System and method for handing over a call from a packet-switched network to a circuit-switched network

• US 20040246990A1
• Filed: 06/04/2003
• Published: 12/09/2004
• Est. Priority Date: 06/04/2003
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Krishnamurthi, Govind, Chaskar, Hemant M.
• Granted Patent: US 8,437,368 B2
• Time in Patent Office: Days
• US Class Current: 370/466
• CPC Class Codes: H04W 36/00224 between packet switched [PS] and circuit switched [CS] network technologies, e.g. circuit switched fallback [CSFB]
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A communications system and method are provided for handing over a call from a packet-switched network (e.g., IP network) to a circuit-switched network (e.g., PLMN, PSTN, etc.). The system includes a first terminal capable of communicating via a packet-switched network and a circuit-switched network, and a second terminal capable of communicating via a circuit-switched network. The system also includes a gateway capable of mapping communications between a packet-switched network and at least one circuit-switched network. The gateway can support communication between the first terminal and the second terminal such that the first terminal has a packet-switched connection with the gateway and the second terminal has a circuit-switched connection with the gateway. The first terminal can then establish a circuit-switch connection with the gateway. Thereafter, the gateway can connect the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal.

Claims

1. A communications system comprising:

a first terminal capable of communicating via a packet-switched network and a circuit-switched network;

a second terminal capable of communicating via a circuit-switched network; and

a gateway capable of mapping communications between a packet-switched network and at least one circuit-switched network,

wherein the gateway is capable of supporting communication between the first terminal and the second terminal such that the first terminal has a packet-switched connection with the gateway and the second terminal has a circuit-switched connection with the gateway, wherein the first terminal is capable of thereafter establishing a circuit-switched connection with the gateway, and wherein the gateway is capable of connecting the established circuit-switched connection between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal to thereby handoff communication from the packet-switched network to the circuit-switched network.

2. A communications system according to claim 1, wherein the first terminal is capable of transmitting a call session ID to the gateway as the first terminal establishes the circuit-switched connection with the gateway, and wherein the gateway is capable of connecting the established circuit-switched connection between the first terminal and the gateway with the circuit-switched connection between the second terminal and the gateway based upon the call session ID.

3. A communications system according to claim 2, wherein the first terminal is further capable of transmitting a shared secret to the gateway as the first terminal establishes the circuit-switched connection with the gateway such that the gateway can verify the shared secret before the circuit-switched connection is established with the first terminal.

4. A communications system according to claim 3, wherein at least one of the first terminal, the gateway and a server in communication with the first terminal and the gateway is capable of generating the call session ID and the shared secret in conjunction with one of the first terminal and second terminal setting up setting up communication with the other terminal.

5. A communications system according to claim 4 further comprising the server in communication with the first terminal and the gateway, wherein the server comprises a Session Initiation Protocol (SIP) server.

6. A communications system according to claim 1, wherein the first terminal is capable of receiving a handoff identifier hosted by the gateway, and wherein the first terminal is capable of establishing the circuit-switched connection with the gateway based upon the handoff identifier.

7. A communications system according to claim 1, wherein the first terminal is capable of establishing the circuit-switched connection with the gateway when a signal strength of the packet-switched connection between the first terminal and the gateway is below a predetermined threshold for more than a predefined period of time, and wherein the gateway is capable of connecting the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal in instances in which the first terminal establishes the circuit-switched connection with the gateway.

8. A communications system according to claim 1, wherein the first terminal comprises a mobile station, and wherein the packet-switched network comprises an Internet Protocol (IP) network.

9. A communications system according to claim 1, wherein the gateway is capable of supporting communication between the first terminal via a packet-switched network and the second terminal via a first circuit-switched network, and wherein the first terminal is capable of thereafter establishing a circuit-switched connection with the gateway via a second circuit-switched network that is different than the first circuit-switched network.

10. A communications system according to claim 1, wherein the gateway is capable of supporting communication between the first terminal via a packet-switched network and the second terminal via a circuit-switched network, and wherein the first terminal is capable of thereafter establishing a circuit-switched connection with the gateway via the same circuit-switched network.

11. A method of handing off communication from a packet-switched network to a circuit-switched network, the method comprising the steps of:

setting up communication between a first terminal and a second terminal over a gateway such that the first terminal has a packet-switched connection with the gateway and the second terminal has a circuit-switched connection with the gateway;

establishing a circuit-switched connection between the first terminal and the gateway via a circuit-switched network; and

connecting the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal.

12. A method according to claim 11, wherein the establishing a circuit-switched connection step includes transmitting a call session ID to the gateway, and wherein the connecting step comprises connecting the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal based upon the call session ID.

13. A method according to claim 12, wherein the establishing a circuit-switched connection step further includes transmitting a shared secret to the gateway, and thereafter verifying the shared secret before establishing the circuit-switched connection.

14. A method according to claim 13 further comprising:

generating the call session ID and the shared secret in conjunction with setting up communication between the first terminal and the second terminal.

15. A method according to claim 11, wherein the establishing a circuit-switched connection step comprises establishing a circuit-switched connection between the first terminal and the gateway based upon a handoff identifier hosted by the gateway.

16. A method according to claim 11 further comprising:

monitoring a signal strength of the packet-switched connection between the first terminal and the gateway,

wherein the establishing a circuit-switched connection step comprises establishing a circuit-switched connection when the signal strength of the packet-switched connection is below a predetermined threshold for more than a predefined period of time, and wherein the connecting step comprise connecting the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal in instances in which the circuit-switched connection is established between the first terminal and the gateway.

17. A method according to claim 11, wherein the setting up communication step comprise setting up communication between the first terminal via a packet-switched network and the second terminal via a first circuit-switched network, and wherein the establishing a circuit-switched connection step comprises establishing a circuit-switched connection between the first terminal and the gateway via a second circuit-switched network that is different than the first circuit-switched network.

18. A method according to claim 11, wherein the setting up communication step comprise setting up communication between the first terminal via a packet-switched network and the second terminal via a circuit-switched network, and wherein the establishing a circuit-switched connection step comprises establishing a circuit-switched connection between the first terminal and the gateway via the same circuit-switched network.

19. A communications system comprising:

a gateway capable of mapping communications between a packet-switched network and at least one circuit-switched network,

wherein the gateway is capable of supporting communication between a first terminal and a second terminal such that the first terminal has a packet-switched connection with the gateway and the second terminal has a circuit-switched connection with the gateway, wherein the first terminal is capable of thereafter establishing a circuit-switched connection with the gateway, and wherein the gateway is capable of connecting the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal to thereby handoff communication from the packet-switched network to the circuit-switched network.

20. A communications system according to claim 19, wherein the gateway is capable of receiving a call session ID as the circuit-switched connection is established with the first terminal, and wherein the gateway is capable of connecting the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the second terminal and the gateway based upon the call session ID.

21. A communications system according to claim 20, wherein the gateway is further capable of receiving a shared secret as the circuit-switched connection is established with the first terminal, and wherein the gateway is capable of verifying the shared secret before the circuit-switched connection is established with the first terminal.

22. A communications system according to claim 21, wherein the gateway is capable of generating the call session ID and the shared secret in conjunction with one of the first terminal and second terminal setting up communication with the other terminal.

23. A communications system according to claim 19, wherein the gateway is capable of hosting a handoff identifier, and wherein the first terminal is capable of establishing the circuit-switched connection with the gateway based upon the bandoff identifier.

24. A communications system according to claim 19, wherein the first terminal is capable of establishing the circuit-switched connection with the gateway when a signal strength of the packet-switched connection between the first terminal and the gateway is below a predetermined threshold for more than a predefined period of time, and wherein the gateway is capable of connecting the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal in instances in which the first terminal establishes the circuit-switched connection with the gateway.

25. A terminal comprising:

a transmitter capable of transmitting communications to a gateway via a packet-switched switched network and a circuit-switched network;

a receiver capable of receiving communications from the gateway via a packet-network and a circuit-switched network; and

a controller capable of controlling the operation of the transmitter and the receiver, wherein the controller is capable of directing the transmitter and receiver to transmit and receive, respectively, communications to and from a second terminal capable such that the terminal has a packet-switched connection with the gateway and the second terminal has a circuit-switched connection with the gateway, and wherein the controller is capable of thereafter establishing a circuit-switched connection between the terminal and the gateway such that the gateway is capable of connecting the established circuit-switched connection with the circuit-switched connection between the gateway and the second terminal to thereby handoff communication from the packet-switched network to the circuit-switched network.

26. A terminal according to claim 25, wherein the controller is capable of directing the transmitter to transmit a call session ID to the gateway as the controller establishes the circuit-switched connection between the terminal and the gateway such that the gateway can connect the established circuit-switched connection with the circuit-switched connection between the second terminal and the gateway based upon the call session ID.

27. A terminal according to claim 26, wherein the controller is further capable of directing the transmitter to transmit a shared secret to the gateway as the controller establishes the circuit-switched connection between the terminal and the gateway such that the gateway can verify the shared secret before the circuit-switched connection is established with the gateway.

28. A terminal according to claim 25, wherein the controller is capable of receiving, via the receiver, a handoff identifier hosted by the gateway, and wherein the controller is capable of establishing the circuit-switched connection between the terminal and the gateway based upon the handoff identifier.

29. A terminal according to claim 25, wherein the controller is capable of establishing the circuit-switched connection with the gateway when a signal strength of the packet-switched connection between the terminal and the gateway is below a predetermined threshold for more than a predefined period of time.

30. A computer program product for handing off communication of a terminal from a packet-switched network to a circuit-switched network, the computer program product comprising a computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program portions comprising:

a first executable portion for setting up communication between the terminal and another terminal over a gateway such that the terminal has a packet-switched connection with the gateway and the other terminal has a circuit-switched connection with the gateway;

a second executable portion for establishing a circuit-switched connection between the terminal and the gateway via a circuit-switched network; and

a third executable portion for connecting the circuit-switched connection established between the terminal and the gateway with the circuit-switched connection between the gateway and the other terminal.

31. A computer program product according to claim 30, wherein the second executable portion establishes the circuit-switched connection by transmitting a call session ID to the gateway, and wherein the third executable portion connects the circuit-switched connection established between the first terminal and the gateway with the circuit-switched connection between the gateway and the second terminal based upon the call session ID.

32. A computer program product according to claim 31, wherein the second executable portion establishes the circuit-switched connection by transmitting a shared secret to the gateway such that the gateway can thereafter verify the shared secret before establishing the circuit-switched connection.

33. A computer program product according to claim 30, wherein the second executable portion establishes the circuit-switched connection between the terminal and the gateway based upon a handoff identifier hosted by the gateway.

34. A computer program product according to claim 30 further comprising:

a fourth executable portion for monitoring a signal strength of the packet-switched connection between the terminal and the gateway,

wherein the second executable portion can establish the circuit-switched connection when the signal strength of the packet-switched connection is below a predetermined threshold for more than a predefined period of time, and wherein the third executable portion can connect the circuit-switched connection established between the terminal and the gateway with the circuit-switched connection between the gateway and the other terminal in instances in which the circuit-switched connection is established between the terminal and the gateway.