Apparatus and method for performing passive sensing

Patent metadata

Field	Value
Publication number	US-2016259041-A1
Application number	US-201415032592-A
Country	US
Kind code	A1
Filing date	Oct 30, 2014
Priority date	Oct 30, 2013
Publication date	Sep 8, 2016
Grant date	—

Abstract

A method and an apparatus are provided for performing passing sensing using wireless digital communications. The wireless digital communications are frame-based with a predefined frame structure. The method includes receiving a reference signal into to a reference channel, wherein the reference signal comprises a direct version of a radio frequency transmission as part of said wireless digital communications; receiving a surveillance signal into a surveillance channel; detecting and extracting portions of the reference signal corresponding to data transmissions based on said predefined frame structure; extracting portions of the surveillance signal corresponding to the extracted portions of the reference signal; performing a cross-correlation on the extracted portions of the reference signal and the surveillance signal to determine a range-Doppler surface; and providing a real-time display of said range-Doppler surface and/or of information derived therefrom.

First claim

1 . A method of performing passing sensing using wireless digital communications, wherein said wireless digital communications are frame-based with a predefined frame structure, said method comprising:
receiving a reference signal into a reference channel, wherein said reference signal comprises a direct version of a radio frequency transmission as part of said wireless digital communications; receiving a surveillance signal into a surveillance channel; detecting and extracting portions of the reference signal corresponding to data transmissions based on said predefined frame structure; extracting portions of the surveillance signal corresponding to the extracted portions of the reference signal; performing a cross-correlation on the extracted portions of the reference signal and the surveillance signal to determine a range-Doppler surface; and providing a real-time display of said range-Doppler surface and/or of information derived therefrom.

2 . The method of claim 1 , wherein detecting and extracting portions of the reference signal includes detecting locations of a predefined synchronization sequence in the reference signal.

3 . The method of claim 2 , wherein detecting and extracting portions of the reference signal includes using the detected locations of said predefined synchronization sequence in the reference signal to determine portions of the reference signal to extract.

4 . The method of claim 1 , wherein said data transmissions comprise physical layer service data units (PSDUs).

5 . The method of claim 1 , wherein detecting and extracting portions of the reference signal includes:
splitting the reference signal into multiple successive segments of equal length; identifying portions of the reference signal such that data transmissions are present in the same time interval in each segment with respect to the start of that segment; and extracting the identified portions of the reference signals.

6 . The method of claim 5 , further comprising setting a minimum duration for said time interval.

7 . The method of claim 1 , wherein extracting portions of the surveillance signal corresponding to the extracted portions of the reference signal includes identifying portions of the surveillance signal with matching timings to the extracted portions of the reference channel, plus allowing for a predefined maximum time delay between the reference signal and the surveillance signal.

8 . The method of claim 1 , wherein performing a cross-correlation on the extracted portions of the reference signal and the surveillance signal to determine a range-Doppler surface comprises:
a) performing a cross-correlation between each extracted portion of the reference signal and its corresponding extracted portion of the surveillance signal to obtain an n by ν matrix, wherein n represents the number of extracted portions from the reference signal, and ν represents the number of timing delays calculated per cross-correlation, to produce the matrix:

[

p

1
,
1

p

1
,
2

…

p

1
,
v

p

2
,
1

p

2
,
2

…

p

2
,
v

⋮

⋮

⋮

⋮

p

n
,
1

p

n
,
2

…

p

n
,
v

]

where P a,b is the bth sample in the ath correlation with a total of ν sampling points; and
b) performing an Fourier transform operation on each column of the this matrix to obtain the range-Doppler surface.

9 . The method of claim 1 , wherein the wireless digital communications comprise active burst and idle bursts, and said method further comprises identifying and discarding the idle bursts prior to detecting and extracting portions of the reference signal corresponding to data transmissions based on said predefined frame structure.

10 . The method of claim 1 , wherein said wireless digital communications are Wi-Fi communications from a wireless access point.

11 . The method of claim 1 , wherein said wireless digital communications are WiMAX or LTE communications.

12 . A method comprising providing multiple receiver units positioned at different locations, each receiver unit receiving a reference signal into a reference channel and a surveillance signal into a surveillance channel, the method comprising:
for each receiver unit, determining a range-Doppler surface in accordance with the method of claim; and combining information from the multiple range-Doppler surfaces from the respective multiple receiver units to provide an enhanced estimate of position and/or velocity.

13 . A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for passing sensing using wire

Assignees

• Ucl Business Plc

Inventors

• Tan Bo
• Woodbridge Karl
• Chetty Kevin

Classifications

• G01S13/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01S13/0218

  Very long range radars, e.g. surface wave radar, over-the-horizon or ionospheric propagation systems (for meteorological use G01S13/95) · CPC title

• G01S7/42

  Diversity systems specially adapted for radar · CPC title

• G01S7/418

  Theoretical aspects · CPC title

• G01S13/003 Primary

  Bistatic radar systems; Multistatic radar systems · CPC title