Research Of Time Synchronization In Wireless Sensor Network

Wireless sensor networks usually contain a lot of self-organization, distribute multi-hop wireless network nodes. The network nodes have integrated collecting, processing and communication all-in-one, and it is network fast, flexible, free from the constraints of wired networks. A huge surge of interest in this filed has been triggered by large potential in a wide range of applications such as: military surveillance; environmental monitoring; medical sanitation; physiological monitoring and so on. As a new research field, WSN has been highly valued by academic and industrial fields, and has become the research hot spot that attracts a wide attention.Time synchronization is a critical piece of infrastructure for any distributed systems and also is an important support technique of WSN, which is a vital for both design and application. However, the complexity, energy, cost between traditional algorithm such as NTP and GPS and WSN prohibit their use in WSN. Because of the costs, power and size constraints of the individual nodes, the time synchronization that adapt to WSN are needed.The research of this thesis is time synchronization in wireless sensor networks. Firstly, we introduces the wireless sensor network nodes structure and characteristic, and the application in practice; Then, the necessity, fundamental principles, existed challenges, evaluation criterion of the perfonnance and some important in design of time synchronization are particularly described. After studying existing technologies of time synchronization and classifying them, some representative synchronization algorithms are discussed deeply, furthermore, analyzing, evaluating and comparing their advantage and disadvantage. Based on these, this paper integrated the RBS algorithm that has been existed, and improved on the time synchronization in more hop networks. During the RBS algorithms time synchronization in the more hop WSN, the synchronization error introduced by instability of the clock frequency and variable delays of message exchange between pair-wise synchronization nodes; it can reduce the synchronization errors by Bayesian estimation's prior information and posterior distribution based on existing synchronization algorithms. By using the OPNET emulator, the simulation shows that the improving algorithms are better than the original one in the synchronization precision. RBS and BETS algorithm to do detailed study in variety of synchronization application, and BETS algorithm has done in-depth research in security. The time synchronization involves many kinds of factors in wireless sensor network, using the simulate software only can validate algorithm in theory, so should validate algorithm in real hardware situation, the final aim is that use the algorithm in real situation.