System and/or Method for Obtaining a Time Reference for a Received SPS Signal

• US 20090256745A1
• Filed: 04/11/2008
• Published: 10/15/2009
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Pon, Rayman Wai
• Granted Patent: US 7,956,805 B2
• Time in Patent Office: Days
• US Class Current: 342/357.420
• 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.

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 part, 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. An article comprising:

a storage medium, said storage medium comprising machine-readable instructions stored thereon which, if executed by a computing platform, are adapted to cause said 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.

11. The article of claim 10, wherein said first and second transmitters are located at respective first and second space vehicles (SVs) which are members of different GNSS constellations.

12. The article of claim 10, 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.

13. The article of claim 12, wherein said instructions, if executed by said computing platform, are further adapted to cause 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.

14. The article of claim 12, wherein said instructions, if executed by said computing platform, are further adapted to cause 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.

15. The article of claim 10, 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.

16. The article of claim 15, wherein said instructions, if executed by said computing platform, are further adapted to cause 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.

17. The article of claim 10, 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.

18. The article of claim 10, 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.

19. 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), said subscriber unit being adapted 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.

20. The subscriber unit of claim 19, wherein said subscriber unit is further adapted to receive said AA message over a terrestrial wireless communication link.

21. The subscriber unit of claim 19, wherein said first and second transmitters are located at respective first and second space vehicles (SVs) which are members of different GNSS constellations.

22. The subscriber unit of claim 19, 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.

23. The subscriber unit of claim 22, wherein said subscriber unit is further adapted 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.

24. The subscriber unit of claim 23, wherein said subscriber unit is further adapted 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.

25. The subscriber unit of claim 19, 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.

26. The subscriber unit of claim 25, wherein said subscriber unit is further adapted 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.

27. The subscriber unit of claim 19, 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.

28. The subscriber unit of claim 19, 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.

29. A system comprising:

a position determination entity (PDE); and

a subscriber unit, the subscriber unit being adapted 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.