Toward Low-Cost Passive Motion Tracking With One Pair of Commodity Wi-Fi Devices

With the popularity of Wi-Fi devices and the development of the Internet of Things (IoT), Wi-Fi-based passive motion tracking has attracted significant attention. Most existing works utilize the Angle of Arrival (AoA), Time of Flight (ToF), and Doppler Frequency Shift (DFS) of the Channel State Information (CSI) to track human motions. However, they usually require multiple pairs of Wi-Fi devices and extensive data training to achieve accurate results, which is unrealistic in practical applications. In this article, we propose Wi -Fi M otion T racking ( WiMT ), a low-cost passive motion tracking system based on a single pair of commodity Wi-Fi devices. WiMT calculates the Doppler velocity and phase difference using the CSI obtained from the transmitter with one antenna and the receiver with three antennas. The Z ero V elocity I dentification and C alibration ( ZVIC ) algorithm is proposed to remove the random noise of Doppler velocity when the target is stationary. We take the Doppler velocity as the measurement and employ a particle filter to estimate the motion trajectory. A particle weight update method based on phase difference information is developed to eliminate particles with low confidence. Experimental results in real indoor environment show that WiMT achieves great performance with a motion tracking median error of 7.28 cm and a nonmoving recognition accuracy of 92.6%.