Patent ID: 7710950
Filing Date: 2010-05-04
Classification: H04L,H04M,H04W

Abstract:
1. A method for use in routing a Session Initiation Protocol (SIP) call in a network environment including a circuit-switched (CS) network and an Internet Protocol (IP) multimedia subsystem (IMS) network, the SIP call being originated in the CS network by a mobile communication device towards a called party identified by a SIP Uniform Resource Indicator (URI) or Tel URI, the method comprising the acts of: causing a SIP Invite message with call information associated with the SIP call to be sent to the IMS network in response to identifying a mobile-originated call request for the SIP call, the call information including at least one of a call reference number related to the SIP call and the URI of the called party; receiving a SIP 380 (Alternative Service) Response message from the IMS network in response to sending the SIP Invite message, the SIP 380 (Alternative Service) Response message including at least one of a call reference number and an E.164 number; and verifying that the call reference number returned from the IMS network remains valid; and after receiving the SIP 380 (Alternative Service) Response message and upon verifying that the returned call reference number remains valid, causing a CS call setup message to be sent to the IMS network for the SIP call, the CS call setup message including the E.164 number for routing the SIP call to the called party.