	US 7,577,427 B2
	System and method of transitioning between cellular and voice over internet protocol communication
Dennis D. Bicker, San Ramon, Calif. (US); and Charles R. Dilley, Antioch, Calif. (US)
Assigned to AT&T Intellectual Property I, L.P., Reno, Nev. (US)
Filed on Nov. 05, 2003, as Appl. No. 10/702,132.
Prior Publication US 2005/0096024 A1, May 05, 2005
This patent is subject to a terminal disclaimer.
Int. Cl. H04M 24/00 (2006.01)

U.S. Cl. 455—417 [455/414.1; 455/436; 370/259]

16 Claims

1. A method of forwarding a call from a mobile phone, the method comprising:

determining that the mobile phone is within range of a wireless local area network base station with voice over internet protocol capability, the mobile phone including a wireless local area network (WLAN) module and a wireless wide area network (WWAN) module;

receiving an internet protocol address associated with the wireless local area network base station via the WLAN module;

sending a call forwarding message including the Internet Protocol (IP) address from the mobile phone to a remote cellular network element of a wide area cellular network via the WWAN module, the call forwarding message to redirect a call destined for the mobile phone to the wireless local area network base station for transmission to the mobile phone;

determining that the mobile phone has moved out of range of the wireless local area network base station and while the mobile phone is out of range of the wireless local area network base station, sending a message to the cellular network element to cancel call forwarding to the wireless local area network base station.