Research Of Time Synchronization Algorithms For Underground Based On Wireless Sensor Network

China has abundant coal resources, and it is an important industry for the developmentof the national economy. With the rapidly development of Wireless Communication, Micro-Electro-Mechanical System and Sensor Technology, the wireless sensor networks as a newcomputing mode will be widely used in various industries. The application of WirelessSensor Networks will have a far-reaching impact to the widely distributed special situationof coal mine in China.As a part of safety monitoring system for underground, time synchronization solve theproblem which the GPS and other basic time service signals cannot provide time informationfor underground environment, and provide an important guarantee for the safety of personneland resources. The traditional time synchronization algorithm can achieve high precisionsynchronization during short period, but the synchronization error will be accumulated withthe increasing of the hop distance,at the same time,the energy consumption will also beserious, which is not suitable for the special application in underground.Therefore, based onthe analysis and research of wireless sensor network, and the underground environment andtime synchronization algorithm, a direction of this paper has been proposed. The newdirection is focus on time synchronization algorithms for underground which is emphasizeon research and implementation based on WSN.First of all, this paper in the view of the phenomenon which the traditional time-syncalgorithm for two-way exchange data packets to achieve high synchronization accuracy willlead to excessive consumption, combined with the special structure of the coal mineenvironment, based on the analysis of bidirectional pair and one-way broadcastsynchronization mechanism, make use of transmission characteristics of radio effectively,a new synchronization algorithm based on cluster structure which is proposed. Experimentshow that the algorithm can solve the problem of the large energy consumption.Secondly, aiming to the characteristics of the high precision, strong robustness and low fault-tolerance for the traditional time synchronization algorithm. Put forward a fault-tolerance wireless sensor network time synchronization algorithm for underground. Throughusing of time reference node election dynamic and avoid sending packets repeat to enhancesnetwork scalability according to analysis of FTSP algorithm. According to the dynamicchanges and half duplex of communication channel, the new algorithm introduced theresidual analysis theory of probability and statistics which to improve the linear regressionalgorithm and judges to the errors so as to enhance the fault tolerance of wireless sensornetwork synchronization algorithm.Improve the stability of the synchronous networkthrough compensating the errors which caused by clock drift and offset in the nodes.Finally, the time synchronization algorithm has been implemented in our testbed, whichis composed of11GainZ nodes through TinyOS.Experimental show that the proposed wireless sensor network time synchronizationalgorithm for underground can use low energy consumption to achieve the synchronizationaccuracy and convergence speed is similar to the traditional algorithm, and the strongrobustness is suitable for large scale of wireless sensor networks for underground.