Assisted handover in a wireless communication system

• US 6,728,540 B1
• Filed: 03/09/1998
• Issued: 04/27/2004
• Est. Priority Date: 03/09/1998
• Status: Expired due to Fees

• Current Assignee: Avaya Incorporated
• Original Assignee: Avaya Technology Corporation Miami Lakes FLA US
• Inventors: Sackett, Raymond A., DeSantis, Charles M.
• Primary Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US09/037,302
• Time in Patent Office: 2,241 Days
• Field of Search: 455/436, 455/437, 455/438, 455/422, 455/439, 455/440, 455/443, 455/450, 455/442, 455/455, 455/446, 455/447
• US Class Current: 455/437
• CPC Class Codes: H04W 36/0061 of neighbour cell information

Abstract

An ongoing communication with a mobile in a current cell of a wireless cellular system is handed over to another cell using information regarding a set of potential handover candidates. This information is transmitted from a base station in the current cell or from another fixed part transmitter in the system. The set of handover candidates for a given mobile in the current cell is determined based on stored adjacency information regarding the cells which are adjacent to the current cell. This adjacency information may be stored after an initial system configuration, based on the actual physical layout of the cells, and may be altered during system operation to reflect the success or failure of particular attempted handovers. The set of potential handover candidates may be in the form of a list of beacons associated with the cells adjacent to the current cell, and may include corresponding channel identifying information such as frequency and time slot. The potential handover candidate information may be transmitted upon receipt of a handover assistance request from the mobile, or may be periodically broadcast throughout the system.

Claims

1. A method of handing over a communication with a mobile in a current cell to another cell in a wireless communication system, the method comprising the steps of:

transmitting information regarding potential handover candidates to the mobile in the current cell, wherein the potential handover candidates are determined based on stored adjacency information, and further wherein the potential handover candidates associated with the transmitted information are restricted to cells that are contiguous with the current cell and the transmitted information includes frequency and time slot information associated with a beacon, determined to be observable by the mobile, for each of the contiguous cells; and

processing an attempted handover to one of the potential handover candidates.

2. The method of claim 1 wherein the transmitting step includes transmitting the information regarding potential handover candidates from a base station in the current cell.

3. The method of claim 1 wherein the transmitting step is carried out in response to a request for handover assistance received in the base station from the mobile.

4. The method of claim 1 wherein the transmitting step includes periodically broadcasting the information regarding potential handover candidates from at least one fixed part transmitter in the system to the mobile.

5. The method of claim 1 wherein the adjacency information is stored in at least one base station of the system in the form of an adjacency matrix which includes, for a given cell, identifiers of all cells contiguous with the given cell.

6. The method of claim 1 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined from the original physical layout of the wireless communication system.

7. The method of claim 1 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined by a base station in each cell of the wireless communication system.

8. A method of handing over a communication with a mobile in a current cell to another cell in a wireless communication system, the method comprising the steps of:

receiving in the mobile in the current cell transmitted information regarding potential handover candidates, wherein the potential handover candidates are determined based on stored adjacency information, and further wherein the potential handover candidates associated with the transmitted information are restricted to cells that are contiguous with the current cell and the transmitted information includes frequency and time slot information associated with a beacon, determined to be observable by the mobile, for each of the contiguous cells; and

initiating in the mobile an attempted handover to one of the potential handover candidates.

9. The method of claim 8 wherein the receiving step includes receiving the transmitted information regarding potential handover candidates from a base station in the current cell.

10. The method of claim 8 wherein the receiving step includes receiving the information regarding potential handover candidates in response to a request for handover assistance transmitted from the mobile to a base station in the current cell.

11. The method of claim 8 wherein the receiving step includes receiving the information regarding potential handover candidates via a periodic broadcast of the information from at least one fixed part transmitter in the system.

12. The method of claim 8 wherein the adjacency information is stored in at least one base station of the system in the form of an adjacency matrix which includes, for a given cell, identifiers of all cells contiguous with the given cell.

13. The method of claim 8 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined from the original physical layout of the wireless communication system.

14. The method of claim 8 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined by a base station in each cell of the wireless communication system.

15. An apparatus for use in handing over a communication with a mobile in a current cell to another cell in a wireless communication system, the apparatus comprising:

a transmitter for transmitting information regarding potential handover candidates to the mobile in the current cell, wherein the potential handover candidates are determined based on adjacency information, and further wherein the potential handover candidates associated with the transmitted information are restricted to cells that are continuous with the current cell and the transmitted information includes frequency and time slot information associated with a beacon, determined to be observable by the mobile, for each of the contiguous cells; and

a memory for storing the adjacency information.

16. The apparatus of claim 15 wherein the transmitter is a base station transmitter in the current cell.

17. The apparatus of claim 15 wherein the transmitter is operative to transmit the information regarding potential handover candidates in response to a request for handover assistance received from the mobile.

18. The apparatus of claim 15 wherein the transmitter is operative to periodically broadcast the information regarding potential handover candidates to the mobile.

19. The apparatus of claim 15 wherein the adjacency information is stored in the memory in the form of an adjacency matrix which includes, for a given cell, identifiers of all cells contiguous with the given cell.

20. The apparatus of claim 15 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined from the original physical layout of the wireless communication system.

21. The apparatus of claim 15 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined by a base station in each cell of the wireless communication system.

22. An apparatus for use in handing over a communication with a mobile in a current cell to another cell in a wireless communication system, the apparatus comprising:

a receiver in the mobile for receiving transmitted information regarding potential handover candidates, wherein the potential handover candidates are determined based on stored adjacency information, and further wherein the potential handover candidates associated with the transmitted information are restricted to cells that are contiguous with the current cell and the transmitted information includes frequency and time slot information associated with a beacon, determined to be observable by the mobile, for each of the continuous cells; and

a controller coupled to the receiver, for initiating in the mobile an attempted handover to one of the potential handover candidates.

23. The apparatus of claim 22 wherein the receiver is operative to receive the transmitted information regarding potential handover candidates from a base station in the current cell.

24. The apparatus of claim 22 wherein the receiver is operative to receive the information regarding potential handover candidates in response to a request for handover assistance transmitted from the mobile to a base station in the current cell.

25. The apparatus of claim 22 wherein the receiver is operative to receive the information regarding potential handover candidates via a periodic broadcast of the information from at least one fixed part transmitter in the system.

26. The apparatus of claim 22 wherein the adjacency information is stored in at least one base station of the system in the form of an adjacency matrix which includes, for a given cell, identifiers of all cells contiguous with the given cell.

27. The apparatus of claim 22 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined from the original physical layout of the wireless communication system.

28. The apparatus of claim 22 wherein the potential handover candidates associated with the transmitted information that are contiguous with the current cell are determined by a base station in each cell of the wireless communication system.