Research On Indoor Passive Positioning Technology Based On Wireless Sensor Network

In recent years,As the target tracking technology is becoming more and more important in security monitoring,fire prevention and anti-explosion prevention,the positioning technology based on wireless sensor network has become a research hotspot in this field.The main principle is to assign a certain amount of wireless sensor network nodes which communicate with each other around the monitoring area and it will form a large number of wireless signal links in the monitoring area.When a target appears in the monitoring area,the radio frequency signal of certain links in the monitoring area is blocked by the target which causes the change of the RSS measurement.Then the location algorithm can realize the real-time output of the target coordinates according to the change of RSS value and node coordinate position.Compared with traditional positioning technology,device-free target localization technology based on wireless sensor can realize the real-time positioning of the target without the target carrying any electronic tag which has great potential for development.This paper fisrtly studies the measurement model of radio-frequency signal attenuation which describes the mathematical relationship between the position of the target in the monitoring area and the changes of RSS.Based on the exponential attenuation model,the improved exponential attenuation model is proposed to further improve the positioning accuracy.The localization algorithm uses the particle filter and at the same time,we use the auxiliary particle filtering to improve the accuracy of positioning.Because of the complexity of the indoor environment,the multipath is abundant.Based on the single channel particle filter location algorithm,a particle filter localization algorithm based on multi-channel fade-level is proposed in this paper.The algorithm has two methods which improve the measurement model.The first method called multi-channel adaptive weight model assign different weights to corresponding channel according to the fade-level of different channels.The second one selects the channel data of close anti-fading link according to the fade-level.In the field experiment.this article also designs a channel-hopping token-ring communication protocol of the measurement node and a receiving communication protocol of the gathering node.The location accuracy of multi-channel is up to 37%higher than that of single channel and the positioning error of single target in 7*7m region can reach 0.2682m.In order to collect real-time measurement data of the monitoring area,...