System and method for detecting false navigation signals

• US 20070194984A1
• Filed: 02/21/2006
• Published: 08/23/2007
• Est. Priority Date: 02/21/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Waid, James
• Granted Patent: US 7,724,184 B2
• Time in Patent Office: Days
• US Class Current: 342/357.59
• CPC Class Codes: G01S 19/215 issues related to spoofing

Abstract

A system and method for detecting and excluding false GPS signals are disclosed, which predict a GPS measurement value with a high degree of confidence, compare the predicted value with measured values, and reject a false measurement based on the comparison results. As one example, a tightly coupled GPS/Inertial Navigation System (GPS/INS) is disclosed, which uses a Kalman filter for comparison of a predicted GPS measurement value with measured values (e.g., the residuals) to form the basis for the rejection of false measurements. This rejection is referred to as a chi-squared reject, and can be extended in time in order to apply the same test to a reacquired signal following the loss of an original validated GPS signal. The Kalman filter propagates the receiver'"'"'s clock bias rate, and enables the system to predict the GPS measurements at the time of reacquisition. The residuals are compared to a limit defined by the uncertainties of the prediction and the measurement errors expected to be involved.

Claims

1. A system for detecting a false navigation signal, comprising:

a navigation receiver, said navigation receiver operable to receive a plurality of navigation signals; and

a processor unit coupled to said navigation receiver, said processor unit operable to;

execute a recursive filter to predict a parameter associated with at least one navigation signal of said plurality of navigation signals;

receive a measurement value associated with said at least one navigation signal;

compare said measurement value with said predicted parameter; and

responsive to a result of said comparison, determine if said at least one navigation is a false navigation signal.

2. The system of claim 1, wherein said navigation receiver is a satellite navigation receiver.

3. The system of claim 1, wherein said navigation receiver is a GPS receiver.

4. The system of claim 1, wherein said false navigation signal comprises a time delayed version of a valid navigation signal.

5. The system of claim 1, wherein said false navigation signal comprises a retransmitted navigation signal.

6. The system of claim 1, wherein said recursive filter comprises a Kalman filter.

7. The system of claim 1, wherein said plurality of navigation signals comprises a plurality of signals transmitted from a plurality of radio-navigation satellites.

8. The system of claim 1, wherein the operation to compare said measurement value with said predicted parameter comprises comparing said measurement value to a predetermined acceptance criteria.

9. The system of claim 1, wherein said measurement value comprises a residual value for at least one of a GPS pseudorange value and a GPS delta range value.

10. The system of claim 1, wherein said predicted parameter comprises at least one error state associated with a predicted measurement value.

11. A system for detecting a false navigation signal, comprising:

means for receiving a plurality of navigation signals;

means for executing a recursive filter to predict a parameter associated with at least one navigation signal of said plurality of navigation signals;

means for receiving a measurement value associated with said at least one navigation signal;

means for comparing said measurement value with said predicted parameter; and

means for determining if said at least one navigation is a false navigation signal, responsive to a comparison performed with said means for comparing.

12. The system of claim 11, wherein said means for receiving a plurality of signals is a satellite navigation receiver.

13. The system of claim 11, wherein said means for receiving a plurality of navigation signals is a GPS receiver.

14. The system of claim 11, wherein said false navigation signal comprises a time delayed and amplified version of a valid navigation signal.

15. The system of claim 11, wherein said false navigation signal comprises a retransmitted GPS signal.

16. A method for detecting a false navigation signal, comprising the steps of:

receiving a plurality of navigation signals;

executing a recursive filter to predict a parameter associated with at least one navigation signal of said plurality of navigation signals;

receiving a measurement value associated with said at least one navigation signal;

comparing said measurement value with said predicted parameter; and

determining if said at least one navigation is a false navigation signal, responsive to the comparing step.

17. The method of claim 16, wherein the step of receiving a plurality of signals is performed with a satellite navigation receiver.

18. The method of claim 16, wherein the step of comparing said measurement value with said predicted parameter comprises a step of comparing said measurement value to a predetermined acceptance criteria.

19. A method for detecting a false navigation signal, comprising the steps of:

determining if a navigation receiver has lost a lock on a transmitted navigation signal;

if said navigation receiver has lost said lock on said transmitted navigation signal, propagating at least one error state associated with an estimated measurement value for said transmitted navigation signal;

determining if said navigation receiver has reacquired said lock on said transmitted navigation signal; and

if said navigation receiver has reacquired said lock, computing a measurement residual value and an acceptance criteria associated with said estimated measurement value, and comparing said measurement residual value with said acceptance criteria.

20. The method of claim 19, further comprising the step of:

determining that a reacquired navigation signal is a false signal if said measurement residual value does not meet said acceptance criteria.

21. A computer program product, comprising:

a computer-usable medium having computer-readable code embodied therein for configuring a computer processor, the computer program product comprising;

a first executable computer-readable code configured to cause a computer processor to cause a navigation receiver to receive a plurality of navigation signals;

a second executable computer-readable code configured to cause a computer processor to execute a recursive filter to predict a parameter associated with at least one navigation signal of said plurality of navigation signals;

a third executable computer-readable code configured to cause a computer processor to receive a measurement value associated with said at least one navigation signal;

a fourth executable computer-readable code configured to cause a computer processor to compare said measurement value with said predicted parameter; and

a fifth executable computer-readable code configured to cause a computer processor to determine if said at least one navigation is a false navigation signal, responsive to an execution of said fourth executable computer-readable code.

22. The computer program product of claim 21, wherein said recursive filter comprises a Kalman filter.