Multi-Hop Extensions of Energy-Efficient Wireless Sensor Network Time Synchronization

We present the multi-hop extensions of the recently proposed energy-efficient time synchronization scheme for wireless sensor networks, which is based on the asynchronous source clock frequency recovery and reversed two-way message exchanges. We consider two hierarchical extensions based on packet relaying and time-translating gateways, respectively, and analyze their performance with respect to the number of layers and the delay variations through simulations. The simulation results demonstrate that the time synchronization performance of the packet relaying, which has lower complexity, is close to that of time-translating gateways.