System and method for distributed signal compression for cooperative geolocation

• US 20070296631A1
• Filed: 06/26/2006
• Published: 12/27/2007
• Est. Priority Date: 06/26/2006
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Ray, Gary A.
• Granted Patent: US 7,365,682 B2
• Time in Patent Office: Days
• US Class Current: 342/387
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

A cooperative geolocation system and method. The system and method involves time stamping a plurality of received signals and modifying, such as compressing, one or more of the received signals, either with the same or with different rates of compression. A processing subsystem including a geolocation processor is used to correlate various pairs of received signals and to extract time difference of arrival (TDOA) or frequency difference of arrival (FDOA) information and to use this information in cooperatively geolocating the signal source emitting the signals being analyzed. The system enables greater rates of data compression, and thus frees up bandwidth in a network in which it is employed, as compared with previously existing cooperative geolocation systems. The present system further can perform the cooperative geolocation determination without first decompressing the compressed signals, but rather performing a correlation process directly on designated pairs of signals to extract the needed TDOA/FDOA information.

Claims

1. A method for geolocating a signal source, comprising:

using a first receiver to receive a signal being emitted by said signal source, and to time stamp said signal as a first signal;

using a second receiver to receive said signal and to time stamp said signal as a second signal;

modifying said second signal using frequency companding to form a reduced bandwidth second signal;

supplying said first signal and said reduced bandwidth second signal to a processing subsystem remote from said first and second receivers;

using said processing subsystem to analyze said time stamp for said reduced bandwidth second signal and said time stamp for said first signal, and correlating said reduced bandwidth second signal and said first signal, to determine a time difference of arrival of said reduced bandwidth second signal relative to said first signal; and

using said time difference of arrival to geolocate said signal source.

2. The method of claim 1, wherein using said first and second receivers comprises using receivers adapted to receive electromagnetic wave signals.

3. The method of claim 1, wherein using said first and second receivers comprises using receivers adapted to receive audio wave signals.

4. The method of claim 1, wherein modifying said second signal comprises compressing said second signal.

5. The method of claim 1, wherein compressing said compressed second signal comprises modulo compressing said compressed second signal to produce a modulo compressed second signal.

6. The method of claim 1, wherein modifying said second signal comprises using non-linear frequency companding to modify said second signal.

7. The method of claim 4, further comprising:

using a third receiver to receive said signal and to time stamp said signal as a third signal; and

modifying said third signal to produce a third signal having a reduced bandwidth; and

using said time stamp for said third signal and said time stamp for said first signal to determine a time difference of arrival for said third signal relative to said first signal.

8. The method of claim 7, wherein modifying said third signal comprises compressing said third signal;

and

wherein said third signal is compressed by a different factor than said second signal.

9. The method of claim 1, wherein correlating said second signal and said first signal comprises analyzing signal peaks from said second signal and said first signal, and selecting a peak from each of said first and second signals having the greatest magnitude.

10. A method for determining a time difference of arrival (TDOA) of a signal being emitted by a signal source, and being received by a plurality of receivers, the method comprising:

using a first receiver to receive said signal being emitted by said signal source, and to time stamp said signal as a first signal;

using a second receiver to receive said signal and to time stamp said signal as a second signal;

modifying said second signal using frequency companding to form a reduced bandwidth second signal;

using said time stamp for said second signal and said time stamp for said first signal, and correlating said second signal and said first signal, to determine a time difference of arrival of said second signal relative to said first signal, without the need to further modify said second signal;

using a third receiver to receive said signal and to time stamp said signal as a third signal;

modifying said third signal to produce a modified third signal having a reduced bandwidth;

using said time stamp for said modified third signal and said time stamp for said first signal to determine a time difference of arrival for said modified third signal relative to said first signal; and

where the second reduced bandwidth signal and said modified third signal include different levels of bandwidth reduction from one another and that also differ from said first signal in bandwidth.

11. The method of claim 10, wherein said signal comprises an electromagnetic wave signal, and said first and second receivers comprise electromagnetic wave receivers.

12. The method of claim 10, wherein said signal comprises an audio signal, and said first and second receivers comprise audio wave receivers.

13. The method of claim 10, wherein modifying said second signal comprises compressing said second signal.

15. The method of claim 10, wherein using a second receiver comprises using a mobile second receiver.

16. The method of claim 10, further comprising using a signal exchange protocol to manage processing of said first and second signals in accordance with predetermined operational parameters.

14. (canceled)

17. A geolocation system for geolocating a signal source that is emitting a signal, the system comprising:

a first subsystem for receiving said signal being emitted by said signal source, and time stamping said signal as a first signal, and transmitting said first signal with said time stamp;

a second subsystem that receives said signal, time stamps said signal as a second signal, modifies said second signal using frequency companding to produce a reduced bandwidth second signal, and transmits said reduced bandwidth second signal;

a processing system for receiving said first signal and said compressed second signal, correlating said second signal and said first signal, and using said time stamps associated with said first and second signals to geolocate said signal without requiring further modification to said second signal.

18. The system of claim 17, wherein said processing system operates to determine a time difference of arrival of said second signal and said first signal.

19. The system of claim 17, wherein at least one of said first and second subsystems comprises an electromagnetic wave receiver, and said signal comprises an electromagnetic wave signal.

20. The system of claim 17, wherein at least one of said first and second subsystems comprises an audio wave receiver, and said signal comprises an audio wave signal.

21. The system of claim 20, further comprising a third subsystem that receives said signal, time stamps said signal as a third signal, modifies said third signal to produce a reduced bandwidth third signal, and transmits said reduced bandwidth third signal to said processing subsystem;

and

said second and third subsystems being adapted to apply different levels of bandwidth reduction such that said first signal, said reduced bandwidth second signal and said reduced bandwidth third signal all have differing bandwidths.