Apparatus to enable fallback to circuit switched domain from packet switched domain

A method for circuit switched (CS) fallback performed by a wireless transmit/receive unit (WTRU), the method comprising:

• providing a transmitter, a receiver and a processor coupled to the transmitter and the receiver for;
• determining whether to perform a CS fallback;
• sending a service request indicating a request to perform a CS fallback, wherein the service request includes CS service information;
• and
• receiving a handover command in response to the service request.

A wireless transmit/receive unit (WTRU) comprising:

• a transmitter, a receiver and a processor, the processor coupled to the transmitter and the receiver and configured to:
• determine whether to perform a CS fallback based on an Internet Protocol (IP) Multimedia Subsystem (IMS) registration status;
• receive a CS service request, sent from a Non-Access Stratum (NAS) of the WTRU on a condition that the WTRU is attached to a CS domain, the CS service request indicating a request to perform a CS fallback;
• 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.