Patent ID: 8599838

Claim:
A user equipment (UE) device operable to originate a call in a network environment including a circuit-switched (CS) network and an Internet Protocol (IP) multimedia subsystem (IMS) network, said call being directed towards a called party having a SIP Uniform Resource Indicator (URI), said UE device comprising: means for providing call information associated with said call to an application server node disposed in said IMS network, said call information including at least one of a call reference number and said called party's SIP URI; means for verifying that said call reference number returned from said application server node in a message remains valid based on a local timer mechanism associated with said UE device, said message including an IP multimedia routing number (IMRN); and means, responsive to verifying that said call reference number is valid, for providing said IMRN to said application server node in order to facilitate a session with respect to said called party.