Detecting signal modulation for motion detection

• US 9,524,628 B1
• Filed: 08/04/2016
• Issued: 12/20/2016
• Est. Priority Date: 08/04/2016
• Status: Active Grant

• Current Assignee: Cognitive Systems Corp.
• Original Assignee: Cognitive Systems Corp.
• Inventors: Omer, Mohammad, Devison, Stephen Arnold, Griesdorf, Dustin
• Primary Examiner(s): Lee, Siu
• Application Number:
  US15/228,418
• Time in Patent Office: 138 Days
• Field of Search: 375/224, 375/316, 375/340, 375/342
• US Class Current: 1/1
• CPC Class Codes: G08B 13/187 by interference of a radiation field
• CPC Class Codes: G08B 13/2491 Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field
• CPC Class Codes: H04L 25/0222 Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

In a general aspect, motion is detected based on wireless signals. In some aspects, a modulation type of a first signal is identified at a motion detector device. The first signal is based on a wireless signal transmitted through a space by a transmitter device and received by the motion detector device. A demodulator at the motion detector device generates a second signal from the first signal by demodulating the first signal according to the identified modulation type. A modulator at the motion detector device generates a third signal from the second signal by modulating the second signal according to the identified modulation type. A channel response is generated based on the first signal and the third signal. The channel response is used to detect motion of an object in the space.

Claims

1. A motion detection method comprising:

identifying a modulation type of a first signal at a motion detector device, the first signal being based on a wireless signal transmitted through a space by a transmitter device and received by the motion detector device;

by operation of a demodulator at the motion detector device, generating a second signal from the first signal, the second signal being generated by demodulating the first signal according to the identified modulation type;

by operation of a modulator at the motion detector device, generating a third signal from the second signal, the third signal being generated by modulating the second signal according to the identified modulation type;

determining a channel response based on the first signal and the third signal; and

using the channel response to detect motion of an object in the space.

2. The motion detection method of claim 1, comprising:

determining a first set of frequency components from the first signal;

determining a second set of frequency components from the third signal; and

by operation of an adaptive coefficient calculator at the motion detector device, determining the channel response based on the first and second sets of frequency components.

3. The motion detection method of claim 2, comprising:

determining a third set of frequency components by modifying the first set of frequency components; and

determining error values from the first set of frequency components and the third set of frequency components; and

by operation of the adaptive coefficient calculator, determining the channel response based on the error values.

4. The motion detection method of claim 1, comprising:

determining signal-to-noise ratios for frequency components of the first signal;

selecting components of the channel response based on the signal-to-noise ratios; and

using the selected components of the channel response to detect motion of the object in the space.

5. The motion detection method of claim 1, comprising extracting an identifier of the transmitter device from the second signal.

6. The motion detection method of claim 5, wherein the identifier comprises a media access control (MAC) address of the transmitter device.

7. The motion detection method of claim 1, wherein the transmitter device comprises a first transmitter device, the wireless signal comprises a first wireless signal, the channel response comprises a first channel response, and the method comprises:

determining a second channel response based on a second wireless signal, the second wireless signal transmitted through a space by a second transmitter device and received by the motion detector device; and

determining a location of the object based on the first and second channel responses.

8. The motion detection method of claim 1, wherein the wireless signal comprises a radio frequency signal transmitted by a wireless network device, and the first signal comprises a baseband signal produced by a radio subsystem at the motion detector device processing the radio frequency signal.

9. The motion detection method of claim 1, wherein identifying the modulation type comprises identifying a first modulation type from a plurality of distinct modulation types.

10. The motion detection method of claim 9, wherein the plurality of distinct modulation types comprises orthogonal frequency-division multiplexing (OFDM) and direct-sequence spread spectrum (DSSS).

11. The motion detection method of claim 1, wherein the wireless signal comprises a first wireless signal, the channel response comprises a first channel response, and the method comprises:

by operation of the demodulator, generating a fifth signal from a fourth signal, the fourth signal based on a second wireless signal transmitted through the space by the transmitter device and received by the motion detector device, the fifth signal generated by demodulating the fourth signal;

by operation of the modulator, generating a sixth signal from the fifth signal, the sixth signal generated by modulating the fifth signal;

determining a second channel response based on the fourth signal and the sixth signal; and

detecting motion of the object in the space based on comparing the first and second channel responses.

12. The motion detection method of claim 1, wherein the wireless signal comprises a header and a payload, and the modulation type is detected based on information in the header.

13. A device comprising:

a modulation detector configured to identify a modulation type of a first signal, the first signal based on a wireless signal transmitted through a space by a transmitter device;

a demodulator configured to receive the first signal and generate a second signal from the first signal, the second signal generated by demodulating the first signal according to the identified modulation type;

a modulator configured to receive the second signal and generate a third signal from the second signal, the third signal generated by modulating the second signal according to the identified modulation type;

processor circuitry configured to receive the first signal and the third signal and to;

determine a channel response based on the first signal and the third signal; and

detect motion of an object in the space based on the channel response.

14. The device of claim 13, wherein the processor circuitry comprises:

a first filter bank configured to determine a first set of frequency components from the first signal;

a second filter bank configured to determine a second set of frequency components from the third signal.

15. The device of claim 14, wherein the processor circuitry comprises:

tunable filters configured to determine a third set of frequency components by modifying the second set of frequency components;

error detectors configured to determine error values from the first set of frequency components and the third set of frequency components; and

an adaptive coefficient calculator configured to determine the channel response based on the error values.

16. The device of claim 13, wherein the processor circuitry is configured to:

determine signal-to-noise ratios for frequency components of the first signal;

select components of the channel response based on the signal-to-noise ratios; and

use the selected components of the channel response to detect motion of the object in the space.

17. The device of claim 13, wherein the demodulator is configured to extract a media access control (MAC) address of the transmitter device.

18. The device of claim 13, wherein the transmitter device comprises a first transmitter device, the wireless signal comprises a first wireless signal, the channel response comprises a first channel response, and the processor circuitry is configured to:

determine a second channel response based on a second wireless signal, the second wireless signal transmitted through a space by a second transmitter device; and

determine a location of the object based on the first and second channel responses.

19. The device of claim 13, further comprising a radio subsystem, wherein the wireless signal comprises a radio frequency signal transmitted by a wireless network device, and the first signal comprises a baseband signal produced by the radio subsystem processing the radio frequency signal.

20. The device of claim 13, wherein identifying the modulation type comprises identifying a first modulation type from a plurality of distinct modulation types, the plurality of distinct modulation types comprising orthogonal frequency-division multiplexing (OFDM) and direct-sequence spread spectrum (DSSS).

21. The device of claim 13, wherein the wireless signal comprises a first wireless signal, the channel response comprises a first channel response, and the processor circuitry is configured to detect motion of the object in the space based on comparing the first channel response and a second channel response, the second channel response based on a second wireless signal transmitted through the space by the transmitter device.

22. A system comprising a motion detector device, the motion detector device comprising:

a radio subsystem configured to receive wireless signals transmitted through a space by a transmitter device, and to generate respective baseband signals based on the received wireless signals; and

a processor subsystem communicably coupled to the radio subsystem and configured to perform operations comprising;

detecting a modulation type of the baseband signals;

generating demodulated signals by demodulating the respective baseband signals according to the identified modulation type;

generating re-modulated signals by modulating the respective demodulated signals according to the identified modulation type;

determining channel responses based on the baseband signals and the re-modulated signals, each channel response based on a respective one of the baseband signals and a corresponding one of the re-modulated signals; and

using the channel responses to detect motion of an object in the space.

23. The system of claim 22, wherein the received wireless signals are based on respective wireless transmissions by the transmitter device, and the motion is detected based on comparing the channel responses associated with wireless transmissions transmitted by the transmitter device at distinct times.

24. The system of claim 22, wherein identifying the modulation type comprises identifying a first modulation type from a plurality of distinct modulation types, the plurality of distinct modulation types comprising orthogonal frequency-division multiplexing (OFDM) and direct-sequence spread spectrum (DSSS).

25. The system of claim 22, wherein the processor subsystem comprises a demodulator configured to generate the demodulated signals and a modulator configured to generate the re-modulated signals.

26. The system of claim 22, further comprising the transmitter device, wherein the transmitter device comprises a wireless access point.