Ultra-wideband radios for time-of-flight-ranging and network position estimation

• US 7,962,150 B2
• Filed: 12/11/2006
• Issued: 06/14/2011
• Est. Priority Date: 04/28/2004
• Status: Expired due to Fees

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Inventors: Hertzog, Claudia A., Romero, Carlos E., Dallum, Gregory E., Dowla, Farid U.
• Primary Examiner(s): SHEDRICK, CHARLES TERRELL
• Application Number:
  US11/637,388
• Publication Number:
  US 20100225541A1
• Time in Patent Office: 1,646 Days
• Field of Search: 455/456.1, 455/456.2, 455/456.3, 455/456.4, 455/456.5, 455/456.6, 340/10.1
• US Class Current: 455/456.1
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

This invention provides a novel high-accuracy indoor ranging device that uses ultra-wideband (UWB) RF pulsing with low-power and low-cost electronics. A unique of the present invention is that it exploits multiple measurements in time and space for very accurate ranging. The wideband radio signals utilized herein are particularly suited to ranging in harsh RF environments because they allow signal reconstruction in spite of multipath propagation distortion. Furthermore, the ranging and positioning techniques discussed herein directly address many of the known technical challenges encountered in UWB localization regarding synchronization and sampling. In the method developed, noisy, corrupted signals can be recovered by repeating range measurements across a channel, and the distance measurements are combined from many locations surrounding the target in a way that minimizes the range biases associated to indirect flight paths and through-wall propagation delays.

Claims

1. An ultra-wideband wireless time-of-flight-ranging and network position estimation method, comprising:

transmitting a first encoded ultra-wideband query;

transmitting a second encoded ultra-wideband query;

subtracting out common signals produced from replies to said first and said second encoded ultra-wideband queries so as to result in one or more desired reply signals;

statistically filtering time of flight information resulting from said desired reply signals so as to produce a plurality of one or more range measurements;

transforming said one or more range measurements into a desired coherent one or more range measurements;

introducing a respective bias correction to said coherent signals; and

calculating a true position estimate of a line-of-sight (LOS) or a non-line-of-sight (NLOS) transmission channel target as a result of processing a predetermined collected number of said filtered and corrected said plurality of range measurements.

2. The method of claim 1, wherein said non-line-of-sight (NLOS) transmission channels comprise at least one target located around corners, inside caves, behind walls, and in buildings.

3. The method of claim 1, further comprising visualizing a floor plan of a building using a ranging device mounted on a moving platform to operate as a transmitter of said encoded ultra-wideband queries.

4. The method of claim 1, wherein said encoded query comprises a single ultra-wideband pulse transmission.

5. The method of claim 1, wherein said encoded query comprises one or more Transmit Reference encoding schemes.

6. The method of claim 1, wherein said position estimation is capable of being determined down to about 1.5 inches.

7. The method of claim 1, wherein the first and second queries are sent to the same receiver.

8. The method of claim 1, wherein statistically filtering time of flight information comprises removing data outliers.

9. The method of claim 1, wherein statistically filtering time of flight information comprises distributing the time of flight information into a histogram having predetermined bin widths, and applying a recursive weighted least squares estimator.

10. The method of claim 1, wherein subtracting out common signals comprises removing reflections of queries that are not replies from a receiver.

11. The method of claim 1, wherein transforming said one or more range measurements into a desired coherent one or more range measurements comprises beamforming.

12. The method of claim 11, wherein beamforming comprises repeating range measurements multiple times and combining the multiple range measurements to enhance coherent reply pulses and minimize uncorrelated noise.

13. The method of claim 12, comprising repeating range measurements at least 100 times.

14. The method of claim 11, wherein beamforming comprises capturing multiple frames of multiple time samples and summing across the frames.

15. The method of claim 14, comprising capturing at least 100 frames.

16. The method of claim 1, wherein introducing a respective bias correction comprises taking multiple range measurements, calculating the position, then recalculating the position with a range of artificial biases, and choosing the solution with lowest overall equation error.