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1. WO2003023441 - SYSTEME ET PROCEDE D'ESTIMATION DE LA POSITION D'UN RECEPTEUR

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

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Claims

We claim:

1. A method to determine location information of a receiver comprising the steps of:

receiving a signal containing a plurality of location-determining signals associated with a plurality of signal sources, wherein each of said signal sources is
associated with a periodic reference signal;

correlating a plurality of signal chunks of said received signal with said reference signals to yield a grid of correlation values;

executing a plurality of probes in said grid to generate a plurality of refined
correlation values;

evaluating said refined correlation values to identify potential acquisitions of said signal sources;

verifying each of said potential acquisitions to yield a plurality of confirmed
acquisitions; and

determining said location information based on said confirmed acquisitions'.

2. The method of claim 1, wherein the duration of said signal chunks is less than a period of said periodic reference signals.

3. The method of claim 1 , wherein said correlating comprises the step of mixing said reference signals with a modulation signal.

4. The method of claim 1, wherein said correlating comprises the step of mixing said received signal with a modulation signal.

5. The method of claim 1, wherein said correlating is based on a navigation signal.

6. The method of claim 1, wherein said correlating comprises the step of applying a plurality of code-phase adjustments.

7. The method of claim 1, wherein said correlating comprises the step of calculating the fast fourier transform of each signal chunk.

8. The method of claim 1, wherein executing said probe comprises:

selecting a signal source;

selecting a hypothesized code-phase;

selecting a plurality of correlation values from said grid, wherein said correlation values are associated with said selected signal source and said selected
hypothesized code-phase, to yield a correlation signal; and calculating the fast fourier transform of said correlation signal, to yield a plurality of refined correlation values associated with a plurality of refined
frequency values.

9. The method of claim 1, wherein said probes are executed in a breadth-first
manner, whereby all signal sources are first probed at a signal duration and then at an increased signal duration.

10. The method of claim 1, further comprising the step of providing a code-phase uncertainty interval, and wherein said probes are associated with a plurality of code-phases within said code-phase uncertainty interval.

11. The method of claim 1 , wherein said evaluating comprises compaiing said refined correlation values with a threshold, and wherein said threshold is based on a
number of code-phase hypotheses and a number of doppler frequency hypotheses.

12. The method of claim 1, wherein said verifying is carried out in increasing signal duration order and comprises the step of refining a doppler frequency estimate.

13. The method of claim 1, wherein said verifying a probe comprises calculating a correlation magnitude curve.

14. The method of the previous claim, wherein said correlation magnitude curve is calculated from an ultra-stacked signal.

15. The method of claim 13, comprising applying a multi-peak test on a selected probe, wherein said multi-peak test comprises the steps of

calculating the number of peaks above a threshold in said correlation magnitude curve; and

discarding said probe if said number of peaks is statistically large.

16. The method of claim 13, further comprising a multi-path test, wherein said multi- path test comprises the step of detecting a large peak ahead of and near to an acquisition peak in said correlation magnitude curve.

17. The method of the previous claim, wherein said multi-path test further comprises the step of resetting said acquisition peak to said large peak.

18. The method of claim 1, further comprising the step of utilizing said confirmed acquisitions to aid the acquisition of other signal sources.

19. The method of claim 1, wherein said aiding comprises the step of ultra-stacking said received signal.

20. The method of claim 1, further comprising the step of ultra-staclcing said received signal based on said confirmed acquisition.

21. The method of claim 1 , further comprising the step of re-parameterizing said grid based on a reduced uncertainty provided by each confirmed acquisition.

22. The method of claim 1, further comprising the step of extracting a refined code- phase estimate from each confirmed acquisition.

23. The method of claim 22, wherein extracting said refined code-phase value
comprises the step of applying a code-phase adjustment.

24. The method of the previous claim, wherein said code-phase adjustments
incorporate a discrepancy between a computationally nominal inter-sample time and a hardware nominal inter-sample time.

25. The method of claim 22, wherein extracting said refined code-phase value
comprises the steps of:

ultra-stacking said received signal, to yield an ultra-stacked signal;

calculating a correlation magnitude curve with said ultra-stacked signal; and

interpolating said correlation magnitude curve to extract said refined code-phase.

26. A location-determining system comprising:

a plurality of signal sources associated with a plurality of periodic reference
signals;

a receiver receiving a signal containing a plurality of location-determining signals transmitted by said signal sources;

means for correlating a plurality of signal chunks of said received signal with said reference signals to yield a grid of correlation values;

means for executing a plurality of probes in said grid to generate a plurality of
refined correlation values;

means for evaluating said refined correlation values to identify potential
acquisitions of said signal sources;

means for verifying each of said potential acquisitions to yield a plurality of
confirmed acquisitions; and

means for determining location information based on said confirmed acquisitions.

27. The system of Claim 26, wherein said means for correlating comprises means for performing fast fourier transforms.

28. The system of Claim 26, wherein said means for correlating comprises means for mixing said reference signal with a modulation signal.

29. The system of Claim 26, wherein said means for correlating comprises means for mixing said received signal with a modulation signal.

30. The system of Claim 26, wherein said means for executing comprises: means for selecting a plurality of correlation values from said grid, wherein said correlation values are associated with a selected signal source and a
selected hypothesized code-phase, to yield a correlation signal; and

means for calculating the fast fourier transform of said correlation signal.

31. The system of Claim 26, wherein said means for verifying comprises means for calculating a magnitude curve.

32. The system of Claim 26, wherein said means for verifying comprises means for ultra-stacking said received signal.

33. The system of Claim 31 , comprising means for applying a multi-peak test.

34. The system of Claim 31, comprising means for applying a multi-path test.

35. The system of Claim 26, comprising means for aiding acquisition of signal
sources with said confirmed acquisition.

36. The system of Claim 26, comprising means for ultra-stacking said received signal based on said confirmed acquisitions.