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.
For a UAV with aerial subscription the SMF+PGW-C determines based on the APN/DNN of the PDN Connection and the presence of the Service Level Device Identity (e.g. the CAA-Level UAV ID of the UAV) that C2 authorization is required. 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.
For a UAV with aerial subscription, if the SMF+PGW-C determines based on the APN/DNN of the PDN Connection and the presence of the Service Level Device Identity (e.g. the CAA-Level UAV ID of the UAV) 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.
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 18.104.22.168.3-1
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 22.214.171.124.2-1
) 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.