# US 8,542,670 B2 · Inter-domain call routing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,670 B2 - Document ID: US8542670B2 - Status: Granted - Kind: B2 - Application number: 11/452,069 - Filed: 2006-06-12 - Published: 2006-12-14 - Granted: 2013-09-24 - Earliest claimed: 2005-06-13 - Assignees: Research In Motion Limited - Applicants: Kaniz Mahdi - Inventors: Kaniz Mahdi - Web page: https://patentgrep.com/patent/US8542670B2 ## CPC - H04Q 3/66: Traffic distributors - H04L 65/103: {in the network} - H04L 65/104: {in the network} - H04L 65/1069: Session establishment or de-establishment - H04L 65/1095: Inter-network session transfer or sharing - H04L 65/1104: Session initiation protocol [SIP] - H04M 7/1285: {Details of finding and selecting a gateway for a particular call} - H04W 92/02: Inter-networking arrangements - H04L 65/1016: IP multimedia subsystem [IMS] - H04M 2207/18: wireless networks - H04M 2207/203: composed of PSTN and data network, e.g. the Internet - H04Q 2213/13098: Mobile subscriber - H04Q 2213/13141: Hunting for free outlet, circuit or channel - H04Q 2213/13196: Connection circuit/link/trunk/junction, bridge, router, gateway - H04Q 2213/13248: Multimedia - H04Q 2213/13282: Call forward, follow-me, call diversion - H04W 8/26: Network addressing or numbering for mobility support - H04Q: SELECTING (switches, relays, selectors H01H; wireless communication networks H04W) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract The present invention provides for routing calls between disparate domains, such as a circuit-switched subsystem and a multimedia subsystem. When a user element is homed in a first domain and roaming in a second domain, an incoming call will arrive at a gateway node in the first domain. As a result, a message identifying the user element and indicating that an incoming call has been received at first gateway node for the first domain is sent to a continuity control function (CCF) residing in the multimedia subsystem. The CCF will create and effect delivery of an inter-domain routing number to the first gateway node. The inter-domain routing number is used by the first gateway node to route the call to the second domain. The inter-domain routing number may be associated with a second gateway node of the second domain. ## Claims ### Claim 1 A method for routing a call for a user element having a directory number from a first domain into a second domain, wherein the user element is homed in the first domain and roaming in the second domain, comprising: receiving a first message identifying the user element and indicating that an incoming call intended for the user element has been routed to a first gateway node for the first domain; temporarily assigning a temporary inter-domain routing number for the incoming call intended for the user element; and providing the temporary inter-domain routing number for the first gateway node to use to route the incoming call into the second domain, wherein one of the first and second domains is a circuit-switched subsystem and another of the first and second domains is a multimedia subsystem, wherein the temporary inter-domain routing number identifies a second gateway node for the second domain, such that the incoming call is routed from the first gateway node of the first domain to the second gateway node of the second domain using the temporary inter-domain routing number and the temporary inter-domain routing number is released after routing the incoming call. ### Claim 2 (depends on 1) The method of claim 1 wherein the first gateway node is one of a mobile switching center or a continuity control function and the second gateway node is the other of the mobile switching center or the continuity control function. ### Claim 3 (depends on 1) The method of claim 1 comprising receiving a second message indicating that the incoming call has been routed to the second gateway node for the second domain and effecting routing of the call to the user element via the second gateway node. ### Claim 4 (depends on 3) The method of claim 3 wherein, when the second domain is the multimedia subsystem, effecting routing of the call to the user element via the second gateway node further comprises obtaining an address associated with the user element in the multimedia subsystem and sending a session request toward the user element. ### Claim 5 (depends on 3) The method of claim 3 wherein when the second domain is the circuit-switched subsystem, effecting routing of the call to the user element via the second gateway node further comprises obtaining a user element identifier based on the inter-domain routing number and sending instructions for the second gateway node to route the call to the user element via the circuit-switched subsystem, the instructions comprising the user element identifier. ### Claim 6 (depends on 1) The method of claim 1 further comprising identifying a location of the user element and determining to route the call to the user element via the second domain based on the location. ### Claim 7 (depends on 1) The method of claim 1 wherein providing the temporary inter-domain routing number comprises generating the temporary inter-domain routing number from a user element identifier and an address of a service supporting the receiving and providing steps. ### Claim 8 (depends on 7) The method of claim 7 wherein providing the temporary inter-domain routing number further comprises generating the temporary inter-domain routing number from a call or session reference number. ### Claim 9 (depends on 1) The method of claim 1 wherein providing the temporary inter-domain routing number comprises generating the temporary inter-domain routing number from a user element identifier and a call or session reference number. ### Claim 10 (depends on 1) The method of claim 1 wherein when the first domain is the multimedia subsystem, further comprising anchoring call signaling for the incoming call in the multimedia subsystem. ### Claim 11 (depends on 1) The method of claim 1 wherein the first message is received in, and the temporary inter-domain routing number is provided from, the multimedia subsystem. ### Claim 12 (depends on 1) The method of claim 1 wherein the first gateway node is a gateway mobile switching center and the first domain is the circuit-switched subsystem. ### Claim 13 (depends on 1) The method of claim 1 wherein the first gateway node is a media gateway controller associated with a media gateway to the multimedia subsystem from the circuit-switched subsystem, and the first domain is the multimedia subsystem. ### Claim 14 (depends on 1) The method of claim 1, wherein the temporary inter-domain routing number is no longer required for the call once the call is routed into the second domain and the temporary routing number can be reused for other incoming calls to the user element or to different user elements. ### Claim 15 A service node for routing a call for a user element having a directory number from a first domain into a second domain, wherein the user element is homed in the first domain and roaming in the second domain, comprising: a communication interface; and a control system associated with the communication interface and adapted to: receive a first message identifying the user element and indicating that an incoming call intended for the user element has been routed to a first gateway node for the first domain; temporarily assign a temporary inter-domain routing number for the incoming call intended for the user element; and provide the temporary inter-domain routing number for the first gateway node to use to route the incoming call into the second domain, wherein one of the first and second domains is a circuit-switched subsystem and another of the first and second domains is a multimedia subsystem, wherein the temporary inter-domain routing number identifies a second gateway node for the second domain, such that the incoming call is routed from the first gateway node of the first domain to the second gateway node of the second domain using the temporary inter-domain routing number and the temporary inter-domain routing number is released after routing the incoming call. ### Claim 16 (depends on 15) The service node of claim 15 wherein the first gateway node is one of a mobile switching center or a continuity control function and the second gateway node is the other of the mobile switching center or the continuity control function. ### Claim 17 (depends on 15) The service node of claim 15 wherein the control system is further adapted to receive a second message indicating that the incoming call has been routed to the second gateway node for the second domain and effecting routing of the call to the user element via the second gateway node. ### Claim 18 (depends on 17) The service node of claim 17 wherein, when the second domain is the multimedia subsystem, to effect routing of the call to the user element via the second gateway node the control system is further adapted to obtain an address associated with the user element in the multimedia subsystem and send a session request toward the user element. ### Claim 19 (depends on 17) The service node of claim 17 wherein, when the second domain is the circuit-switched subsystem, to effect routing of the call to the user element via the second gateway node the control system is further adapted to obtain a user element identifier based on the temporary inter-domain routing number and send instructions for the second gateway node to route the call to the user element via the circuit-switched subsystem, the instructions comprising the user element identifier. ### Claim 20 (depends on 15) The service node of claim 15 wherein the control system is further adapted to identify a location of the user element and determine to route the call to the user element via the second domain based on the location. ### Claim 21 (depends on 15) The service node of claim 15 wherein to provide the temporary inter-domain routing number the control system is further adapted to generate the temporary inter-domain routing number from a user element identifier and an address of a service supporting the control system when the control system receives the first message and provides the temporary inter-domain routing number. ### Claim 22 (depends on 21) The service node of claim 21 wherein to provide the temporary inter-domain routing number the control system is further adapted to generate the temporary inter-domain routing number from a call or session reference number. ### Claim 23 (depends on 15) The service node of claim 15 wherein to provide the temporary inter-domain routing number the control system is further adapted to generate the temporary inter-domain routing number from a user element identifier and a call or session reference number. ### Claim 24 (depends on 15) The service node of claim 15 wherein when the first domain is the multimedia subsystem, the control system is further adapted to anchor call signaling for the incoming call in the multimedia subsystem. ### Claim 25 (depends on 15) The service node of claim 15 wherein the first message is received in, and the temporary inter-domain routing number is provided from, the multimedia subsystem. ### Claim 26 (depends on 15) The service node of claim 15 wherein the first gateway node is a gateway mobile switching center and the first domain is the circuit-switched subsystem. ### Claim 27 (depends on 15) The service node of claim 15 wherein the first gateway node is a media gateway controller associated with a media gateway to the multimedia subsystem from the circuit-switched subsystem, and the first domain is the multimedia subsystem. ### Claim 28 (depends on 15) The service node of claim 15, wherein the temporary inter-domain routing number is no longer required for the call once the call is routed into the second domain and the control system is further adapted to reuse the temporary inter-domain routing number for other incoming calls to the user element or to different user elements.