The Research Of Range-free Localization Algorithm In Wireless Sensor Network

With the development of the human detection field, the development and application of information technology has been gradually applied to every aspect of social production and living, then integrates a variety of cutting-edge technology of wireless sensor network (WSN) arises at the historic moment.Wireless sensor network (WSN) is a self-organized wireless network which is composed of a series of sensor nodes with wireless communication ability, has been becoming the current hot research area of concern.In wireless sensor network management technology, including the time synchronization technology, positioning technology, security technology and data management technology, and the positioning technology is the basis of the wireless sensor network (WSN) other relevant technology.This is because in the wireless sensor network (WSN), the detection area randomly deployed a large number of sensor nodes, the role of these sensor nodes is to timely detection area of the object detection, learn and collect the related information need be checked, and sent to workers in order to analyze.In the process of testing information, and tested the physical geographical location, has an important influence on information collection, if the geographic information of test object don’t know, then the test data, there is no any meaning. If Want to get meaningful data, will know testing object location, you must also use node localization of wireless sensor network (WSN) to get to know the corresponding location information. Therefore, the positioning technology in the application of sensor networks play a crucial role.The node localization algorithm in WSN location technology according to the different classification basis, can have a variety of categories. And the current main classification is the basis whether need to know the distance between nodes to estimate the distance or Angle, according to the feature of this algorithm can be divided into based on distance and based on the range.For the problems in wireless sensor network node location technology, many researchers carried on the thorough research. In the actual environment, the energy consumption of the sensor nodes are often limited, and its reliability is not good, at the same time, the distribution of sensor nodes is random and network of larger scale, plus node communications limited, these problems ultimately increased the node positioning error,so many improved node localization method are put forward. In these algorithms, mostly around the range-free and the distance measuring the two types of localization algorithm to improve the error of the problems. Positioning algorithm based on distance measuring RSSI, TO A, TDOA, etc, this kind of algorithm of node localization accuracy requirement is very high, is mainly used in the application of more strict with error. And on the basis of the range-free localization algorithm, such as DV-HOP, Centroid, Amorphous and so on, this kind of locating method of positioning error is relaxed, low hardware requirements. Although the positioning precision of positioning algorithm based on the range-free below the positioning algorithm based on distance, but in some application scenarios, positioning algorithm based on distance measurement is affected by various factors (such as energy consumption, network bandwidth, software and hardware overhead) restrictions to achieve, in comparison, on the basis of the range-free algorithm can be more easy to implement, so the study of the ranging based algorithm to the attention of the many experts and scholars. And this article is aimed at non ranging localization algorithm for research.Article began briefly describes the background of wireless sensor network related knowledge, then explaining the terminology, classification algorithm and the calculation method of coordinates in the wireless sensor network (WSN), and then to the classical theory of DV-HOP positioning method of thought has made the further thorough analysis, shows the existing problems of algorithm and the theory analysis, points out the factors affected the accuracy of DV-HOP localization algorithm:the average hop distance of node, hop count between nodes, the calculation method of coordinates, energy consumption of sensors and node deployment and so on. Starting from these factors, in order to improve precision of the algorithm for the purpose.analysis and improve a more effective DV-HOP localization algorithm, namely PEDV-HOP localization algorithm. The algorithm for the classical algorithm of error factors, have three improvements:1. According to the calculation method of the average of every hop distance in DV-HOP localization algorithm, optimize the average jump error so that make the distance between nodes closer to the real value. First unknown node receives the average jump error of beacon nodes which within the scope, and then modify hop distance by average hop distance error.Finally pick up the average value of the average every hop distance of all the beacon nodes as the per hop distance of unknown node.2. In view of the calculation method of node coordinates in localization algorithm, the unknown node coordinate calculation method was improved, make deformation for the existing formula,the distance formula of beacon node which nearest the unknown node respectively divided by other distance formula, In order to improve the positioning accuracy, joined the weighted least squares method in the formula.3. Updated the coordinates of the unknown node optimization.Finally we use matlab to simulation experiment, the DV-HOP algorithm and another two algorithm were compared with PEDV-HOP algorithm, the simulation results show that the PEDV-HOP localization algorithm in positioning accuracy and positioning error of the average more than another localization algorithm.