System and method to obtain signal acquisition assistance data

• US 8,432,312 B2
• Filed: 08/19/2011
• Issued: 04/30/2013
• Est. Priority Date: 04/25/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gaal, Peter, Sheynblat, Leonid, Patrick, Christopher, Riley, Wyatt Thomas
• Primary Examiner(s): Issing, Gregory C
• Application Number:
  US13/214,055
• Publication Number:
  US 20120220294A1
• Time in Patent Office: 620 Days
• Field of Search: 342/357.64, 342/357.68, 342/357.69
• US Class Current: 342/357.64
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver

Abstract

Signal acquisition assistance data is obtained for receiving devices such as wireless position assisted location devices seeking signals from any source, such as satellite vehicles and base stations. The data may be obtained from previously acquired data, based upon evaluation of changes in parameters such as time and location that may jeopardize validity. In some cases the data may be adjusted for the changes in parameters. Refined data may be calculated by a receiver using partial measurements of signal sets, particularly if the acquisition assistance data provided by a remote entity includes more distinct parameters than have typically been provided. New data need not be obtained until the validity of previous data expires due to limitations upon temporal extrapolation using Doppler coefficients, unless mobile station movement that cannot be compensated is detected, and jeopardizes validity of the previous data.

Claims

1. A method of acquiring a signal at a telecommunications system receiver with the aid of acquisition assistance data, the method comprising:

a) obtaining acquisition assistance data at the receiver, the acquisition assistance data being provided by an entity remote from the receiver;

b) determining, subsequently to a time of obtaining the acquisition assistance data, to acquire a particular signal;

c) obtaining an estimate of a receiver clock bias from the previously obtained acquisition assistance data;

d) evaluating a validity of the previously obtained acquisition assistance data for use in acquiring the particular signal, wherein evaluating the validity is based at least in part on a lapsed time since the estimate of the receiver clock bias was obtained and an amount of a mobile station clock frequency error associated with the receiver clock bias; and

e) calculating an expected time of arrival parameter of the particular signal based in part on the estimate of the receiver clock bias determined from the previously obtained acquisition assistance data.

2. The method of claim 1 wherein said expected time of arrival parameter is an expected value.

3. The method of claim 1 wherein said expected time of arrival parameter is an expected window.

4. The method of claim 1 wherein the receiver is a cellular telecommunications system mobile station.

5. The method of claim 1 further comprising using the estimate of the receiver clock bias to calculate an estimated time of arrival and arrival time uncertainty window at the receiver for acquiring the particular signal if the previously obtained acquisition assistance data is determined to be still valid.

6. The method of claim 1 further comprising requesting new acquisition assistance data from the entity remote from the receiver if more than a threshold quantity of time has elapsed since the previous acquisition assistance data was obtained.

7. The method of claim 6 wherein a value of the threshold depends upon an order of an equation describing Doppler shift for which the receiver has accurate coefficients.

8. The method of claim 1 wherein said evaluating comprises determining whether the receiver has moved by an amount that jeopardizes the validity of the previously obtained acquisition assistance data.

9. The method of claim 1 further comprising:

determining to acquire a plurality of signals;

acquiring a first of the plurality of signals; and

employing measured parameters of the first of the plurality of signals to calculate a search window for acquiring another of the plurality of signals.

10. The method of claim 1 further comprising modifying the previously obtained acquisition assistance data to compensate for movement of the receiver since the acquisition assistance data was obtained.

11. The method of claim 10 further comprising determining that the receiver has moved based upon a comparison between a present neighbor list and a previous neighbor list.

12. The method of claim 10 further comprising determining that the receiver has moved based upon a comparison between a presently active base station set for the receiver and a previously active base station set for the receiver.

13. The method of claim 10 further comprising determining that the receiver has moved based upon comparison between a present serving base station for the receiver and a previous serving base station for the receiver.

14. A telecommunications system receiver comprising:

a) obtaining means for obtaining acquisition assistance from an entity remote from the receiver;

b) determining means for determining, subsequently to a time of obtaining the acquisition assistance data, to acquire a particular signal;

c) clock bias means for obtaining an estimate of a receiver clock bias from the previously obtained acquisition assistance data;

d) evaluating means for evaluating a validity of the previously obtained acquisition assistance data for use in acquiring the particular signal, the evaluating means being configured to evaluate the validity based at least in part on a lapsed time since the estimate of the receiver clock bias was obtained and an amount of a mobile station clock frequency error associated with the receiver clock bias; and

e) calculating means for calculating an expected time of arrival parameter of the particular signal based in part on the estimate of the receiver clock bias determined from the previously obtained acquisition assistance data.

15. The receiver of claim 14 wherein said expected time of arrival parameter is an expected value.

16. The receiver of claim 14 wherein said expected time of arrival parameter is an expected window.

17. The receiver of claim 14 further comprising means for using the estimated receiver clock bias to calculate an estimated time of arrival and arrival time uncertainty window at the receiver for acquiring the particular signal if the previously obtained acquisition assistance data is determined to be still valid.

18. The receiver of claim 14 further comprising means for requesting new acquisition assistance data from the entity remote from the receiver if more than a threshold quantity of time has elapsed since the previous acquisition assistance data was obtained.

19. The receiver of claim 18 wherein a value of the threshold depends upon an order of an equation describing Doppler shift for which the receiver has accurate coefficients.

20. The receiver of claim 14 wherein said evaluating means are configured to determine whether the receiver has moved by an amount that jeopardizes the validity of the previously obtained acquisition assistance data.

21. The receiver of claim 14 further comprising:

means for acquiring a first of a plurality of signals; and

means for employing measured parameters of the first of the plurality of signals to calculate a search window for acquiring a second of the plurality of signals.

22. The receiver of claim 14 wherein the receiver is a mobile station configured for operation in a cellular telecommunications network.

23. The receiver of claim 22 further comprising means for modifying the previously obtained acquisition assistance data to compensate for movement of the mobile station since the acquisition assistance data was obtained.

24. The receiver of claim 23 further comprising means for determining that the mobile station has moved based upon a comparison between a present neighbor list and a previous neighbor list.

25. The receiver of claim 23 further comprising means for determining that the mobile station has moved based upon a comparison between a presently active base station set for the mobile station and a previously active base station set for the mobile station.

26. The receiver of claim 23 further comprising means for determining that the mobile station has moved based upon comparison between a present serving base station for the mobile station and a previous serving base station for the mobile station.

27. A computer program product, for acquiring a signal at a telecommunications system receiver with the aid of acquisition assistance data, residing on a non-transitory processor-readable medium comprising instructions configured to cause the processor to:

a) obtain acquisition assistance data at the receiver, the acquisition assistance data being provided by an entity remote from the receiver;

b) determine, after the acquisition assistance data are obtained, to acquire a particular signal;

c) obtain an estimate of a receiver clock bias from the previously obtained acquisition assistance data;

d) evaluate a validity of the previously obtained acquisition assistance data for use in acquiring the particular signal, based at least in part on a lapsed time since the estimate of the receiver clock bias was obtained and an amount of a mobile station clock frequency error associated with the receiver clock bias; and

e) calculate an expected time of arrival parameter of the particular signal based in part on the estimate of the receiver clock bias determined from the previously obtained acquisition assistance data.

28. The computer program product of claim 27 wherein said expected time of arrival parameter is an expected value.

29. The computer program product of claim 27 wherein said expected time of arrival parameter is an expected window.

30. The computer program product of claim 27 further comprising instructions configured to cause the processor to use the estimate of the receiver clock bias to calculate an estimated time of arrival and arrival time uncertainty window at the receiver for acquiring the particular signal if the previously obtained acquisition assistance data is determined to be still valid.

31. The computer program product of claim 27 further comprising instructions configured to cause the processor to request new acquisition assistance data from the entity remote from the receiver if more than a threshold quantity of time has elapsed since the previous acquisition assistance data was obtained.

32. The computer program product of claim 31 wherein a value of the threshold depends upon an order of an equation describing Doppler shift for which the receiver has accurate coefficients.

33. The computer program product of claim 27 wherein the instructions configured to cause the processor to evaluate the validity of the previously obtained acquisition assistance data are configured to cause the processor to determine whether the receiver has moved by an amount that jeopardizes the validity of the previously obtained acquisition assistance data.

34. The computer program product of claim 27 further comprising instructions configured to cause the processor to:

determine to acquire a plurality of signals;

acquire a first of the plurality of signals; and

employ measured parameters of the first of the plurality of signals to calculate a search window for acquiring another of the plurality of signals.

35. The computer program product of claim 27 further comprising instructions configured to cause the processor to modify the previously obtained acquisition assistance data to compensate for movement of the receiver since the acquisition assistance data was obtained.

36. The computer program product of claim 35 further comprising instructions configured to cause the processor to determine that the receiver has moved based upon a comparison between a present neighbor list and a previous neighbor list.

37. The computer program product of claim 35 further comprising instructions configured to cause the processor to determining that the receiver has moved based upon a comparison between a presently active base station set for the receiver and a previously active base station set for the receiver.

38. The computer program product of claim 35 further comprising instructions configured to cause the processor to determine that the receiver has moved based upon comparison between a present serving base station for the receiver and a previous serving base station for the receiver.