| Summary: | Time synchronization is becoming a general requirement for wireless sensor networks to wake up sensor nodes and achieve successful communications among the nodes. It is, however, challenging for multi-hop sensor networks to synchronize all the distributed nodes autonomously with minimum power consumption. This paper proposes a low power time synchronization protocol called density table-based synchronization (DTSync). It selects a minimal sequence of synchronization steps by estimating the density of the neighboring nodes and mapping these nodes in a density table. The proposed protocol attempts to minimize the power consumption by reducing the number of messages exchanged among the nodes. We evaluate the proposed protocol using software simulation and then real wireless networks with sensor hardware. Compared with a prior method, such as hierarchy reference broadcast synchronization (HRTS), DTSync achieves substantially fewer synchronization messages and thus lower power consumption. In addition, DTSync is guaranteed to synchronize all nodes in any multi-hop networks, whereas the previous methods are not guaranteed to synchronize all nodes. Simulation experiments demonstrate that DTSync reduces the number of synchronization messages by more than 40 times compared with HRTS for a large network of 1500 node.
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