Distance Measurement Based on Linear Phase Correlation in WiFi CSI

Abstract

In this paper, we propose a new distance measurement algorithm based on WiFi Channel State Information (CSI). In order to resolve the phase error in traditional commodity WiFi devices, we design a system based on the Universal Software Radio Peripheral (USRP) with GNU Radio to analyze and separate the mixed phase errors. After the calibration of the CSI phase, it is found that the clock divider phase offset (DPO), which is introduced by the random phase offset in the clock, will affect the CSI phase, and a clustering-based method is proposed to remove the effect of DPO. We recover the linear relationships among the subcarriers phase and combine the center subcarrier phase to estimate the distance. In our algorithm, we can complete the distance measurement by using only one frequency band. Experiment results indicate that our algorithm can achieve centimeter-level accuracy in distance measurement.