Method And Apparatus For Mitigating Multipath Effects At A Satellite Signal Receiver Using a Sequential Estimation Filter

• US 20070096978A1
• Filed: 06/30/2006
• Published: 05/03/2007
• Est. Priority Date: 10/27/2005
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Global Locate Incorporated (Broadcom, Inc.)
• Inventors: Podshivalov, Sergei, Abraham, Charles, van Diggelen, Frank
• Granted Patent: US 7,253,768 B2
• Time in Patent Office: Days
• US Class Current: 342/357.61
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/42 Determining position

Abstract

A method and apparatus for mitigating multipath effects in a satellite signal receiver is described. The method includes computing at least one pseudorange residual as a function of (i) a measured pseudorange to a given satellite, and (ii) an expected pseudorange to the given satellite, which is derived by mathematically projecting a pseudorange to the given satellite. The method also includes applying the measured pseudorange to a sequential-estimation filter, which is configured to solve a navigation-solution problem, when the pseudorange residual satisfies a given threshold.

Claims

1. A method for mitigating multipath effects in a satellite-signal receiver, comprising:

computing at least one pseudorange residual as a function of a measured pseudorange to a given satellite and an expected pseudorange to the given satellite, wherein the expected pseudorange is derived by mathematically projecting a pseudorange to the given satellite; and

when the pseudorange residual satisfies a given threshold, applying the measured pseudorange to a sequential-estimation filter for solving a navigation-solution problem.

2. The method of claim 1, further comprising:

deriving the expected pseudorange by applying to another sequential-estimation filter at least one a-priori parameter for mathematically projecting the pseudorange to the given satellite.

3. The method of claim 1, wherein the measured pseudorange comprises a sub-millisecond pseudorange.

4. The method of claim 1, wherein the sequential estimation filter comprises any of a Kalman filter and a batch filter.

5. The method of claim 1, further comprising:

applying the pseudorange residual to the given threshold.

6. The method of claim 1, further comprising:

applying the pseudorange residual to the given threshold, wherein the threshold defines a range of values, and wherein the pseudorange residual satisfies the given threshold when the pseudorange residual has a value that is within the range of values.

7. The method of claim 6, further comprising adjusting the range of values.

8. The method of claim 7, wherein adjusting the range of values comprises reducing the range of values by some amount of values when at least one current state of the sequential-estimation filter is known.

9. The method of claim 8, wherein the at least one current state comprises a magnitude of a covariance of an estimated state.

10. The method of claim 7, wherein adjusting the range of values comprises enlarging the range of values by an amount of values when at least one current state of the sequential-estimation filter is not known.

11. The method of claim 10, wherein the at least one current state comprises a magnitude of a covariance of an estimated state.

12. The method of claim 7, wherein the adjusting the range of values comprises any of reducing and enlarging the range of values by an amount of values in response to a number of satellites in view of the satellite-signal receiver, a Dilution of Precision, signal quality, and combination thereof.

13. The method of claim 6, wherein the range of values comprises a range between about a negative 100 meters and positive 100 meters.

14. An apparatus for mitigating multipath effects in a satellite-signal receiver, comprising:

memory operable to store executable instructions; and

a processor operable to obtain from the memory the executable instruction and execute the executable instructions to;

compute at least one pseudorange residual as a function of a measured pseudorange to a given satellite and an expected pseudorange to the given satellite, wherein the expected pseudorange is derived by mathematically projecting a pseudorange to the given satellite; and

apply the measured pseudorange to a sequential-estimation filter for solving a navigation-solution problem when the pseudorange residual satisfies a given threshold.

15. The apparatus of claim 14, wherein the processor is further operable to execute the executable instructions to:

derive the expected pseudorange by applying to another sequential-estimation filter at least one a-priori parameter for mathematically projecting the pseudorange to the given satellite.

16. The apparatus of claim 14, wherein the processor is further operable to execute the executable instructions to:

apply the pseudorange residual to the given threshold.

17. The apparatus of claim 14, wherein the processor is further operable to execute the executable instructions to:

apply the pseudorange residual to the given threshold, wherein the threshold defines a range of values, and wherein the pseudorange residual satisfies the given threshold when the pseudorange residual has a value that is within the range of values.

18. The apparatus of claim 14, wherein the processor is further operable to execute the executable instructions to:

adjust the range of values.

19. The apparatus of claim 14, wherein the processor is further operable to execute the executable instructions to:

reduce the range of values by some amount of values when at least one current state of the sequential-estimation filter is known.

20. The apparatus of claim 14, wherein the processor is further operable to execute the executable instructions to:

enlarge the range of values by an amount of values when at least one current state of the sequential-estimation filter is not known.

21. A mobile device, comprising:

a satellite signal receiver operable to process signals from at least one satellite to obtain a measured pseudorange; and

a processor operable to compute at least one pseudorange residual as a function of a measured pseudorange to a given satellite and an expected pseudorange to the given satellite, wherein the expected pseudorange is derived by mathematically projecting a pseudorange to the given satellite; and

to apply the measured pseudorange to a sequential-estimation filter for solving a navigation-solution problem when the pseudorange residual satisfies a given threshold.

22. The mobile device of claim 21, wherein the processor is further operable to derive the expected pseudorange by applying to another sequential-estimation filter at least one a-priori parameter for mathematically projecting the pseudorange to the given satellite.