Filtering channel responses for motion detection
In a general aspect, a set of observed frequency-domain channel responses is filtered to remove noise or distortions that are not related to changes in the physical environment. In some aspects, for each frequency-domain channel response, a time-domain channel response is generated based on the frequency-domain channel response; and a filtered time-domain channel response is generated based on a constraint applied to the time-domain channel response. Additionally, a reconstructed frequency-domain channel response is generated based on the filtered time-domain channel response. An error signal is also generated, and a determination is made as to whether the error signal satisfies a criterion. The error signal can be indicative of a difference between the frequency-domain channel response and the reconstructed frequency-domain channel response. In response to each of the error signals satisfying the criterion, motion of an object in a space is detected based on the set of frequency-domain channel responses.
1. A method comprising:
obtaining a frequency-domain channel response based on a wireless signal transmitted through a space, the wireless signal including frequency components in a first channel and in a second channel different from the first channel;
generating a time-domain channel response based on the frequency-domain channel response;
generating a filtered time-domain channel response based on a constraint applied to the time-domain channel response, the constraint being determined by a maximum attenuation the pulse can experience in the space and be received by a receiving wireless communication device;
generating a reconstructed frequency-domain channel response based on the filtered time-domain channel response; and
determining a state of the space based on the reconstructed frequency-domain channel response.
2. The method of claim 1 , wherein the wireless signal is formatted according to a wireless communication standard.
3. The method of claim 2 , wherein the first channel and the second channel are channels according to the wireless communication standard.
4. The method of claim 1 , wherein the wireless signal was transmitted between a first wireless communication device supporting multiple channels and a second wireless communication device supporting multiple channels.
5. The method of claim 4 , wherein the first wireless communication device is a first access point or a first client device, and wherein the second wireless communication device is a second access point or a second client device.
6. The method of claim 4 , wherein supporting multiple channels, by the first wireless communication device, includes supporting:
transmitting wireless signals on a plurality of channels that includes the first channel and the second channel; and
receiving wireless signals on a plurality of channels that includes the first channel and the second channel.
7. The method of claim 1 , wherein the time-domain channel response comprises a plurality of time domain pulses with each time domain pulse comprising an amplitude coefficient and a pulse time.
8. The method of claim 7 , wherein the constraint comprises a constraint on the pulse time of each of the plurality of time domain pulses in the time-domain channel response.
9. The method of claim 7 , wherein the constraint comprises a constraint on the amplitude coefficient of each of the plurality of time domain pulses in the time-domain channel response.
10. The method of claim 1 , wherein the wireless signal comprises an orthogonal frequency division multiplexing (OFDM) signal, and the frequency-domain channel response is based on one or more training fields in a PHY frame of the OFDM signal.
11. The method of claim 1 , wherein obtaining the frequency-domain channel response based on the wireless signal transmitted through the space comprises obtaining a set of frequency-domain channel responses based on a set of wireless signals transmitted through the space, wherein the set of wireless signals includes the wireless signal, the method further comprising:
for each frequency-domain channel response:
generating a respective time-domain channel response based on the respective frequency-domain channel response;
generating a respective filtered time-domain channel response based on a constraint applied to the respective time-domain channel response;
generating a respective reconstructed frequency-domain channel response based on the respective filtered time-domain channel response; and
wherein determining the state of the space based on the reconstructed frequency-domain channel response comprises determining the state of the space based on the respective reconstructed frequency-domain channel responses.
12. A device comprising:
one or more processors;
memory storing instructions that are operable when executed by the one or more processors to perform operations comprising:
obtaining a frequency-domain channel response based on a wireless signal transmitted through a space, the wireless signal including frequency components in a first channel and in a second channel different from the first channel;
generating a time-domain channel response based on the frequency-domain channel response;
generating a filtered time-domain channel response based on a constraint applied to the time-domain channel response, the constraint being determined by a maximum attenuation the pulse can experience in the space and be received by a receiving wireless communication device;
generating a reconstructed frequency-domain channel response based on the filtered time-domain channel response; and
determining a state of the space based on the reconstructed frequency-domain channel response.
13. The device of claim 12 , wherein the wireless signal is formatted according to a wireless communication standard.
14. The device of claim 13 , wherein the first channel and the second channel are channels according to the wireless communication standard.
15. The device of claim 12 , wherein the wireless signal was transmitted between a first wireless communication device supporting multiple channels and a second wireless communication device supporting multiple channels.
16. The device of claim 15 , wherein the first wireless communication device is a first access point or a first client device, and wherein the second wireless communication device is a second access point or a second client device.
17. The device of claim 15 , wherein supporting multiple channels, by the first wireless communication device, includes supporting:
transmitting wireless signals on a plurality of channels that includes the first channel and the second channel; and
receiving wireless signals on a plurality of channels that includes the first channel and the second channel.
18. The device of claim 12 , wherein the time-domain channel response comprises a plurality of time domain pulses with each time domain pulse comprising an amplitude coefficient and a pulse time.
19. The device of claim 18 , wherein the constraint comprises a constraint on the pulse time of each of the plurality of time domain pulses in the time-domain channel response.
20. The device of claim 18 , wherein the constraint comprises a constraint on the amplitude coefficient of each of the plurality of time domain pulses in the time-domain channel response.
21. The device of claim 12 , wherein the wireless signal comprises an orthogonal frequency division multiplexing (OFDM) signal, and the frequency-domain channel response is based on one or more training fields in a PHY frame of the OFDM signal.
22. The device of claim 12 , wherein obtaining the frequency-domain channel response based on the wireless signal transmitted through the space comprises obtaining a set of frequency-domain channel responses based on a set of wireless signals transmitted through the space, wherein the set of wireless signals includes the wireless signal, the operations further comprising:
for each frequency-domain channel response:
generating a respective time-domain channel response based on the respective frequency-domain channel response;
generating a respective filtered time-domain channel response based on a constraint applied to the respective time-domain channel response;
generating a respective reconstructed frequency-domain channel response based on the respective filtered time-domain channel response; and
wherein determining the state of the space based on the reconstructed frequency-domain channel response comprises determining the state of the space based on the respective reconstructed frequency-domain channel responses.