Patent ID: 8666402

Claim:
A method for triggering IMS (IP Multimedia Subsystem) registration in IMS, comprising: receiving, by a first user equipment, an IMS registration triggering indication message from a network side or a second user equipment, wherein the IMS registration triggering indication message comprises wireless environment information of the second user equipment; based on the wireless environment information of the second user equipment, determining, by the first user equipment, that the wireless environment information of the second user equipment supports simultaneous CS (circuit switching) and PS (packet switching) services; based on the determining that wireless environment information of the second user equipment supports simultaneous CS and PS services, determining, by the first user equipment, to initiate the IMS registration to the IMS and triggering the first user equipment to initiate the IMS registration to the IMS; wherein the IMS registration triggering indication message is sent to the first user equipment by interacting signaling between the second user equipment and the first user equipment.