Patent ID: 7170879

Claim:
A method for inter-working a radio access network (RAN) in an internet protocol (IP) based core network (CN), comprising: establishing a traffic connection between a first mobile station (MS) and a first base station subsystem for IP (BSS-IP) using a prescribed protocol upon receiving a call connection request message from the first MS, the establishing including transmitting a call connection request message from the first MS through the first BSS-IP to a wireless call agent (WCA), confirming completion of the traffic connection to the first MS and transmitting a response message from the first BSS-IP to the WCA; interpreting, at the WCA, a directory number (DN) of a second MS as requested by the first MS and establishing a traffic connection between the second MS and a second BSS-IP using a prescribed protocol, the WCA being coupled between the first BSS-IP and the second BSS-IP; generating a ring-back tone using a prescribed protocol so that the first MS receives the ring-back tone; and stopping the generation of the ring-back tone using a prescribed protocol if the second MS responds, and establishing a call connection between the first MS and the second MS.