Patent ID: 7876743
Filing Date: 2011-01-25
Classification: H04L,H04M

Abstract:
1. A method of setting up a session between first and second peer user terminals of a communication system, wherein at least one of the peer user terminals is a dual-mode mobile terminal having access to an Internet Protocol (IP) based packet switched network and a circuit switched access network, said session extending at least in part across the circuit switched access network, the method comprising the steps of: transporting signaling to initiate the session via the IP based packet switched network using a call control protocol which is also used for setting up end-to-end packet switched sessions, the signaling being Session Initiation Protocol (SIP) signaling exchanged between the dual mode mobile terminal and a SIP server of an IP Multimedia Core Network Subsystem (IMS); sending a notification from the SIP server to a gateway server that one or more conversational bearers must be established, the gateway server terminating the circuit switched session within the system; after notification from the SIP server, sending from the gateway server to the dual-mode mobile terminal, a callback telephone number; and calling the callback telephone number by the dual-mode mobile terminal to establish a circuit switched call with the gateway server.