| Sensing technology obtains information by sensors. A Wireless Sensor Network(WSN) is composed of sensors which collaboratively constitute a network system to detect information.The study of WSN applies in military, environment, medical, family and industry and so on. But at the same time, it faces many challenges, such as network technology, signal processing, distributed algorithm and etc. Timing requirements for sensor nodes of different applications of WSN vary.Some systems have high demand on timing precision and only the timing synchronization of every node can collaboratively complete the tasks of accurate perception, information collection and target monitoring in the complex physical environment. These networks make the synchronization technology be crucial to the communication of WSN.The synchronization technology of wired network has gotten a lot of attention. However, they are not suitable for wireless sensor networks.This paper introduces three synchronization principle of WSN timing synchronization technology and matured mechanism of synchronization algorithm, which establishes a good foundation on researching WSN multi-hop timing synchronization technology. Mainly included as following aspects:(1) The timing synchronization mechanism of receiver to receiver has been crucially researched. The typical algorithm—RBS synchronization algorithm should be mastered and the multi-hop regional synchronization status of RBS must be researched deeply. It is discovered that the transmitters only can be the third-party node and they can’t synchronize with receivers in the RBS multi-hop algorithm. Furthermore, the RBS algorithm brings more overhead in the process of operation.(2)Under the multi-hop case against RBS problems, the References Broadcast Ring Synchronization(RBRS) was presented. The algorithm establishes physical ring topology and adopts broadcast packets and least-squares linear regression method for time synchronization of the entire network. The MATLAB software is for simulation and experimental results show that compared with RBS multi-hop algorithm, the RBRS algorithm significantly reduces synchronization overhead and transmitter can be synchronized with receiver.(3)RBRS algorithm, although there are some advantages, but there is not much improvement in synchronization accuracy. Therefore, IRBRS (Improved References Broadcast Ring Synchronization, IRBRS) algorithm is proposed. In order to achieve synchronization, variable cycle synchronization method and the least squares linear regression is added to implement small and medium multi-hop network time synchronization. The simulation follows the RBRS algorithm simulation environment, and the experimental results show that IRBRS algorithm further reduces synchronization overhead and energy consumption, while simultaneously significantly improved accuracy.(4)In the network system hardware design process, firstly, network hardware model was set up and network node was emphasized. According to the requirements of network system, TMS320F2812 was chosen to work as the CPU of node while nRF24L01 worked as wireless chip of transmitter-receiver module. Furthermore, F2812 minimum system and network nodes were designed. In the network system, network nodes are responsible for sending and receiving the debugging of network node beacon group in single area. The experimental results show that compared with RBRS and RBS arithmetic, IRBRS has better clock correction precision of the network node in accordance with analysis result and simulation result, which achieved good results. In terms of software design, F2812D control process and the notes’ process of sending and receiving were designed. And On the basis of the system, debugging and testing were executed.However, due to the conditions and time limit, the multiple hops RBS timing synchronization algorithm only be researched to this step. Multifarious topological structure, limited node energy and storage resource and so on can be further considered and explored in the future. |
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