Time synchronization plays an important role in wireless sensor networks (WSNs). Due to the unique features of WSNs such as remote deployment, low-cost hardware, and restrictive energy supply, accurate and robust time synchronization is still a challenging task. Many approaches have been proposed to improve the performance and efficiency of time synchronization. Existing schemes, however, do not pay enough attention to the impacts of varying network topology properties, including network diameter, degree distribution, and the like. They can experience unexpected performance degradation in many real systems. To address these issues, we present a novel approach, which tries to improve the performance of existing time synchronization algorithms by introducing a virtual overlay. We propose an integrated model, called topo-refiner, which encodes the impact of different network topology features to the precision and robustness of time synchronization. Also, we design a novel optimization algorithm to build a virtual overlay from the underlying communication network. Our approach is orthogonal to existing clock synchronization methods, and can improve their performance by operating these methods atop the virtual layer. Finally, in order to verify the effectiveness of our approach, we conduct extensive simulations on synthetic and real system traces, as well as testbed experiments. Results show that topo-refiner is practical, and quickly adapts to varying time synchronization accuracy requirements for applications in WSNs.
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