Energy Stimulated Time Synchronization for Energy Harvesting Wireless Networks

In this work, we develop a new energy-preserving time synchronization method, called the energy stimulated time sync (ESTS), for ultra-low-power wireless networks with energy harvesting capabilities. Compared with existing methods, ESTS does not rely on timestamp exchange but uses short energy tones to synchronize the nodes within the receiving range. ESTS is a centralized synchronization method based on a fully-passive wake-up radio (WuR) circuit, which can provide a variety of synchronization accuracy to meet different application requirements while consuming much lower energy than timestamp-based synchronization methods. We have implemented ESTS on Microchip ATmega256RFR2 system-on-chip (SoC). According to experiment results, ESTS can achieve an average of 5 ms and 70 $\mu$ s time precision for rough synchronization and fine synchronization, respectively. Moreover, the fully-passive WuR circuit consumes zero energy in the idle status. In the entire synchronization process, the rough synchronization only needs to be performed once, and the node consumes as low as 4 $\mu$ J of energy for each fine synchronization, making ESTS a promising solution for ultra-low-power wireless networks.