Patent ID: 8644833

Claim:
A method for effecting a handoff of a multi-mode mobile station from a first wireless network to a second wireless network, said multi-mode mobile station having a first interface for wireless communication with said first wireless network and a second interface for wireless communication with said second wireless network, said method comprising: establishing a call between said multi-mode mobile station and an endpoint, such that said call includes a first call leg between said endpoint and an anchor point of a first serving system and a second call leg between said anchor point and said multi-mode mobile station via said first wireless network; storing in a mobility server 1) a first registration entry regarding a connection of said multi-mode mobile station with said first wireless network, and 2) call information regarding said call in an activity log stored in the mobility server, said call information including a unique identifier of said call in said first serving system, wherein said unique identifier includes a session identifier; during said call, determining that said second wireless network is available and preferred; a second serving system transmitting registration information for said second registration entry in response to said second wireless network being available, said registration information including said identification of said multi-mode mobile station and an identification of said second serving system; storing a second registration entry regarding a connection of said multi-mode mobile station with said second wireless network; said multi-mode mobile station transmitting a handoff request via said second wireless network, said mobility server receiving said handoff request, wherein said handoff request requests establishment of a call to a predetermined directory number; in response to said handoff request, identifying said first serving system from said call information and then said mobility server setting up a third call leg between said anchor point and said multi-mode mobile station via said second wireless network in response to said second registration entry; and dropping said second call leg after said third call leg is set up in order to effect a soft handoff from said first wireless network to said second wireless network, wherein said handoff is transparent to said multi-mode mobile station.