Apple Inc.
Steering of roaming in 5G systems

Abstract:

Systems and methods of providing steering of roaming (SOR) information in a 5G VPLMN are described. A UE receives a REGISTRATION ACCEPT message from an AMF of the VPLMN during initial or mobility registration of the UE in the VPLMN and DL NAS TRANSPORT message thereafter. The message has a Payload container information element (IE) set to secured packet. The SOR information indicates a list of preferred PLMN/access technology combinations, which is uploaded to a memory after a successful security check to verify that the list of preferred PLMN/access technology combinations is provided by the UDM of the HPLMN and is not tampered with by the VPLMN. When the message also contains a request for acknowledgment of successful security check of the list of preferred PLMN/access technology combinations, the UE transmits to the AMF the acknowledgment in a REGISTRATION COMPLETE or a DL NAS TRANSPORT message.