TDOA Estimation of a Single Wi-Fi Access Point Based on CSI

Abstract

Single access point (Access Point, AP) positioning can significantly improve the availability and signal coverage of Wi-Fi positioning. Time difference of arrival (TDOA) is an available positioning signal for single access point positioning. This paper proposes an arrival (TDOA) estimation algorithm of a single Wi-Fi access point based on channel state information (CSI). The algorithm first constructs a spatial spectrum estimation model through the phase shift introduced by each subcarrier of each antenna of a single access point, then use the smoothing algorithm to get a smooth CSI matrix. TDOA does not directly utilize the signal arrival time, compared with TOA, there is no need to maintain accurate clock synchronization, and the accuracy of delay estimation is relatively improved. Experiments verify that TDOA estimates have reached sub-nanosecond error accuracy.