METHOD AND APPARATUS TO ENABLE FALLBACK TO CIRCUIT SWITCHED DOMAIN FROM PACKET SWITCHED DOMAIN

摘要

A method and apparatus are used to perform a Circuit Switched (CS) fallback in wireless communications. The Non-Access Stratum (NAS) of the apparatus determines whether to perform a CS fallback based on an Internet Protocol (IP) Multimedia Subsystem (IMS) registration status, and sends a service request indicating a request to perform the CS fallback when the WTRU is attached to a CS domain. The apparatus also includes an Access Stratum (AS) that receives the CS service request from the NAS, sends 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 receives a handover conunand in response to the CS service request.