Patent ID: 10616849

Abstract:
One disclosure of the present specification provides a method for a proxy-call session control function (P-CSCF) of a home public land mobile network (H-PLMN) to register a roaming user equipment with an IP multimedia subsystem (IMS) network. The method may comprise the steps of: receiving an identifier of a visited public land mobile network (V-PLMN) in which a user equipment is roaming, wherein the identifier of the V-PLMN is received in a state where packet data network (PDN) connection for the user equipment is established but the user equipment is not registered with the IMS network; receiving, from the user equipment, a REGISTER message for registration with the IMS network; adding the identifier of the V-PLMN to a header of the REGISTER message; and transmitting the REGISTER message to which the identifier of the V-PLMN is added to an Interrogating-CSCF (I-CSCF).