Patent ID: 8830959

Claim:
A method for controlling a call handover between a first telecommunication network and a second telecommunication network, comprising: detecting, by a voice call continuity application server(VCC AS), a state of a current call of a user equipment (UE), when receiving a handover request from the UE, in communication with the first telecommunication network, determining, by the VCC AS whether the current call is in a Ring Back Tone state in accordance with the detection result; and returning, by the VCC AS, information to the UE, wherein the information comprises one of: a rejection response message to reject the handover request when the current call is in the Ring Back Tone state, and information that the handover request is waiting to be processed or is being processed when the current call is in the Ring Back Tone state; wherein if the information returned to the UE comprises information that the handover request is waiting to be processed or is being processed, then proceeding with the call handover after off-hook at an Other End Point; wherein the rejection response message contains a Try-After head instructing the UE to retry after a period of time; and wherein the first telecommunication network is an IP multimedia subsystem (IMS) domain, and the second telecommunication network is a Circuit Switched (CS) domain.