Cellular mobile telephone network operation

• US 6,801,772 B1
• Filed: 05/08/2001
• Issued: 10/05/2004
• Est. Priority Date: 12/08/1998
• Status: Expired due to Term

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Lobley, Nigel Clive, Townend, Jonathan Richard
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): RAMPURIA, SHARAD K
• Application Number:
  US09/831,296
• Time in Patent Office: 1,246 Days
• Field of Search: 455/437, 455/436, 455/424, 455/426.2, 455/525, 455/439, 370/331-333
• US Class Current: 455/436
• CPC Class Codes: H04W 36/00835 Determination of neighbour cell lists

Abstract

Where a call of one cellular telephone network has a cell of another network as neighbor, a dedicated control channel for a mobile station which is registered with the public network and whose subscriber has access privileges for the private network, carries neighboring cell data for the cell of the private network. Consequently, the mobile station (provides measurement reports for cells of both network and can be preferentially handed over to the cell of the private network by the public network.

Claims

1. A method of operating a cellular telephone system having a subset of base stations only available to some subscribers to the system, the method comprising:

transmitting, to each mobile station, neighboring base station data for constructing a list of beacon identities for base stations neighboring the mobile station'"'"'s serving base station, the transmission being made in a control channel, dedicated to the particular mobile station, wherein the list of beacon identities includes members of the said subset only if the subset is available to the mobile station'"'"'s subscriber,

receiving signal reports from the mobile station for the plurality of base stations,

and controlling a handover by selecting a base station for use by the mobile station based on said reports and on whether the base station is a member of the subset,

the handover being controlled such that mobile stations for which access to the subset of base stations is permitted are not handed over to base stations not forming part of the subset unless the signal reports for the base stations indicate that reliable communication cannot be effected between the mobile station and any member of the subset.

2. A method as in claim 1, wherein the transmitted data is configured for the generation of a beacon identity list including a beacon identity for a base station in said subset.

3. A method as in claim 2, wherein said base station serves a cell located wholly within a cell served by a base station which is not a member of the subset.

4. A method as in claim 1, wherein the base stations of the subset comprise the base stations of a private network to which the subscriber has access.

5. A method as in claim 1, wherein the base stations of the subset use a different radio technology to that used by the serving base station.

6. A method as in claim 1, further comprising:

maintaining a record of the neighbor relationship between a first base station in the subset of base stations and a second base station not in the subset,

determining whether the mobile station'"'"'s subscriber, when the mobile station is located in a cell served by said first base station of the public network, has an access-granting relationship with the base stations of the subset, and

transmitting the data identifying the beacon identity of the second base station in said dedicated control channel if the mobile station'"'"'s subscriber has said access-granting relationship with the base stations of the subset.

7. A method as in claim 1, wherein the neighboring base station data is arranged for the generation of a first beacon identity list if the mobile unit to which the list is to be transmitted does not have access to base stations in the subset, and a second beacon identity list similar to the first beacon identity list but extended to include a beacon identity of a base station in the subset if the mobile unit to which the list is to be transmitted has access to such base stations.

8. A method as in claim 1, wherein a handover of a mobile station currently served by a base station not of the subset to a base station of the subset is initiated if the signal report for that base station indicates that reliable communication can be effected with the mobile station using that base station.

9. A method as in claim 1, wherein handover of a mobile station currently served by a base station of the subset to a base station not of the subset is only initiated if the signal reports indicate that reliable communication cannot be continued using any base station in the subset.

10. A cellular mobile telephony system configured to perform a method as in claim 1.

11. A cellular mobile telephony system comprising a plurality of base stations under the control of one or more controllers, the base stations control means comprising:

means for generating, for each of one or more mobile stations currently served by the base stations, data by which the mobile station may construct a list of beacon identities for base stations neighboring the mobile station'"'"'s serving base station,

means for identifying whether a predetermined subset of the base stations is available for use by the mobile station'"'"'s subscriber, and including the beacon identities of such base stations only if they are so available;

transmission means for transmitting said data in a control channel, dedicated to the particular mobile station,

means for receiving signal reports from the mobile station for the plurality of base stations, and

means for controlling a handover by electing a base station for use by the mobile station based on said reports and on whether the base station is a member of the subset, the handover being controlled such that mobile stations for which access to the subset of base stations is permitted are not handed over to base stations not forming part of the subset unless the signal reports for the base stations indicate that reliable communication cannot be effected between the mobile station and any member of the subset.

12. A system as in claim 11, wherein the data transmitted includes a beacon identity list including beacon identities for a base station in said subset.

13. A system as in claim 12, wherein said base station serves a cell located wholly within a cell served by a base station which is not a member of the subset.

14. A system as in claim 11, wherein the base stations of the subset comprise the base stations of a private network to which predetermined subscribers have access.

15. A system as in claim 11, wherein the base stations of the subset use a different radio technology compared to that used by the serving base station.

16. A system as in claim 11, further comprising:

means for maintaining a record of the neighbor relationship between a first base station in the subset of base stations and a second base station not in the subset,

means for determining whether the mobile station'"'"'s subscriber, when the mobile station is located in a cell served by said first base station of the public network, has an access-granting relationship with the base stations of the subset, and

means for transmitting the data identifying the beacon identity of the second base station in said dedicated control channel if the mobile station'"'"'s subscriber has said access-granting relationship with the base stations of the subset.

17. A system as in claim 11, further comprising:

means for generation of a first beacon identity list if the mobile unit to which the list to be transmitted does not have access to base stations in the subset, and for generating a second beacon identity list similar to the first beacon identity list but, extended to include a beacon identity of a base station in the subset if the mobile unit to which the list is to be transmitted has access to such base stations.

18. A system as in claim 11, wherein the handover means is arranged to initiate handover of a mobile station currently served by a base station not of the subset to a base station of the subset if the signal report for that base station indicates that reliable communication can be effected with the mobile station using that base station.

19. A system as in claim 11, wherein the handover means is arranged to initiate handover of a mobile station currently served by a base station of the subset to a base station not of the subset only if the signal reports indicate that reliable communication cannot be continued using any base station in the subset.

20. A method for controlling handover of a mobile station to a different base station in a cellular telephone system having a subset of base stations only available to some mobile station subscribers, said method comprising:

controlling handover of mobile stations for which subscriber access to said subset is permitted such that handover to a base station not in the subset does not occur unless reliable communication cannot be effected with any base station of the subset.

21. A cellular mobile telephony system comprising plural base stations and including a subset of base stations only available to some authorized mobile station subscribers, said system comprising:

means in each authorized mobile station for measuring received signal strength from each base station of the subset and communicating same to controller; and

a controller which uses said received signal strength measurements to effect handover of an authorized mobile station out of said subset only if reliable communication cannot be expected with any base station of the subset.