Poster abstract: Practical limits of WiFi time-of-flight echo techniques

Time-of-flight echo techniques have been proposed to estimate the distance between a local and a target station over regular WiFi radio devices. Their current main shortcoming is that they are affected by severe noise components at both stations. Our aim in this work is to quantify the noise level introduced by the target in order to derive practical limits of the ranging accuracy achievable using off-the-shelf devices. For this purpose, we develop a low-noise experimental platform which allows us to measure the echo-reply delay with very high accuracy. Our preliminary results with two popular chipsets from different manufacturers show that the median echo-reply delay at the target is never equal to the nominal SIFS value, and it deviates by approximately 10-20 ns over time, suggesting a practical ranging accuracy limit of 3 m.