Orthogonal frequency division multiplexing-based time difference of arrival estimation

This study presents a spectral approach to estimate the time difference of arrival (TDOA) between a reference unit, composed of a pair of very close antennas (small baseline regarding the operating bandwidth), acting as a known fixed location transmitter, and a mobile unit acting as a single antenna receiver. It uses the channel frequency response (CFR) based on an orthogonal frequency division multiplexing multicarrier communications in a multiple-input-single-output antenna configuration. By handling the CFR responses, seen as wideband interferometric signals, the authors minimise a cost function expressed as the difference between measured channel response and a predefined direct model. Effects of noise and multipath are evaluated and mitigated by the averaging process. The overall performances of the system are analysed, and the experimental validation is systematically led. In a small-scale indoor environment, it has been shown that the TDOA can be accurately estimated with higher accuracy than the conventional techniques. The proposed method allows, for example, estimating TDOAs of about 2 ns when using a null-to-null bandwidth of 100 MHz. Such an approach, based on existing communication systems, and suitable for the 5G norm, can be useful for several applications needing accurate positioning, without requiring complex dedicated infrastructure.