METHOD AND DEVICE FOR HANDING OVER VOICE OVER INTERNET PROTOCOL (VOIP) CALL FROM PACKET SWITCH DOMAIN TO CIRCUIT SWITCH DOMAIN

摘要

A method for handing over a voice over internet protocol (VoIP) call from packet switch (PS) domain to circuit switch (CS) domain in a communication system is provided. The communication system includes a VoIP session anchor device, a CS control device of the CS domain and a PS control device of the PS domain. When the CS control device receives a handover request from the PS control device, the method includes the following steps: the first time period is computed, wherein the first time period is the required time for the CS control device sending a message to the remote terminal of the VoIP call; the first time period and the preset second time period are compared, wherein the second time period is the required time for the CS control device sending a message to the local terminal of the VoIP call; according to the comparison result, sending a session handover request to the VoIP session anchor device and sending a cell handover request to the PS control device are controlled, enabling the session handover of IP multimedia subsystem (IMS) layer and the cell handover of layer 2 to occur simultaneously or nearly simultaneously. The present invention also relates to a device for handing over a VoIP call from the PS domain to the CS domain.