Research On The Technology Of Positioning In WSN

With the development of CDMA cellular networks, the cellular mobile communication system develops swift. The wireless positioning technology is broadly used, services in the network based on mobile position, such as public safety, emergency alarm, bill based on mobile position, car and traffic management, navigation and wireless resources management etc. all of these have something to do with wireless positioning. The location of mobile position is mainly carried out in the Wireless Sensor Network (WSN).The positioning of node is a research focus in wireless sensor network, and it is the foundation of the service based on the node position. Therefore, the study of the node positioning in WSN have important significance.In this paper, we summarize the wireless sensor network firstly, introduce it's structure and characteristic. Then we do some research on the node positioning in WSN. The method of positioning node is mainly divided into two sorts, one is based on the measured distance (range based), the other one do not need to measure the distance (range free), and there are lots of methods in each sort. In the actual system, the transmission of signal is not along line of sight (LOS) all the time, when blocked by mountains and tall buildings, it will transmit accord scattering and refraction, which is called non line of sight (NLOS) transmission. The NLOS transmission of signal will introduce into NLOS error, which will reduce the accuracy of positioning. People propose several methods to restrain and reduce the NLOS influence in recent years, all of which can be classified into three. The first one is judge the NLOS signal, if the signal is NLOS signal, and then apply some rule to reconstruct the measurement signal in LOS environment. The second one is weighted all signals, the rule is that: add a big weighting on the LOS signals and add a small weighting on the NLOS signals. Which can reduces the influence of NLOS error. The third one is to pick up the LOS signals from all received.In this paper, we focus on the last two algorithms, the classical algorithm for the second one method is Residual weighting (Rwgh) algorithm proposed by Pi-Chun Chen, and the classical algorithm for the third method is Residual Test (RT) algorithm proposed by Yiu-Tong Chen, For we sort the set into different subsets when we judge whether the one is LOS one, the computation complexity is very high. Aimed at this shortcoming, in this paper, we proposed an algorithm which can reduce the computation complexity of RT, and it is called Simplified Residual Test (SRT) algorithm, SRT algorithm reduce the computation complexity according to optimize the set selection procedure. When we judge whether the ones have the same size have LOS set, if there is no LOS set, with some rule, we get a LOS signal, in the next judgement procedure, we can judge the ones that include the picked LOS signals only, and when we get 4 LOS signals, we can compute the position of unknown node.In this paper, we simulate the performance of the algorithms in different environments and parameters with MATLAB. According to the simulation results, we can see that, the performance of SRT is close to RT and it can reduce the computation complexity of RT's. The algorithm satisfied the desire in all environments.