Research On Key Technologies In Wireless Sensor Network Range-based Localization

Wireless sensor network (WSN) is becoming a new approach of information collection. It is widely applied in the military, the medical treatment, the environmental monitoring and so on. Since the data collection, object tracking and mesh topology managing are significant only when the positions of corresponding sensor nodes have been identified, therefore, as one of the core technologies, the nodes locating plays a pivotal role in the WSN application.In the beginning of this paper, some problems in the present localization are described. Then the advantages and disadvantages of various range-based algorithms are analysed, and the conclusion shows that RSSI (Receive Single Strength Indicator) is more adapt to the low-cost and low-power wireless sensor field than others because of its low hardware requirements. Finally, some experiments were done with MICAz nodes which are provided by Crossbow. The conclusion of the experiments is that RSSI change when the angle of the antenna change, and we get the rule. To get high precision of distance with radio irregularity in WSN, a muti-node localization method based on RSSI is brought up. According the positions of some special achor nodes, we acquire the position approximately, predict the angle of each antenna , then process the RSSI based on the angle, calculate distances for each pairs of nodes, and use the positions of anchor nodes to predict the position of the node precisely. And get more accurate angles.Becouse RSSI value is instable,the distance based on RSSI value is not accurate.To get precise position when distances is not accurate,we have analyzed Maximum Likelihood Estimation method,then transplant MDS (multidimensional scaling) to location in WSN .The MDS method not only use the unaccurate distances between the achor nodes and the nodes to be located,but also use the accurate distances between the achor nodes and the achor nodes, finally get accurate position, The experiment s show that the average location error is less than Maximum Likelihood Estimation method by 5%.We use MICAz to create a WSN location system.Use nesc and TinyOS to code for nodes,to collect data and send data to base station.The PC collect the data for serial port ,we code a software system using c#,process data .