Using MIMO training fields for motion detection
In a general aspect, various fields of a PHY frame are used for motion detection. In some aspects, a first training field and a second, different training field are identified in a PHY frame of each wireless signal transmitted between wireless communication devices in a wireless communication network. A first time-domain channel estimate and a second time-domain channel estimate are generated for each wireless signal. The first time-domain channel estimate is based on a first frequency-domain signal included in the first training field, while the second time-domain channel estimate is based on a second frequency-domain signal included in the second training field. A determination is made whether motion has occurred in a space during the time period based on the first time-domain channel estimates, and a location of the motion within the space is determined based on the second time-domain channel estimates.
1. A method, comprising:
receiving wireless signals transmitted through a space over a time period, wherein the wireless signals are transmitted between wireless communication devices in a wireless communication network and are formatted according to a wireless communication standard;
identifying a first training field and a second, different training field in an orthogonal frequency-division multiplexing (OFDM)-based PHY frame of each wireless signal;
generating, for each wireless signal:
a first time-domain channel estimate based on a first frequency-domain signal included in the first training field of the wireless signal; and
a second time-domain channel estimate based on a second frequency-domain signal included in the second training field of the wireless signal, wherein a temporal resolution of the first time-domain channel estimate is lower than a temporal resolution of the second time-domain channel estimate;
determining whether motion has occurred in the space during the time period based on the first time-domain channel estimates; and
determining a location of the motion within the space based on the second time-domain channel estimates.
2. The method of claim 1 , wherein a frequency resolution of the first frequency-domain signal is lower than a frequency resolution of the second frequency-domain signal.
3. The method of claim 1 , wherein the first training field includes a legacy training field of the OFDM-based PHY frame, and the second training field includes a multiple-input-multiple-output (MIMO) training field of the OFDM-based PHY frame.
4. The method of claim 3 , wherein the MIMO training field includes a high-efficiency long training field (HE-LTF).
5. The method of claim 3 , wherein the MIMO training field includes a very high throughput long training field (VHT-LTF).
6. The method of claim 3 , wherein the MIMO training field includes a high throughput long training field (HT-LTF).
7. The method of claim 1 , wherein the wireless communication standard is an IEEE 802.11 standard.
8. The method of claim 1 , wherein the wireless communication network is a wireless local area network (WLAN).
9. The method of claim 1 , wherein determining the location of the motion within the space comprises determining a direction of the motion within the space based on the second time-domain channel estimates.
10. A non-transitory computer-readable medium comprising instructions that are operable, when executed by data processing apparatus, to perform operations comprising:
receiving wireless signals transmitted through a space over a time period, wherein the wireless signals are transmitted between wireless communication devices in a wireless communication network and are formatted according to a wireless communication standard;
identifying a first training field and a second, different training field in an orthogonal frequency-division multiplexing (OFDM)-based PHY frame of each wireless signal;
generating, for each wireless signal:
a first time-domain channel estimate based on a first frequency-domain signal included in the first training field of the wireless signal; and
a second time-domain channel estimate based on a second frequency-domain signal included in the second training field of the wireless signal, wherein a temporal resolution of the first time-domain channel estimate is lower than a temporal resolution of the second time-domain channel estimate;
determining whether motion has occurred in the space during the time period based on the first time-domain channel estimates; and
determining a location of the motion within the space based on the second time-domain channel estimates.
11. The non-transitory computer-readable medium of claim 10 , wherein determining the location of the motion within the space comprises determining a direction of the motion within the space based on the second time-domain channel estimates.
12. The non-transitory computer-readable medium of claim 10 , wherein a frequency resolution of the first frequency-domain signal is lower than a frequency resolution of the second frequency-domain signal.
13. The non-transitory computer-readable medium of claim 10 , wherein the first training field includes a legacy training field of the OFDM-based PHY frame, and the second training field includes a multiple-input-multiple-output (MIMO) training field of the OFDM-based PHY frame.
14. The non-transitory computer-readable medium of claim 13 , wherein the MIMO training field includes a high-efficiency long training field (HE-LTF).
15. The non-transitory computer-readable medium of claim 13 , wherein the MIMO training field includes a very high throughput long training field (VHT-LTF).
16. The non-transitory computer-readable medium of claim 13 , wherein the MIMO training field includes a high throughput long training field (HT-LTF).
17. The non-transitory computer-readable medium of claim 10 , wherein the wireless communication standard is the IEEE 802.11 standard.
18. The non-transitory computer-readable medium of claim 10 , wherein the wireless communication network is a wireless local area network (WLAN).
19. A system comprising:
a plurality of wireless communication devices in a wireless communication network, the plurality of wireless communication devices configured to transmit wireless signals, formatted according to a wireless communication standard, through a space over a time period;
a computer device comprising one or more processors operable to perform operations comprising:
identifying a first training field and a second, different training field in an orthogonal frequency-division multiplexing (OFDM)-based PHY frame of each wireless signal;
generating, for each wireless signal:
a first time-domain channel estimate based on a first frequency-domain signal included in the first training field of the wireless signal; and
a second time-domain channel estimate based on a second frequency-domain signal included in the second training field of the wireless signal, wherein a temporal resolution of the first time-domain channel estimate is lower than a temporal resolution of the second time-domain channel estimate;
determining whether motion has occurred in the space during the time period based on the first time-domain channel estimates; and
determining a location of the motion within the space based on the second time-domain channel estimates.
20. The system of claim 19 , wherein a frequency resolution of the first frequency-domain signal is lower than a frequency resolution of the second frequency-domain signal.
21. The system of claim 19 , wherein the first training field includes a legacy training field of the OFDM-based PHY frame, and the second training field includes a multiple-input-multiple-output (MIMO) training field of the OFDM-based PHY frame.
22. The system of claim 21 , wherein the MIMO training field includes a high-efficiency long training field (HE-LTF).
23. The system of claim 21 , wherein the MIMO training field includes a very high throughput long training field (VHT-LTF).
24. The system of claim 21 , wherein the MIMO training field includes a high throughput long training field (HT-LTF).
25. The system of claim 19 , wherein the wireless communication standard is the IEEE 802.11 standard.
26. The system of claim 19 , wherein the wireless communication network is a wireless local area network (WLAN).
27. The system of claim 19 , wherein determining the location of the motion within the space comprises determining a direction of the motion within the space based on the second time-domain channel estimates.
28. The system of claim 19 , wherein the computer device is one of the wireless communication devices.