Patent ID: 8149820

Claim:
A method for use in a network node, the method comprising: the network node receiving, from a first wireless transmit/receive unit (WTRU), a Session Initiation Protocol (SIP) Invite message that indicates a request for a second WTRU to participate in a combined circuit-switched (CS) and IP Multimedia Subsystem (IMS) session with the first WTRU, wherein the combined CS and IMS session between the first WTRU and the second WTRU includes a CS call at the second WTRU and a PS session at the second WTRU, and a voice over IP (VoIP) call at the first WTRU; the network node communicating with the second WTRU to establish the combined CS and IMS session; and the network node sending a SIP OK message to the first WTRU, wherein the SIP OK message indicates that the second WTRU has accepted the combined CS and IMS session.