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

在本研究中，我们开发了新的传感器网络中的位置估计方法、时间同步方法和节能方法。并对这些方法的有效性和可行性进行了评价。本研究的结果如下：(1)利用ToA位置估计技术的高精度时间同步系统。(2)求解非线性联立方程的位置估计方法。(3)考虑室内屏蔽影响的测量误差减小方法。(4)信标节点选择算法，提高传感器节点位置测量精度。(5)集群间可扩展多跳网络的构建方法。(6)传感器网络拓扑部分重构方法。在(1)的研究中，研究了仅利用传感器节点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，即迭代测量的累积误差问题。在(3)和(4)中，在有多个信标节点可用于估计传感器节点间距离的情况下，我们开发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，我们开发了利用节点位置信息实现高效网络集群的构建方法。在(6)中，我们开发了一种构造方法，在每个节点自由移动的环境下，实现了高效的网络拓扑结构，以节省电力。

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.