Research, Wireless Sensor Network Node Localization Algorithm Based On The Polyhedron Centroid

With the rapid development of embedded computing, wireless communication, distributed information processing and micro electro mechanical system(MEMS), wireless sensors, which have the abilities of perception, process date and wireless communication, and wireless sensor networks have become a growing research field. Because sensor nodes are deployed randomly and densely in the wireless sensor networks area, the precise positions of the sensors may not be known in advance; but to the actual application, it is not useful to know the monitor information of a sensor without position knowledge. Therefore, determining the positions of sensors is a key problem in variety applications to the wireless sensor networks.This paper presents a positioning algorithm for 3-D space. There are a lot of positioning algorithms in wireless sensor network, but most of them assumed that the sensor nodes are deployed in a 2-D plane. First, assuming that there are some anchor nodes in WSN, the positions of which are already known, geometric relationships and communication constraints among the unknown nodes and the anchor nodes are founded based on the assistant three-dimensional coordinates system. Then the constructing method of a curving three-dimensional graph containing an unknown node is persented based on the geometric relationships and communication constraints. The curving 3-D graph is constructed by calculating several profiles and curving planes. It is converted to a plane 3-D graph, which is composed of several profiles, to diminish the communication and computational load of WSN. Sequentially, the centroid of the curving 3-D graph is obtained by calculating the centroid of plane 3-D graph. Finally, the centroid of curving 3-D graph is taken to be the estimated position of the unknown node. The algorithm fetches up the blank of algorithms which are used to position the unknown nodes in a 3-D WSN. The algorithm is range-free, distributed and based exclusively on connectivity. Since the algorithm is very simple and only the communication (needed is) between the anchor nodes and the unknown node needed, the communication and computational loads are very small. A theoretical analysis and simulation results show that it is suitable for all sizes of low-power wireless sensor networks.In addition, the lack of a generally applicable positioning algorithm for WSN motivates us to devise a more efficient one to meet the require of high precision. An optimization positioning algorithm based on GA (Genetic Algorithm) is devised to improve the result of 3-D space position. The nodes' model is set up, and the location problem is simplified into that of solving function extremum. The GA is used to solve the model while the result of 3-D space positioning algorithm is regarded as some parameters of GA, and the solution is regarded as the estimate position of the unknown code. The simulation results show that the position accuracy is improved by this way, and it suits for some special cases in which high precision is required.