS NF decides the AMF(s) based on the geographic area info and obtains the UE list in the target area from AMF by reusing the event "Number of UEs present in a geographical area" with any UE in the event filter. The UAS NF may also include "Aerial UE" indication and/or "PDU session established for DNN(s) subject to aerial service" as event filters. If the target area cannot be mapped to 3GPP network areas, UAS NF provides a TA List which is larger than the target area to the AMF(s)/MME(s) for the list of UEs to be queried. The AMF(s)/MME(s) identifies UEs corresponding to the geographic area info and may also filter out the list of UAVs based on checking for UEs with aerial subscriptions, if "Aerial UE" indication was included as an event filter in the request from UAS NF/NEF. In addition, the AMF(s) may also further identify UAVs that have successfully established PDU session for DNN(s) subject to aerial services, if it was included as an event filter in the request from UAS NF/NEF.
3. [Optional] UAS NF to GMLC: From the list of UEs generated in step 2, for UAVs that are in target areas that do not map to 3GPP network areas, the UAS-NF then queries the UAV(s) location from GMLC.
4. [Conditional] If step 3 above was executed, from the list of locations returned by the GMLC, the UAS NF compares the UAV's locations to the target area (provided in step 1 above) to identify the UAV to be included in the report for USS.
5. For either the UAV list received from the AMF(s)/MME(s), or the UAV list identified in step 4, the UAS NF performs the filtering by checking for each reported 3GPP UAV ID whether there is match for the corresponding UUAA context.
6. UAS NF to USS: UAS NF responds to the USS/TPAE with the list of filtered UAVs (step 5). The CAA Level UAV ID, if available, may be provided by the UAS NF in the response message to USS/TPAE. If the USS performed the UUAA of the UAV, or the UAS NF is configured to know the USS is authorized to receive such information, then the 3GPP UAV ID is also included.
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5.4 Direct C2 Communication
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5.4.1 General
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A UAV that supports Direct C2 Communication may establish direct PC5 link with a UAV-C. Only NR PC5 is supported for Direct C2 Communication. The UAV that is engaged in Direct C2 Communication may or may not be capable of connection with 3GPP network. The UAV is authorized by the USS for establishing Direct C2 Communication with the UAV-C. The UAV-C with which the UAV performs Direct C2 Communication may be pre-configured in the UAV or provided by the network as described in clause 5.4.3. The UAV may be preconfigured with the A2X service type for direct C2 Communication, direct C2 pairing information (e.g. Application Layer ID of the UAV-C), a default Destination Layer-2 ID for initial signalling to establish unicast connection, authorization policy for direct C2 Communication.
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5.4.2 Authorization policy for A2X Direct C2 Communication service
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Authorization policy parameters as described in clause 6.2.1.2.1 for A2X are leveraged using a service type indicating Direct C2 Communication where applicable.
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5.4.3 Procedure for C2 authorization by the USS for using the A2X Direct C2 Communication service
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5.4.3.1 General
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If the UAV is capable of 3GPP network connection and is served by a PLMN, the UAV performs the Direct C2 Communication authorization either as part of the UUAA-MM procedure in 5GS described in clause 5.2.2 or as part of the C2 Authorization during UUAA-SM procedure described in clause 5.2.5. In either case, if the UAV supports Direct C2 Communication and intends to request C2 authorization for Direct C2 Communication to the USS, it shall include an indication for Direct C2 Communication authorization in the authorization request.
If the UAV is not capable of 3GPP network connection or is not in coverage of a PLMN at the moment of performing authorization of Direct C2 Communication, or when the UAV does not use any PLMN resources for UAS services, Direct C2 Communication is authorized based on pre-configured policies in the UAV (e.g. at the application layer).
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5.4.3.2 Authorization of Direct C2 Communication service via UUAA-MM
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In 5GS, the UUAA-MM procedure may be used to authorize direct C2 communication described in clause 5.2.2 with the following enhancements:
- In step 1 of clause 5.2.2.1: When the UAV needs to establish a direct PC5 link required for connectivity to UAV-C (i.e. Direct C2 Communication), the UAV may include an authorization request for Direct C2 Communication by providing a C2 Aviation Payload with an indication that the authorization is for Direct C2 Communication. In addition, the UAV includes the direct C2 pairing information (if available) in the C2 Aviation Payload.
- In steps 2 and 3 of clause 5.2.2.2: if the UAV included the C2 Aviation Payload in step 1 of clause 5.2.2.1, the C2 Aviation Payload is also included
- In steps 5 and 6 of clause 5.2.2.2: If the authorization request for Direct C2 Communication was included in step 1 of clause 5.2.2.1, the USS sends the C2 Authorization result and in the case of success, may include a direct C2 pairing information containing the UAV-C's Application Layer ID in the C2 Authorization Payload, which are further forwarded to the UAV/UE.
If the UAV attempts Direct C2 Communication authorization via UUAA-MM and receives no response, the UAV shall perform Direct C2 Communication via UUAA-SM.
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5.4.3.3 Authorization of Direct C2 Communication service via UUAA-SM
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In 5GS, the following procedures are used to request C2 authorization for Direct C2 Communication to the USS:
- The procedure for C2 Authorization request during UUAA-SM procedure in 5GS as specified in clause 5.2.5.2.1 with the following enhancements:
- In step 0: When the UAV needs to establish a direct PC5 link required for connectivity to UAV-C (i.e. Direct C2 Communication), the C2 Aviation Payload sent by the UAV includes an indication that the authorization is also for Direct C2 Communication. In addition, the UAV includes the direct C2 pairing information (if available) in the C2 Aviation Payload.
- In step 4: If the authorization request for Direct C2 Communication was included in step 0 and the C2 authorization is successful, the USS may include direct C2 pairing information containing the UAV-C's Application Layer ID in the C2 Authorization Payload which is further forwarded to the UAV/UE.
- The procedure for UE initiated PDU Session Modification for C2 Communication as specified in clause 5.2.5.2.2 with the following enhancements:
- In step 2: When the UAV needs to establish a direct PC5 link required for connectivity to UAV-C (i.e. Direct C2 Communication), the C2 Aviation Payload sent by the UAV includes an indication that the authorization is also for Direct C2 Communication. In addition, the UAV includes the direct C2 pairing information (if available) in the C2 Aviation Payload.
- In step 6: If the authorization request for Direct C2 Communication was included in step 2 and the C2 authorization is successful, the USS may include direct C2 pairing information containing the UAV-C's Application Layer ID in the C2 Authorization Payload which is further forwarded to the UAV/UE.
- The procedure for UE initiated PDU Session Establishment for C2 Communication as specified in clause 5.2.5.2.3 with the following enhancements:
- In step 1: When the UAV needs to establish a direct PC5 link required for connectivity to UAV-C (i.e. Direct C2 Communication), the C2 Aviation Payload sent by the UAV includes an indication that the authorization is also for Direct C2 Communication. In addition, the UAV includes the direct C2 pairing information (if available) in the C2 Aviation Payload.
- In step 4: If the authorization request for Direct C2 Communication was included in step 1 and the C2 authorization is successful, the USS may include direct C2 pairing information containing the UAV-C's Application Layer ID in the C2 Authorization Payload which is further forwarded to the UE in the Naf_Authentication_AuthenticateAuthorize response.
In EPS, the following procedures are used to request C2 authorization for Direct C2 Communication to the USS:
- The procedure for C2 Authorization request during UUAA-SM procedure in EPS as specified in clause 5.2.5.3.0 with the following enhancements:
- In step 0: When the UAV needs to establish a direct PC5 link required for connectivity to UAV-C (i.e. Direct C2 Communication), the C2 Aviation Payload sent by the UAV includes an indication that the authorization is also for Direct C2 Communication. In addition, the UAV includes the direct C2 pairing information (if available) in the C2 Aviation Payload.
- In step 5: If the authorization request for Direct C2 Communication was included in step 0 and the C2 authorization is successful, the USS may include direct C2 pairing information containing the UAV-C's Application Layer ID in the C2 Authorization Payload which is further forwarded to the UAV/UE.
- The procedure for UE requested PDN connectivity for C2 authorization as specified in clause 5.2.5.3.1 with the following enhancements:
- In step 1: When the UAV needs to establish a direct PC5 link required for connectivity to UAV-C (i.e. Direct C2 Communication), the C2 Aviation Payload sent by the UAV includes an indication that the authorization is also for Direct C2 Communication. In addition, the UAV includes the direct C2 pairing information (if available) in the C2 Aviation Payload.
- In step 4: If the authorization request for Direct C2 Communication was included in step 1 and the C2 authorization is successful, the USS may include direct C2 pairing information containing the UAV-C's Application Layer ID in the C2 Authorization Payload which is further forwarded to the UAV/UE.
- The procedure for UE requested bearer resource modification of an existing PDN connection for C2 authorization as specified in clause 5.2.5.3.2 with the following enhancements:
- In step 1: When the UAV needs to establish a direct PC5 link required for connectivity to UAV-C (i.e. Direct C2 Communication), the C2 Aviation Payload sent by the UAV includes an indication that the authorization is also for Direct C2 Communication. In addition, the UAV includes the direct C2 pairing information (if available) in the C2 Aviation Payload.
- In step 4: If the authorization request for Direct C2 Communication was included in step 1 and the C2 authorization is successful, the USS may include direct C2 pairing information containing the UAV-C's Application Layer ID in the C2 Authorization Payload which is further forwarded to the UAV/UE.
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5.4.4 Procedure for Direct C2 Communication establishment
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The procedures for Direct C2 Communication leverages A2X Unicast mode communication over PC5 reference point as defined in clause 6.2.2.1.3 and clause 6.3.3.2.
To establish Direct C2 communication the procedure for A2X unicast mode Layer-2 link establishment over PC5 reference point as defined by clause 6.3.3.2 and the accordingly referred description in clause 6.3.3.1 of TS 23.287 [11] with the following enhancements and differences:
- In step 3:
- the A2X Service Info is set to A2X service type for direct C2 Communication. The A2X service type for direct C2 Communication may be preconfigured in the UAV.
- the Source User Info is set to the Application Layer ID of the UAV.
- the Target User Info is set to the Application Layer ID of the UAV-C. If the Application Layer ID of the UAV-C is provided by the network as described in clause 5.4.3, that Application Layer ID is used. Otherwise, the preconfigured Application Layer ID of the UAV-C is used.
- The destination Layer-2 ID is set to a default Destination Layer-2 ID for initial signalling to establish unicast connection as preconfigured in the UAV.
In this Release, only Unicast mode communication over PC5 reference point is supported for Direct C2 Communication.
NOTE: Security aspects of Direct C2 Communication is defined by SA WG3.
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5.5 Broadcast Remote ID
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5.5.1 Broadcast Remote ID using PC5
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Broadcast Remote ID leverages A2X broadcast communication mode as defined in clauses 6.2.2.1.2 and 6.3.3.1, for both UAV UEs that register to the MNO network(s) and UAVs that operate out of coverage.
The content of the messages for BRID is defined according to regional regulations for BRID (e.g. message set of ASTM F3411.19 [13] or ASD-STAN prEN 4709-002 P1 [14]) and optionally according to regional mean of compliance documents.
Authorization and provisioning of policy parameters for A2X communication over PC5 reference point as described in clause 6.2.1.2 is leveraged. Where applicable, an A2X service type indicating Broadcast Remote ID is used.
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5.5.2 Broadcast Remote ID using MBS
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5.5.2.1 Policy/Parameter provisioning
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Policy parameters provisioning as described in clause 6.2.1.3 for A2X communication over Uu reference point is leveraged. Where applicable an A2X service type indicating Broadcast Remote ID is used.
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5.5.2.2 Broadcast Remote ID reception via MBS
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The A2X Broadcast Remote ID service is identified with a corresponding service type.
The Broadcast Remote ID sent by a UAV UE to an A2X application server identified by A2X service type set to Broadcast Remote ID is as a A2X message routed to UAV UEs via MBS sessions using the mechanisms and procedures described in clause 6.2.2.2.2.
The content of the A2X message is the Broadcast Remote ID, e.g. as defined in ASTM F3411.19 [13] or ASD‑STAN prEN 4709-002 P1 [14].
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5.5.2.3 QoS handling
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QoS is handled as described in clause 6.2.4.2 for delivery of A2X message over MBS.
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5.5.2.4 MBS service area mapping
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Broadcast Remote ID using MBS facilitates procedures and mechanisms for MBS service area mapping for A2X communication with MBS as specified in clause 6.3.4.2.1 in accordance with:
- UE applies to a UAV UE.
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5.6 Mechanisms for Detect and Avoid (DAA)
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5.6.1 Mechanisms for Detect and Avoid (DAA) based on PC5
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DAA leverages procedures and mechanisms as defined for A2X in clause 6. This includes the corresponding references to TS 23.287 [11] below.
NOTE 1: The content of the messages for DAA are defined according to the regional regulations for DAA and is out of scope of 3GPP.
The detection and deconfliction of potential collisions between UAVs is locally performed between UAVs using direct UAV to UAV communication over PC5. The USS may be informed of the potential collision situation.
Deconflicting policy which indicates the communication mode (unicast or broadcast) used for deconflicting for A2X is defined in 6.2.1.2.1.
Authorization and provisioning of policy parameters for A2X communication over PC5 reference point as described in clause 6.2.1.2 is leveraged.
Figure 5.6.1-1: DAA procedure based on PC5
1. UAV1 receives broadcast messages from UAV2 in PC5-U messages, that may include application layer DAA payload, e.g. CAA-level UAV ID, velocity, heading direction, position.
2. UAV1 passes the DAA payload to the upper layer. The application layer detects a conflict, based on the broadcast messages received from UAV2, e.g. by comparing it with its own trajectory and location. If the application layer in the UAV1 detects a potential collision situation, it initiates a collision avoidance/conflict resolution procedure with UAV2.
3. Optionally, UAV1 may inform its own USS about the detected potential collision by including peer UAV2 ID(s).
NOTE 2: The communication between UAV and USS for potential collision notification is out of scope of this specification.
4. UAV1 selects a communication mode (broadcast or unicast) for DAA deconfliction based on the input received from the application layer and A2X Policy. If unicast deconfliction mode is selected then step 4a is executed, otherwise, messages in steps 5 and 6 are exchanged using broadcast mode as defined in clause 6.3.1 of TS 23.287 [11].
4a. Optional: If unicast deconfliction mode is selected, then UAV1 triggers Layer-2 link establishment for unicast communication with UAV2 by applying to A2X the procedure defined in clause 6.3.3.1 of TS 23.287 [11] with the following clarifications:
- If the Target User Info is included in the Direct Communication Request message, Application layer ID of the target UE (UAV2) can be the one retrieved from the step 1, e.g. CAA-level UAV ID.
- If the Target User Info is not included in the Direct Communication Request message, the UEs that are interested in using the announced A2X service type(s) over a PC5 unicast link with UAV1 responds by establishing the security with the UAV1.
The steps 5 and 6 are then exchanged over the established unicast link.
5. UAV1 sends to UAV2 a DAA deconfliction message, e.g. deconfliction request message which may include collision detection alert, its CAA-level UAV IDs and the one(s) from other detected conflicting UAV(s) and deconflicting specific parameters (e.g. trajectory correction information to avoid collision).
NOTE 3: The deconflicting specific parameters are application layer content and is out of scope of this specification.
6. UAV2 replies to provide agreed DAA deconflicting policy, its updated trajectory and other info, e.g. message deconfliction status response, conflict resolved alert, CAA-level UAV IDs of participating UAVs from the receiving UAV.
Subsequent messages may be exchanged between UAVs until traffic conflict resolution is reached (e.g. for mutual position/trajectory monitoring) based on application layer mechanisms.
7. After the successful traffic conflict resolution, if unicast deconfliction mode was selected, the UAV1 triggers Layer-2 link release procedure as described in clause 6.3.3.3 of TS 23.287 [11].
NOTE 4: While it is assumed that all UAVs in the area can be involved for DAA, the procedure shows only two UAVs for simplicity.
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5.7 Ground-based DAA for an Area
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5.7.1 Functional Description
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This clause provides a network-assisted (ground based) DAA mechanism. It is applicable for a specific area, such as a stadium or arena where UAVs are used e.g. for filming an event. It is based on a ground-based entity, Area Airspace Manager (AAM), that is able to detect UAVs in the specific area and provide local steering policies to the individual UASs in order to avoid the UAVs crashing into each other or different structures etc. The policy may e.g. include allowed flying zones and positions allowed for the specific UAV. The policy may also apply to a specific outdoor area, e.g. an event, where specific measures to avoid collision between drones are established locally.
NOTE 1: The policies provided by the AAM is application specific steering/DAA policies that are out of scope of 3GPP. The same or different local policies can be provided to the UAVs in the arena. UAVs can, for example, be given different fly zones in the arena just like people have different seating in an arena.
The high-level principles of the network-assisted (ground based) DAA are:
- The arena/area has a ground-based entity Area Airspace Manager (AAM). The AAM includes one or more UEs enabled for use of PC5. The AAM may also have a direct connection to the Data Network.
- For the applicable airspace of the area/arena the AAM defines individually adapted local collision avoidance rules for correspondingly located UAVs.
NOTE 2: How the AAM can determine the local steering policy for collision avoidance is out of scope of 3GPP. It can e.g. be based on maps of the area/arena and detailed information about the facilities together with an awareness of the current usage need for the airspace.
- Provisioning of AAM local collision avoidance rules to a UAV/UE must comply with the policies for PC5 operations received from the 5GC or being preconfigured in the UE.
- Detected UAVs are identified by their coordinates and by the Remote ID as retrieved by Broadcast Remote ID (BRID) or Network Remote ID (NRID) mechanisms dependent on the method used by the UAV.
NOTE 3: How the AAM can scan the UAVs in specific area is out of scope of 3GPP.
NOTE 4: How the AAM retrieves the Remote ID for detected UAVs is out of scope of 3GPP. For example, in case of BRID different UAVs can use different methods, such as WLAN, Bluetooth or PC5 direct communication, for broadcasting the Remote ID and in case of NRID the AAM will, based on the geolocation of the UAV, retrieve the Remote ID from the USS at application layer. For the NRID case the AAM will typically have to be authorized by the UTM to be allowed to retrieve the Remote ID.
- Based on the retrieved Remote ID, the AAM activates PC5 communication with each detected UAV by triggering establishment of an A2X PC5 unicast link based on procedures described in clause 6 using the UAV's Remote-ID as Application-Layer-ID (i.e. Target User Info) in the Direct Communication Request message.
For Direct Communication over PC5 the UAV and AAM shall comply with the authorization and provisioning principles described in clause 4.2.1.2.2 including the following considerations:
- The default destination Layer-2 ID to be used for initial signalling to establish a unicast connection for the A2X service.
- Parameters for Groupcast are not applicable.
NOTE 5: Use of LTE PC5 for the unicast is not supported in this Release.
- The AAM uses PC5 unicast link to provide each UAV present in the arena/area with local DAA policies as user traffic.
- A UAV that receives local collision avoidance related policies from the AAM over PC5 may forward the policies to its UAV-C so that the UAV-C can steer the UAV accordingly by use of C2 communication (e.g. over Uu, PC5, or other means) in order to enforce the local policies and avoid collisions.
NOTE 6: Whether and how to forward the policies from UAV to its UAV-C and how UAV-C uses the policies is out of scope of 3GPP.
NOTE 7: A UAV-C that receives local collision avoidance policies from an AAM, can inform the AAM about its network address (e.g. IP address or URL) in order to enable direct AAM to UAV-C communication via Data Network. How a UAV-C communicates with the AAM is out of scope of 3GPP.
Figure 5.7.1-1: Logical architecture for ground based DAA
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5.7.2 Procedures
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Figure 5.7.2-1: High-level procedure for Ground-based DAA for an Area
Ground-based DAA for an area leverages the procedures and mechanisms defined for A2X. Any references to TS 23.287 [11] made in this clause shall be interpreted in accordance with corresponding definitions and descriptions for A2X in clause 6.
Prerequisites: The AAM/UE and the UAVs/UEs are configured to use an A2X service for Ground-based DAA for an area.
1. The UAVs/UEs listens for signals on the correspondingly destination Layer-2 ID configured for the used service type in accordance with clause 6.3.3.1 of TS 23.287 [11] (Fig 6.3.3.1-1 step 1).
2. The AAM can scan the airspace over the area/arena for UAVs, e.g. by making use of upward pointing radars and cameras etc. For each detected UAV it determines the coordinates.
NOTE 1: How step 2 and step 3 are done is out of 3GPP scope.
3. The AAM retrieves for each detected UAV the corresponding Remote-ID using the method applicable for the specific UAV. Methods which may be used includes broadcast of Remote-ID via PC5, WiFi and Bluetooth and also Network Remote ID.
How this is done is out of the 3GPP scope.
4. For each detected UAV/UE the AAM establishes a PC5 direct communication link with the discovered UAV for AAM to UAS interaction by performing the Layer-2 link establishment procedure as described when Target User Info is included in clause 6.3.3.1 of TS 23.287 [11] (Fig 6.3.3.1-1 step 2, 3 4a, 5a and 6). The AAM application layer provides a service type indicating the A2X service "Ground-based DAA for an area" and the retrieved Remote-ID as target UE's Application Layer ID. As a result of this procedure a PC5 unicast direct communication link enabling bidirectional data exchange is set up between the application layer in the AAM and the UAV application layer of the UAV/UE having the specified Remote-ID.
5. Optionally the UAV/UE may, when the PC5 unicast direct communication link between the AAM and the UAV/UE has been set up for NR, activate a corresponding bidirectional communication connection extending the link from the UAV to the UAV-C using the specific communication technology used for C2 communication (may e.g. be LR Wi-Fi or PC5). This enables packets received on the link (i.e. from the AAM) to be forwarded to the UAV-C and packets received from the UAV-C to be forwarded on the link (i.e. towards the AAM). Implementation aspects for this step are out of scope for 3GPP.
6. Using the PC5 unicast direct communication link the AAM and the UAV establishes a bidirectional communication channel for exchange of messages. Optionally this channel can be extended to involve the UAV-C using the bi-directional tunnel. The protocol and implementation aspects for this step are out of scope for 3GPP.
NOTE 2: The UAV-C and/or the UAV can use the communication channel to provide application specific information to the AAM, how and what information is out of 3GPP scope. Based on awareness of the current UAV traffic situation, local info and plans for the area/arena, the AAM determines locations and flight paths appropriate for the specific UAV such that collisions can be avoided and creates a corresponding application specific steering policy being out of scope of 3GPP.
7. The AAM provides the determined steering policy to the specific UAV using the activated communication channel. Optionally it can be forwarded to the UAV-C which can return corresponding C2 commands. Protocols, semantics and syntax for handling this are application specific and out of 3GPP scope.
8. The UAV is steered to avoid collisions in accordance with received policy and using mechanisms that are out of scope for 3GPP.
NOTE 3: A UAV-C that optionally receives local policies for DAA from an AAM, can inform the AAM of its address (e.g. IP address or URL) to enable direct AAM to UAV-C communication via Data Network.
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5.8 Void
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5.9 Void
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5.10 Void
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5.11 Void
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5.12 Pre-flight Planning and In-flight Monitoring for UAVs
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5.12.1 General
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5G network may support pre-flight planning and in-flight monitoring for UAVs via the NEF service exposure. The USS/UTM may request assistance information to NEF of pre-flight planning and in-flight monitoring for UAV, after the UAV establishes user plane connection with the USS/UTM.
In the case of pre-flight planning, USS/UTM may request assistance information from the NEF for the following purposes:
(1) To determine the most suitable flight path among several candidate flight paths:
USS/UTM provides multiple planned flight paths to the network and network leverages the network analytics, e.g. Movement Behaviour Analytics and/or QoS Sustainability Analytics, to determine the most suitable (in terms of the provided criteria, e.g. fastest, shortest) planned flight path among the provided candidates.
NOTE 1: It is expected that the USS/UTM provides flight path information using a set of 4-point polygons (contains geographical coordinates describing a rectangular shape of a geographical area), height information (optional) and corresponding timestamps/time schedule for the flight, if available. For each of the latitude, longitude, height (if applicable) and time schedule (if applicable) value, the USS/UTM can provide either lowest/highest values (i.e. a range) or accuracy values.
(2) To derive a flight path(s) for the requested starting and destination points for a UAV's flight:
USS/UTM provides to the network information about the UAV's starting and destination points for the flight and the network leverages the network analytics e.g. Movement Behaviour Analytics and/or QoS Sustainability Analytics that can be exposed via NEF, to be used by the USS/UTM to determine a detailed flight path(s) for the UAV. NEF responds to the USS/UTM with the collected network analytics outputs to assist with the pre-flight planning.
NOTE 2: Destination and/or a next point in the flight path can be described using an ellipsoid point with altitude and uncertainty ellipsoid as specified in clause 5.6 of TS 23.032 [21].
(3) Output QoS information along the flight path:
USS/UTM provides multiple planned flight paths to the network and network leverages QoS Sustainability Analytics to output QoS information for each of the provided flight paths.
In the case of in-flight monitoring, in addition to QoS Sustainability Analytics request, USS/UTM can provide the UAV flight path and corresponding (arriving) time to the network, in order for the network to verify whether the UAV's exact location matches the scheduled location represented by the waypoint.
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5.12.2 Procedure for NEF Assisted Pre-flight Planning
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Figure 5.12.2-1: Procedure for NEF Assisted Pre-flight Planning
1. The UAV establishes a PDU Session for communication with the USS/UTM as described in clause 5.2.3.
2. (via application layer) The UAV requests the pre-flight planning service from the USS/UTM.
3. The USS/UTM determines to request a pre-flight assistance information from the 5GC and derives the information to provide to the NEF/UAS NF.
NOTE 1: The content of pre-flight planning service information derived at USS is out of scope of 3GPP.
4. The USS/UTM sends an Nnef_RetrieveInfoUAVFlight_Get request with the indication to provide a pre-flight planning assistance for a target UAV (i.e. aerial UE). The request message includes identifier of the UAV (e.g. GPSI), information about the starting and ending points (and any intermediate point, if any) for the flight. The request may also include requirements on the flight path (e.g. on time, fastest, shortest), candidate flight path(s) (either received from the UAV or locally derived at the USS/UTM) and accuracy level of predictions relevant to the flight planning.
5. The NEF maps parameters included in the received Nnef_RetrieveInfoUAVFlight_Get request from the USS/UTM to information used by the 3GPP system (e.g. map the geographical area into an area of interest that is represented by a list of Cell IDs, gNB IDs or TAIs). The NEF determines services needed for the request and relevant NFs, e.g. NEF service on UAV tracking and mode (UAV location reporting mode, UAV presence monitoring mode, List of Aerial UEs in a geographic area), NWDAF analytics service (Movement Behaviour analytics and/or QoS Sustainability Analytics), GMLC service (e.g. Ranging/Sidelink Positioning location).
6. If the NEF determines that the 5GS cannot satisfy the requirements provided by the USS/UTM on flight planning (e.g. cannot get predictions relevant to the flight planning from NWDAF with the required accuracy level), the NEF rejects the pre-flight planning request from the USS/UTM and the NEF may include the details about the reasons of the rejection inside the response; steps 8-15 are skipped.
7. (via application layer) If the USS/UTM receives the response to the Nnef_RetrieveInfoUAVFlight_Get with the rejection of the pre-flight planning in step 6, the USS/UTM may respond to the UAV's pre-flight planning request and include the received details rejection reason(s) if available.
8. If the NEF determines to proceed with the pre-flight planning, the NEF performs steps 2-5 of clause 5.3.4 to determine a list of UAVs in the areas of interest.
NOTE 2: Steps 9-11 are optional and can be invoked independently of each other and based on the NEF decision in step 5.
9. The NEF subscribes/requests for notification on Movement Behaviour analytics from NWDAF as defined in clause 6.21.4 of TS 23.288 [20]. The request includes an identifier of the UAV (e.g. GPSI) obtained in step 4 and height information of the UAV; other parameters included in the request are described in clause 6.21.4 of TS 23.288 [20]. Additionally, if the list of UAVs in the areas of interest is obtained in step 8, it may be used by the NEF to request Movement Behaviour analytics from NWDAF.
10. The NEF subscribes/requests for notification on QoS Sustainability analytics from NWDAF as defined in clause 6.9.1 of TS 23.288 [20]. The request includes an identifier of the UAV (e.g. GPSI) obtained in step 4 and the UAV's flight path information; other parameters included in the request are described in clause 6.9.1 of TS 23.288 [20]. Additionally, if the list of UAVs in the areas of interest is obtained in step 8, it may be used by the NEF to request QoS Sustainability analytics from NWDAF.
11. The NEF may request GMLC service(s), e.g. Ranging/Sidelink positioning location as defined in clause 6.20.4 of TS 23.273 [8]. The list of UAVs in the areas of interest output from step 8 may be used by the NEF to request the GLMC service on Ranging/Sidelink Positioning location.
12. The NEF generates the pre-flight assistance information based on the outputs from steps 8-10. The pre-flight assistance information may contain the best matching path(s) among the ones provided by the USS/UTM in step 4, or potential flight path information if candidate flight path(s) are not provided in step 4.
13. The NEF responds to the USS/UTM with the pre-flight assistance information.
14. The USS/UTM derives the flight path(s) using the retrieved pre-flight assistance information and flight planning mechanisms); these mechanisms are outside the scope of 3GPP.
15. (via application layer) The USS/UTM responds to the UAV with the planned flight path(s).
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5.12.3 Procedure for NEF Assisted In-flight Monitoring
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Figure 5.12.3-1: Procedure for NEF Assisted In-flight Monitoring
NOTE: The NFs in Figure 5.12.3-1 represents all the other NFs beside GMLC and NEF/UAS NF involved in the procedure.
1. The USS/UTM sends an Nnef_UAVFlightAssistance_Create request with an indication to provide the in-flight monitoring of a target UAV to NEF. The request includes an identifier of the UAV (e.g. GPSI) and information about the flight path(s), monitoring mode (e.g. UAV location monitoring, flight trajectory monitoring, flight environment monitoring, Ranging/Sidelink positioning location monitoring, QoS Sustainability analytics), report requirements (e.g. report format (event triggered or periodically), assistance information (e.g. the monitoring results, information generated from the monitoring results)). . Additionally, the request may include the planned fight path(s) if the fight trajectory is set for the monitoring mode, a list of UAVs in the areas of interest if the flight environment is set for the monitoring mode, preset value for distance if the monitoring mode is set to Ranging/Sidelink positioning.
2. The NEF maps the parameters in the Nnef_UAVFlightAssistance_Create request from the USS/UTM to information used by the 3GPP system. The NEF determines services needed for the message and relevant NFs, e.g. NEF service on UAV tracking (UAV location reporting mode, UAV presence monitoring mode, List of Aerial UEs in a geographic area), GMLC service (Ranging/Sidelink Positioning location), NWDAF analytics service (QoS Sustainability Analytics).
3. If the NEF is not able to provide the requested information for in-flight monitoring, the NEF rejects the USS/UTM's request for the in-flight monitoring and the NEF may include in the Nnef_UAVFlightAssistance_Create response the details about the reason for rejecton, if available.
4. For UAV's location monitoring, the NEF executes steps 2-5 of clause 5.3.2 to obtain the location of the target UAVs.
5. For fight trajectory monitoring, the NEF executes steps 2-4 of clause 5.3.3. Upon to the request message in step 1 for reporting, the NEF may compare the monitored flight path with the planned fight path (if provided in step 1) and generates a report about whether the UAV is following the assigned path/trajectory.
6. For flight environment monitoring, the NEF executes steps 2-5 of clause 5.3.4 to obtain the information of aerial UEs presence in the same geographic area as the target UAV.
7. For QoS Sustainability analytics, the NEF requests the NWDAF service as described in clause 6.9.1 of TS 23.288 [20]. The subscribe/request message include an identifier of the UAV (e.g. GPSI) obtained in step 4 and the UAV's flight path information; other parameters included in the request are described in clause 6.9.1 of TS 23.288 [20]. The list of UAVs in the area of interest is obtained in step 8 and it may be used by the NEF to request the NWDAF on QoS Sustainability analytics.
8. For location monitoring via Ranging/Sidelink positioning service, the NEF requests the GLMC service for Ranging/Sidelink Positioning location results as described in clause 6.20.4 of TS 23.273 [8], the procedure of SL-MT-LR for periodic, triggered Location Events (steps 1-20 for initiation of the monitoring, steps 21-31 for periodic monitoring). If the NEF does not have a list of UAVs in the area of interest, the NEF obtains the list of UAVs in the areas of interest in step 6 and use the obtained list as an input to request GLMC service for Ranging/Sidelink Positioning location.
9. The NEF notifies the USS/UTM using an Nnef_UAVFlightAssistance_Notify about the monitoring results (e.g. the location of the target UAV, indication on whether the UAV follows the flight path, the target UAV's presence in areas of interest, information about whether any other aerial UE/UAV is present in the same geographic area as the target UAV, distance to other UAVs and whether this distance is smaller than the preset value(s)).
Steps 4-9 may be repeated for report monitoring results periodically.
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5.13 Multiple USS serving different geographical areas
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5.13.1 USS changeover
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In cases when a UAV moves over geographical areas served by different USSs, a 3GPP network may assist the UAV UE to perform a changeover from one USS to another. The following describes the interactions in order to perform the changeover:
- USS can serve the UAV within its geographical area and each USS may have an overlap with a geographical area primally served by another USS, i.e. USS' areas may not be strictly separated. A geographical area of a USS does not necessary identically match to tracking areas or cells of a 3GPP network. However, TAI(s) or cell IDs can be used by NEF to translate/map this information and vice versa whenever required.
- Each USS is aware of its neighbouring USSs, border area(s) that it has with its neighbour USSs and possible border-crossing points for UAV.
- USSs can communicate with each other using means outside the scope of the 3GPP specification.
- USS can trigger a changeover by determining that a UAV is approaching a border its service and requesting an NEF/UAS NF to assist with the changeover.
- USS can determine whether a changeover to another USS needs to take place. The determination can be based, for instance, on a notification from the network and/or information about a UAV's next point in the flight path in a pre-flight planning request. If the changeover is required, a serving USS is able to determine a possible USS (one or more) that can serve as a target USS and can trigger communication with them to determines candidate USS border-crossing point(s) for the UAV.
NOTE: For this purpose, the serving USS relies on the pre-established knowledge that are outside the scope of 3GPP.
- Alternatively, the determination can be based on a trigger from a UAV by sending, for example, a pre-flight planning request with a next point in the flight path outside an area of authority/responsibility of a serving USS.
To determine a changeover needs to take place and collecting the required information from all suitable target USSs, a serving USS requests the core network to assist with a changeover. The request goes to the NEF/UAS NF and includes the information received from the suitable target USSs and any additional information the NEF might need to perform this task (e.g. addresses of the suitable target USSs, requirements on the flight path, candidate flight path(s), accuracy level of predictions relevant to the flight monitoring). Based on the information in the request, the NEF/UAS NF determines the relevant NFs and specific service operations it needs to invoke to collect the required information for UAV flight planning/monitoring to determine with a defined likelihood that the UAV will leave the service area of one USS and moves into area of another USS (e.g. NWDAF analytics service for Movement Behaviour analytics, GMLC service for Ranging/Sidelink Positioning location, AMF for UAV's presence in bordering cells/TAs, AMF service for UAV's deviation for the expected/assigned trajectory). The serving USS also subscribes to get notified when it is time to make the changeover.
Once the serving USS detects that the UAV has left or is about to leave its service area (for instance, based on UAV's presence in a border TA/cell), the serving USS may determine to trigger USS changeover to a target USS to serve the UAV. The currently serving USS communicates with the selected target USS and passes the target USS the following information in order to establish communication towards UAV and 5GC:
- which exposure services and notification are of relevance for the UAV;
- UAV's identifiers;
- any other information required by the target USS or by the UAV itself to establish the connection and perform authorization (e.g. a token containing information about the serving USS, the UAV, the target USS and some other parameters such as issue date, validity data, or expire date).
The serving USS also informs the UAV about the changeover to the new target USS and may instruct the UAV (directly or via NEF/UAS NF) to reconnect and authorize with the target USS as well as trigger the exposure services towards 5GC NFs similar to what the previous serving USS had before the changeover. UUAA procedure defined in clause 5.2 is performed by the UAV for authorization with the target USS and NEF/UAS NF uses the target USS address received from the serving USS to forward the UUAA request. Once the changeover is complete and the UAV enters a TA/cell in the area served by a new USS, the new serving USS informs the old serving USS about the completion.
In order to continue with the changeover procedure, 3GPP system expects the new serving USS to respond to the notification in such a way confirming to the network about the completion of the changeover for the UAV. A UUAA authenticated context shall be established between the UAV and the new USS before the UAV interact with the new USS.
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5.13.2 Procedure for USS changeover during a UAV flight
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Procedure for USS changeover in cases when a UAV moves over geographical areas served by different USS is shown in Figure 5.13.2-1.
NOTE 1: This procedure can be used in conjunction with the NEF-assisted pre-flight planning as specified in clause 5.12.
NOTE 2: USS changeover is independent of AMF(s) or NEF(s) changes, i.e. both a serving USS and a target USS can be served by the same 5GC NFs (e.g. AMF, NEF/UAS NF) during the entire UAV flight from the starting point to the next point in the flight path via the USS-determined flight path(s).
NOTE 3: Security aspects of the USS changeover procedure is defined in TS 33.256 [10].
Figure 5.13.2-1: Procedure for UAV changeover from one USS to another serving different geographical areas
1. The UAV establishes a PDU Session for communication with a serving USS (shown as USS 1 in Figure 5.13.2-1) as described in clause 5.2.3.
2a. (via application layer) The UAV requests the pre-flight planning service from the serving USS, if needed. The request message includes an identifier of the UAV (e.g. GPSI, CAA-Level UAV ID), information of the starting and next point for the flight, requirements on the flight route (e.g. on time, shortest, highest, the farthest from a no-transmit zone) and may include candidate flight path(s) if available.
2b. The serving USS determines the need for the changeover to another USS based on the information about UAV's next point in the flight path or notification from the core network (e.g. UAV location reporting events from AMF/GMLC/LMF when serving USS has subscribed to such events).
3. The serving USS determines neighbouring USSs (one or more) that can serve as a target USS and triggers communication with all suitable target USSs (USS 2 in Figure 5.13.2-1) to determine candidate border-crossing point(s) for the UAV.
NOTE 4: The serving USS determines suitable target USSs as well as a candidate border-crossing points between the serving USS and potential target USSs by means outside the scope of the 3GPP; for this purpose several criteria/metrics can be used, e.g. location of the next point in the flight path, area that a specific USS serves, a number of UAVs in the area served by a specific USS, proximity to no-transmit zones, USS load, etc.
NOTE 5: A border-crossing point can be described using the Polygon shape as specified in clause 5.4 of TS 23.032 [21].
NOTE 6: It is assumed not more than one border-crossing point per tracking area.
The serving USS in cooperation with the UTM derives any other information (e.g. acceptable deviations from the assigned flight plan/route) that can be used by 5GC to assist with the USS changeover and/or to provide flight planning assistance information.
NOTE 7: The exact information that a USS can use for this purpose is outside the scope of the 3GPP, however, it can contain, for instance, information about UAV capability, geographical coordinates of the candidate border-crossing point(s), indication to reconnect to the network once the UAV enters a TA served by another USS, information about no-transmit zone (NTZ), etc.
4. The USS invokes an Nnef_RetrieveInfoUAVFlight_Get request to the NEF/UAS NF to collect from the core network information for the changeover. Inside the request, the serving USS includes the information derived in step 3 (e.g. indication about USS changeover, list of addresses for suitable target USS, a list of candidate border-crossing point(s), information about the starting and ending points for the flight, acceptable deviations for flight plan/route), UAV's identifier (e.g. GPSI) and other parameters such as requirements on the flight path, candidate flight path(s), accuracy level of predictions relevant to the flight planning.
NOTE 8: In this procedure mentioned service operations can be reused for pre-flight planning procedure as described in clause 5.12.
5. When the NEF/UAS NF receives the Nnef_RetrieveInfoUAVFlight_Get request from the serving USS with the indication about the USS changeover, the NEF/UAS NF translates/maps, if required, the parameters included in the USS request to 3GPP identifiers. For instance, the NEF determines a cell ID/tracking area identifier (TAI) of the cell/TA where the UAV-requested starting and next point in the flight path are located; similarly, if the request includes an indication that UAV will cross the USS-border and/or a list of the candidate border-crossing point(s) in form of geographical coordinates, the NEF maps them to a list of border cell IDs/TAIs.
The NEF determines the relevant NFs and specific service operations it needs to invoke to collect the required information for the serving USS for the purpose of UAV flight planning (e.g. NWDAF analytics service for Movement Behaviour analytics, GMLC service for Ranging/Sidelink Positioning location, AMF for UAV's presence in bordering TAs/cells, AMF service for UAV's deviation for the expected/assigned trajectory, UDM service for expected UE behaviour parameter provision).
6. The NEF/UAS NF invokes service operations towards the identified NFs as described in Steps 8-12 of the procedure for the NEF-assisted pre-flight planning, see clause 5.12.
7. If the NEF/UAS NF receives a list of candidate border-crossing points, the NEF/UAS NF identifies the AMFs serving NG-RAN nodes in all identified border TA(s)/cell(s); for that the NEF/UAS NF uses the Nnrf_NFDiscovery service from NRF. Once the AMF(s) information is retrieved, the NEF/UAS NF invokes an Namf_EventExposure_Subscribe request to subscribe to the UE/UAV's presence in area of interest wherein the area of interest is set to cell ID(s)/TAI(s) of the border cells(s)/TA(s).
8. The NEF/UAS NF responds to the Nnef_RetrieveInfoUAVFlight_Get request with the collected information from the 5GC NFs for UAV's flight path between the starting point and all candidate USS border-crossing point(s).
9. Based on the received information, the serving USS selects the target USS from the list of pre-selected suitable USSs (step 3) and starts communication to request the target USS (USS 2 in Figure 5.13.2-1) to prepare for the USS changeover and, if required, to perform the flight planning for the UAV from the border-crossing point(s) to the next point in the flight path that is located in the geographical area served by the target USS.
10. The target USS (USS 2) performs Steps 4 - 8 to plan the UAV flight across its geographical area towards the UAV's next point in the flight path.
11. The target USS (USS 2) provides the serving USS (USS 1) information about UAV's flight path(s) from a border cell(s)/TA(s) to the next point in the flight path (e.g. primary flight path, secondary/alternative flight path etc.).
12. (via application layer not defined in this specification) If the UAV requests a pre-mission flight planning in step 2a, the serving USS responds to this request with the planned flight routes and time schedule for the entire flight from the starting point to the next point in the flight path.
13. The serving USS sends an Nnef_UAVFlightAssistance_Create request to the NEF/UAS NF with the information about the planned UAV flight path(s), see clause 4.4.1.1.3.3. In this request, the serving USS may also include additional flight path information for each of the segment of the paths (served by USS 1 and USS 2), for instance, UAV's speed, flight height/altitude and/or time schedule for crossing/spending at each of the TAs/cells.
14. The NEF/UAS NF may invoke additional services with 5GC NFs: with AMF to determine the UAV deviation from the expected UAV's flight trajectory (e.g. primary/secondary flight paths); with UDM to update the Expected UE Behaviour parameters via the parameter provision; with the NWDAF for the Movement Behaviour analytics of the UE/UAV to determine whether the UAV will likely leave the USS area and continue following the flight path or not.
The expected UAV's flight trajectory may possibly consist of multiple segments where each of the segments are identified by geographical areas that are served by a different USSs (e.g. the currently serving USS and the target USS for the changeover).
14a. The NEF/UAS NF may use the AMF event exposure service to get notified when the UAV does not follow (i.e. deviates from) the assigned flight plan. In this case, the NEF/UAS NF sends a Namf_EventExposure_Subscribe request to the serving AMF with the planned flight path information, which consists of a list of 3GPP locations (i.e. TAIs or cell IDs), a time schedule describing when the UE shall be present at these locations, height/altitude range and, optionally, acceptable deviations, e.g. the UAV not arriving on time.
14b. The NEF/UAS NF invokes the parameter provisioning service from the UDM (i.e. Nudm_ParameterProvision_Update, see clause 4.15.6.3 of TS 23.502 [3]) to provision the planned flight path information, which consists of a list of 3GPP locations (i.e. TAIs or cell IDs and, optionally, height/altitude information) together with the time schedule describing when the UE shall be present at these locations, optionally, acceptable deviations, e.g. UAV is not arriving on time or UAV flies below/above the assigned flight altitude.
14c. The NEF/UAS NF invokes a Nnwdaf_AnalyticsInfo_Request / Nnwdaf_AnalyticsSubscription_Subscribe service operation towards the NWDAF in order to obtain the Movement Behaviour analytics of the UE/UAV as described in clause 6.21 of TS 23.288 [20].
15. If the NEF/UAS NF subscribes (in step 7) to UAV's presence in the borders cell(s)/TA(s)s, the AMF notifies the NEF/UAS NF once the UAV enters a border cell/TA of the serving USS about the event (i.e. UAV enters the Area of Interest). Similarly, if the NEF/UAS NF subscribes for event reporting when the UAV deviating from the expected/assigned trajectory and/or moving across different trajectory segments, the AMF notifies the NEF/UAS NF when either of the events are detected.
16. When the NEF/UAS NF receives a report from the AMF indicating the UAV is deviating the assigned flight plan, the NEF/UAS NF may invoke an Ngmlc_Location_ProvideLocation service request to a GMLC to get a accurate position of the UAV. In such case, the GMLC performs the 5G-MT-LR procedure to retrieve the accurate UAV location via AMF/LMF (as specified in TS 23.273 [8]) and provide the UAV location to the NEF/UAS NF in an Ngmlc_Location_ProvideLocation service response.
17. If the NEF/UAS NF determines that the UAV is leaving the geographical area served by the serving USS (USS 1), the NEF/UAS NF sends a Nnef_UAVFlightAssistance_Notify (as described in clause 4.4.1.1.3.5) to the serving USS in which it includes information about which/when border-crossing point will be used by the UAV so that the USS timely triggers the changeover.
18. The serving USS communicates with the target USS to execute the changeover for the UAV; this communication and details are outside the scope of the 3GPP specification, however, it is expected that a serving USS pass the target USS the information on which exposure services/notifications are of relevance for the UAV (e.g. subscribed events and UAS NF address), UAV's identifiers (e.g. GPSI, CAA-Level UAV ID) and other information required by the target USS (or UAV itself) to establish the connection.
19. The AMF serving a border TA/cell on the target USS's side (USS 2) notifies a serving NEF/UAS NF about the UAV's presence in the border TA/cell and the NEF/UAS NF invokes the Nnef_UAVFlightAssistance_Notify service operation to further notify the target USS.
20. The serving USS (USS 1) informs the UAV via application layer (not defined in this specification) about the changeover to the new USS (USS 2). If required USS (USS 1) may instruct the UAV to execute the UUAA procedure with the new USS (USS 2) when initiated by the USS 2.
Additionally, USS 1 may instruct USS 2 to invoke the exposure services towards 5GC NFs similar to what the previous USS had before the changeover.
NOTE 9: Steps 19 and 20 can continue in parallel and not intended to imply sequential processing.
21. After receiving the required information from the serving USS (the exact details are outside the scope of the 3GPP specification), the target USS responds to the Nnef_UAVFlightAssistance_Notify from the NEF/UAS NF in such a way completing the changeover for the UAV.
22. The new USS (i.e. the target USS) sends an Nnef_UAVFlightAssistance_Update request to the NEF/UAS NF with the information about a new Notification Target Address to receive notifications from the implicit subscription invoked via the Nnef_UAVFlightAssistance_Create request by the previous serving USS in step 13.
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5.14 Support of Network-Based/Assisted DAA
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5.14.1 Functional Description
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This clause provides a network-based/assisted DAA mechanism. To enable NWDAA, the following information can be utilised:
- Absolute location of a UAV provided by the LoCation Service;
- Relative Location of UAVs provided by the Ranging Service;
- Output of Relative Proximity Analytics provided by NWDAF.
Absolute location of a UAV is generated/derived in 5G network by using the existing LCS feature defined in TS 23.273 [8]. USS may request to GMLC to obtain one or multiple UAV location as defined in clauses 6.2.1, 6.3.1 or 6.20.5 of TS 23.273 [8]. As an example, USS may use the absolute location of the UAV(s) provided by the network to e.g. calculate relative distance of the pair of UAVs and based on that to deal with the UAV tactical deconfliction, collision avoidance etc.
Relative location of a UAVs is provided in 5G network by using the existing LCS Ranging feature defined in TS 23.273 [8]. USS may send a Ranging request to GMLC to obtain relative location between one and multiple UAVs as defined in clauses 6.20.3 or 6.20.4 of TS 23.273 [8]. USS may use the relative location of the UAV(s) to avoid collision.
USS (acting as an AF) may request Relative Proximity Analytics provided by NWDAF for the purpose of DAA.
NOTE: How USS uses the relative distance of UAVs or absolute location of a UAV or Output of Relative Proximity Analytics to determine the potential collisions is out of 3GPP scope.
To deconflict the potential collisions, the USS notifies the potential collision to the UAV UE or AAM or UAV-C which is responsible to inform the paired UAV about the collision. When the notification of the potential collision is received by AAM, it performs the deconfliction by triggering the mechanism specified for ground-based DAA for an area in clause 5.7.2. When the UAV UE receives the potential collision notification from USS or the paired UAV-C, it performs the deconfliction by triggering the mechanism specified for DAA based on PC5 in clause 5.6.1.
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5.14.2 Procedure for UAV Triggered Network-assisted DAA
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Figure 5.14.2-1: Procedure for UAV/UAV-C Triggered Network-assisted DAA
1. The UAV establishes a PDU Session for communication with the USS as described in clause 5.2.3.
2. The DAA service may be triggered by UAV(s). The UAV(s) (via its paired UAV-C) requests DAA service from USS. The request message includes identifier of the UAV(s) (e.g. GPSI(s), CAA-Level UAV ID(s)). USS derives information on DAA service and decides to subscribe/request to 5GC for GMLC service on Ranging/Sidelink Positioning location and/or Relative Proximity predictions on collision from NWDAF.
NOTE 1: The other content of DAA service information derived at USS is out of scope.
3. The USS may request GMLC service via NEF:
- The USS may request GMLC service via NEF for Ranging/Sidelink Positioning location results, i.e. the relative positioning between UAV UEs as described in clause 6.20.3 of TS 23.273 [8] for one notification, or clause 6.20.4 of TS 23.273 [8] for notifications (steps 1-20 for initiation monitoring, steps 21-31 for monitoring periodic).
- USS as AF may send the absolute positioning request to GMLC, including UAV UE1 ID (UE1 GPSI) and UAV UE2 ID (UE2 GPSI) as described in clauses 6.2 and 6.3.1. GMLC replies to USS of the absolute location of UAV 1 and UAV 2. USS calculates the relative positioning result based on the UAV UE1 absolute location and UAV UE2 absolute location.
NOTE 2: USS can request same or different GMLC for the UAV1 and UAV 2 location, e.g. depending on which PLMN the UAV registers.
4. The USS may request NWDAF service via NEF:
4a. The USS may subscribe or request notification on Relative Proximity predictions provided by NWDAF via NEF by invoking Nnef_AnalyticsExposure_Subscribe service operation as defined in clause 6.1.1.2 of TS 23.288 [20] or Nnef_AnalyticsExposure_Fetch service operation as defined in clause 6.1.2.2 of TS 23.288 [20]. The subscribe/request message include identifier of the UAV(s) (e.g. GPSI(s)). The other parameters included in the request are described in clause 6.19 of TS 23.288 [20].
4b. After NEF receives the request from the USS, the NEF interacts with the NWDAF as described in the procedure in clause 6.19.4 of TS 23.288 [20]. The NEF maps the parameters in the request from the USS to information used by the 3GPP system. The NWDAF interacts with GMLC for UE position. If the requested type of location is "current or last known location" and the requested maximum age of location information is available, the GMLC verifies whether it stored the previously obtained location estimate of the target UE. If the previously obtained location estimates of the target UE exist and meets the age of location requirement, the GMLC sends it to the NWDAF; if it does not exist, the GMLC sends provide positioning request to AMF to determine current location for the target UE and sends it to the NWDAF.
4c. If the NEF receives the response from the NWDAF, the NEF notifies the USS with the Relative Proximity predictions by invoking Nnef_AnalyticsExposure_Notify service operation for a Subscribe-Notify model as defined in clause 6.1.1.2 of TS 23.288 [20] or Nnef_AnalyticsExposure_Fetch service operation for a Request-Response model as defined in clause 6.1.2.2 of TS 23.288 [20].
NOTE 3: Steps 3 and 4 can be performed in any order (e.g. simultaneously, sequentially, or alternately).
NOTE 4: There is a possibility that between steps 3 and 4b, GMLC receives concurrent location requests from NEF and NWDAF and GMLC can decide to combine the concurrent location requests by fully executing one of the requests and using the ensuing location estimate result(s) to satisfy the other request(s) without fully executing the latter, as defined in TS 23.273 [8].
5. If receiving the location of UAV1 and UAV2, USS calculates the relative positioning result for UAV UE1 location and UAV UE2 location from step 1 and step 2. The USS estimates the potential collision based on the information received in step 3 and/or the predictions from step 4c. The USS informs the UAV-C(s) the potential collision. The message may include collision alert, predicted time of collision, CAA-level UAV IDs of the paired UAVs which may collision (e.g. UAV 1 and UAV 2), deconflicting specific parameters (e.g. trajectory correction information to avoid collision).
USS may be replaced by TPAE.
6. The UAV-C(s) informs its paired UAV(s) the potential collision and information received from the USS, include collision alert, predicted time of collision, CAA-level UAV IDs of the paired UAVs which may collision and deconflicting specific parameters (e.g. trajectory correction information to avoid collision).
7. UAVs performs operations to avoid collision.
7a. If both the two UAVs which may collision (e.g. UAV 1 and UAV 2) been informed by their paired UAV-C(s), the UAVs can be steered to avoid collision in accordance with the received information (e.g. trajectory correction information to avoid collision) and using mechanisms that are out of scope for 3GPP.
7b. If only one of the two UAVs which may collision (e.g. UAV 1) been informed by its paired UAV-C, the UAV 1 triggers conflict resolution procedure with UAV 2 as described in steps 4-7 in clause 5.6.1.
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5.14.3 Procedure for AAM Triggered Network-assisted DAA
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Figure 5.14.3-1: Procedure for AAM Triggered Network-assisted DAA
1. As described in clause 5.7.2 steps 1-6, the UAV(s) listens for signals on the correspondingly destination Layer-2 ID configured for the used service type. The AAM scans the airspace over the area/arena for UAV(s), retrieves for each detected UAV the corresponding Remote-ID and establishes a PC5 direct communication link with the discovered UAV. Using the PC5 unicast direct communication link the AAM and the UAV establishes a bidirectional communication channel for exchange of messages.
2. The AAM establishes a PDU Session for communication with the USS as described in clause 5.2.3.
3. The AAM may request network assist DAA service from USS. The request message includes identifier of the UAV(s) (e.g. GPSI(s), CAA-Level UAV ID(s)). USS derives information on DAA service and decides, e.g. to request GMLC service for Ranging/Sidelink Positioning location, to subscribe/request to NWDAF for Relative Proximity predictions on collision.
NOTE: The other content of DAA service information derived at USS is out of scope.
4. The USS requests GMLC service for Ranging/Sidelink Positioning location and/or subscribes/requests notification on Relative Proximity predictions provided by NWDAF via NEF, as described in steps 3-6 of clause 5.14.2.
5. The USS estimates the potential collision based on the received information/analytics in step 4. The USS informs the AAM the potential collision. The message may include collision alert, predicted time of collision, CAA-level UAV IDs of the paired UAVs which may collision (e.g. UAV 1 and UAV 2), deconflicting specific parameters (e.g. trajectory correction information to avoid collision).
6. The AAM provides the determined steering policy to the specific UAVs (e.g. UAV 1 and UAV 2) according to the information received in step 5 and the UAVs are steered to avoid collisions in accordance with received policy and using mechanisms that are out of scope for 3GPP, as described in clause 5.7.2 steps 7-8.
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5.14.4 Procedure for USS Triggered Network-assisted DAA
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Figure 5.14.4-1: Procedure for USS Triggered Network-assisted DAA
1. The UAV and UAV-C establish PDU Session for communication with the USS as described in clause 5.2.3.
2. The USS may decide to trigger NWDAA based on application layer request.
3. The USS requests absolute location of UAV(s) based on the identifiers received in step 2 by invoking the 5GC-MT-LR procedure for the commercial location service in clause 6.1.2 or Initial and Reporting of Location Events in clause 6.3.1 or 5GC-MT-LR procedure using SL positioning in clause 6.20.5 of TS 23.273 [8].
4. [Optional] The USS may subscribe or request notification on Relative Proximity predictions provided by NWDAF via NEF by invoking Nnef_AnalyticsExposure_Subscribe service operation as defined in clause 6.1.1.2 of TS 23.288 [20] or Nnef_AnalyticsExposure_Fetch service operation as defined in clause 6.1.2.2 of TS 23.288 [20]. The subscribe/request message include identifier of the UAV(s) (e.g. GPSI(s)).
5. [Optional] If the step 4 is performed, after NEF receive the request from the USS, the NEF interacts with the NWDAF as described in the procedure in clause 6.19.4 of TS 23.288 [20]. The NEF maps the parameters in the request from the USS to information used by the 3GPP system.
The NWDAF interacts with GMLC for UE position. If the requested type of location is "current or last known location" and the requested maximum age of location information is available, the GMLC verifies whether it stored the previously obtained location estimate of the target UE. If the previously obtained location estimates of the target UE exist and meets the age of location requirement, the GMLC sends it to the NWDAF; if it does not exist, the GMLC sends provide positioning request to AMF to determine current location for the target UE and sends it to the NWDAF.
6. [Optional] If the NEF receives the response from the NWDAF, the NEF notifies the USS with the Relative Proximity predictions by invoking Nnef_AnalyticsExposure_Notify service operation for a Subscribe-Notify model as defined in clause 6.1.1.2 of TS 23.288 [20] or Nnef_AnalyticsExposure_Fetch service operation for a Request-Response model as defined in clause 6.1.2.2 of TS 23.288 [20].
7. The USS performs step 7a and 7b or step 7C.
7a. If the USS detects the potential collision based on the information received in step 3 and/or step 6, the USS notifies the potential collision to UAV-C.
7b. [Conditional] If the step 7a is performed, the UAV-C further notifies the potential collision to UAV.
7c. If the USS detects the potential collision based on the information received in step 3 and/or step 6 is performed, the USS notifies the potential collision to UAV UE.
8. If the USS detects the potential collision based on the information received in step 3 and/or step 6, the USS notifies to potential collision to AAM.
NOTE: The notification in steps 7a, 7b and 8 is out of 3GPP scope. As an example, the notification may include collision alert, predicted time of collision, CAA-level UAV IDs of the paired UAVs which may collision (e.g. UAV 1 and UAV 2), deconflicting specific parameters (e.g. trajectory correction information to avoid collision).
9. [Conditional] If the step 8 is performed, to avoid confliction, steps 6-8 in high-level procedure for Ground-based DAA for an Area in clause 5.7.2 are performed.
10. [Conditional] If the step 7b or step 7c is performed, to avoid confliction, steps 4a-7 in DAA procedure based on PC5 in clause 5.6.1 are performed.
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5.15 Support of No-Transmit Zones
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The following principles are applied to support of NTZ for UAV UEs.
1) NTZ enforcement applies to the UE that is a UAV UE (i.e. an aerial UE that is a UE with aerial subscription).
2) UAV UEs supporting NTZ regulations are configured/provisioned with NTZ assistance information comprising of a mandatory list of the restricted frequency band(s) with Geographical Area (including coordinates with longitude, latitude and altitude restrictions) and optional time restriction, so that these UAV UEs are aware of the presence of NTZs.
3) NTZ enforcement by UAV UE applies for both LTE and NR.
4) An NTZ can map to one or more cells or a fraction of one or more cells, or overlap different cells in a mobile operator network.
NOTE 1: Replanning of existing tracking areas and cells based on the presence of NTZs is not assumed.
NOTE 2: NTZ mapping to cells will have no impacts on 3GPP specifications, hence application of NTZ to cells is UE implementation-specific.
5) UAV UE shall neither transmit nor attempt to transmit in the NTZ (i.e. in the geographic area of the NTZ, within the restricted frequency bands, and within the time restrictions when provided), regardless of the service type including emergency services. NAS layer and AS layer in the UAV UE without using AS signalling, are used to prevent the UAV UE to send data or signalling while in the NTZ.
6) For UAV UEs outside of the NTZ, the normal EPS/5GS procedures apply.
7) UAV UEs supporting NTZ regulations are configured/provisioned with NTZ assistance information, so that these UAV UEs are aware of the presence of NTZs.
The UAV UE(s) configured with the NTZ assistance information is responsible to provide such assistance information to the AS layer in the UE for the UE's AS layer to perform NTZ enforcement in implementation dependent ways:
NOTE 3: It is assumed that UAV UE is configured with NTZ assistance information before registering for UAS services with the 3GPP system, if the local regulation requires NTZ.
The above NTZ assistance information is made available to the UAV UE in following ways:
- pre-configured;
- configured by using mechanism that is out of 3GPP scope.
The UAV UE(s) configured with the NTZ assistance information is expected to perform the following:
a) enforces NTZ based on the configured/provisioned NTZ assistance information.
b) does not transmit any signalling or data within the restricted frequency bands upon applying NTZ enforcement.
c) when in an NTZ, does not select/reselect any cells in restricted frequency bands.
d) when in an NTZ, does not send measurement reports to the RAN about cells in restricted frequency bands.
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5.16 Altitude reporting for aerial UEs
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5.16.1 General
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In order to assist a USS/UTM with aerial UE's flight planning and monitoring, the 5GS may enable configuration of aerial UEs (UAVs) to perform altitude reporting. This may include providing aerial UEs with threshold values for altitude reporting and/or request reporting periodicity (e.g. threshold-based, event-based, periodic). For that, the 5GS may determine altitude thresholds and periodicity with which an aerial UE should report its altitude. Altitude thresholds can be derived, for instance, based on the flight path information provided by the serving USS/UTM during a pre-flight planning request or a USS changeover request. Delivery of the altitude thresholds and reporting periodicity can be done via application layer or via node-level signalling as specified in clause 5.16.2. The 5GS should forward the altitude measurements results to the AMF and NEF/UAS NF in the case of node-level signalling. When the aerial UE's flight altitude meets the altitude reporting conditions, the aerial UE's altitude information is reported as specified in clause 5.16.3.
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5.16.2 Instructing aerial UEs to perform altitude reporting
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Procedure shown in Figure 5.16.2-1 specifies how the 5GS instructs the aerial UEs (UAVs) to perform altitude reporting, considering requests from a USS/UTM for assistance with UAV's flight. This procedure can be used in conjunction with the NEF-assisted pre-flight planning, in-flight monitoring and USS changeover as specified in clauses 5.12.2, 5.12.3 and 5.13, respectively.
Figure 5.16.2-1: Procedure for instructing aerial UEs for altitude reporting
1. UAS NF/NEF assists the USS/UTM with pre-fligh planning, in-flight monitoring and/or USS changeover based on the received request, which is either a Nnef_RetrieveInfoUAVFlight_Get or a Nnef_UAVFlightAssistance_Create, as specified in clauses 5.12 or 5.13.
2. Based on the flight path information included in step 1 and other information obtained as a result of either of the procedures (i.e. NEF-assisted pre-flight planning specified in clause 5.12.2, NEF-assisted in-flight monitoring specified in clause 5.12.3, or USS changeover specified in clause 5.13.2), the UAS NF/NEF determines minimum and maximum values of altitudes (i.e. altitude range) for UAV's flight across each of the determined tracking areas (TAs) from the starting point to the destination point.
The determined minimum and maximum altitude values for each of the UAV UE is used by the UAS NF/NEF to derive altitude thresholds for altitude reporting events.
NOTE 1: Event H1 and H2 for altitude-based reporting specified in clause 5.5.4.21 and clause 5.5.4.22 of TS 38.331 [23] can be used for altitude thresholds and event-based reporting.
Additionally, the UAS NF/NEF determines whether to request the aerial UE to report its altitude information periodically, threshold-based (e.g. altitude becomes a higher/lower than the provided threshold, multiple threshold values can be provided) or event-based (e.g. change of a tracking area/NG-RAN node).
3. Delivering the UAS NF/NEF-derived altitude thresholds and, optionally, the indication about reporting periodicity (i.e. threshold-based, event-based, or periodic) for UE's altitude reporting to the aerial UE(s).
Option A: Application layer.
3a. The UAS NF/NEF sends the derived altitude threshold values and provides indication about the required periodicity of the reporting (on demand, event-triggered, periodic, or per change of the altitude, or change of a specific geographical area) to the serving USS/UTM either in a Nnef_RetrieveInfoUAVFlight_Get response message or in a Nnef_UAVFlightAssistance_Notify message depending on the procedure that has triggered the UAS NF/NEF to derive the altitude thresholds for the aerial UE.
4a. The USS/UTM sends the altitude reporting thresholds and, optionally, indication about reporting periodicity (and any additional information required to perform the reporting, e.g. a list of TA(s)/NG-RAN node identifier(s) for event-based reporting, periodicity value for periodic reporting) to the UAV over the application layer for the UAV's consumption.
NOTE 2: Application layer reporting itself is outside of 3GPP scope.
Option B: Node-level signalling.
Editor's note: This requires RAN to provide further enhancement of the procedure under RAN responsibility.
3b. The UAS NF/NEF may send an Namf_EventExposure_Subscribe request to the AMF to get notified about events of UAV's deviation from the assigned trajectory (i.e. Event ID = "Assigned Trajectory") as specified in clause 5.2.2.3.1 of TS 23.502 [3]. Inside the subscription request, the UAS NF/NEF may include the derived altitude thresholds and indication about reporting periodicity for the UE's altitude reporting.
Additionally, the UAS NF/NEF may also include an indication to perform UE's altitude reporting for all aerial UEs in a specific TA(s) or NG-RAN node(s).
4b. The AMF sends the corresponding N2 messages to all applicable NG-RAN node(s).
5b. The NG-RAN node(s) instructs the relevant UE(s) to perform altitude reporting as requested by the UAS NF/NEF (via AMF).
NOTE 3: Aspects related to AMF informing NG-RAN regarding instructing UEs to perform altitude reporting are specified in TS 38.413 [24].
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5.16.3 Reporting UE's altitude information
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A procedure for reporting aerial UE's altitude information to the core network is shown in Figure 5.16.3-1. The reporting can be done by the aerial UE based on the received altitude reporting thresholds and indication about reporting periodicity as specified in clause 5.16.2.
Figure 5.16.3-1: Procedure for reporting of UE's altitude information
0. An aerial UE receives request to perform its altitude information reporting as specified in clause 5.16.2. The request may include altitude reporting thresholds and, optionally, indication about reporting periodicity.
1. UE's flight altitude meets the previously provided altitude reporting conditions (i.e. altitude thresholds and, optionally, reporting periodicity).
Option A: Application layer.
2a. The UE may report the altitude information over the application layer to the serving USS/UTM in case the USS/UTM has provided altitude reporting threshold and, optionally, indication about reporting periodicity in step 4a in clause 5.16.2.
NOTE 1: Application layer reporting itself is outside of 3GPP scope.
3a. The USS may invoke the Nnef_UAVFlightAssistance_Update to inform the UAS NF/NEF about UE's altitude and time stamp of the altitude.
Option B: Node-level signalling.
1b. The UE provides a report with the altitude information to the NG-RAN.
NOTE 2: Aspects related to a UE providing altitude information to an NG-RAN node are specified by RAN in TS 38.331 [23].
2b. After receiving a report with the altitude information from the UE, the NG-RAN node should, for instance, add a time stamp indicating when the altitude information has been received from the UE; the NG-RAN sends the UE's altitude information report in an N2 message to the AMF.
3b. The AMF provides the UAS NF/NEF the altitude information report inside a Namf_EventExposure_Notify request.
4. The UAS NF/NEF together with the USS determines the impact on UAV's flight path based on the received altitude information report; this aspect is outside the scope of the 3GPP.
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6 Aircraft-to-Everything (A2X) services
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6.1 Architecture model and concepts
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6.1.1 General concept
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There are two modes of operation for A2X communication, namely A2X communication over PC5 reference point and A2X communication over Uu reference point. These two operation modes may be used by a UE independently of different A2X communications.
A2X communications over PC5 reference point are supported by LTE and/or NR.
A2X communications over Uu reference point are supported by NR connected to 5GC.
A2X leverages both LTE PC5 as defined in TS 23.285 [12] and NR PC5. For LTE PC5 in EPS, the network scheduled operation mode defined in TS 23.285 [12] is not supported and the A2X uses only the UE autonomous resources selection mode.
Groupcast mode for NR based PC5 is not supported.
Subscription to A2X services based on the user's profile stored in the UDM is supported as described in clause 6.2.5.
Both UAV UEs that utilize Uu connectivity and that do not utilize Uu connectivity (i.e. either UAV UEs that are Uu capable and do not use Uu) are supported. A UAV without utilizing Uu capabilities may use A2X for C2 communication, BRID and DDAA and be configured via A2X1 over a transport outside the scope of 3GPP.
NOTE 1: UAV UEs without utilizing Uu capabilities are part of the 3GPP ecosystem since they use A2X1 for configuration by a A2X Application Server and implement PC5 connectivity specified by 3GPP.
Both UAVs with UICC and UAVs without UICC (i.e. with no subscription to an MNO) are supported. UAVs with no UICC can only perform A2X communications when authorized for "not served by E-UTRA" and "not served by NR".
No specific authorization of the use of PC5 for A2X services (i.e. BRID, DDAA, Ground based DAA) is required by the USS. For UAVs without UICC, or UAVs with UICC that are out of coverage or are served by a PLMN where UUAA has not been performed, the use of PC5-based communications for A2X services is authorized only by A2XP via pre-configuration or A2X1.
In this version of the specification, UAV UEs may support A2X capability for A2X communication over PC5 reference point and/or A2X capability for A2X communication over Uu reference point.
In this Release, communication over PC5 between the UAV UEs served by different PLMNs is possible in NR when the UAV UEs use the same sidelink carrier.
UAV UEs that use the UE autonomous resources selection based on pre-configuration for NR PC5 can communicate over NR PC5 independently of the serving PLMN. The UE shall support the procedures described in clause 5.1.2.2 of TS 23.287 [11], for both E-UTRA and NR, so that the UE can perform A2X communications over PC5 reference point when "not served by E-UTRA" and "not served by NR". The UE, in order to perform these procedures, shall reliably locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorized to transmit.
NOTE 2: It is out of scope of the present specification to define how the UE can locate itself in a specific Geographical Area. When the UE is in coverage of a 3GPP RAT, it can for example, use information derived from the serving PLMN. When the UE is not in coverage of a 3GPP RAT, it can use other techniques, e.g. Global Navigation Satellite System (GNSS). User provided location is not a valid input.
NOTE 3: It is assumed that any security of A2X solution is addressed by SA WG3.
NOTE 4: The A2X application layer schemes developed in other SDOs are outside the scope of this specification.
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fe86991d3e142214ebb7d1b178b6c24b
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23.256
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6.1.2 Architectural reference model
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fe86991d3e142214ebb7d1b178b6c24b
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23.256
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6.1.2.1 PC5 and Uu based A2X architecture reference model
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fe86991d3e142214ebb7d1b178b6c24b
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23.256
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6.1.2.1.1 Non-roaming 5G System architecture for A2X communication over PC5 and Uu reference points
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Clause 4.2.3 describes the non-roaming architectures for A2X communications.
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fe86991d3e142214ebb7d1b178b6c24b
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23.256
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6.1.2.1.2 Roaming 5G System architecture for A2X communication over PC5 and Uu reference points
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Clause 4.2.4 describes the roaming architectures for A2X communications.
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fe86991d3e142214ebb7d1b178b6c24b
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23.256
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6.1.2.1.3 Inter-PLMN 5G System architecture for A2X communication over PC5 reference point
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In the case of inter-PLMN A2X communication over PC5 reference point, the PC5 parameters need to be configured in a consistent way among the UEs within a certain region. The architecture for the Inter-PLMN PC5 case is similar to the one defined in clauses 4.2.3 and 4.2.4.
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fe86991d3e142214ebb7d1b178b6c24b
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23.256
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6.1.2.2 AF-based service parameter provisioning for A2X communication
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The 5G System provides NEF services to enable communication between NFs in the PLMN and A2X Application Server. Figure 6.1.2.2-1 shows the high level view of AF-based service parameter provisioning for A2X communications. The A2X Application Server may provide A2X service parameters to the PLMN via NEF. The NEF stores the A2X service parameters in the UDR.
Figure 6.1.2.2-1: 5G System architecture for AF-based service parameter provisioning for A2X communications
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fe86991d3e142214ebb7d1b178b6c24b
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23.256
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6.1.2.3 MBS for Uu based A2X architecture reference model
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A2X leverages what is defined for V2X in TS 23.287 [11] clause 4.2.2A with the following differences:
- V2X is replaced by A2X.
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