Deep Inspection of the Noise in WiFi Time-of-Flight Echo Techniques

Time-of-flight (ToF) echo techniques have been proposed to estimate the distance between a local and a target station using regular WiFi radio devices. As of today, there is little understanding of the noise sources from ToF measurements. We conduct extensive experimental tests based on a customized WiFi echo technique implementation residing in the core of the 802.11 MAC processor and a high-resolution signal analysis of the WiFi traffic captured with a wideband oscilloscope. We discern the root of the error components in WiFi echo technique measurements and statistically characterize the offset noise added by the target station. Our measurements provide key insights to model the sources of noise and guidance for the design of robust distance estimators.