System and/or method for determining sufficiency of pseudorange measurements

• US 7,656,348 B2
• Filed: 08/24/2006
• Issued: 02/02/2010
• Est. Priority Date: 05/19/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ahmed, Rizwan, Rowitch, Douglas Neal
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): LIU, HARRY K
• Application Number:
  US11/510,334
• Publication Number:
  US 20070268177A1
• Time in Patent Office: 1,258 Days
• Field of Search: 342/357.02, 342/357.17
• US Class Current: 342/357.31
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073

Abstract

The subject matter disclosed herein relates to a system and method for determining a sufficiency of measurements for locating positions. In one example, although claimed subject matter is not so limited, a process to improve accuracy of pseudorange measurements may be terminated in response to a weighting of quantitative assessments of at least some of such pseudorange measurements.

Claims

1. A method comprising:

determining quantitative assessments of accuracy associated with a plurality of pseudorange measurements to space vehicles (SVs) at a location, wherein the plurality of pseudorange measurements are determined at a satellite positioning system (SPS) receiver;

weighting at least some of said quantitative assessments according to geometries associated with said SVs to generate weighted quantitative assessments;

determining a location accuracy metric based on the weighted quantitative assessments; and

selectively performing a SV signal search process in the SPS receiver to improve said accuracy of said plurality of said pseudorange measurements based in part on the location accuracy metric.

2. The method of claim 1, and further comprising determining said quantitative assessments of said accuracy associated with said plurality of said pseudorange measurements based, at least in part, on root mean square error estimates associated with said pseudorange measurements.

3. The method of claim 1, and further comprising determining said weighting of at least some of said quantitative measurements based, at least in part, on elevation angles associated with locations of said SVs.

4. The method of claim 3, and further comprising determining said weighting of at least some of said quantitative measurements based, at least in part, on azimuth angles associated with said locations of said SVs.

5. The method of claim 1, wherein said location accuracy metric comprises a weighted horizontal dilution of precision.

6. The method of claim 1, wherein said process to improve said accuracy of said plurality of said pseudorange measurements comprises processing signals received from at least some of said SVs over a dwell.

7. The method of claim 1, wherein said selectively performing said process to improve said accuracy of said plurality of pseudorange measurements further comprises:

selectively performing said process to improve said accuracy in response to a comparison of said location accuracy metric with a threshold value.

8. An apparatus comprising:

a computing platform, said computing platform being adapted to;

determine quantitative assessments of accuracy associated with a plurality of pseudorange measurements to space vehicles (SVs) at a location;

weight at least some of said quantitative assessments according to geometries associated with said SVs to generate weighted quantitative assessments;

determine a location accuracy metric based on the weighted quantitative assessments; and

selectively perform a SV signal search process to improve said accuracy of said plurality of said pseudorange measurements based in part on the location accuracy metric.

9. The apparatus of claim 8, wherein said computing platform is further adapted to determine said quantitative assessments of said accuracy associated with said plurality of said pseudorange measurements based, at least in part, on root mean square error estimates associated with said pseudorange measurements.

10. The apparatus of claim 8, wherein said computing platform is further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on elevation angles associated with locations of said SVs.

11. The apparatus of claim 10, wherein said computing platform is further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on azimuth angles associated with said locations of said SVs.

12. The apparatus of claim 8, wherein said location accuracy metric comprises a weighted horizontal dilution of precision.

13. The apparatus of claim 8, wherein said process to improve said accuracy of said plurality of said pseudorange measurements comprises processing signals received from at least some of said SVs over a dwell.

14. The apparatus of claim 8, wherein said computing platform is further adapted to:

selectively perform said process to improve said accuracy in response to a comparison of said location accuracy metric with a threshold value.

15. An article comprising:

a storage medium comprising machine-readable instructions stored thereon which, when executed, are adapted to;

determine quantitative assessments of accuracy associated with a plurality of pseudorange measurements to space vehicles (SVs) at a location;

weighting at least some of said quantitative assessments according to geometries associated with said SVs to generate weighted quantitative assessments;

determining a location accuracy metric based on the weighted quantitative assessments; and

selectively perform a SV signal search process to improve said accuracy of said plurality of said pseudorange measurements based in part on the location accuracy metric.

16. The article of claim 15, wherein said machine-readable instructions, when executed, are further adapted to determine said quantitative assessments of said accuracy associated with said plurality of said pseudorange measurements based, at least in part, on root mean square error estimates associated with said pseudorange measurements.

17. The article of claim 15, wherein said machine-readable instructions, when executed, are further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on elevation angles associated with locations of said SVs.

18. The article of claim 17, wherein said machine-readable instructions, when executed, are further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on azimuth angles associated with said locations of said SVs.

19. The article of claim 15, wherein said location accuracy metric comprises a weighted horizontal dilution of precision.

20. The article of claim 15, wherein said process to improve said accuracy of said plurality of said pseudorange measurements comprises processing signals received from at least some of said SVs over a dwell.

21. The article of claim 15, wherein said machine-readable instructions, when executed, are further adapted to:

selectively perform said process to improve said accuracy in response to a comparison of said location accuracy metric with a threshold value.

22. A system comprising:

a position determination entity (PDE); and

a subscriber unit, the subscriber unit being adapted to;

receive an acquisition assistance message from said PDE over a terrestrial wireless communication link, said acquisition assistance message comprising information indicative of geometries associated with space vehicles (SVs);

determine quantitative assessments of accuracy associated with a plurality of pseudorange measurements to at least some of said SVs;

weight at least some of said quantitative assessments according to geometries associated with said SVs to generate weighted quantitative assessments;

determine a location accuracy metric based on the weighted quantitative assessments; and

selectively perform a SV signal search process to improve said accuracy of said plurality of said pseudorange measurements based in part on the location accuracy metric.

23. A position determination entity comprising:

a receiver to receive pseudorange measurements to space vehicles (SVs) from a subscriber station over a data link, said position determination entity being adapted to;

determine quantitative assessments of accuracy associated with at least some of said received pseudorange measurements;

weight at least some of said quantitative assessments according to geometries associated with said SVs to generate weighted quantitative assessments;

determine a location accuracy metric based on the weighted quantitative assessments; and

selectively initiate a SV signal search process to improve said accuracy of said plurality of said pseudorange measurements based in part on the location accuracy metric.

24. The position determination entity of claim 23, wherein said position determination entity is further adapted to determine said quantitative assessments of said accuracy associated with said plurality of said pseudorange measurements based, at least in part, on root mean square error estimates associated with said pseudorange measurements.

25. The position determination entity of claim 23, wherein said position determination entity is further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on elevation angles associated with locations of said SVs.

26. The position determination entity of claim 25, wherein said position determination entity is further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on azimuth angles associated with said locations of said SVs.

27. The position determination entity of claim 23, wherein said position determination entity is further adapted to:

selectively initiate said process to improve said accuracy in response to a comparison of said location accuracy metric with a threshold value.

28. The position determination entity of claim 23, and further comprising a transmitter to transmit a message to said subscriber station to terminate said process.

29. A subscriber unit comprising:

receiver to receive an acquisition assistance (AA) message from a data link, said AA message comprising information indicative of geometries associated with space vehicles (SVs), said subscriber unit being adapted to;

determine quantitative assessments of accuracy associated with a plurality of pseudorange measurements to at least some of said SVs;

weight at least some of said quantitative assessments according to geometries associated with said SVs to generate weighted quantitative assessments;

determine a location accuracy metric based on the weighted quantitative assessments; and

selectively perform a SV signal search process to improve said accuracy of said plurality of said pseudorange measurements based in part on the location accuracy metric.

30. The subscriber station of claim 29, wherein said subscriber station is further adapted to determine said quantitative assessments of said accuracy associated with said plurality of said pseudorange measurements based, at least in part, on root mean square error estimates associated with said pseudorange measurements.

31. The subscriber station of claim 29, wherein said subscriber station is further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on approximations of elevation angles associated with locations of said SVs received in said AA message.

32. The subscriber station of claim 31, wherein said subscriber station is further adapted to determine said weighting of at least some of said quantitative measurements based, at least in part, on approximation of said azimuth angles associated with said locations of said SVs received in said AA message.

33. The subscriber station of claim 29, wherein said process to improve said accuracy of said plurality of said pseudorange measurements comprises processing signals received from at least some of said SVs over a dwell.

34. The subscriber station of claim 29, wherein said subscriber station is further adapted to:

selectively perform said process to improve said accuracy in response to a comparison of said location accuracy metric with a threshold value.

35. A method comprising:

correlating, with a correlator, a code phase of a received signal to determine a pseudorange measurement to each of a plurality of space vehicles (SVs) at a location;

determining, with a subscriber station processing unit, quantitative assessments of accuracy associated with a plurality of pseudorange measurements;

determining, with the subscriber station processing unit, a horizontal dilution of precision value based on the quantitative assessments;

comparing, with the subscriber station processing unit, the horizontal dilution of precision value to a predetermined threshold; and

selectively performing a SV signal search process in a satellite positioning system receiver to improve said accuracy of said plurality of said pseudorange measurements based in part on the comparison.