Patent ID: 8837444

Claim:
A method for setting up a call from a non-Internet Protocol Multimedia Subsystem (non-IMS) telecommunication network, comprising a Network Gateway Node (NGN), to a Serving Call Session Control Function (S-CSCF) serving a called terminal in an Internet Protocol Multimedia Subsystem (IMS) network, wherein the NGN executes steps comprising: sending, in response to receiving an initial call setup request message in the non-IMS telecommunication network, an information request message to a combined database node comprising a Home Location Register (HLR) and a Home Subscriber Server (HSS) for obtaining routing information for a setup of the call, the information request message comprising an indicator indicating that the NGN is an integrated NGN configured with a Gateway Mobile Switching Center (GMSC) portion operatively connected to a Media Gateway Control Function (MGCF) portion that interfaces the non-IMS telecommunication network with the IMS network; receiving from the combined database node, a response message including one of: an address of the S-CSCF serving the called terminal; and S-CSCF capability information indicating S-CSCF capabilities required for the call; and when the response message includes the address of the S-CSCF serving the called terminal, routing the call directly to the S-CSCF that serves the called terminal in the IMS network.