DOMAIN TRANSFER METHOD FOR VOICE CALL CONTINUITY SERVICE AND THEREFOR SYSTEM

摘要

A domain transfer method for a VCC(Voice Call Continuity) service and a system therefor are provided to enable a VCC AS(Application Server) to select a progressing access call leg as a target exactly, for which the VCC AS will perform domain transfer when domain transfer from a CS network to an IMS(Internet Protocol Multimedia Subsystem) network or domain transfer from the IMS network to the CS network is requested, thereby providing stably the VCC service. A domain transfer method for a VCC service and a system therefor comprises the following steps of: allowing a UE(User Equipment)(201) to transmit an SIP(Session Initiation Protocol) INVITE message requesting a voice call through an IMS network to a VCC AS(211) supporting the VCC service(215~227); allowing the VCC AS to respond to the SIP INVITE message and allocate a call reference number for the IMS voice call; allowing the VCC AS to transmit a response message including the call reference number to a UE and providing the voice call between the UE and the VCC AS(231~241); allowing the UE to transmit a CS(Circuit Switched) SETUP message including the call reference number to the VCC AS through a CS domain, to which the UE belongs, for requesting the CS voice call through a CS network during the voice call(243,247); allowing the VCC AS to select the call leg of the IMS voice call corresponding to the call reference number by using the call reference number included in the CS SETUP message and transfer the call leg to the CS network from the IMS network(271); and providing the voice call between the UE and the VCC AS through the CS network when the domain transfer is completed(295,299).