METHODS AND APPARATUS FOR A NAVIGATION SYSTEM WITH REDUCED SUSCEPTIBILITY TO INTERFERENCE AND JAMMING

• US 20080062039A1
• Filed: 11/07/2005
• Published: 03/13/2008
• Est. Priority Date: 11/07/2005
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Ferrell, Barton G., Ledvina, Brent M., Bencze, William J., Gutt, Gregory M., Cohen, Clark E., Whelan, David A., Brumley, Robert W., Psiaki, Mark L.
• Granted Patent: US 7,372,400 B2
• Time in Patent Office: Days
• US Class Current: 342/357.01
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: H04K 3/255 based on redundancy of transmitted data, transmission path or transmitting source
• CPC Class Codes: H04K 3/90 related to allowing or preventing navigation or positioning, e.g. GPS

Abstract

A navigation system provides a significant level of protection against all forms of interference or jamming to GPS in a cost-effective way. The system employs a network of ground reference stations and Low Earth Orbiting (LEO) satellites in conjunction with GPS. A common-view ranging geometry to a GPS satellite is established that links a reference station and a user. A second common-view geometry to a LEO satellite between the same reference station and user pair is also established. The ground stations synthesize real-time aiding signals by making carrier phase measurements of GPS the LEO satellite signals. This aiding information is transmitted via the LEO satellites to the user receiver at high power to penetrate ambient jamming. The user receiver locks onto the carrier phase of the LEO satellite, demodulates the aiding information, then applies the carrier phase measurements and the aiding information to enable extended coherent measurements of the GPS signals. The system thereby recovers the GPS signals that would otherwise be lost to the jamming.

Claims

1. A navigation system comprising:

a reference receiver;

a user receiver;

a global positioning system (GPS) satellite in common view of said reference receiver and said user receiver, wherein said reference receiver and said user receiver receive a carrier ranging signal from said GPS satellite;

a first low earth orbit (LEO) satellite in common view of said reference receiver and said user receiver, wherein said reference receiver and said user receiver are configured to calculate respective first and second measurements of an LEO carrier ranging signal received from said first LEO satellite;

said user receiver configured to receive, via said LEO satellite, said first measurement from said reference receiver and apply said first and second measurements to construct an a priori estimate of a signal phase of said GPS carrier ranging signal received by said user receiver, wherein said a priori estimate is used as the basis of an extended integration of said carrier ranging signal at said user receiver.

2. A navigation system according to claim 1, further comprising a plurality of LEO satellites, wherein one or more of said plurality of LEO satellites contributes to said a priori estimate.

3. A navigation system according to claim 1, wherein said user receiver employs ephemeris information to determine said a priori estimate, wherein said a priori estimate is a small fraction of wavelength over the extended integration interval.

4. A navigation system according to claim 1, further including a plurality of GPS satellites, wherein a plurality of respective carrier ranging signals from said GPS satellites are combined by said receiver to form a navigation solution.

5. A navigation system according to claim 2, further including a plurality of GPS satellites, wherein a plurality of respective carrier ranging signals from said GPS satellites are combined by said receiver to form a navigation solution.

6. A navigation system according to claim 1, wherein said extended integration is used to recover code phase ranging information embedded in said carrier ranging signal from said GPS satellite.

7. A navigation system according to claim 6, wherein said code phase ranging information from said plurality of GPS satellites is used to calculate a position and a clock offset of said user receiver.

8. A navigation system according to claim 1, wherein said first and second measurements provide said user receiver with a precise relative time estimate between said reference receiver and said user receiver.

9. A navigation system according to claim 7, wherein said code phase ranging information provides said user receiver with a time estimate that is both precise with respect to said reference receiver time, and is accurate with respect to GPS time.

10. A navigation system according to claim 5, wherein a geometry change of said plurality of LEO and GPS satellites is employed by said user receiver to estimate the system biases.

11. A navigation system according to claim 5, further comprising a plurality of LEO satellites, wherein orthogonalization is employed by said user receiver to partition tracking bias state variables associated with said plurality of GPS satellites, said plurality of LEO satellites, and a clock associated with said user receiver.

12. A navigation system according to claim 5, wherein said user receiver is stationary.

13. A navigation system according to claim 7, wherein said user receiver operates under low dynamics.

14. A navigation system of claim 5, wherein an inertial navigation system within said user receiver is employed to subtract out the motion of said user receiver.

15. A navigation system of claim 14, wherein a set of bias corrections generated by said inertial navigation system are sufficient to provide accuracy to less than a small fraction of a wavelength over an interval of said extended integration.

16. A navigation system according to claim 5, wherein said reference station is mobile.

17. A navigation system according to claim 16, wherein said reference station is a second LEO satellite.

18. A navigation system of claim 16, wherein said reference receiver is a component of said first LEO satellite.

19. A navigation method wherein a reference receiver and a user receiver receive a carrier ranging signal from a GPS satellite in common view, comprising the steps of:

measuring, by said reference receiver, a carrier ranging signal from a first LEO satellite in view to produce a first measurement;

measuring, by said user receiver, a carrier ranging signal from a second LEO satellite in view to produce a second measurement;

said first LEO satellite and said second LEO satellite measuring carrier ranging crosslink signals from each other to produce a third and a fourth measurement, respectively;

conveying said first, third, and fourth measurements from said reference receiver and said first and second LEO satellites to said user receiver;

using said first, second, third, and fourth measurements to construct an a priori estimate of a phase of the carrier ranging signal from the GPS satellite; and

using said a priori estimate as the basis of an extended integration of said GPS satellite signal received by said user receiver.

20. The method of claim 19, wherein carrier ranging signals from one or more GPS satellites are combined to form a navigation solution.

21. The method of claim 20, wherein an inertial navigation system is employed to subtract out the motion of said user receiver.

22. The method of claim 21, wherein the bias corrections of said inertial navigation system are sufficient to provide accuracy to less than a small fraction of a wavelength over said extended integration interval.

23. A navigation method wherein a reference receiver and user receiver receive a carrier ranging signal from a GPS satellite in common view, comprising the steps of:

measuring, by said reference receiver and said user receiver, a carrier ranging signal from a first LEO satellite in common view to produce first and second measurements, respectively;

conveying said first measurement to said user receiver,

applying, by said user receiver, said first and second measurements to construct an a priori estimate of a phase of said GPS carrier ranging signal,

using said a priori estimate as the basis of an extended integration of said GPS satellite signal received by said user receiver.

24. The navigation method of claim 23, wherein one or more LEO satellites contribute to said a priori estimate of the incoming GPS signal phase.

25. The navigation method of claim 23, wherein carrier ranging signals from one or more GPS satellites are combined to form a navigation solution.

26. The navigation method of claim 24, wherein the carrier ranging signals from a plurality of GPS satellites are combined to form a navigation solution.

27. The navigation method of claim 23, wherein precise streaming feed forward ephemeris information is used to achieve a priori estimates of carrier phase that are a small fraction of wavelength over the extended integration interval.

28. The navigation method of claim 26, wherein a centralized regulator models and controls one or more correlators, one or more inertial sensors, one or more tracking bias states, and one or more clock states within said user receiver.

29. The navigation method of claim 28, wherein said centralized regulator calculates and conveys precise streaming feed forward carrier phase information to each of said correlators to achieve a priori estimates of incoming carrier phase that are accurate to a small fraction of wavelength over said extended integration interval.

30. The navigation method of claim 29, wherein orthogonalization is employed to partition tracking bias state variables associated with said plurality of GPS satellites, said one or more LEO satellites, and a set of common-mode components, including a user clock.

31. The navigation method of claim 30, wherein said orthogonalization is triangular.