Proposal of generalized vernier effect and its practical advantage for RF time-of-flight ranging between sensor nodes in wireless sensor networks

Accurate ranging technique is indispensable for node localization in wireless sensor networks (WSNs), and there are various ranging techniques/systems using physical characteristics of RF signals. The RF time-of-flight (ToF) ranging technique in a short distance is still difficult to implement since both a high precision clock system and complex signal processing are required to exactly measure RF ToF. This paper presents an improvement of time resolution based on the generalized vernier effect (GVE) by which it is possible to accurately measure short-range RF ToF using low operating clocks of several megahertz. The GVE-based RF ToF measurement methodology is certified through experiments to measure a singular sensing pattern with respect to RF round-trip time using a prototype of the synch-free RF ToF measurement system, which is a practical RF ToF ranging system for application to the localization of WSNs.