Method and apparatus for performing signal correlation using historical correlation data
View Patent ↗A method and apparatus for estimating a satellite signal parameter in a satellite positioning system receiver is described. In an example, a plurality of correlation results between a satellite signal and a reference signal is generated in response to a command from a processor. At least one satellite signal parameter is estimated from the plurality of correlation results using a co-processor integrated within the satellite positioning system receiver. The at least one satellite signal parameter is then provided to the processor.
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, wherein said reference signal is associated with a particular pseudo-random code;
estimating at least one satellite signal parameter from the plurality of correlation results 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 cellular 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.