Method of mixed data assisted and non data assisted navigation signal acquisition, tracking and reacquisition

• US 7,859,456 B2
• Filed: 10/10/2006
• Issued: 12/28/2010
• Est. Priority Date: 10/10/2006
• Status: Active Grant

• Current Assignee: CSR Technology Holdings Inc. (Qualcomm, Inc.)
• Original Assignee: SiRF Technology Holdings Incorporated (Qualcomm, Inc.)
• Inventors: Qiu, Zongde, Wang, Chi-Shin, Jia, Zhike
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Mull; Fred H
• Application Number:
  US11/548,204
• Publication Number:
  US 20080084336A1
• Time in Patent Office: 1,540 Days
• Field of Search: 342/357.12, 342/357.15, 342/357.63, 342/357.64, 342/357.66
• US Class Current: 342/357.63
• CPC Class Codes: G01S 19/246 involving long acquisition integration times, extended snapshots of signals or methods specifically directed towards weak signal acquisition
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver

Abstract

The present invention provides systems and methods for enabling a navigation signal receiver to perform both data assisted and non-data assisted integration to provide better integration during signal acquisition, reacquisition and tracking. In data assisted integration mode, a receiver uses known or predicted data bits to remove the modulated data bits of a received signal prior to integration. In non data assisted integration mode, when the data bits are not known or predictable, the receiver uses an optimal estimation or maximum likelihood algorithm to determine the polarities of the modulated data bits of the received signal. This may be done by determining which of various possible bit pattern yields the maximum integrated power. When the modulated data bits are not known or predictable over a limited range, the receiver carries out data assisted integration over the known or predictable data bits and additional non data assisted integration.

Claims

1. A method of acquisition, tracking and reacquisition of weak navigation signals at a receiver, comprising:

predicting or retrieving navigation data bits; and

performing integration on a received signal by switching between data assisted, non-data assisted and mixed data assisted/non data assisted modes based on known or predicted data bits of the received signal.

2. The method of claim 1, wherein the known or predicted data bits are predicted, retrieved from receiver memory, or from received signal demodulation.

3. The method of claim 1, wherein a single integration can be mixed with both data assisted and non data assisted integration.

4. The method of claim 3, wherein the mixed data assisted and non data assisted integration comprises:

removing modulated data from the received signal over a length of known or predicted data bits;

performing integration on the received signal with the removed data modulation until the integration power exceeds a first threshold;

if the power does not exceed the first threshold, then

continuing to integrate the received signal in the non data assisted mode in stages, wherein a threshold is associated with each stage; and

terminating the integration at one of the steps if the combined integration power exceeds the threshold for that step.

5. The method of claim 4, wherein an optimal estimation or maximum likelihood algorithm is used in the non data assisted mode.

6. The method of claim 4, wherein the integration in the non data assisted mode continues until all samples are integrated.

7. The method of claim 4, further comprising declaring signal acquisition, signal tracking, or signal reacquisition successful when the combined integration power exceeds the threshold in any of the stages or else declaring a failure.

8. The method of claim 4, wherein the integration is coherent or non-coherent.

9. The method of claim 1, the set of data bits can constitute a complete navigation word or part of the word forming an incomplete word.

10. The method of claim 9, wherein the complete word is used when it passes a parity check and additionally passes a data integrity check.

11. The method of claim 10, wherein the data integrity check involves comparing the complete word with historic or predicted data.

12. The method of claim 10, wherein the data integrity check involves ensuring that a navigation parameter decoded from the word is within a predefined range.

13. The method of claim 10, wherein the data integrity check involves checking for a predetermined variation pattern in the data value of the word.

14. The method of claim 9, wherein the incomplete word is used when it passes a data integrity check.

15. The method of claim 14, wherein the data integrity check involves comparing the incomplete word with historic or predicted data.

16. The method of claim 14, wherein the data integrity check involves ensuring that a navigation parameter decoded from the incomplete word is within a predefined range.

17. The method of claim 14, wherein the data integrity check involves checking for a predetermined variation pattern in the data value of the incomplete word.

18. The method of claim 1, further comprising:

using multi-channels to ensure that the data bits are error free comprising,

integrating received signals in separate channels for the same sample set, wherein the integration in one of the channels is data assisted and the integration in the other channel is non data assisted; and

determining the correctness of the data bits based on the integration powers for the data assisted and non data assisted integrations.

19. The method of claim 1, wherein a continuous data assisted integration is performed for a duration of 1.2 seconds at every six seconds based on predictable TLM and HOW words.

20. The method of claim 1, wherein data assisted integration is more preferred during tracking.

21. The method of claim 1, wherein the start time of integration is selected such that a maximum possible available bits are used in data assisted integration.

22. The method of claim 1, further comprising using partially demodulated or predicted navigation data to predict the Doppler frequency offset, rate of change of Doppler frequency, and PN code phase offset, all of which are used to improve the Time-To-First-Fix of the receiver.

23. The method of claim 1, further comprising using partially demodulated or predicted navigation data to improve data decoding sensitivity.

24. The method of claim 23, wherein the improvement in sensitivity is compounded.

25. The method of claim 1, further comprising using data assisted mode for tracking under a weak signal environment to calibrate a local frequency generator and other baseband parameters.

26. A receiver for acquiring, tracking and reacquiring navigation satellite signals, comprising:

a radio frequency front-end for receiving satellite signals;

a baseband section for processing a received signal into correlation values; and

a processor coupled to the baseband section, wherein the processor predicts or retrieves navigation data bits, and performs integration on the received signal by switching between data assisted, non-data assisted and mixed data assisted/non data assisted modes based on known or predicted data bits of the received signal.

27. The receiver of claim 26, wherein the known or predicted data bits are predicted, retrieved from receiver memory, or from received signal demodulation.

28. The receiver of claim 26, wherein the processor is capable of performing a single integration mixed with both data assisted and non data assisted integration.

29. The receiver of claim 28, wherein the processor performs mixed data assisted and non data assisted integration by removing modulated data from the received signal over a length of known or predicted data bits, performing integration on the received signal with the removed data modulation until the integration power exceeds a first threshold, and if the power does not exceed the first threshold, then continuing to integrate the received signal in the non data assisted mode in stages, wherein a threshold is associated with each stage, and terminating the integration at one of the steps if the combined integration power exceeds the threshold for that step.

30. The receiver of claim 29, wherein the processor uses an optimal estimation or maximum likelihood algorithm in the non data assisted mode.

31. The receiver of claim 29, wherein the processor performs the integration in the non data assisted mode until all samples are integrated.

32. The receiver of claim 29, wherein the processor declares signal acquisition, signal tracking, or signal reacquisition successful when the combined integration power exceeds the threshold in any of the stages or else declares a failure.

33. The receiver of claim 29, wherein the integration is coherent or non-coherent.

34. The receiver of claim 26, the set of data bits can constitute a complete navigation word or part of the word forming an incomplete word.

35. The receiver of claim 34, wherein the processor uses the complete word when it passes a parity check and additionally passes a data integrity check.

36. The receiver of claim 35, wherein the data integrity check involves comparing the complete word with historic or predicted data.

37. The receiver of claim 35, wherein the data integrity check involves ensuring that a navigation parameter decoded from the word is within a predefined range.

38. The receiver of claim 35, wherein the data integrity check involves checking for a predetermined variation pattern in the data value of the word.

39. The method of claim 34, wherein the processor uses the incomplete word when it passes a data integrity check.

40. The receiver of claim 39, wherein the data integrity check involves comparing the incomplete word with historic or predicted data.

41. The receiver of claim 39, wherein the data integrity check involves ensuring that a navigation parameter decoded from the incomplete word is within a predefined range.

42. The receiver of claim 39, wherein the data integrity check involves checking for a predetermined variation pattern in the data value of the incomplete word.

43. The receiver of claim 26, further comprising multiple channels in the baseband section, and wherein the processor integrates received signals in separate channels for the same sample set, wherein the integration in one of the channels is data assisted and the integration in the other channel is non data assisted, and determines the correctness of the data bits based on the integration powers for the data assisted and non data assisted integrations.

44. The receiver of claim 26, wherein the processor performs a continuous data assisted integration for a duration of 1.2 seconds at every six seconds based on predictable TLM and HOW words.

45. The receiver of claim 26, wherein data assisted integration is preferred during tracking.

46. The receiver of claim 26, wherein the start time of integration is selected such that a maximum possible available bits are used in data assisted integration.

47. The receiver of claim 26, wherein the processor uses partially demodulated or predicted navigation data to predict the Doppler frequency offset, rate of change of Doppler frequency, and PN code phase offset, all of which are used to improve the Time-To-First-Fix of the receiver.

48. The receiver of claim 26, wherein the processor uses partially demodulated or predicted navigation data to improve data decoding sensitivity.

49. The receiver of claim 48, wherein the improvement in sensitivity is compounded.

50. The receiver of claim 26, wherein the processor uses data assisted mode for tracking under a weak signal environment to calibrate a local frequency generator and other baseband parameters.