Method for performing inter-system handovers in a mobile communication system

• US 20060258358A1
• Filed: 08/11/2005
• Published: 11/16/2006
• Est. Priority Date: 05/11/2005
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Nokia Corporation
• Inventors: Kallio, Juha
• Granted Patent: US 7,640,036 B2
• Time in Patent Office: Days
• US Class Current: 455/437
• CPC Class Codes: H04L 65/1016 IP multimedia subsystem [IMS]
• CPC Class Codes: H04L 65/1043 Gateway controllers, e.g. media gateway control protocol [MGCP] controllers
• CPC Class Codes: H04L 65/1095 Inter-network session transfer or sharing
• CPC Class Codes: H04W 36/0066 of control information between different types of networks in order to establish a new radio link in the target network
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 76/30 Connection release
• CPC Class Codes: H04W 80/00 Wireless network protocols or protocol adaptations to wireless operation
• CPC Class Codes: H04W 80/10 adapted for application session management, e.g. SIP [Session Initiation Protocol] connection management H04W76/00; arrangements for session management H04L67/14
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: H04W 88/16 Gateway arrangements

Abstract

The invention relates to a method for performing inter-system handovers in a communication system comprising at least a mobile station, a call state control function, a first and a second call control node, a first and a second media gateway and a radio network node. The handover is achieved by way of connecting a call control node to a call state control function. The call control node allocates a media gateway for the session established. The session media bearers are routed via the media gateway. The call control node acts as an anchor node for the handover. As the mobile station moves to a new cell a media bearer is established to the media gateway from the mobile station via the new cell.

Claims

1. A method for performing inter-system handovers in a communication system comprising at least a mobile station, a call state control function, a first call control node and a second call control node, a first media gateway and a second media gateway and a radio network node, the method comprising:

receiving a session set-up message from said mobile station to said call state control function;

providing said session set-up message to said first call control node;

said first call control node allocating said first media gateway for establishing at least one first media bearer from said first media gateway towards said mobile station;

detecting a handover condition in said mobile station;

said mobile station sending a handover request to said first call control node via said call state control function;

said first call control node determining said second call control node identity based on cell information in said handover request;

said first call control node sending the handover request to said second call control node;

said second call control node allocating radio resources for said mobile station via said radio network node and allocating said second media gateway;

establishing at least one second media bearer between said first media gateway and said second media gateway;

said mobile station contacting said second call control node using said allocated radio resources via said radio network node; and

removing said at least one first media bearer between said mobile station and said first media gateway.

2. The method according to claim 1, the method further comprising:

receiving a registration message from said mobile station to said call state control function;

fetching subscriber data associated with said mobile station from a Home Subscriber Server to said call state control function;

determining in said call state control function whether said registration message must be provided to said first call control node;

providing said registration message to said first call control node;

determining in said first call control node whether said mobile station supports inter-system handover;

performing location update procedure between said first call control node and a Home Location Register; and

said first call control node acknowledging said registration message to said mobile station via said call state control function.

3. The method according to claim 1, the method further comprising:

said mobile station determining the availability of an unlicensed radio band;

said mobile station sending a session set-up message via said unlicensed radio band;

said mobile station determining the availability of a licensed radio band and cell information associated with said licensed radio band; and

said mobile station performing decision on handover to said licensed radio band.

4. The method according to claim 3, wherein said licensed radio band is used by at least one of the Global System of Mobile communications, the General Packet Radio System and the Universal Mobile Telecommunication System.

5. The method according to claim 3, wherein said unlicensed radio band is used by at least one of a Wireless Local Area Network, a Bluetooth™

base transceiver station and a short range point-to-point radio base transceiver station.

6. The method according to claim 1, wherein said first call control node and said second call control node are Mobile Switching Center Servers

7. The method according to claim 1, wherein said at least one first media bearer is transmitted over Internet Protocol between said mobile station and said first media gateway.

8. The method according to claim 1, wherein said radio resources comprise at least one radio channel.

9. The method according to claim 8, wherein each of said at least one radio channel comprises at least one of a carrier frequency, a timeslot, a spreading code and an Orthogonal Frequency Division Multiplexing sub-carrier.

10. The method according to claim 1, wherein said mobile station comprises a Session Initiation Protocol user agent.

11. The method according to claim 1, wherein said communication system comprises an IP Multimedia Subsystem.

13. The system according to claim 11, the system wherein said call state control function is further configured to receive a registration message from said mobile station, to fetch subscriber data associated with said mobile station from a Home Subscriber Server, to determine whether said registration message must be provided to said first call control node and to provide said registration message to said first call control node, and

said first call control node is configured to determine whether said mobile station supports inter-system handover, to perform a location update procedure towards a Home Location Register and to acknowledge said registration message to said mobile station via said call state control function.

14. The system according to claim 11, wherein said mobile station is configured to determine the availability of an unlicensed radio band, to send a session set-up message via said unlicensed radio band, to determine the availability of a licensed radio band and cell information associated with said licensed radio band and to perform decision on handover to said licensed radio band.

15. The system according to claim 14, wherein said radio network node is configured to be connected to a base transceiver station, said base transceiver station being configured to use said licensed band.

16. The system according to claim 11, the system further comprising:

a second base transceiver station configured to communicate with said call state control function and to communicate with said mobile station using at least one of a Wireless Local Area Network protocol, a Bluetooth™

protocol and a short range point-to-point radio protocol.

17. The system according to claim 16, the system further comprising:

a session border controller configured to communicate with said mobile station via said second base transceiver station and to transmit said at least one first media bearer over Internet Protocol towards said first media gateway.

18. The system according to claim 11, wherein said first call control node and said second call control node are Mobile Switching Center Servers.

19. The system according to claim 11, wherein said radio resources comprise at least one radio channel.

20. The system according to claim 19, wherein each said at least one radio channel comprises at least one of a carrier frequency, a timeslot, a spreading code and an Orthogonal Frequency Division Multiplexing sub-carrier.

21. The system according to claim 11, wherein said mobile station comprises a Session Initiation Protocol user agent.

22. The system according to claim 1, wherein said communication system comprises an IP Multimedia Subsystem.

12. A system comprising:

a radio network node;

a call state control function configured to receive a session set-up message from a mobile station, to provide said session set-up message to a first call control node;

said first call control node configured to allocate a first media gateway for establishing at least one first media bearer from a first media gateway towards said mobile station, to determine a second call control node identity based on cell information in a handover request, to send the handover request to said second call control node and to request the removing of at least one first media bearer from said first media gateway towards said mobile station;

said mobile station configured to detect the handover condition, to send a handover request to said first call control node via said call state control function and to contact said second call control node using allocated radio resources via said radio network node; and

said second call control node configured to allocate said radio resources for said mobile station via said radio network node, to allocate a second media gateway and to request the establishment of at least one second media bearer between said first and said second media gateway.

23. A call control node comprising:

a call control entity configured to receive a set-up request message from a call state control function, to allocate a first media gateway, to request the establishing of at least one first media bearer from said first media gateway towards a mobile station, to determine a second call control node identity based on cell information in a handover request from said call state control function, to send said handover request to said second call control node, to allocate radio resources for said mobile station via a radio network node, to allocate a second media gateway, to request the establishment of at least one second media bearer between said first media gateway and said second media gateway, to request the removing of at least one first media bearer between said first media gateway and second media gateway.

24. An electronic device comprising:

a communication entity configured to determine the availability of an unlicensed radio band, to send a session set-up message via unlicensed radio band towards a call state control function, to determine the availability of a licensed radio band and cell information associated with said licensed radio band, to perform decision on handover to said licensed radio band, to send a handover request towards said call state control function, to receive a handover command from said call state control function and to indicate connection establishment towards a call control node.

25. A computer program embodied within a computer readable medium, wherein when the compter program is executed on a data processing system the computer program is configured to perform the steps of:

receiving a session set-up request message from a call state control function;

allocating a first media gateway;

requesting the establishing of at least one first media bearer from said first media gateway towards a mobile station;

determining the identity of a call control node based on cell information in a handover request from said call state control function;

sending said handover request to said call control node;

receiving a handover preparation request from said call control node;

establishing a handover session towards said call control node; and

requesting the removing of said at least one first media bearer from said first media gateway towards a mobile station.

26. The computer program according to claim 25, wherein said computer readable medium is a removable memory card.

27. The computer program according to claim 25, wherein said computer readable medium is a magnetic or an optical disk.

28. A call control node comprising:

means for receiving a set-up request message from a call state control function, for allocating a first media gateway, for requesting the establishing of at least one first media bearer from the first media gateway towards a mobile station, for determining a second call control node identity based on cell information in a handover request from said call state control function, for sending the handover request to said second call control node, for allocating radio resources for said mobile station via a radio network node, for allocating a second media gateway, for requesting the establishment of at least one second media bearer between said first media gateway and said second media gateway, and for requesting the removing of at least one first media bearer between said first media gateway and second media gateway.

29. An electronic device comprising:

means for determining an availability of an unlicensed radio band, for sending a session set-up message via the unlicensed radio band towards a call state control function, for determining the availability of a licensed radio band and cell information associated with said licensed radio band, for performing decision on handover to said licensed radio band, for sending a handover request towards said call state control function, for receiving a handover command from said call state control function and for indicating connection establishment towards a call control node.