The Research Of Time-synchronization In Wireless Sensor Networks

As the rapid development of wireless communication technology, sensor technology, embedded computing technology, integrated circuit technology, emerges a new information acquisition and processing technology-WSN:wireless sensor network. WSN is a data-centric, wireless communication, self-organized network which is composed of a large number of sensor nodes. It set data acquisition, data process and communication as one, has low-price, quickly network, flexible, low-consumption and has broad application prospects in defense of military, industrial control, environmental monitoring, health care, home appliances and other areas. WSN as a new application area has become one of the research focus and arouses many countries'academic and industry highly attention at international.Time-synchronization is very important for most net application, especially in WSN; it is one of support technologies of WSN. Because of the frequency deviation, temperature changes and electromagnetic interference, their time will gradually deviate in WSN, but the distributed systems, such as environmental monitoring, target tracking, sleep together and so on need time-synchronization between nodes. Time synchronization mechanism has very important significance in wireless sensor networks.This article start with time-synchronization focuses in wireless sensor. First reviews the structure of WSN nodes, network architecture, protocol stack structure and the characteristics, application prospects, and then analyzed the importance of time-synchronization, main constraints and major source of time-synchronization error, followed by classified various existing technologies and deeply study some representative algorithm, puts them analyzed and compared.This article proposed one cluster first and then synchronize time-synchronization algorithm which based on TPSN synchronization algorithm. The improved time-synchronization mechanism first cluster and divided network nodes into cluster-head nodes and general nodes which is similar with TPSN algorithm. We designated coordinator cluster the net independently based on the advantages of energy, while also considered the case of new node join and leave. In the synchronization phase, the node to be synchronized calculated and stored the clock deviation ratio with the reference node in synchronization process. At the other time of instantaneous time, the node to be synchronized calculates accurate time use the stored ratio, and it eliminates the impact of the frequency offset in time-synchronization, improves synchronization accuracy. In order to verify the superiority of the improved algorithm, we use Jennic's JN5139-ZigBee module built a simple experimental platform, and run the improved algorithm and the not on the platform. Experimental results show that the new synchronization algorithm has higher synchronization accuracy, and less demand for information transmission, which can effectively save energy.