Low-cost, low-power geolocation system

• US 6,934,626 B2
• Filed: 05/13/2003
• Issued: 08/23/2005
• Est. Priority Date: 05/13/2002
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Tingley, Robert D.
• Primary Examiner(s): Nguyen, Tan Q.
• Application Number:
  US10/437,423
• Publication Number:
  US 20030229445A1
• Time in Patent Office: 833 Days
• Field of Search: 701/207, 701/213, 701/214, 701/215, 340/988, 340/992, 340/993, 342/357.01, 342/357.07, 342/357.08, 342/357.09, 342/357.12, 342/450, 342/453, 342/463, 342/357.14
• US Class Current: 701/207
• CPC Class Codes: G01S 11/026 using moving transmitters
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0278 involving statistical or probabilistic considerations G01S5/0252, G01S5/0294 take precedence

Abstract

A system and method for determining the location of a transmission source by processing the magnitude of the transmitted signal received at a plurality of receivers with a statistical model of the signal propagation characteristics associated with the signal space between the source and each of the receivers. The system and method also are capable of determining a route of travel between the transmission source and a receiver and/or alternate location.

Claims

1. A method for determining the location of a transmission source, the method comprising the steps of:

receiving at a plurality of signal receiving locations at least one signal from a transmission source;

determining a signal magnitude of each of the at least one transmission signal received at the plurality of signal receiving locations; and

processing each of the signal magnitudes with a statistical model of the signal propagation characteristics associated with the signal space between the transmission source and each of the receiving locations to determine the location of the transmission source;

wherein the location is at least in part determined by at least one signal magnitude, and by a distance power gradient of the transmission source relative to at least one of the plurality of signal receiving locations.

2. The method of claim 1 wherein the step of processing comprises:

processing information associated with a physical environment between the transmission source and each of the receiving locations.

3. The method of claim 2 wherein the step of processing comprises:

determining a route of travel between the transmission source and at least one of the receiving locations.

4. The method of claim 2 wherein the step of processing comprises:

determining a route of travel between the transmission source and an alternate location.

5. The method of claim 2 wherein the information associated with a physical environment includes state information associated with elements of a route of travel between the transmission source and an alternate location.

6. The method of claim 5 wherein the state information includes whether a door is open or closed.

7. The method of claim 1 wherein the transmission source is mobile.

8. The method of claim 1 wherein the transmission source signal comprises a signal representative of a characteristic of the transmission source.

9. The method of claim 1 wherein the transmission source signal comprises a signal representative of a characteristic of a person in contact with the transmission source.

10. The method of claim 1 wherein the statistical model of the signal propagation characteristics comprises data representative of the manner in which the at least one signal from the transmission source changes with respect to the distance of the at least one signal from the transmission source.

11. The method of claim 1 wherein the step of processing comprises performing an optimization procedure to determine the location of the transmission source.

12. The method of claim 11 wherein the optimization procedure comprises averaging at least two position estimates.

13. The method of claim 11 wherein the optimization procedure comprises a Kalman filter.

14. A system for determining the location of a transmission source comprising:

a transmission source capable of transmitting at least one signal;

a plurality of receivers each capable of receiving the at least one transmitted signal;

a processor capable of determining signal magnitudes of the at least one transmitted signal as received by each of the plurality of receivers and capable of processing each of the signal magnitudes with a statistical model of the signal propagation characteristics associated with the signal space between the transmission source and each of the receiving locations to determine the location of the transmission source;

wherein the location is at least in part determined by at least one signal magnitude, and by a distance power gradient of the transmission source relative to at least one of the plurality of receivers.

15. The system of claim 14 wherein the processor is capable of processing information associated with a physical environment between the transmission source and each of the receiver locations.

16. The system of claim 15 wherein the processor determines a route of travel between the transmission source and at least one of the receivers.

17. The system of claim 15 wherein the processor determines a route of travel between the transmission source and an alternate location.

18. The system of claim 15 wherein the information associated with a physical environment includes state information associated with elements of a route of travel between the transmission source and an alternate location.

19. The system of claim 18 wherein the state information includes whether a door is open or closed.

20. The system of claim 14 wherein the transmission source is mobile.

21. The system of claim 14 wherein the transmission signal comprises a signal representative of a characteristic of the transmission source.

22. The system of claim 14 wherein the transmission signal comprises a signal representative of a characteristic of a person in contact with the transmission source.

23. The system of claim 14 wherein the statistical model of the signal propagation characteristics comprises data representative of the manner in which the at least one signal from the transmission source changes with respect to the distance of the at least one signal from the transmission source.

24. The system of claim 14 wherein the processor is capable of performing an optimization procedure to determine the location of the transmission source.

25. The system of claim 24 wherein the optimization procedure includes averaging at least two position estimates.

26. The system of claim 24 wherein the optimization procedure includes a Kalman filter.

27. A system for determining the location of a transmission source, comprising a log likelihood function of the general form:

$\ln <br><br>\left(p_{a/x,y}<br><br>\left(a/x,y\right)\right)=\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>\ln <br><br>\left({\frac{a_n<br><br>\mathrm{\pi <br><br>}}{2<br><br>P_n}<br><br>\left[{\left(x-x_n\right)}^2+{\left(y-y_n\right)}^2\right]}^{\frac{g_n}{2}}\right)-\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>\left({\frac{a_n^2<br><br>\mathrm{\pi <br><br>}}{4<br><br>P_n}<br><br>\left[{\left(x-x_n\right)}^2+{\left(y-y_n\right)}^2\right]}^{\frac{g_n}{2}}\right);<br><br>$

wherein x is a location along an X-axis of a Cartesian coordinate system;

y is a location along a Y-axis of a Cartesian coordinate system that is orthogonal to the X-axis;

x_n represents an X-axis location of an n^th receiver in the Cartesian coordinate system;

y_n represents an Y-axis location of an n^th receiver in the Cartesian coordinate system;

a_n is a measured signal strength at the location of the n^th receiver;

g_n is a distance power gradient of the n^th receiver relative to the transmitter;

P_n is a power received by the n^th receiver at a location one meter from a transmitter; and

p_a/x,y is a likelihood function.

28. A method for determining the location of a receiver, the method comprising the steps of:

receiving at a receiver a plurality of signals from a plurality of transmission sources;

determining a signal magnitude of each of the plurality of signals received at the receiver; and

processing each of the signal magnitudes with a statistical model of the signal propagation characteristics associated with the signal space between the receiver and each of the plurality of transmission sources to determine the location of the receiver, wherein the location is at least in part determined by at least one signal magnitude, and by a distance power gradient of the receiver relative to at least one of the plurality of transmission sources.