A Time Synchronization Circuit with an Average 4.6 ns One-Hop Skew for Wired Wearable Networks

This paper describes and evaluates a fully digital circuit for one-way master-to-slave highly precise time synchronization in a low-power, wearable system equipped with a set of sensor nodes connected in a mesh network. Sensors are connected to each other with conductive yarns that are used as one-wire bidirectional communication links. The circuit is designed to perform synchronization in the Medium Access Control (MAC) layer. In each sensor node, the synchronization circuit provides a synchronized, programmable clock signal and a real-time counter for time stamping. Experimental results obtained with an implementation in 0.35 μm CMOS technology for a network of electromyography sensors show that the circuit keeps the one-hop average clock skew below 4.6 ns, a value small enough to satisfy many wearable application requirements.