Generalized vernier effect and its application to precise RF Time-of-Flight measurement for wireless sensor networks

In order to exactly measure time delay of RF signal to travel a short distance, both high precision clock system and complex signal processing is absolutely required. This report proposes a novel methodology based on generalized vernier effect (GVE) to precisely measure RF Time-of-Flight (ToF) for wireless sensor networks (WSNs) without such complicated contraptions to realize the reliable RF ToF estimation. The new methodology adopts two heterogeneous clocks having low operating frequencies around 10MHz so that new virtual time resolution is generated, which is much smaller than the intrinsic time resolution of two clock sources; consequently, it makes it possible for a slow operating clock to accurately measure RF ToF. We certified the validity of the proposed methodology based on GVE through experiments to measure RF ToF using a prototype of the synch-free RF ToF measurement system, which was suggested as a practical system of RF ToF ranging for application to WSNs.