On the Multihop Performance of Synchronization Mechanisms in High Propagation Delay Networks

We analyze the single and multihop performance of time synchronization mechanisms for challenging environments characterized by high propagation delays, low duty-cycle operation, and imprecise clocks, such as underwater acoustic sensor networks. We find that receiver-receiver-based schemes are unsuitable for such environments, and therefore focus primarily on sender-receiver schemes. According to our analysis, a one-way dissemination approach provides good clock skew estimation but poor offset estimation while a two-way exchange approach provides accurate offset estimation but imprecise clock skew estimation. In average, using one-way scheme can result in significant cumulative propagation error over multiple hops, and using two-way can lead to high variance of propagation error. We develop and analyze a hybrid one-way dissemination/two-way exchange technique, and verify the performance of our hybrid scheme through trace-based experiments. The results suggest that this hybrid approach can provide bounded average error propagation in multihop settings and significantly lower variance of propagation error.