The Research Of Time Synchronization Algorithms In Wireless Sensor Networks

Wireless Sensor network(WSN),which is made by the convergence of sensor, nested computation, networks and wireless communication technologies, is a novel technology of acquiring and processing information. It is a late-model wireless networks without infrastructures and can be used for testing, sensing, collecting and processing information of monitored objects. As a new research field, WSN provides lots of challengeable projects to the domestic and international scholars.Time synchronization is a critical piece of infrastructure for any distributed systems and also is an important support technique of WSN, applications such as environment monitoring, navigation guidance need the collected data with accurate time information, otherwise the data is not integrated. Besides, the data aggregation, TDMA timing, synchronization of period sleeping of WSN all need global clock synchronization. For most applications, the requirement of accuracy is not high and the nodes in WSN are extraordinarily limited in resource, designing energy efficient synchronization algorithm under the request of time accuracy is the emphasis of this paper.By summarizing the application background of WSN time synchronization, the algorithms which have been already proposed are analyzed and compared .In order to reduce the overall energy dissipated in the network, an event-triggered time synchronization algorithm is presented. This algorithm is composed of two phases: calculations of frequency skews and clock synchronization. In this algorithm, nodes'clocks run by their own rates, when an event occurs, firstly, each related node calculates the clock crystal frequency skew by linear regression, then estimates round-trip delay and synchronization difference by exchanging synchronization signals. The simulation results indicate that the algorithm can save energy efficiently and prolong the life of networks if the event occurs in low frequency.