The Research On Smartfilter-based Wireless Sensor Network Time Synchronization Technology

In recent years, wireless sensor network (WSN) is considered the most developing Information-Internet Network in this century. It is not only to achieve the information communication among objects, but also to lead the intelligent development of network. Therefore, the study on wireless sensor network technology has enormous scientific value.Time synchronization technology provides a unified time standard for WSN in information collection and information exchange process. It is a real-time communication technology based on wireless communication link which includes time information transmission. Because of the restriction on nodes energy consumption, cost price, the high density of nodes etc. in WSN, the provided time synchronization technology has not been compatible in the network. For the research on time synchronization technology, the researchers has proposed some synchronization algorithms which are based on the time synchronization models and has achieved some theory achievement on synchronization precision, synchronization power consumption and synchronization error. But these algorithms are restricted in the practical application of WSN. The research focus in this paper is designing a higher precision, lower power and higher compatibility smart-filter synchronization algorithm which is based on the ZigBee protocol stack of the WSN system and to achieve low power transmission rate.Firstly, in the ZigBee-based WSN, we propose two different time synchronization algorithms for different network application needs, which use filtering method based on synchronization error optimization and is on the basis of different network topologies and network hops. In the single-hop topology network, a Sender-Receiver synchronization algorithm mode which is based on Sender-Receiver synchronization communication is realized, which meets the local synchronization requirements. The algorithm mode is based on communication distance between nodes, the energy amount of node, and use the way that is reducing the exchange amount of synchronization beacon in transmission link. In the multi-hop topology network, it realizes global synchronization needs. The cluster head of nodes is selected based on communication way among link data packet, forming a cluster network which has identify nodes. And then, the cluster heads of the different clusters is logically connected by vertical, and the cluster member nodes implement synchronization algorithm within the cluster by horizontal.Secondly, for the intrinstic time offset in the proposed synchronization algorithm, we correct the time error of synchronization model and the noise jamming of channel, which takes the Kalman filtering principle. Besides, we use linear synchronization error to dynamically track clock offset, which greatly reduces the synchronization error and meets the high accuracy of synchronization requirements. In this paper, we simulate in MATLAB platform, and the filtering principle is tested in three areas: synchronization error, synchronization consumption and synchronization accuracy. The results show good synchronization performance and realize multi-application design of the algorithms.Finally, we give a time synchronization work instance on locating the nodes in WSN. In order to reduce energy consumption, we use protocol time synchronization method in the sleep/wake-up mechanism of the locating nodes to achieve time work in locating system, which provides a instance model for low-power-based WSN design.