Method for handing over a terminal during a non steady voip call, network element, device and system

Abstract

The present invention provides a method for handing over a terminal from a packet switching domain to a circuit switching domain during a non steady state of a call, a network element managing service centralization and continuity, an access device, a network element managing mobility of a terminal, as well as a communication system at least comprising at least a terminal, a network element managing service centralization and continuity, an access device and a network element managing mobility of a terminal. The method comprises a first network element anchoring the call based on the call setup request received from the terminal, and storing a provisional response returned to the terminal and the state of the call; the terminal detecting that a handover is necessary and sending a measurement report to an access network; the access network deciding to request a second network element for handover, upon detection of a signaling bearer while the measurement report meets handover condition; the second network element deciding to send the first network element a PS to CS handover request upon detection of the signaling bearer, after receiving a request for handover from the access network; and after reception of said handover request, if the first network element detects that the call is in the non steady state, than it checks the previously stored provisional response and sends the provisional response to a third network element, whereby completing the session handover procedure and updating the remote end.