SYSTEM AND METHOD FOR INBOUND ROAMING IN IP MULTIMEDIA SUBSYSTEM NETWORKS

摘要

A system and method for enabling a UE to roam to a visited IMS-based network from a home network that does not have an IMS infrastructure. A visiting UE sends to an Intelligent Roaming Application Server (I-RAS) in the visited network, a first SIP Registration message that includes a SIP URI identifying the UE as a visitor from a home network that does not have an IMS infrastructure. The I-RAS rejects the registration, but includes a temporary Tel URI in the rejection message. The UE sends a second Registration message using the temporary Tel URI, which is forwarded to a Visited S-CSCF for authentication. The S-CSCF returns authentication vectors, which the UE uses to compute ciphering parameters and establish an IPSEC connection with a Visited P-CSCF. The UE then sends a third Registration message, which is accepted, and registration in the visited network is complete. The I-RAS acts as a pseudo Visited MSC/VLR and performs an update location procedure with the visiting UE's home network.