Method and apparatus for effecting handoff between different cellular communications systems

• US 6,594,489 B2
• Filed: 02/14/2002
• Issued: 07/15/2003
• Est. Priority Date: 12/07/2001
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Holcman, Alejandro R.
• Primary Examiner(s): Nguyen, Lee
• Assistant Examiner(s): Ferguson, Keith
• Application Number:
  US10/077,502
• Publication Number:
  US 20030109256A1
• Time in Patent Office: 516 Days
• Field of Search: 455/432, 455/436, 455/437, 455/438, 455/439, 455/440, 455/442, 455/443, 455/445, 455/403, 455/422, 455/410, 455/411, 455/517, 455/550, 370/331, 370/313, 370/329, 380/270, 380/247, 380/272, 380/277
• US Class Current: 455/432.1
• CPC Class Codes: H04L 63/0457 wherein the sending and receiving network entities apply dynamic encryption, e.g. stream encryption cryptographic mechanisms or cryptographic arrangements for stream encryption H04L9/065
• CPC Class Codes: H04L 63/061 for key exchange, e.g. in peer-to-peer networks cryptographic mechanisms or cryptographic arrangements for key agreement H04L9/0838
• CPC Class Codes: H04L 63/16 Implementing security features at a particular protocol layer
• CPC Class Codes: H04W 12/04 Key management, e.g. using generic bootstrapping architecture [GBA]
• CPC Class Codes: H04W 36/1443 between licensed networks
• CPC Class Codes: H04W 80/02 Data link layer protocols

Abstract

A method of effecting handoff of a mobile station from a first base station in a first cellular communications system controlled by a first mobile switching control station to a second base station in a second, different cellular system controlled by a second mobile switching control station is described. The method comprises generating for the mobile station a cipher key for use by the mobile station during communication in the second cellular communications system. The cipher key is generated by the mobile station from a private key assigned to the mobile station for the second cellular communications system and from a random number generated by the second cellular communications system. The cipher key is then communicated to the first mobile system and a private long code is generated for use by the mobile station during communication in the first cellular communications system.

Claims

1. A method of effecting handoff of a mobile station from a first base station in a first cellular communications system controlled by a first mobile switching control station to a second base station in a second, different cellular system controlled by a second mobile switching control station, the method comprising:

generating for the mobile station a cipher key for use by the mobile station during communication in the second cellular communications system, the cipher key being generated by the mobile station from a private key assigned to the mobile station for the second cellular communications system and from a random number generated by the second cellular communications system;

communicating the cipher key to the first mobile system; and

generating for the mobile station a private long code for use by the mobile station during communication in the first cellular communications system.

2. The method as claimed in claim 1, wherein the first system comprises a channel for transferring data between the system and the mobile station, and wherein the method further comprises transmitting the cipher key to the system using the channel for transferring data.

3. The method as claimed in claim 2, wherein the channel is a paging channel.

4. The method as claimed in claim 1, wherein the first cellular communications system comprises a first base station controlled by a first mobile switching control station and the second cellular communications system comprises a second base station controlled by a second mobile switching control station, the method comprising:

measuring at the mobile station a parameter of a signal transmitted by said first base station;

measuring at the mobile station a parameter of a signal transmitted by said second base station;

communicating a signal quality message from the mobile station via the first base station to said first mobile switching control station, when the parameters reach a predetermined condition;

generating at the first mobile switching control station information for a channel request message for the second mobile switching control station;

communicating the information from said first mobile switching control station to said mobile station;

generating at the mobile station from the information from the first mobile switching control station a channel request message for the second mobile switching control station; and

communicating the channel request message from the mobile station to the second mobile switching control station.

5. The method as claimed in claim 4, further comprising generating at the second mobile switching control station channel information identifying a channel in the second communications system for the mobile station.

6. The method as claimed in claim 5, further comprising establishing communication between said mobile unit and said second base station in the identified channel.

7. The method as claimed in claim 6, further comprising discontinuing communication between said mobile unit and said first base station.

8. The method as claimed in claim 4, wherein said parameter corresponds to signal strength.

9. The method as claimed in claim 4, wherein said first cellular communications system is a CDMA system.

10. The method as claimed in claim 9, wherein said second cellular communications system is a GSM system.

11. A mobile station comprising:

a first transceiver chain operable to receive and transmit signals with a first base station in a first cellular communications system;

a second transceiver chain operable to receive and transmit signals with a second base station in a second cellular communications system; and

a controller for;

receiving a random number generated by the second cellular communications system;

generating for the mobile station a cipher key for use by the mobile station during communication in the second cellular communications system, the cipher key being generated from a private key assigned to the mobile station for the second cellular communications system and from the received random number;

communicating the cipher key to the first mobile system; and

generating a private long code for use by the mobile station during communication in the first cellular communications system.

12. The mobile station as claimed in claim 11, further comprising means for transmitting the cipher key to the first system using a channel in the system for transferring data.

13. The mobile station as claimed in claim 12, wherein the channel is a paging channel.

14. The mobile station as claimed in claim 11, further comprising:

means for measuring a parameter of a signal transmitted by said first base station;

means for measuring a parameter of a signal transmitted by said second base station;

means for communicating a signal quality message from the mobile station via the first base station to said first cellular communications system, when the parameters reach a predetermined condition;

means for receiving from the first base station information for a channel request message for the second cellular communications system;

means for generating from the information from the first base station a channel request message for the second cellular communications system; and

means for communicating the channel request message to the second mobile switching control station.

15. The mobile station as claimed in claim 14, wherein the controller is further for receiving from said second base station channel information identifying a channel in the second communications system for the mobile station.

16. The mobile station as claimed in claim 15, wherein the controller is arranged to respond to the channel information by establishing communication between said mobile unit and said second base station in the identified channel.

17. The mobile station as claimed in claim 16, wherein the controller is arranged to respond to the channel information by discontinuing communication between said mobile unit and said first base station.

18. The mobile station as claimed in claim 14, wherein said parameter corresponds to signal strength.

19. The mobile station as claimed in claim 14, wherein said first cellular communications system is a CDMA system.

20. The mobile station as claimed in claim 19, wherein said second cellular communications system is a GSM system.

21. An apparatus for affecting handoff of a mobile station from a first base station in a first cellular communications system controlled by a first mobile switching control station to a second base station in a second, different cellular system controlled by a second mobile switching control station, the method comprising:

means for generating for the mobile station a cipher key for use by the mobile station during communication in the second cellular communications system, the cipher key being generated by the mobile station from a private key assigned to the mobile station for the second cellular communications system and from a random number generated by the second cellular communications system;

means for communicating the cipher key to the first mobile system; and

means for generating for the mobile station a private long code for use by the mobile station during communication in the first cellular communications system.

22. The apparatus as claimed in claim 21, wherein the first system comprises a channel for transferring data between the system and the mobile station, and wherein the apparatus further comprises means for transmitting the cipher key to the system using the channel for transferring data.

23. The apparatus as claimed in claim 22, wherein the channel is a paging channel.

24. The apparatus as claimed in claim 21, wherein said first cellular communications system is a CDMA system.

25. The apparatus as claimed in claim 24, wherein said second cellular communications system is a GSM system.