Patent ID: 8306531

Claim:
A system for a mobile Circuit Switched (CS) user to access an IP Multimedia Subsystem (IMS) network, comprising the IMS network for providing IMS services, and a CS access network, and further comprising: a Register Proxy Function (RPF) entity, comprising a first interface for communicating with the IMS network and a second interface for communicating with the CS access network, and configured to map a CS registration event which is originated by the mobile CS user through the second interface to an IMS registration event, and initiate registration to the IMS network through the first interface on behalf of the mobile CS user; wherein the configuration of the RFP entity to initiate registration to the IMS network through the first interface on behalf of the mobile CS user comprises at least one of: configured to send the mapped IMS registration event to an IMS network entity wherein the IMS network entity is configured to perform IMS registration for the mobile CS user directly without authenticating the mobile CS user, and complete the registration process, if the IMS network entity determines that the registration is initiated by the mobile CS user; and configured to send the mapped IMS registration event to an IMS network entity wherein the IMS network entity is configured to perform IMS registration for the mobile CS user according to information carried in the mapped IMS registration event and complete the registration process, if the IMS network entity determines that the registration is initiated by the mobile CS user.