Systems and methods for mitigating multipath signals

• US 7,881,407 B2
• Filed: 08/27/2008
• Issued: 02/01/2011
• Est. Priority Date: 04/30/2004
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Kohli, Sanjai, Chansarkar, Mangesh, Xie, Gang
• Primary Examiner(s): Bocure; Tesfaldet
• Application Number:
  US12/199,066
• Publication Number:
  US 20080309553A1
• Time in Patent Office: 888 Days
• Field of Search: 375/316, 375/340, 375/343, 340/539.1, 340/539.13, 701/207, 701/213, 701/215, 342/352, 342/357.01, 342/357.06, 342/357.12, 342/357.15, 342/350, 342/357.2, 342/357.21, 342/357.25, 342/357.22
• US Class Current: 375/316
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop
• CPC Class Codes: H04B 2201/70715 with application-specific features
• CPC Class Codes: H04B 7/216 Code division or spread-spectrum multiple access [CDMA, SSMA]

Abstract

Systems and methods for mitigating multipath signals in a receiver are provided. In this regard, a representative system, among others, includes a receiver comprising an antenna being configured to receive signals from a plurality of satellites, and a computing device being configured to: generate pseudorange measurements based on the received satellites signals, process the generated pseudorange measurements to reduce its pseudorange residuals based on statistical modeling in order to mitigate multipath errors, and compute navigation solutions based on the processed pseudorange measurements. A representative method, among others, for mitigating multipath signals in a receiver, comprises: receiving the pseudorange measurements; processing the received pseudorange measurements to reduce its pseudorange residuals based on statistical modeling in order to mitigate multipath errors; and computing navigation solutions based on the processed pseudorange measurements.

Claims

1. A receiver comprising:

an antenna being configured to receive signals from a plurality of satellites; and

a computing device being configured to;

generate pseudorange measurements based on the received satellites signals;

process the generated pseudorange measurements to reduce their pseudorange residuals based on statistical modeling in order to mitigate multipath errors, and

compute navigation solutions based on the processed pseudorange measurements.

2. The receiver as defined in claim 1, further comprising a radio frequency front end unit being configured to down-convert, magnify, filter, and digitize the received satellites signals into digital immediate frequency (IF) signals.

3. The receiver as defined in claim 2, further comprising a baseband digital signal processing (DSP) unit that acquires and tracks the received satellites signals and then generates pseudorange measurements according to the received satellites signals.

4. The receiver as defined in claim 1, wherein the computing device processes the received pseudorange measurements by way of selecting a statistical model module that generates a statistical representation to describe the received pseudorange measurements.

5. The receiver as defined in claim 4, wherein the statistical model module corresponding with the pseudorange residuals are pre-computed based on off-line test data samples.

6. The receiver as defined in claim 5, wherein at least one set of statistical model module is built for each different group of pseudorange residuals, the pseudorange residuals being grouped based on corresponding signals elevation, signal-to-noise ratio and residual magnitude.

7. The receiver as defined in claim 6, wherein the statistical model module utilizes a Gaussian mixture, the statistical model module being used to approximate the actual distribution of residual samples for each group of residuals.

8. The receiver as defined in claim 4, wherein the computing device processes the received pseudorange measurements by way of modifying the generated statistical representation to reduce the pseudorange residuals of the received pseudorange measurements.

9. The receiver as defined in claim 8, wherein the computing device modifies the generated statistical representation by way of transforming each received pseudorange measurement into multiple pseudorange measurement components, each measurement component corresponding to a respective Gaussian component in a selected Gaussian mixture model.

10. The receiver as defined in claim 9, wherein each component has an association probability corresponding to the pseudorange residuals of the received pseudorange measurements.

11. The receiver as defined in claim 10, wherein the computing device computes the navigation solutions, in part, by way of de-weighting the association probability of each component.

12. The receiver as defined in claim 8, wherein the computing device modifies the generated pseudorange measurements by way of computing an effective residual and variance of the generated statistical model corresponding to the received pseudorange measurements.

13. The receiver as defined in claim 12, wherein the computing device computes the navigation solutions based on the received effective residual and variance.

14. A method for mitigating multipath signals in a receiver, comprising:

receiving the pseudorange measurements;

processing the received pseudorange measurements to reduce their pseudorange residuals based on statistical modeling in order to mitigate multipath errors; and

computing navigation solutions based on the processed pseudorange measurements.

15. The method as defined in claim 14, wherein processing the received pseudorange measurements comprises selecting a statistical model module that generates a statistical representation to describe for the received pseudorange measurements.

16. The method as defined in claim 15, wherein processing the received pseudorange measurements comprises modifying the generated statistical representation to reduce the pseudorange residuals of the received pseudorange measurements.

17. The method as defined in claim 16, wherein modifying the generated statistical representation comprises splitting the generated statistical representation of the received pseudorange measurements into multiple components, each component having an association probability corresponding to the pseudorange residuals of the received pseudorange measurements.

18. The method as defined in claim 17, wherein computing the navigation solutions includes de-weighting the association probability of each component.

19. The method as defined in claim 16, wherein modifying the generated statistical representation comprises computing an effective residual and variance of the generated statistical model corresponding to the received pseudorange measurements.

20. The method as defined in claim 19, wherein computing the navigational solutions is based on the computed effective residual and variance.

21. The method as defined in claim 14, further comprising:

determining whether the received pseudorange measurements have a certain value of multipath signals; and

responsive to determining that the received pseudorange measurements have the certain value of multipath signals, computing navigation solutions based on the received pseudorange measurements without the step of processing the received pseudorange measurement.

22. The method as defined in claim 21, wherein determining whether the received pseudorange measurements have the certain value of multipath signals comprises determining whether the received pseudorange measurements pass at least one threshold corresponding to at least one of elevation, signal-to-noise ratio and residual magnitude, and responsive to determining that the received pseudorange measurements passed the at least one threshold corresponding to at least one of elevation, signal-to-noise ratio and residual magnitude, computing navigation solutions based on the received pseudorange measurements without the step of processing the received pseudorange measurement, wherein the elevation, signal-to-noise ratio and residual magnitude thresholds is derived mostly based on enormous navigation performance testing and analyses.

23. A navigation system comprising:

a plurality of satellites that transmit signals; and

a receiver comprising;

an antenna being configured to receive signals from a plurality of satellites, and

a computing device being configured to;

generate pseudorange measurements based on the received satellites signals,

select a statistical model module for the received pseudorange measurements,

generate a statistical representation to describe the received pseudorange measurements based on the selected statistical model module,

modify the generated statistical representation to reduce the pseudorange residuals of the received pseudorange measurements in order to mitigate multipath errors, and

compute navigation solutions based on the modified statistical representation of the received pseudorange measurements.

24. The navigation system as defined in claim 23, wherein the computing device modifies the generated statistical representation by way of splitting the received pseudorange measurements into multiple components, each component having an association probability corresponding to the pseudorange residuals of the received pseudorange measurements, the computing device being configured to de-weight the association probability of each component and computes the navigational solutions based, in part, on the de-weighted multiple components.

25. The navigation system as defined in claim 23, wherein the computing device modifies the generated statistical representation by way of computing an effective residual and variance corresponding to the generated statistical representation of the received pseudorange measurements, the computing device being configured to compute the navigational solutions based on the computed effective residual and variance.

26. A method for global positioning system (GPS) navigation, the method comprising:

tracking at least one GPS signal from a GPS satellite, including receiving the pseudorange measurements and performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal;

reacquiring the at least one GPS signal, including performing a plurality of additional early correlations and a plurality of additional late correlations so as to create an expanded capture window for maintaining the synchronization;

processing the received pseudorange measurements, in response to the tracking at least one GPS signal and the reacquiring at least one GPS signal, to reduce their pseudorange residuals based on statistical modeling in order to mitigate multipath errors; and

computing navigation solutions based on the processed pseudorange measurements.

27. The method as defined in claim 26, wherein performing the plurality of additional early correlations and the plurality of additional late correlations comprises:

generating a plurality of code samples that are correlated with the at least one GPS signal; and

delaying each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by the fraction of a chip.

28. The method as defined in claim 26, wherein performing the plurality of additional early correlations and the plurality of additional late correlations comprises:

generating a plurality of code samples that are correlated with the at least one GPS signal; and

delaying each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by a multiple of the fraction of a chip.

29. A method for global positioning system (GPS) navigation, the method comprising:

tracking at least one GPS signal from a GPS satellite, including receiving the pseudorange measurements and performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal;

processing the received pseudorange measurements, in response to the tracking at least one GPS signal, to reduce their pseudorange residuals based on statistical modeling in order to mitigate multipath errors; and

computing navigation solutions based on the processed pseudorange measurements.

30. A receiver comprising:

means for receiving signals from a plurality of satellites;

means for generating pseudorange measurements based on the received signals;

means for processing the generated pseudorange measurements to reduce pseudorange residuals based at least in part on statistical modeling that mitigates multipath errors; and

means for computing navigation solutions based at least in part on the processed pseudorange measurements.

31. The receiver as defined in claim 30, further comprising means to down-convert, magnify, filter, and digitize the received signals into digital immediate frequency (IF) signals.

32. The receiver as defined in claim 30, further comprising means for acquiring and tracking the received signals and generating pseudorange measurements according to the received signals.

33. The receiver as defined in claim 30, further comprising:

means for generating a statistical representation to describe the received pseudorange measurements based on the selected statistical model; and

means for modifying the generated statistical representation to reduce the pseudorange residuals of the received pseudorange measurements in order to mitigate multipath errors.

34. The receiver as defined in claim 33, further comprising means for modifying the generated statistical representation by transforming each received pseudorange measurement into multiple pseudorange measurement components, wherein each pseudorange measurement component corresponds to a respective Gaussian component in a selected Gaussian mixture model.

35. The receiver as defined in claim 33, further comprising means for modifying the generated pseudorange measurements by computing an effective residual and variance of the generated statistical representation corresponding to the received pseudorange measurements.