High-resolution time of arrival estimation for OFDM-based transceivers

A novel algorithm for time of arrival (TOA) estimation for OFDM-based transceivers is presented. The algorithm processes the sampled baseband signal to obtain a high-resolution estimate of the TOA of the OFDM symbol. In the first step, the algorithm obtains a sample-resolution estimate of the TOA by finding the peak of the absolute value of the cross-correlation of the in-phase and quadrature received signals with the known transmitted symbol. In the second step, the algorithm refines this estimate to sub-sample resolution by estimating the phase delay of the received signal based on the gradient of a linear fit to the phase difference between the transmitted and received sub-carriers (in the frequency domain). The algorithm was applied to the long training sequence (LTS) symbol of the IEEE wireless local area network (WLAN) 802.11 g preamble. In real-world experiments, the algorithm was found to achieve a mean TOA estimation error of 49 cm in a low multi-path line-of-sight environment for ranges of 1–7 m.