Patent ID: 8599791

Claim:
A wireless transmit/receive unit (WTRU) comprising: a processor comprising: a Non-Access Stratum (NAS) configured to determine whether to perform a Circuit Switched (CS) fallback based on an Internet Protocol (IP) Multimedia Subsystem (IMS) registration status, and send a service request indicating a request to perform a Circuit Switched (CS) fallback on a condition that the WTRU is attached to a CS domain; and an Access Stratum (AS) configured to receive the CS service request from the NAS, send an indication of the CS service request in a Radio Resource Control (RRC) message to an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), wherein the RRC message includes CS service information, and receive a handover command in response to the CS service request.