Patent ID: 7155225

Claim:
A subscriber unit (SU) that is SIP enabled for facilitating a handoff of the SU from a SIP-enabled wireless local area network (WLAN), the handoff made to a wireless wide area network (WAN), the SU assigned an enterprise address E 1 and a cellular address C 1 , the SU comprising: a dual-band transceiver for communicating wirelessly on two frequency bands; and a processor coupled to the dual-band transceiver for controlling the dual-band transceiver, wherein the processor is programmed to: cooperate with the dual-band transceiver to determine whether the first SU is about to leave the WLAN; determine whether the SU is involved in a call on E 1 ; and in response to determining that the SU is about to leave the WLAN, and that the SU is involved with the call on E 1 , send a SIP message with a contact address of C 1 to the WLAN, the SIP message resulting in transferring the call from E 1 to C 1 .