System and/or method for obtaining a time reference for a received SPS signal

• US 7,956,805 B2
• Filed: 04/11/2008
• Issued: 06/07/2011
• Est. Priority Date: 04/11/2008
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Pon, Rayman Wai
• Primary Examiner(s): Mull; Fred H
• Application Number:
  US12/101,955
• Publication Number:
  US 20090256745A1
• Time in Patent Office: 1,152 Days
• Field of Search: 342/357.12, 342/357.15, 342/357.73, 342/357.69
• US Class Current: 342/357.73
• CPC Class Codes: G01S 19/13 Receivers
• CPC Class Codes: G01S 19/246 involving long acquisition integration times, extended snapshots of signals or methods specifically directed towards weak signal acquisition

Abstract

The subject matter disclosed herein relates to a system and method for obtaining time references for signals received from transmitters in a satellite and/or terrestrial navigation system.

Claims

1. A method comprising:

obtaining a first time reference associated with a first SPS signal received at a reference location from a first transmitter; and

obtaining a second time reference associated with a second SPS signal acquired at said reference location from a second transmitter based, at least in part, on said first time reference and on an estimated difference between a first range to said first transmitter from said reference location and a second range to said second transmitter from said reference location, in response to a determination that an uncertainty associated with said estimated difference is less than a threshold associated with an information duration of said second SPS signal.

2. The method of claim 1, wherein said first and second transmitters are located at respective first and second space vehicles (SVs) which are members of different GNSS constellations.

3. The method of claim 1, wherein said first transmitter is located on a first space vehicle (SV) which is a member of a GPS constellation and said second transmitter is located at a second SV which is a member of a Galileo constellation.

4. The method of claim 3, wherein said obtaining said second time reference associated with said second SPS signal further comprises:

detecting a rate ½

Viterbi boundary in a data signal modulating said second SPS signal; and

determining said second time reference based, at least in pan, on said detected rate ½

Viterbi boundary.

5. The method of claim 3, wherein said obtaining said second time reference associated with said second SPS signal further comprises:

detecting boundaries in a periodic code sequence modulating said second SPS signal; and

determining said second time reference based, at least in part, on said detected boundaries.

6. The method of claim 1, wherein said first transmitter is located at a satellite vehicle (SV) which is a member of a Galileo constellation and said second transmitter is located at a second SV which is a member of a GPS constellation.

7. The method of claim 6, wherein said obtaining said second time reference associated with said second SPS signal further comprises:

detecting bit edge boundaries in a data signal modulating said second SPS signal; and

determining said second time reference based, at least in part, on said detected bit edge boundaries.

8. The method of claim 1, wherein said first transmitter is located on a first space vehicle (SV) which is a member of a GPS constellation, and said SPS signal comprises an L1C signal.

9. The method of claim 1, wherein said second transmitter is located at a satellite vehicle (SV) which is a member of a GPS signal and said first SPS signal comprises an L1C signal.

10. The method of claim 1, and further comprising:

determining whether said uncertainty associated with said estimated difference is less than said threshold associated with said information duration of said second SPS signal.

11. The method of claim 10, wherein said uncertainty is determined based, at least in part, on a single-signed uncertainty associated with said reference location.

12. The method of claim 10, wherein said uncertainty is determined based, at least in part, on at least one of:

an estimated azimuth angle to said first transmitter from said reference location, an estimated azimuth angle to said second transmitter from said reference location;

an estimated elevation angle to said first transmitter from said reference location, and/or and estimated elevation angle to said second transmitter from said reference location.

13. The method of claim 10, wherein said uncertainty represents a single-sided uncertainty, and said determining comprises:

determining whether said single-sided uncertainty is less than one-half of said threshold value.

14. The method of claim 10, wherein said uncertainty represents a two-sided uncertainty.

15. The method of claim 10, wherein said information duration is based, one least in part, on a repeating period of information in said second SPS signal.

16. An article comprising:

a storage medium, said storage medium comprising machine-readable instructions stored thereon which are executable by a computing platform to;

obtain a first time reference associated with a first SPS signal received at a reference location from a first transmitter, and

obtain a second time reference associated with a second SPS signal acquired at said reference location from a second transmitter based, at least in part, on said first time reference and on an estimated difference between a first range to said first transmitter from said reference location and a second range to said second transmitter from said reference location, in response to a determination that an uncertainty associated with said estimated difference is less than a threshold associated with an information duration of said second SPS signal.

17. The article of claim 16, wherein said first and second transmitters are located at respective first and second space vehicles (SVs) which are members of different GNSS constellations.

18. The article of claim 16, wherein said first transmitter is located on a first space vehicle (SV) which is a member of a GPS constellation and said second transmitter is located at a second SV which is a member of a Galileo constellation.

19. The article of claim 18, wherein said instructions are further executable by said computing platform to:

detect a rate ½

Viterbi boundary in a data signal modulating said second SPS signal; and

determine said second time reference based, at least in part, on said detected rate ½

Viterbi boundary.

20. The article of claim 18, wherein said instructions are further executable by said computing platform to:

detect boundaries in a periodic code sequence modulating said second SPS signal; and

determine said second time reference based, at least in part, on said detected boundaries.

21. The article of claim 16, wherein said first transmitter is located at a satellite vehicle (SV) which is a member of a Galileo constellation and said second transmitter is located at a second SV which is a member of a GPS constellation.

22. The article of claim 21, wherein said instructions are further executable by said computing platform to:

detect bit edge boundaries in a data signal modulating said second SPS signal; and

determine said second time reference based, at least in part, on said detected bit edge boundaries.

23. The article of claim 16, wherein said first transmitter is located on a first space vehicle (SV) which is a member of a GPS constellation, and said SPS signal comprises an L1C signal.

24. The article of claim 16, wherein said second transmitter is located at a satellite vehicle (SV) which is a member of a GPS signal and said first SPS signal comprises an L1C signal.

25. The article of claim 16, wherein said information duration is based, one least in part, on a repeating period of information in said second SPS signal.

26. A subscriber unit comprising:

a receiver to receive an acquisition assistance (AA) message comprising information indicative of locations of first and second space vehicles (SVs) and

a processor to;

obtain a first time reference associated with a first SPS signal received at a reference location from a first transmitter; and

obtain a second time reference associated with a second SPS signal acquired at said reference location from a second transmitter based, at least in part, on said first time reference and on an estimated difference between a first range to said first transmitter from said reference location and a second range to said second transmitter from said reference location, in response to a determination that an uncertainty associated with said estimated difference is less than a threshold associated with an information duration of said second SPS signal.

27. The subscriber unit of claim 26, wherein said receiver to receive said AA message over a terrestrial wireless communication link.

28. The subscriber unit of claim 26, wherein said first and second transmitters are located at respective first and second space vehicles (SVs) which are members of different GNSS constellations.

29. The subscriber unit of claim 26, wherein said first transmitter is located on a first space vehicle (SV) which is a member of a GPS constellation and said second transmitter is located at a second SV which is a member of a Galileo constellation.

30. The subscriber unit of claim 29, wherein said processor, to:

detect a rate ½

Viterbi boundary in a data signal modulating said second SPS signal; and

determine said second time reference based, at least in part, on said detected rate ½

Viterbi boundary.

31. The subscriber unit of claim 30, wherein said processor to:

detect boundaries in a periodic code sequence modulating said second SPS signal; and

determine said second time reference based, at least in part, on said detected boundaries.

32. The subscriber unit of claim 26, wherein said first transmitter is located at a satellite vehicle (SV) which is a member of a Galileo constellation and said second transmitter is located at a second SV which is a member of a GPS constellation.

33. The subscriber unit of claim 32, wherein said processor to:

detect bit edge boundaries in a data signal modulating said second SPS signal; and

determine said second time reference based, at least in part, on said detected bit edge boundaries.

34. The subscriber unit of claim 26, wherein said first transmitter is located on a first space vehicle (SV) which is a member of a GPS constellation, and said SPS signal comprises an L1C signal.

35. The subscriber unit of claim 26, wherein said second transmitter is located at a satellite vehicle (SV) which is a member of a GPS signal and said first SPS signal comprises an L1C signal.

36. The subscriber unit of claim 26, wherein said information duration is based, one least in part, on a repeating period of information in said second SPS signal.

37. A system comprising:

a position determination entity (PDE); and

a subscriber unit to;

receive an acquisition assistance (AA) message from said PDE over a terrestrial wireless communication link, said AA message comprising information indicative of locations of first and second transmitters;

estimate a difference between a first range from a reference location to said first transmitter and a second range from said reference location to said second transmitter based, at least in part, on said information;

obtain a first time reference associated with a first SPS signal received at a reference location from said first transmitter; and

obtain a second time reference associated with a second SPS signal acquired at said reference location from said second transmitter based, at least in part, on said first time reference and on an estimated difference between a first range to said first transmitter from said reference location and a second range to said second transmitter from said reference location, in response to a determination that an uncertainty associated with said estimated difference is less than a threshold associated with an information duration of said second SPS signal.

38. The system of claim 37, wherein said information duration is based, one least in part, on a repeating period of information in said second SPS signal.

39. An apparatus comprising:

means for obtaining a first time reference associated with a first SPS signal received at a reference location from a first transmitter; and

means for obtaining a second time reference associated with a second SPS signal acquired at said reference location from a second transmitter based, at least in part, on said first time reference and on an estimated difference between a first range to said first transmitter from said reference location and a second range to said second transmitter from said reference location, in response to a determination that an uncertainty associated with said estimated difference is less than a threshold associated with an information duration of said second SPS signal.

40. The apparatus of claim 39, wherein said first and second transmitters are located at respective first and second space vehicles (SVs) which are members of different GNSS constellations.

41. The apparatus of claim 39, and further comprising:

means for determining whether said uncertainty associated with said estimated difference is less than said threshold associated with said information duration of said second SPS signal.

42. The apparatus of claim 39, wherein said information duration is based, one least in part, on a repeating period of information in said second SPS signal.