RECOVERY FROM POSITION AND TIME OUTLIERS IN POSITIONING

• US 20120182182A1
• Filed: 12/14/2011
• Published: 07/19/2012
• Est. Priority Date: 12/15/2010
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Riley, Wyatt Thomas, Daita, Lalitaprasad V., Morrison, William James, Farmer, Dominic Gerard, Wu, Jie
• Granted Patent: US 9,423,505 B2
• Time in Patent Office: Days
• US Class Current: 342/357.58
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/396 Determining accuracy or reliability of position or pseudorange measurements
• CPC Class Codes: G01S 19/45 by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement

Abstract

A mobile device may use one or more outlier detectors to detect likelihoods that an outlier condition exists for a satellite positioning system (SPS) position fix. In some implementations, an outlier detector may compare a computed position fix to an element of assistance data to generate an outlier likelihood. A decision to perform a recovery operation may be made based, at least in part, on a generated outlier likelihood. In some implementations, a computed reliability of the position fix may also be considered in making a recovery decision.

Claims

1. A machine implemented method comprising:

detecting an erroneous condition responsive to a determination of fitness of an estimated location of a mobile device computed based, at least in part, on an initial position; and

in response to said detection of said erroneous condition, restarting a process at said mobile device to obtain a position fix independently of said initial position and said computed location estimate.

2. The method of claim 1, wherein:

said initial position is obtained from assistance data.

3. The method of claim 1, wherein:

said initial position is based, at least in part, on a base station ID acquired at said mobile device.

4. The method of claim 1, wherein:

said obtaining said position fix further comprises obtaining said position fix based, at least in part, on acquisition of a plurality of satellite positioning system signals at said mobile station.

5. The method of claim 4, wherein:

said obtaining said position fix further comprises obtaining said position fix using ephemeris and/or almanac information.

6. The method of claim 1, wherein:

said obtaining said position fix further comprises initiating a full sky scan to acquire one or more satellite positioning system signals.

7. The method of claim 1, wherein:

said detecting said erroneous condition responsive to said determination of fitness of said estimated location of said mobile device further comprises comparing said estimated location to said initial position.

8. An apparatus comprising:

a satellite positioning system (SPS) receiver to;

acquire SPS signals from positioning satellites and compute an estimated location of said apparatus using said acquired SPS signals; and

a processor to;

detect an erroneous condition responsive to a determination of fitness of an estimated location of said apparatus based, at least in part, on an initial position, and restart a process at said apparatus to obtain a position fix independently of said initial position and said computed location estimate in response to said detection of said erroneous condition.

9. The apparatus of claim 8, wherein:

said initial position is obtained from assistance data.

10. The apparatus of claim 8, wherein:

said initial position is based, at least in part, on a base station ID acquired at said apparatus.

11. The apparatus of claim 8, wherein:

said obtaining a position fix includes acquiring a plurality of SPS signals at said apparatus.

12. The apparatus of claim 11, wherein:

said obtaining a position fix includes obtaining ephemeris and/or almanac information for SPS satellites.

13. The apparatus of claim 8, wherein:

said obtaining a position fix includes initiating a full sky scan to acquire one or more SPS signals.

14. The apparatus of claim 8, wherein:

said detecting said erroneous condition further comprises comparing said estimated location to said initial position.

15. An apparatus comprising:

a digital storage medium having instructions stored thereon executable by a computing system to;

detect an erroneous condition responsive to a determination of fitness of an estimated location of a mobile device computed based, at least in part, on an initial position; and

in response to said detection of said erroneous condition, restart a process at said mobile device to obtain a position fix independently of said initial position and said computed location estimate.

16. The apparatus of claim 15, wherein said initial position is obtained from assistance data.

17. The apparatus of claim 15, wherein said initial position is based, at least in part, on a base station ID acquired at said mobile device.

18. The apparatus of claim 15, wherein:

said obtaining said position fix further comprises obtaining said position fix based, at least in part, on acquisition of a plurality of SPS signals at said mobile station.

19. The apparatus of claim 18, wherein:

said obtaining said position fix further comprises obtaining said position fix using ephemeris and/or almanac information.

20. The apparatus of claim 15, wherein:

said obtaining said position fix further comprises initiating a full sky scan to acquire one or more SPS signals.

21. The apparatus of claim 15, wherein:

said detecting said erroneous condition responsive to said determination of fitness of said estimated location of said mobile device further comprises comparing said estimated location to said initial position.

22. An apparatus comprising:

means for detecting an erroneous condition responsive to a determination of fitness of an estimated location of a mobile device computed based, at least in part, on an initial position; and

means to restart a process at said mobile device to obtain a position fix independently of said initial position and said computed location estimate in response to said detection of said erroneous condition.

23. The apparatus of claim 22, wherein:

said initial position is obtained from assistance data.

24. The apparatus of claim 22, wherein:

said initial position is based, at least in part, on a base station ID acquired at said mobile device.

25. The apparatus of claim 22, wherein:

said means to restart said process further comprises;

means for obtaining said position fix based, at least in part, on acquisition of a plurality of SPS signals at said mobile station.

26. The apparatus of claim 25, wherein:

said means to restart said process further comprises;

mean for obtaining said position fix using ephemeris and/or almanac information.

27. The apparatus of claim 22, wherein:

said means to restart said process further comprises;

means for initiating a full sky scan to acquire one or more SPS signals.

28. The apparatus of claim 22, wherein:

said means for detecting said erroneous condition responsive to said determination of fitness of said estimated location of said mobile device further comprises means for comparing said estimated location to said initial position.

29. A machine implemented method comprising:

checking a position fix of a satellite positioning system (SPS) receiver for consistency with assistance data used to generate said position fix; and

determining whether to generate a new position fix using less than all of said assistance data based, at least in part, on results of said checking said position fix.

30. The method of claim 29, further comprising:

computing a reliability of said position fix;

wherein said determining whether to generate said new position fix is based, at least in part, on said reliability of said position fix and said results of said checking said position fix.

31. The method of claim 29, wherein said checking said position fix comprises:

comparing said position fix to a first element of said assistance data to generate a first outlier likelihood; and

comparing said position fix to a second element of said assistance data to generate a second outlier likelihood;

wherein said determining whether to generate said new position fix is based, at least in part, on said first and second outlier likelihoods.

32. The method of claim 29, further comprising:

instructing an SPS receiver to re-acquire satellites using less than all of said assistance data if a determination is made to generate said new position fix.

33. The method of claim 29, wherein:

said less than all of said assistance data includes a predefined subgroup of elements of said assistance data.

34. The method of claim 29, wherein:

said less than all of said assistance data includes no assistance data.

35. The method of claim 29, wherein:

said less than all of said assistance data is selected based, at least in part, on said results of said checking said position fix.

36. The method of claim 29, wherein:

said assistance data includes one or more of the following;

an estimate of current location, an estimate of SPS time, almanac data, and ephemeris data.

37. An apparatus comprising:

a satellite positioning system (SPS) receiver to;

acquire positioning satellites using assistance data, compute a position fix using SPS signals received from acquired satellites, and calculate a reliability of said position fix;

a plurality of outlier detectors to compare said position fix to elements of said assistance data to generate outlier likelihood information; and

a recovery manager to determine whether to instruct said SPS receiver to compute a new position fix using less than all of said assistance data based, at least in part, on said reliability of said position fix and said outlier likelihood information.

38. The apparatus of claim 37, wherein:

said plurality of outlier detectors includes a first outlier detector to compare said position fix to a rough position estimate of said assistance data to generate a first outlier likelihood indication.

39. The apparatus of claim 37, wherein:

said plurality of outlier detectors includes a second outlier detector to compare said position fix to an estimated SPS time of said assistance data to generate a second outlier likelihood indication.

40. The apparatus of claim 37, wherein:

said plurality of outlier detectors includes a first outlier detector having a variable threshold that is capable of being adjusted over time to improve performance of said apparatus.

41. The apparatus of claim 37, wherein:

said less than all of said assistance data includes a predefined subgroup of elements of said assistance data.

42. The apparatus of claim 37, wherein:

said less than all of said assistance data includes no assistance data.

43. The apparatus of claim 37, wherein:

said less than all of said assistance data is selected based, at least in part, on said outlier likelihood information.

44. An apparatus comprising:

a digital storage medium having instructions stored thereon executable by a computing system to;

check a position fix of a satellite positioning system (SPS) receiver for consistency with assistance data used to generate said position fix; and

determine whether to generate a new position fix using less than all of said assistance data based, at least in part, on results of said check of said position fix.

45. The apparatus of claim 44, wherein said digital storage medium further includes instructions to:

compute a reliability of said position fix, wherein said determination of whether to generate said new position fix is based, at least in part, on said reliability of said position fix and said results of said check of said position fix.

46. The apparatus of claim 44, wherein said instructions to check said position fix include instructions to:

compare said position fix to a first element of said assistance data to generate a first outlier likelihood; and

compare said position fix to a second element of said assistance data to generate a second outlier likelihood;

wherein said determination of whether to generate a new position fix is based, at least in part, on said first and second outlier likelihoods.

47. An apparatus comprising:

means for acquiring satellites of a satellite positioning system (SPS) using assistance data;

means for computing a position fix using signals received from satellites acquired by said means for acquiring satellites;

means for generating a reliability of said position fix;

means for generating outlier likelihoods by comparing said position fix to elements of said assistance data; and

means for determining whether to initiate a recovery procedure to compute a new position fix based, at least in part, on said outlier likelihoods.

48. The apparatus of claim 47, wherein:

said means for determining includes means for determining whether to initiate said recovery procedure based, at least in part, on said reliability and said outlier likelihoods.

49. The apparatus of claim 47, wherein:

said means for determining whether to initiate a recovery procedure instructs said means for acquiring satellites to re-acquire satellites using less than all of said assistance data if a determination is made to initiate a recovery procedure.

50. The apparatus of claim 49, wherein:

said less than all of said assistance data includes a specific subset of said assistance data.

51. The apparatus of claim 49, wherein:

said means for determining includes means for selecting said less than all of said assistance data based, at least in part, on said outlier likelihoods.

52. The apparatus of claim 49, wherein:

said less than all of said assistance data includes no assistance data.

53. The apparatus of claim 49, wherein:

said means for generating outlier likelihoods includes means for modifying thresholds used to compare said position fix to elements of said assistance data over time.

54. A machine implemented method comprising:

detecting an erroneous condition responsive to a comparison of a time observed from acquisition of one or more positioning signals at a mobile device and a time reference obtained from positioning assistance data; and

in response to said detection of said erroneous condition, restarting a process at said mobile device to obtain a position fix independently of said positioning assistance data.

55. A machine implemented method comprising:

detecting an erroneous condition responsive to an evaluation of a consistency of information observed from acquisition of one or more positioning signals at a mobile device and an initial position obtained from positioning assistance data; and

in response to said detection of said erroneous condition, restarting a process at said mobile device to obtain a position fix independently of said initial position and said computed location estimate.

56. A machine implemented method comprising:

detecting an erroneous condition responsive to an evaluation of a consistency of a speed of a mobile device computed based, at least in part, on one or more position fixes obtained at said mobile device and Doppler information obtained from positioning assistance data; and

in response to said detection of said erroneous condition, restarting a process at said mobile device to obtain a position fix independently of said initial position and said computed location estimate.