Method for use of azimuth and bearing data to select a serving sector for a mobile station

• US 7,881,263 B1
• Filed: 07/31/2007
• Issued: 02/01/2011
• Est. Priority Date: 07/31/2007
• Status: Active Grant

• Current Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Original Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Inventors: Oroskar, Siddharth S., Canjeevaram, Ashvini G., Shetty, Manoj, Vargantwar, Sachin R., Rai, DeveshKumar
• Primary Examiner(s): Chou; Albert T
• Application Number:
  US11/831,373
• Time in Patent Office: 1,281 Days
• Field of Search: 4554561-4566, 455/439, 370/331
• US Class Current: 370/331
• CPC Class Codes: H04W 36/32 by location or mobility data, e.g. speed data
• CPC Class Codes: H04W 36/322 by location data

Abstract

A method for selecting a wireless coverage sector to serve a mobile station, such as in response to a handoff request that designates a sector-identifier that represents two or more possible sectors. A serving radio access network (RAN) may identify potential sectors in the region and may then select the sector whose azimuth is closest to the geographic bearing of the mobile station from the sector'"'"'s base station. Further, in the event of a tie between two or more sectors or in other circumstances, the RAN may also take into consideration how close the mobile station is to various base stations, such as selecting the sector to whose base station the mobile station is closest. In a system that uses neighbor lists to govern handoff, the invention can help to facilitate handoff in a scenario where a mobile station requests handoff to a sector not listed in the mobile station'"'"'s neighbor list.

Claims

1. A method of facilitating mobile station handoff, the method comprising:

receiving into a radio access network, from a mobile station served by the radio access network, a message requesting handoff of the mobile station to a sector, wherein the message designates the sector by an ambiguous parameter that represents two or more sectors each defined by a respective base station and having an azimuth from the respective base station; and

responsively (i) for each sector, comparing a geographic location of the mobile station with a geographic location of the base station defining the sector, to determine a respective bearing of the mobile station from the base station defining the sector, (ii) selecting a given sector whose azimuth corresponds closest to the determined bearing of the mobile station from the base station defining the given sector, and (iii) sending to the mobile station a directive for the mobile station to hand off to the given sector.

2. The method of claim 1, wherein the ambiguous parameter comprises a PN-offset that is not contained in a neighbor list of the mobile station when receiving the message requesting handoff.

3. The method of claim 1, wherein

comparing a geographic location of the mobile station with a geographic location of the base station defining the sector, to determine a respective bearing of the mobile station from the base station defining the sector comprises:

comparing latitude and longitude of the mobile station with latitude and longitude of the base station defining the sector to determine as the bearing a compass bearing of the mobile station from the base station defining the sector.

4. The method of claim 3, wherein selecting the given sector whose azimuth corresponds closest to the determined bearing of the mobile station from the base station defining the given sector comprises:

if the compass bearing is closest to north, selecting as the given sector a sector whose azimuth is closest to 0 degrees from north;

if the compass bearing is closest to northeast, selecting as the given sector a sector whose azimuth is closest to 45 degrees from north;

if the compass bearing is closest to east, selecting as the given sector a sector whose azimuth is closest to 90 degrees from north;

if the compass bearing is closest to southeast, selecting as the given sector a sector whose azimuth is closest to 135 degrees from north;

if the compass bearing is closest to south, selecting as the given sector a sector whose azimuth is closest to 180 degrees from north;

if the compass bearing is closest to southwest, selecting as the given sector a sector whose azimuth is closest to 225 degrees from north;

if the compass bearing is closest to west, selecting as the given sector a sector whose azimuth is closest to 270 degrees from north; and

if the compass bearing is closest to northwest, selecting as the given sector a sector whose azimuth is closest to 315 degrees from north.

5. The method of claim 1, wherein the message from the mobile station comprises a Pilot Strength Management Message (PSMM), and wherein the directive to the mobile station comprises a Handoff Direction Message (HDM).

6. The method of claim 1, wherein receiving the message requesting handoff comprises receiving the request via an air interface between the radio access network and the mobile station, and wherein sending the directive to the mobile station comprises transmitting the directive to the mobile station via the air interface.

7. The method of claim 6, further comprising reserving at least one resource in the given sector for use by the mobile station, and wherein the directive carries an indication of the at least one reserved resource, whereby the mobile station reads the indication and uses the at least one reserved resource.

8. The method of claim 7, wherein the at least one reserved resource comprises a Walsh code.

9. The method of claim 1, further comprising:

in the event of a tie between two or more sectors, selecting as the target sector one of the two or more sectors whose base station is closest to the mobile station.

10. A method of facilitating mobile station handoff, the method comprising:

receiving into a radio access network, from a mobile station served by the radio access network, a request for handoff of the mobile station;

responsively identifying a plurality of potential sectors for the requested handoff, each potential sector having a respective azimuth from a base station defining the sector;

for each potential sector, comparing a geographic location of the mobile station with a geographic location the base station defining the potential sector, to determine a respective bearing of the mobile station from the base station defining the potential sector;

selecting as a target sector a potential sector whose azimuth is closest to the bearing of the mobile station from the base station defining the selected potential sector; and

directing the mobile station to hand off to the target sector.

11. The method of claim 10, wherein the received request for handoff of the mobile station carries an ambiguous parameter that represents two or more sectors, and wherein identifying the plurality of potential sectors comprises referring to stored data to identify the sectors represented by the ambiguous parameter.

12. The method of claim 11, wherein the ambiguous parameter comprises a PN-offset that is not contained in a neighbor list of the mobile station when receiving the request for handoff.

13. The method of claim 10, wherein comparing a geographic location of the mobile station with a geographic location the base station defining the potential sector, to determine a respective bearing of the mobile station from the base station defining the potential sector comprises:

comparing latitude and longitude of the mobile station with latitude and longitude of the base station defining the potential sector to determine as the bearing a compass bearing of the mobile station from the base station defining the potential sector.

14. The method of claim 13, wherein selecting as the target sector the potential sector whose azimuth is closest to the bearing of the mobile station from the base station defining the selected potential sector comprises:

if the compass bearing is closest to north, selecting as the target sector a potential sector whose azimuth is closest to 0 degrees from north;

if the compass bearing is closest to northeast, selecting as the target sector a potential sector whose azimuth is closest to 45 degrees from north;

if the compass bearing is closest to east, selecting as the target sector a potential sector whose azimuth is closest to 90 degrees from north;

if the compass bearing is closest to southeast, selecting as the target sector a potential sector whose azimuth is closest to 135 degrees from north;

if the compass bearing is closest to south, selecting as the target sector a potential sector whose azimuth is closest to 180 degrees from north;

if the compass bearing is closest to southwest, selecting as the target sector a potential sector whose azimuth is closest to 225 degrees from north;

if the compass bearing is closest to west, selecting as the target sector a potential sector whose azimuth is closest to 270 degrees from north; and

if the compass bearing is closest to northwest, selecting as the target sector a potential sector whose azimuth is closest to 315 degrees from north.

15. The method of claim 10, wherein the request for handoff comprises a Pilot Strength Management Message (PSMM), and wherein directing the mobile station to hand off to the target sector comprises sending a Handoff Direction Message (HDM) to the mobile station.

16. The method of claim 10, wherein receiving the request for handoff comprises receiving the request via an air interface between the radio access network and the mobile station, and wherein directing the mobile station to hand off to the target sector comprises transmitting to the mobile station via the air interface a handoff directive.

17. The method of claim 16, further comprising reserving at least one resource in the target sector for use by the mobile station, and wherein the handoff directive carries an indication of the at least one reserved resource, whereby the mobile station reads the indication and uses the at least one reserved resource.

18. The method of claim 17, wherein the at least one reserved resource comprises a Walsh code.

19. The method of claim 10, further comprising:

in the event of a tie between two or more potential sectors, selecting as the target sector one of the two or more potential sectors whose base station is closest to the mobile station.