Patent ID: 8160559

Claim:
A method for a Mobile-Terminated (MT) call in an Internet Protocol (IP) Multimedia Subsystem (IMS) network, said MT call being originated by a calling party towards a User Equipment (UE) device, comprising: receiving a message for said MT call at a network node and determining that said MT call is to be delivered to said UE device over a Circuit-Switched (CS) domain; storing call information relating to said MT call and associating an IP Multimedia Routing Number (IMRN) with at least a portion of said call information in a mapping relationship; transmitting an incoming call request message using a USSD message to said UE device, wherein the incoming call request includes said IMRN, an A-party ID of the calling party and an indication that said USSD message is for delivery of said MT call; receiving said IMRN back from said UE device pursuant to a Mobile-Originated (MO) CS call terminating at said network node, wherein said IMRN is used as a destination number; and upon verifying that said IMRN is valid, sending a response message towards the calling party and sending a response to effectuate an end-to-end path for said MT call between said calling party and said UE device.