Patent ID: 8560410

Claim:
A method for determining a billing region to utilize for charging a mobile subscriber for an Internet Protocol Multimedia Subsystems (“IMS”) session, wherein the IMS session is conducted between the subscriber's mobile device and an IMS core network, the method comprising: receiving a public Internet Protocol (“IP”) address associated with the mobile device during registration of the mobile device with the IMS core network; sending a query to a geolocation server for an estimated physical location of the mobile device, wherein the query includes an indication of the received public IP address; determining an estimated physical location of the mobile device based at least in part on the received public IP address; receiving the estimated physical location of the mobile device from the geolocation server; identifying a billing Cell Global Identification (“CGI”) that is associated with the estimated physical location of the mobile device, the billing CGI is a dummy CGI that is not associated with a physical cell site in a radio access network that uses licensed frequency spectrum; and providing the billing CGI to a billing server in conjunction with a session identifier that is associated with the IMS session, wherein the billing server is configured to determine a billing region from the billing CGI.