Studies on Location Estimation Methods Based on Time Synchronization in Sencor Networks

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In this research, we have developed new location estimation method, time synchronization method, and power saving method in the sensor network. Also we have evaluated the effectiveness and feasibility of these methods. The results in this research as follows.(1) Highly accurate time synchronization system by utilizing ToA location estimation technology.(2) Location estimation method by solving nonlinear simultaneous equations.(3) Measurement error reduction method for considering the influence of shield in room.(4) Selection algorithm of beacon node to improve measurement accuracy of location of sensor node.(5) Construction method of scalable multi hop network between clusters.(6) Partial reconstruction method of sensor network topology.In the research of (1), the method to estimate the distance and location at the same time by using only the wireless communication between sensor nodes was studied. In (2), we proposed a new numerical processing method to resolve one of the problems of conventional measurement methods, namely the problem of cumulative errors by iterative measurements. In (3) and (4), in the case when there are many beacon nodes which can be used for estimating the distance between sensor nodes, we developed the selection method of beacon nodes to improve the reliability and accuracy of estimated distance. In (5), we developed the construction method which achieves an efficient network cluster by using the location information of the node. In (6), we developed the construction method which achieves an efficient network topology for the power saving under the environment which each node moves freely.