METHOD AN APPARATUS FOR TRACKING MOTION USING RADIO FREQUENCY SIGNALS

• US 20170090026A1
• Filed: 05/04/2015
• Published: 03/30/2017
• Est. Priority Date: 05/02/2014
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Joshi, Kiran, Kotaru, Manikanta, Bharadia, Dinesh, Katti, Sachin
• Granted Patent: US 11,209,536 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 13/538 eliminating objects that have not moved between successive antenna scans, e.g. area MTi
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar

Abstract

Techniques for a motion tracing device using radio frequency signals are presented. The motion tracing device utilizes radio frequency signals, such as WiFi to identify moving objects and trace their motion. Methods and apparatus are defined that can measure multiple WiFi backscatter signals and identify the backscatter signals that correspond to moving objects. In addition, motion of a plurality of moving objects can be detected and traced for a predefined duration of time.

Claims

1. A method for detecting motion in an environment, comprising:

transmitting a radio frequency signal;

receiving a composite signal comprising a plurality of backscatter signals, wherein the plurality of the backscatter signals correspond to a reflection of the radio frequency signal from one or more objects in the environment, wherein the one or more objects comprise at least one moving object and one or more static objects; and

detecting the at least one moving object in accordance with the composite signal.

2. The method of claim 1, wherein detecting the at least one moving object comprises:

estimating one or more parameters corresponding to a plurality of backscatter signals corresponding to the at least one moving object, the one or more parameters being estimated by progressively removing one or more backscatter signals corresponding to the one or more static objects from the composite signal.

3. The method of claim 2, wherein the one or more parameters are estimated for a plurality of time stamps during a first time period, the method further comprising:

generating a plurality of image frames, each corresponding to one of the plurality of time stamps, each image frame having a plurality of pixels, each pixel corresponding to one of the plurality of backscatter signals; and

identifying a plurality of associations between the plurality of pixels in the plurality of image frames.

4. The method of claim 3, further comprising:

identifying a plurality of paths corresponding to the at least one moving object in accordance with the plurality of associations.

5. The method of claim 4, further comprising:

determining one or more motion categories by finding one or more associations between the identified plurality of paths and the at least one moving object; and

determining a number of moving objects corresponding to the number of motion categories.

6. The method of claim 3, wherein the plurality of associations between the plurality of pixels in the plurality of image frames are identified by performing a Hungarian Algorithm.

7. The method of claim 2, wherein the one or more parameters correspond to one or more of an angle of arrival of a backscatter signal at a receiver, attenuation, and delay since the radio frequency signal was transmitted.

8. The method of claim 2, wherein the composite signal comprises a first portion received from a first antenna and a second portion received from a second antenna different from the first antenna, and the one or more parameters corresponding to the plurality of backscatter signals are estimated based at least on a difference between the first portion and second portion of the composite signal.

9. The method of claim 1, further comprising:

transmitting information corresponding to the one or more moving objects to a server; and

receiving estimated location of the one or more moving objects from the server.

10. A method for tracing motion, comprising:

receiving information corresponding to one or more moving objects from one or more devices, wherein the information comprises one or more parameters corresponding to one or more backscatter signals being reflected from the one or more moving objects;

estimating location of at least one of the one or more moving objects in accordance with the received information from the one or more devices.

11. The method of claim 10, further comprising:

identifying a plurality of paths corresponding to the at least one moving object in accordance with the received information.

12. The method of claim 11, further comprising:

determining one or more motion categories by finding one or more associations between the identified plurality of paths and the at least one moving object; and

determining a number of moving objects corresponding to the number of motion categories.

13. The method of claim 11, further comprising:

tracing motion of the at least one moving object in accordance with the identified plurality of paths.

14. The method of claim 10, wherein the one or more parameters comprise one or more of an angle of arrival of a backscatter signal at a device, attenuation of the backscatter signal, and a delay corresponding to the backscatter signal.

15. The method of claim 10, wherein estimating the location comprises:

estimating the location of at least one of the moving objects using extended Kalman filter.

16. An apparatus for detecting motion in an environment, comprising:

a transmitter;

one or more receivers;

a memory; and

at least one processor coupled to the transmitter, the one or more receivers and the memory, the at least one processor configured to;

transmit a radio frequency signal;

receive a composite signal comprising a plurality of backscatter signals, wherein the plurality of the backscatter signals correspond to a reflection of the radio frequency signal from one or more objects in the environment, wherein the one or more objects comprise at least one moving object and one or more static objects; and

detect the at least one moving object in accordance with the composite signal.

17. The apparatus of claim 16, wherein the at least one processor is further configured to:

estimate one or more parameters corresponding to a plurality of backscatter signals corresponding to the at least one moving object, the one or more parameters being estimated by progressively removing one or more backscatter signals corresponding to the one or more static objects from the composite signal.

18. The apparatus of claim 17, wherein the one or more parameters are estimated for a plurality of time stamps during a first time period, the at least one processor is further configured to:

generate a plurality of image frames, each corresponding to one of the plurality of time stamps, each image frame having a plurality of pixels, each pixel corresponding to one of the plurality of backscatter signals; and

identify a plurality of associations between the plurality of pixels in the plurality of image frames.

19. The apparatus of claim 18, wherein the at least one processor is further configured to:

identify a plurality of paths corresponding to the at least one moving object in accordance with the plurality of associations.

20. The apparatus of claim 19, wherein the at least one processor is further configured to:

determine one or more motion categories by finding one or more associations between the identified plurality of paths and the at least one moving object; and

determine a number of moving objects corresponding to the number of motion categories.

21. The apparatus of claim 18, wherein the plurality of associations between the plurality of pixels in the plurality of image frames are identified by performing a Hungarian Algorithm.

22. The apparatus of claim 17, wherein the one or more parameters correspond to one or more of an angle of arrival of a backscatter signal at a receiver, attenuation, and delay since the radio frequency signal was transmitted.

23. The apparatus of claim 17, wherein the composite signal comprises a first portion received from a first antenna and a second portion received from a second antenna different from the first antenna, and the one or more parameters corresponding to the plurality of backscatter signals are estimated based at least on a difference between the first portion and second portion of the composite signal.

24. The apparatus of claim 16, wherein the at least one processor is further configured to:

transmit information corresponding to the one or more moving objects to a server; and

receive estimated location of the one or more moving objects from the server.

25. An apparatus for tracing motion, comprising:

one or more receivers;

a memory; and

at least one processor coupled to the one or more receivers and the memory, the at least one processor configured to;

receive information corresponding to one or more moving objects from one or more devices, wherein the information comprises one or more parameters corresponding to one or more backscatter signals being reflected from the one or more moving objects; and

estimate location of at least one of the one or more moving objects in accordance with the received information from the one or more devices.

26. The apparatus of claim 25, wherein the at least one processor is further configured to:

identify a plurality of paths corresponding to the at least one moving object in accordance with the received information.

27. The apparatus of claim 26, wherein the at least one processor is further configured to:

determine one or more motion categories by finding one or more associations between the identified plurality of paths and the at least one moving object; and

determine a number of moving objects corresponding to the number of motion categories.

28. The apparatus of claim 26, wherein the at least one processor is further configured to:

trace motion of the at least one moving object in accordance with the identified plurality of paths.

29. A non-transitory processor-readable medium for detecting motion in an environment, comprising processor-readable instructions configured to cause one or more processors to:

transmit a radio frequency signal;

receive a composite signal comprising a plurality of backscatter signals, wherein the plurality of the backscatter signals correspond to a reflection of the radio frequency signal from one or more objects in the environment, wherein the one or more objects comprise at least one moving object and one or more static objects; and

detect the at least one moving object in accordance with the composite signal.

30. A non-transitory processor-readable medium for tracing motion in an environment, comprising processor-readable instructions configured to cause one or more processors to:

receive information corresponding to one or more moving objects from one or more devices, wherein the information comprises one or more parameters corresponding to one or more backscatter signals being reflected from the one or more moving objects; and

estimate location of at least one of the one or more moving objects in accordance with the received information from the one or more devices.