Patent ID: 7366514

Claim:
A method of transferring a packet switched call carried over a first network to a circuit switched call carried over a second network, comprising: receiving a handoff notification request from a packet call controller at a network controller of the second network, the handoff notification request instructing the network controller to send a call transfer request to the packet call controller when a handoff request for a mobile station is received by the network controller, the call transfer request requesting transfer from a packet switched call carried over the first network to a circuit switched call over the second network; receiving a serving controller notification request to a location register, the serving controller notification request requesting notification of a circuit switching controller in the second network with which the mobile station is registered at least when a change in circuit switching controller registration takes place; sending at least one serving controller notification indicating the circuit switching controller with which the mobile station is registered; and wherein the receiving step receives the handoff notification request from the indicated circuit switching controller.