Systems and methods for positioning using multipath signals

• US 20080198072A1
• Filed: 01/19/2006
• Published: 08/21/2008
• Est. Priority Date: 01/19/2005
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Dowdle, John R., Gustafson, Donald E., Elwell, John M.
• Granted Patent: US 7,679,561 B2
• Time in Patent Office: Days
• US Class Current: 342/450
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 19/428 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/02525 Gathering the radio frequency fingerprints
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination

Abstract

A signal processing technique for RF active, passive, or aided localization approaches that utilizes multipath signals as additional measurements with a filter or estimator, e.g., a nonlinear filter. The filter uses indirect and direct path measurements or any other available signals to build parametric models of observable indirect paths. If one or more direct path measurements are subsequently lost (e.g., due to obstruction), the filter maintains an estimate of the position of the person or object of interest using indirect path measurements.

Claims

1. A method for positioning using a multipath wireless signal, the method comprising the steps of:

determining an initial position;

generating information relating at least one position to at least one characteristic of at least one multipath wireless signal received at the at least one position;

receiving a subsequent wireless multipath signal; and

establishing a position based on the subsequent signal and the generated information.

2. The method of claim 1 wherein determining an initial position comprises:

causing a tag to receive, at a plurality of positions, at least one transmitted signal;

determining the magnitude of the at least one signal received by the tag at each position;

determining the magnitude of at least one signal received by the tag at the initial position; and

using the determined signal magnitudes and a statistical model to estimate the initial position.

3. The method of claim 2 wherein the statistical model comprises data indicative of signal propagation characteristics associated with a signal space between the tag and each of a plurality of signal transmitters.

4. The method of claim 1 wherein the step of establishing comprises computing a plurality of candidate locations and selecting a most likely location therefrom.

5. The method of claim 4 wherein the most likely location is determined using a statistical test.

6. The method of claim 1 wherein generating information comprises characterizing at least a partial geometry of the interior environment and a geometry of multipath signals therein, the multipath geometry comprising lengths of indirect path segments from a wireless source to points of reflection within the environment.

7. The method of claim 6 wherein the indirect path-segment lengths are represented by path-delay measurements.

8. The method of claim 1 wherein the at least one characteristic comprises path delay.

9. The method of claim 8 wherein the generated information relates path delay to locations within the environment.

10. The method of claim 1 wherein the at least one characteristic comprises path-segment lengths.

11. The method of claim 10 wherein the generated information relates path-segment lengths to locations within the environment.

12. The method of claim 1 wherein the wireless multipath signal is generated by a Global Positioning System (GPS) transmitter.

13. The method of claim 1 wherein the wireless multipath signal is generated by a transmitter.

14. The method of claim 1 wherein determining the initial position comprises making a direct path measurement of the initial position.

15. The method of claim 14 wherein the direct path measurement is a measurement of received signal strength.

16. The method of claim 1 wherein determining the initial position comprises utilizing prior knowledge of the initial position.

17. The method of claim 1 wherein the related position is the initial position.

18. The method of claim 1 wherein the generated information comprises at least one parameter.

19. An apparatus for positioning using a multipath wireless signal, the apparatus comprising:

a memory comprising information relating at least one position to at least one characteristic of at least one multipath wireless signal received at the at least one position;

a receiver for receiving a subsequent wireless multipath signal; and

circuitry for determining a position based on the subsequent signal and the generated information.

20. The apparatus of claim 19 wherein the information characterizes at least a partial geometry of the interior environment and a geometry of multipath signals therein, the multipath geometry comprising lengths of indirect path segments from a wireless source to points of reflection within the environment.

21. The apparatus of claim 20 wherein the indirect path-segment lengths are represented by path-delay measurements.

22. The apparatus of claim 19 wherein the at least one characteristic comprises path delay.

23. The apparatus of claim 22 wherein the information relates path delay to locations within the environment.

24. The apparatus of claim 19 wherein the at least one characteristic comprises path-segment lengths.

25. The apparatus of claim 24 wherein the information relates path-segment lengths to locations within the environment.

26. The apparatus of claim 19 wherein the wireless multipath signal is generated by a Global Positioning System (GPS) transmitter.

27. The apparatus of claim 19 wherein the wireless multipath signal is generated by a transmitter.

28. The apparatus of claim 19 wherein the related position is the initial position.

29. The apparatus of claim 19 wherein the information comprises at least one parameter.