Patent ID: 8537775

Claim:
A method for use in a wireless transmit/receive unit (WTRU), the method comprising: the WTRU registering with a Call Session Control Function (CSCF) in an Internet Protocol (IP) Multimedia Subsystem (IMS) via a first wireless network of a first network type; the WTRU transmitting a first session initiation protocol (SIP) message to an application server in the IMS via the first wireless network, wherein the first SIP message includes a media independent handover (MIH) message; and the WTRU establishing an application session with a second WTRU via the first wireless network; the WTRU communicating with the second WTRU according to the application session via the first wireless network using a first Internet Protocol (IP) address; the WTRU performing a handover from the first wireless network to a second wireless network of a second network type; the WTRU obtaining a second IP address for communicating in the second wireless network; the WTRU transmitting a second SIP message via the second wireless network for continuing the application session in the second wireless network, wherein the second SIP message indicates the second IP address; and the WTRU communicating with the second WTRU according to the application session via the second wireless network using the second IP address.