Wireless sensor networks have received a lot of attention recently due to their wide applications, such as target tracking, environment monitoring, and scientific exploration in dangerous environments. It is usually necessary to have a cluster of sensor nodes share a common view of a local clock time, so that all these nodes can coordinate in some important applications, such as time slotted MAC protocols, power-saving protocols with sleep/listen modes, etc. In this paper, we present an accurate time synchronization protocol cluster-based power efficient (CBPE) for sensor networks. Unlike the previous protocols, all nodes aren't synchronized to some reference nodes or sink node, but to a virtual clock. Moreover, thinking about an optimal tradeoff between energy consumption and accuracy. The optimal skew is the minimal depth of a particular spanning tree-of the topology graph induced by respecting the energy budgets. In this protocol, at first a virtual backbone network was established, each cluster-head synchronizes to a virtual clock, which is maintained by two root nodes. In the scheme, the pair of nodes is synchronized to each other using linear least square. At last, linear regression time synchronization is performed in every cluster. The simulation results show that the time synchronization protocol is simple and accurate. It is low power and can be used for wireless sensor network applications.
