Content for  TS 23.256  Word version:  18.2.0

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.

Steps 1 - 3 performed as in Figure 5.10.2-1 of TS 23.401. 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.

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.

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.

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).

The UAS NF/NEF forwards the information received from the USS in the Nnef_Authentication_AuthenticateAuthorize response sent to the SMF+PGW C.

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.

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, 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.

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.

The UE establishes a PDN Connection for USS communication as described in clause 5.2.3.

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. 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.

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.

The UE requested bearer resource modification procedure completes as in Figure 5.4.5-1 of TS 23.401.

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).

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 UE, MME or RAN.