Smart subdivision of base station candidates for position location accuracy

• US 6,154,657 A
• Filed: 10/21/1997
• Issued: 11/28/2000
• Est. Priority Date: 10/21/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bengkvist, Bengt, Grubeck, Hans George
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): Gelin, Jean Alland
• Application Number:
  US08/967,330
• Time in Patent Office: 1,134 Days
• Field of Search: 455/456, 455/422, 455/432, 455/435, 455/436, 455/437, 455/440, 455/464, 455/509, 455/512, 455/513, 455/525, 455/527, 455/67.1, 455/457, 455/423, 342/457, 342/387, 342/357
• US Class Current: 455/456.2
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

In a cellular telephone system of the type having the capability of making measurements useful in determining the location of a mobile station, at least one such measurement is made. The measurement is made in accordance with a cost function which minimizes the costs to the systems. A position fix of the mobile station is determined using the cost function and the measurement.

Claims

1. A method for determining the position of a mobile station whose approximate location is known in a cellular telephone system having a plurality of base stations with known locations, which comprises:

defining a function, which describes the cost of performing positioning measurements within the system involving system resources including a certain subset of base stations and a certain channel for positioning measurements;

selecting a subset of base stations and a channel, which minimizes the cost of the resources within the system when performing the positioning measurements;

assigning the mobile station to said channel;

performing the positioning measurements relating to the position of the mobile station from said selected set of base stations having known locations on said channel; and

obtaining a position fix estimate within a required degree of accuracy based upon said positioning measurements.

2. A method according to claim 1, wherein said function is dependent on the time when measurements are performed.

3. A method according to claims 1 or 2, wherein said function is dependent on the time period, within which measurements are performed.

4. A method according to claims 1 or 2, wherein said function is dependent on predictions of the accuracy of said position fix estimate.

5. A method according to claims 1 or 2, wherein said function is dependent on which channels are used for the said measurements.

6. A method according to claims 1 or 2, wherein said function is dependent on predictions of the accuracy of said measurements on different channels.

7. A method according to claim 6, where said predictions of measurement accuracies are dependent on the signal quality.

8. A method according to claims 1 or 2, wherein said function is dependent on the number of base stations in said subset.

9. A method according to claims 1 or 2, wherein said function is dependent on prior knowledge of the mobile position.

10. A method according to claim 9, wherein said function is dependent on an estimate of the accuracy of said mobile position.

11. A method according to claims 1 or 2, wherein said function is dependent on the load distribution in the network for a certain choice of said channel and said subset of base stations.

12. A method according to claims 1 or 2, wherein said function is dependent on the measurement methods used for said channel and said subset of base stations.

13. A method according to claims 1 or 2, wherein said function is dependent on the cost of using a high quality channel.

14. A method according to claims 1 or 2, wherein said function is dependent on the locations of said base stations.

15. A method according to claims 1 or 2, wherein said function is dependent on the estimated geometric dilution of precision.

16. A method according to claim 12, wherein one of the said measurement methods is the time of arrival measurement method.

17. A method according to claim 12, wherein one of the said measurement methods is the time difference of arrival measurement method.

18. A method according to claims 12, wherein one of the said measurement methods is the angle of arrival measurement method.

19. A method according to claims 1 or 2, wherein one base station at the time performs measurements in said subset of base stations, that is measurements are performed in a sequential order.

20. A method according to claim 19, wherein a new subset of base stations and a new channel according to said function can be selected for every step in said sequential order.

21. A method according to claim 20, wherein said mobile station is assigned to said new channel.

22. A method according to claim 20, wherein said function is dependent on previous measurements in said sequential order.

23. A method according to claim 20, wherein said function is dependent on the cost due to a change of channel assignment.

24. A method according to claim 20, wherein said function is dependent on the cost due to a change of subset of base station.

25. The method according to claim 1 wherein the step of assigning the mobile station to a channel includes assigning the mobile station to one of the base stations from the subset of base stations for the specific purpose of performing the measurement.

30. The system according to claim 25 wherein the means for obtaining a position fix estimate includes a Taylor series estimation.

31. The method according to claim 30 wherein the step of performing measurements is selected from performing a time of arrival measurement, performing a time difference of arrival measurement, or performing an angle of arrival measurement.

26. A positioning system for a cellular telephone system having a plurality of base stations with known locations and at least one mobile station whose approximate location is known, which comprises:

means for defining a function, which describes the cost of performing positioning measurements within the system involving system resources including a certain subset of base stations and a certain channel for positioning measurements;

means for selecting a subset of base stations and a channel, which minimizes the cost of the resources within the system when performing the positioning measurements;

means for assigning the mobile station to said channel;

means for performing positioning measurements relating to the position of the mobile station from said selected set of base stations having known locations on said channel; and

means for obtaining a position fix estimate within a required degree of accuracy based upon said positioning measurements.

27. The system according to claim 26 wherein the means for assigning the mobile station to a channel includes assigning the mobile station to one of the base stations from the subset of base stations for the specific purpose of performing a measurement.

28. The system according to claim 27 wherein the means for obtaining a position fix estimate includes a Taylor series estimation.

29. The system according to claim 28 wherein the means for performing measurements is selected from means for performing a time of arrival measurement, means for performing a time difference of arrival measurement, or means for performing an angle of arrival measurement.