Method and apparatus for performing signal correlation using historical correlation data

1. A method of estimating a satellite signal parameter in a satellite positioning system receiver, comprising:

generating a plurality of correlation results between a satellite signal and a reference signal in response to a command from a processor;

estimating at least one satellite signal parameter from the plurality of correlation results using a co-processor integrated within the satellite positioning system receiver; and

providing the at least one satellite signal parameter to the processor.

2. The method of claim 1 , further comprising:

estimating at least one receiver parameter using the at least one satellite signal parameter.

3. The method of claim 1 , wherein the plurality of correlation results comprises a correlation history defined by at least one sequence of correlation results corresponding to a respective at least one relative time delay between the satellite signal and the reference signal.

4. The method of claim 3 , wherein the at least one satellite signal parameter comprises a Doppler offset for the satellite signal relative to the satellite positioning system receiver.

5. The method of claim 4 , wherein the estimating step comprises:

computing a plurality of complex cross-products using the correlation history; and

combining the complex cross-products to compute the Doppler offset.

6. The method of claim 5 , wherein the estimating step further comprises:

frequency correcting the correlation history using the Doppler offset; and

repeating the computing step and the averaging step using the frequency corrected correlation history to re-compute the Doppler offset.

7. The method of claim 5 , wherein the estimating step further comprises:

integrating the correlation history over a pre-defined interval.

8. The method of claim 4 , further comprising:

estimating a frequency of an oscillator in the satellite positioning system receiver in response to the Doppler offset.

9. The method of claim 3 , wherein the at least one satellite signal parameter comprises navigation data bits.

10. The method of claim 9 , wherein the estimating step comprises:

computing a plurality of complex dot-products using the correlation history; and

thresholding the plurality of complex dot-products to identify phase transitions within the correlation history.

11. The method of claim 10 , wherein the estimating step further comprises:

frequency correcting the correlation history using a Doppler offset.

12. The method of claim 10 , wherein the estimating step further comprises:

integrating the correlation history over a pre-defined interval.

13. The method of claim 3 , wherein the at least one satellite signal parameter comprises a navigation bit timing of the satellite signal.

14. The method of claim 13 , wherein the estimating step comprises:

determining, in response to the correlation history, a plurality of estimates of signal level using one or more receiver frequency and bit timing hypotheses.

15. The method of claim 13 , wherein the estimating step comprises:

computing a plurality of complex dot-products using the correlation history;

selecting a bit-timing offset;

summing complex dot-products from the plurality of complex dot-products that correspond to the selected bit timing offset; and

repeating the selecting step and the summing step for a plurality of bit-timing offsets to form a histogram.

16. The method of claim 15 , wherein the estimating step further comprises:

frequency correcting the correlation history using a Doppler offset.

17. The method of claim 15 , wherein the estimating step further comprises:

integrating the correlation history over a pre-defined interval.

18. The method of claim 13 , further comprising:

estimating a timing error associated with the satellite positioning system receiver using the navigation bit timing.

19. The method of claim 1 , wherein the at least one satellite signal parameter comprises at least one noise statistic measurement associated with the satellite signal.

20. The method of claim 1 , further comprising:

using the at least one satellite signal parameter to configure the satellite positioning receiver when performing further correlations.

21. The method of claim 1 , wherein the generating step comprises storing the plurality of correlation results in a memory within the satellite positioning system receiver.

22. An apparatus for estimating a satellite signal parameter in a satellite positioning system receiver, comprising:

a correlator for generating a plurality of correlation results between a satellite signal and a reference signal in response to a command from a processor;

a co-processor, integrated within the satellite positioning system receiver, for estimating at least one satellite signal parameter from the plurality of correlation results; and

wherein the processor receives the at least one satellite parameter.

23. The apparatus of claim 22 , further comprising:

a memory for storing the plurality of correlation results.

24. The apparatus of claim 22 , wherein the co-processor comprises at least one of:

a complex modulator for frequency correcting the plurality of correlation results;

a complex power unit for computing power in response to the plurality of correlation results;

a complex cross-product unit for computing complex cross-products in response to the plurality of correlation results;

a complex dot-product unit for computing complex dot-products in response to the plurality of correlation results;

a coherent integration unit for coherently integrating the plurality of correlation results;

a non-coherent integration unit for non-coherently integrating the plurality of correlation results; and

a noise statistics unit for determining noise statistics in response to the plurality of correlation results.

25. The apparatus of claim 22 , wherein the plurality of correlation results comprises a correlation history defined by at least one sequence of correlation results corresponding to a respective at least one relative time delay between the satellite signal and the reference signal.

26. The apparatus of claim 25 , wherein the co-processor is adapted to:

compute a plurality of complex cross-products using the correlation history; and

combine the complex cross-products to compute a Doppler offset.

27. The apparatus of claim 26 , wherein the co-processor is further adapted to:

frequency correct the correlation history using the Doppler offset; and

re-compute the Doppler offset in response to the frequency corrected correlation history.

28. The apparatus of claim 26 , wherein the co-processor is further adapted to:

integrate the correlation history over a pre-defined interval.

29. The apparatus of claim 25 , the co-processor is adapted to:

compute a plurality of complex dot-products using the correlation history; and

threshold the plurality of complex dot-products to identify phase transitions within the correlation history.

30. The apparatus of claim 29 , wherein the co-processor is further adapted to:

frequency correct the correlation history using a Doppler offset.

31. The apparatus of claim 29 , wherein the co-processor is further adapted to:

integrate the correlation history over a pre-defined interval.

32. The apparatus of claim 25 , wherein the co-processor is adapted to:

compute a plurality of complex dot-products using the correlation history;

select a bit-timing offset;

sum complex dot-products from the plurality of complex dot-products that correspond to the selected bit timing offset; and

repeat selection and summation for a plurality of bit-timing offsets to form a histogram.

33. The apparatus of claim 32 , wherein the co-processor is further adapted to:

frequency correct the correlation history using a Doppler offset.

34. The apparatus of claim 32 , wherein the co-processor is further adapted to:

integrate the correlation history over a pre-defined interval.

35. The apparatus of claim 22 , wherein the co-processor is adapted to compute at least one noise statistic in response to the plurality of correlation results.