Patent ID: 8681737

Claim:
A method for inter-technology handoff of a communication session in a communication system comprising an Internet Protocol Multimedia Subsystem (IMS) capable of communicating with a user equipment via each of an intervening packet data network and an intervening circuit switched network, the method comprising: conveying forward link session traffic to, and receiving reverse link session traffic from, a user equipment via the packet data network; determining to hand off the communication session; in response to determining to hand off the communication session to the circuit switched network, conveying, by a Circuit Switched Proxy of the packet data network to the user equipment, information concerning a target Mobile Switching Center of the circuit switched network; conveying, by the user equipment to a Voice Call Continuity Application Server of the IMS and via the packet data network, a target cell identity and a Mobile Switching Center identity; instructing, by the Voice Call Continuity Application Server via the Circuit Switched Proxy of the packet data network, the target Mobile Switching Center to prepare for a handover, wherein instructing comprises conveying a Mobile Application Part message by the Voice Call Continuity Application Server to the Circuit Switched Proxy and conveying a Mobile Application Part message by the Circuit Switched Proxy to the target Mobile Switching Center; continuing to anchor the session in the Voice Call Continuity Application Server; acquiring, by a target Base Station Subsystem associated with the target Mobile Switching Center, the user equipment; and providing, by the target Base Station Subsystem, the user equipment with communication session services.