Method and apparatus for performing signal correlation using historical correlation data
First Claim
Patent Images
1. In a satellite positioning receiver, a method for estimating a receiver parameter comprising:
- a) selecting a relative time delay between a signal received from a satellite and a reference signal;
b) generating a correlation history comprising a sequence of correlation results for the relative time delay; and
c) estimating at least one receiver parameter from the correlation history.
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Abstract
A method and apparatus for computing a convolution between an input GPS signal and a reference code by generating the convolution result in real time without storing unprocessed signal samples. The apparatus comprises a vector multiplier running at high speed to achieve the same result as a vector multiplier sized to process an entire epoch. Additionally, historical correlation data is used to correct frequency and timing errors.
80 Citations
42 Claims
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1. In a satellite positioning receiver, a method for estimating a receiver parameter comprising:
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a) selecting a relative time delay between a signal received from a satellite and a reference signal;
b) generating a correlation history comprising a sequence of correlation results for the relative time delay; and
c) estimating at least one receiver parameter from the correlation history. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14)
d) using the at least one receiver parameter when performing further correlations.
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3. The method of claim 2 wherein the further correlations are performed on different signals from a different satellite than said signal received from the satellite.
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4. The method of claim 2 wherein the further correlations are performed using a standard correlation mode.
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5. The method of claim 1 wherein the at least one receiver parameter comprises a frequency of a receiver oscillator.
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6. The method of claim 1 wherein the at least one receiver parameter comprises a receiver timing error.
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7. The method of claim 6 wherein the receiver timing error is a modulo 20 millisecond estimate of an offset of a receiver clock with respect to a satellite reference time.
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8. The method of claim 6 wherein the at least one receiver parameter further comprises a frequency of a receiver oscillator.
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10. The method of claim 1 further comprising:
dividing the received signal into in-phase and quadrature components; and
separately performing steps b) and c) on the in-phase and quadrature components.
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11. The method of claim 1 further comprising generating navigation data bits from the correlation history.
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12. The method of claim 1 wherein step c) comprises:
applying the correlation history to a sequential estimation algorithm to estimate at least one of signal frequency and bit timing.
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13. The method of claim 1, further comprising:
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repeating steps a) and b) for at least one additional signal received from a respective at least one additional satellite to generate a respective at least one additional correlation history;
wherein the at least one receiver parameter is further estimated from the at least one additional correlation history.
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14. The method of claim 1, further comprising:
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repeating steps a) and b) for at least one additional relative time delay between the signal and the reference signal to generate a respective at least one additional correlation history;
wherein the at least one receiver parameter is further estimated from the at least one additional correlation history.
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9. In a satellite positioning receiver, a method for estimating a receiver Parameter comprising:
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a generating a correlation history comprising a sequence of correlation results for a signal received from at least one satellite, said generating comprising;
(a1) dividing a pseudorandom reference code into a plurality of code segments;
(a2) selecting a code segment;
(a3) forming an inner product between said selected code segment and a set of digital signal samples to produce a partial correlation;
(a4) repeating steps (a2) and (a3) to produce a plurality of partial correlations; and
(a5) summing the plurality of partial correlations as each partial correlation is produced to form a plurality of correlations; and
b) estimating at least one receiver parameter from the correlation history.
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15. In a satellite positioning receiver, a method for estimating at least one receiver parameter from a correlation history comprising:
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a) determining, in response to the correlation history, a plurality of estimates of signal level using a receiver frequency and bit timing hypothesis;
b) determining, in response to signal level estimates, estimates of at least one receiver parameter that provides a frequency and bit timing for the receiver that substantially maximizes signal level. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
(c) frequency correcting the correlation history;
(d) integrating the correlation history over a navigation bit period;
(e) computing a signal level for the signal within the navigation bit period;
(f) summing a plurality of successive signal level values to form an integrated signal level value as the signal level to be maximized.
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17. The method of claim 16 wherein said signal level is at least one of signal power and signal magnitude.
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18. The method of claim 15 wherein said signal level is at least one of signal power and signal magnitude.
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19. The method of claim 15 further comprising:
searching over frequency to determine a maxima in signal level.
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20. The method of claim 19 wherein searching comprises a downhill simplex method.
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21. The method of claim 15 further comprising:
searching over bit timing to determine a maxima in signal level.
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22. The method of claim 15 further comprising:
searching over frequency and bit timing to determine a maxima in signal level.
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23. Apparatus for estimating at least one receiver parameter in a satellite positioning receiver comprising:
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a) means for selecting a relative time delay between a signal received from a satellite and a reference signal;
b) means for generating a correlation history comprising a sequence of correlation results for the relative time delay; and
c) means for estimating at least one receiver parameter from the correlation history. - View Dependent Claims (24, 25, 26, 27, 28, 29, 31, 32, 33)
(d) a correlator for using the receiver parameter when performing further correlations.
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25. The apparatus of claim 24 wherein the further correlations are performed on different signals from a different satellite than said signal received from at the satellite.
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26. The apparatus of claim 23 wherein the at least one receiver parameter comprises a frequency of a receiver oscillator.
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27. The apparatus of claim 23 wherein the at least one receiver parameter comprises a receiver timing error.
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28. The apparatus of claim 27 wherein the receiver parameter further comprises a frequency of a receiver oscillator.
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29. The apparatus of claim 27 wherein the receiver timing error is a modulo 20 millisecond estimate of an offset of a receiver clock with respect to a satellite reference time.
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31. The apparatus of claim 23 further comprising:
means for dividing the received signal into in-phase and quadrature components; and
separately processing the in-phase and quadrature components.
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32. The apparatus of claim 23 further comprising means for generating navigation data bits from the correlation history.
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33. The apparatus of claim 23 further comprising:
means for determining an estimate relating to a signal level at a frequency and bit timing hypothesis.
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30. Apparatus for estimating at least one receiver parameter in a satellite positioning receiver comprising:
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a) means for generating a correlation history comprising a sequence of correlation results from signals received from at least one satellite, said means for generating comprising;
(a1) means for dividing a pseudorandom reference code into a plurality of code segments;
(a2) means for selecting a code segment;
(a3) means for forming an inner product between said selected code segment and a set of digital signal samples to produce a partial correlation;
(a4) means for repeatedly operating means (a2) and (a3) to produce a plurality of partial correlations; and
(a5) means for summing the plurality of partial correlations as each partial correlation is produced to form a plurality of correlations; and
b) means for estimating at least one receiver parameter from the correlation history.
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34. A computer readable medium storing software that, when executed by a processor, causes a satellite positioning receiver to perform a method for estimating at least one receiver parameter from a correlation history comprising:
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a) determining, in response to the correlation history, a plurality of estimates of signal level, using a receiver frequency and bit timing hypothesis;
b) determining, in response to the signal level estimates, estimates of at least one receiver parameter that provides a frequency and bit timing for the receiver that substantially maximizes signal level. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41)
(c) frequency correcting the correlation history;
(d) integrating the correlation history over a navigation bit period;
(e) computing a signal level for the signal within the navigation bit period;
(f) summing a plurality of successive signal level values to form an integrated signal level value as the signal level to be maximized.
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36. The method of claim 35 wherein said signal level is at least one of signal power and signal magnitude.
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37. The method of claim 35 further comprising:
searching over frequency to determine a maxima in signal level.
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38. The method of claim 35 further comprising:
searching over bit timing to determine a maxima in signal level.
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39. The method of claim 34 wherein said signal level is at least one of signal power and signal magnitude.
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40. The method of claim 34 further comprising:
searching over frequency and bit timing to determine a maxima in signal level.
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41. The method of claim 40 wherein searching comprises a downhill simplex method.
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42. In a satellite positioning receiver, a method for estimating a receiver parameter, comprising:
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producing a plurality of correlation results between a signal received from at least one satellite and a reference signal;
storing each correlation result of the plurality of correlation results as each correlation result is produced to generate a correlation history; and
estimating at least one receiver parameter from the correlation history.
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Specification