The UAV sends an Attach Request to the MME. The UAV includes the Aviation Connectivity payload which contains the allocated CAA-Level UAV ID and flight/pairing information in the message.
The MME authenticates the UAV and establishes the security.
The MME determines the subscription is an aerial subscription and selects the SMF+PGW-C to establish the default bearer.
The MME sends a Create Session Request message to the SMF+PGW-C. The message includes the Aviation Connectivity payload.
The SMF+PGW-C responds with a Create Session Response. At this point the UAV is restricted from sending user plane traffic.
The MME sends an Attach Accept message to the UAV.
The UAV responds with an Attach Complete message to the MME.
The SMF+PGW-C requests a UAV authentication and authorization from the UFES and includes the Aviation Connectivity payload in the request.
The UFES forwards the information to the USS/UTM. Only authorized USS/UTMs will be used in order to ensure only legitimate entities can provide authorization for UAVs.
Step 10a. and 10b.
There can be several round trips required for authentication of the UAV by the USS/UTM depending on the authentication method used by the USS/UTM and UAV. The authentication method and the content of messages used for authentication are out of scope of 3GPP. The content of the messages is carried in containers that are passed along and not processed by the entities between the UAV and USS/UTM.
On a successful authentication and authorization of the UAV, the USS/UTM stores the 3GPP UAV ID with the CAA-level UAV ID. The USS/UTM informs the UFES that the UAV has been successfully authenticated and authorized by the USS/UTM. The USS/UTM includes authorization information for both the network and the UAV.
The UFES further informs the SMF+PGW-C that the UAV has been successfully authenticated and authorized by the USS/UTM. The UFES passes the received authorization information onto the SMF+PGW-C. The SMF+PGW-C stores the network authorization information as part of the UE context. The network authorization information further contains the information whether USS/UTM authentication and authorization is required during future registrations and whether to allow UE to establish PDN connections(s) dedicated for the UAS service with or without further USS/UTM authentication and authorization. The network part of the authorization data contains authorization information applicable to existing PDN connections, which influence SMF+PGW-C decisions for the traffic on these connections. For example, the information may indicate to disable all connectivity of the UAV except for the connectivity to USS/UTM.
The SMF+PGW-C sends the Update Bearer Request message to the MME and include the UAV authorization information. The MME responds with the Update Bearer Response message. The SMF+PGW-C also set the traffic filters to allow traffic based on the received authorization information.
The MME passes the UAV authorization information to the UAV to inform the UAV that the authorization was successful. The UAV authorization information contains any needed aviation information, e.g. a new CAA-level UAV ID.
If using different PDN connections for C2 traffic, the UAV triggers a PDN connection set-up procedure which may include a further UAV authentication and authorization.
C2 traffic can start to pass between UAV and UAVC.