On The Multi-Hop Extension of Energy-Efficient WSN Time Synchronization   Based on Time-Translating Gateways
  We report preliminary results of a simulation study on the multi-hop extension of the recently-proposed energy-efficient wireless sensor network time synchronization scheme based on time-translating gateways. Unlike the single-hop case, in multi-hop time synchronization a sensor node sends measurement data to a head node through gateways which translate the timestamp values of the received measurement data. Through simulations for two-hop time synchronization, we analyze the impact of the addition of a gateway and its translation of timestamp values on the clock frequency and measurement time estimation and thereby demonstrate the feasibility of the multi-hop extension of the energy-efficient WSN time synchronization based on time-translating gateways. 
Qimeng Liao and Kyeong Soo Kim
cs.NI