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

在本研究中，我们提出了新的位置估计方法、时间同步方法以及传感器网络中的节能方法。并对这些方法的有效性和可行性进行了评估。研究结果如下：(1)利用TOA位置估计技术构建高精度时间同步系统。(2)通过求解非线性联立方程组进行位置估计。(3)考虑室内屏蔽影响的测量误差减小方法。(4)提高传感器节点位置测量精度的信标节点选择算法。(5)簇间可扩展多跳网络的构建方法。(6)传感器网络拓扑的部分重构方法。在(1)的研究中，研究了仅利用传感器节点之间的无线通信同时估计距离和位置的方法。在(2)中，我们提出了一种新的数值处理方法来解决传统测量方法的一个问题，即迭代测量累积误差的问题。在(3)和(4)中，当有多个信标节点可用于估计传感器节点之间的距离时，我们提出了信标节点的选择方法，以提高估计距离的可靠性和准确性。在(5)中，我们提出了一种利用节点的位置信息来构建高效的网络簇的方法。在(6)中，我们提出了一种构建方法，在每个节点自由移动的环境下，实现了一个高效的节电网络拓扑。

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.