Communication system including an interworking mobile switching center for call termination
View Patent ↗A communication system includes User Equipment ( 111 ), Radio Access Network (RAN) ( 121 ), a packet-switched domain ( 131 ), an IP Multimedia Subsystem (IMS) ( 141 ), a circuit-switched domain ( 151 ), a Domain Name System (DNS) ( 165 ), a Charging Gateway Function (CGF) ( 134 ), an EIR ( 135 ), a Transport Signaling Gateway (T-SGW) ( 146 ), and a Roaming Signaling Gateway (R-SGW) ( 147 ). The CS domain ( 151 ) includes an interworking Mobile Switching Center (iMSC) ( 201 ). The iMSC ( 201 ) translates the CS domain registration, call control, feature control, and feature invocation procedures associated with the access technology to standard SIP procedures. The media gateway (MGW) ( 173 ) under the control of the iMSC ( 201 ) converts the air interface media flow into a packet stream that is managed by SIP procedures within the IMS ( 141 ). The iMSC ( 201 ) thereby allows for interworking between circuit-switched and packet-switched domains for call terminations.
1. A method for terminating a call request to a mobile unit being served by an interworking Mobile Switching Center (iMSC) in a communication system comprising a circuit-switched domain, and an Internet Protocol (IP) Multimedia Subsystem (IMS), the method comprising:
sending from the mobile unit to the iMSC a circuit-switched domain registration message;
sending from the iMSC to the IMS a registration indication on behalf of the mobile unit via SIP that identifies the iMSC as the current location at which the mobile unit can be reached;
receiving a call intended for the mobile unit at the IMS;
forwarding by the IMS the call intended for the mobile unit to the iMSC via Session Initiation Protocol (SIP) on an Mx interface, the Mx interface connecting the iMSC to a Call State Control Function (CSCF) in the IMS;
sending by a Serving CSCF (S-CSCF) located in the IMS SIP messages; and
perfomring by the iMSC interworking between SIP call control procedures on the Mx interface and circuit-switched call control procedures towards the mobile unit.
2. A method for terminating a call request in accordance with claim 1 , wherein the step of receiving a call intended for the mobile unit at the IMS comprises receiving a call request from a Public Switched Telephone Network (PSTN).
3. A method for terminating a call request in accordance with claim 2 , wherein the IMS receives the call request from the PSTN via a Media Gateway Control Function (MGCF), an Interworking Call State Control Function (I-CSCF), and a Serving Call State Control Function (S-CSCF).
4. A method for terminating a call request in accordance with claim 1 , wherein the step of receiving a call intended for the mobile unit at the IMS comprises receiving a call request from a second IMS.
5. A method for terminating a call request in accordance with claim 4 , wherein the IMS receives the call request from the second IMS via an Interworking Call State Control Function (I-CSCF) and a Serving Call State Control Function (S-CSCF).
6. A method for terminating a call request in accordance with claim 1 , wherein the step of receiving a call intended for the mobile unit at the IMS comprises receiving a call request from a Public Land Mobile Network (PLMN).
7. A method for terminating a call request in accordance with claim 6 , wherein the IMS receives the call request from the PLMN via a Media Gateway Control Function (MGCF), an Interworking Call State Control Function (T-CSCF), and a Serving Call State Control Function (S-CSCF).
8. A method for terminating a call request in accordance with claim 1 , wherein the step of receiving a call intended for the mobile unit at the IMS comprises receiving a call request from a SIP endpoint.
9. A method for terminating a call request in accordance with claim 8 , wherein the IMS receives the call request from the SIP endpoint via an IP multimedia network, an Interworking Call State Control Function (I-CSCF), and a Serving Call State Control Function (S-CSCF).
10. A method for terminating a call request in accordance with claim 8 , wherein the SIP endpoint is outside of the Public Land Mobile Network (PLMN).
11. A method for terminating a call request in accordance with claim 1 , wherein the step of sending by the S-CSCF SIP messages comprises sending the SIP messages directly to the iMSC.
12. A method for terminating a call request in accordance with claim 1 , wherein the step of sending by the S-CSCF SIP messages comprises sending the SIP messages to an Interworking Call State Control Function (I-CSCF) in the IMS.
13. A method for terminating a call request in accordance with claim 12 , wherein the I-CSCF forwards the SIP messages to the iMSC.
14. A method for terminating a call request in accordance with claim 1 , wherein the step of performing interworking between SIP call control procedures comprises mapping call states between SIP and an over-the-air call control protocol.
15. A method for terminating a call request in accordance with claim 1 , wherein the step of performing interworking between SIP call control procedures comprises mapping messages between SIP and an over-the-air call control protocol.
16. A method for terminating a call request in accordance with claim 1 , wherein the step of performing interworking between SIP call control procedures comprises mapping message parameters between SIP and an over-the-air call control protocol.