LF-WD: Device-Free Walking Direction Estimation with Low-Frequency CSI Acquisition

Most channel state information (CSI)-based moving target localization and tracking techniques use CSI acquisition at over 100 Hz, which may result in degradation of the communication capability. To address this, this study proposes a devicefree walking-direction estimation method using low-frequency CSI acquisition at approximately 10 Hz. The key enabling idea is to utilize the relationship between the standard deviation of the CSI and length of the reflected path. In detail, we prove that the inversely proportional relationship between them. The experimental evaluation revealed that the accuracy of the binary classification of the walking direction, i.e., approaching or receding, was 81.3%.