Passive Non-cooperative Target Location Method And Technology Research Based On Wireless Sensor Network

Nowadays, location information has been a military action and the necessary basic data information in daily life, playing an importance role in many fields. Using the GPS devices outdoors has become a common ways of traveling, but with the city building density increasing, the traditional GPS location cannot work normally, due to its inherent penetrating questions in indoor and urban canyons place. At the same time, the accurate location information is required to improve constantly by the public, and recently many wireless location technologies were sprung up, such as the orientation of WLAN, cellular networks and wireless sensor network localization, etc. While a common defect is asked to be carried and match the positioning device among the above positioning system, and the existing positioning methods failure in some emergency case or the environment, where the factors cannot be satisfied. In order to overcome the shortage of the positioning technology, Device-free Localization was proposed, based on the wave shadow fading characteristics of device target location technology.The location technology adopts the WSN nodes to form a positioning system which cost little, nodes get the Received Signal Strength (RSS) of the corresponding link with communicating with each other, and we can get the information about the location of the target according to the target's influence on the wireless link. The technology not only can overcome most of the existing positioning systems asked target to carry the deficiencies of the positioning device, but also have much advantage when comparing with the existing ultra-wideband radar, infrared and video cameras non-cooperative positioning technologies, such as low cost, high precision and can be used in the dark, in the smoke and in sheltered environment. Existing research has showed DFL technique have a broad application prospect in the hostage rescue, the intruder detection, elderly care and monitoring respiration rate.Despite the DFL technology got rapid development in recent years, due to the RSS value easily affected by environmental factors in the practical measurement, it have the time-varying characteristics, therefore the existing DFL technology positioning accuracy is not high enough, the reliability is still insufficient. Aiming at this problem, in this article, we start from the perspective of the software and hardware experiment location platform, detailed study of more than indoor and outdoor environment of static positioning algorithm and dynamic tracing algorithm, including the following three parts:1. Designing and building the location system. The system based on the Zigbee chip CC2530 which is designed by Texas Instruments company, we designed the peripheral circuit of CC2530 and put the serial port, program rewrite function, power supply circuit together to one circuit system. In the aspects of the software, we have designed and modified the MAC layer, HAL layer and application layer of the Z-stack protocol stack for the purpose of letting all nodes can quickly location messages sent polling, the location messages contained in the previously received the corresponding node number and the RSS values, the coordinator records the RSS and send it to PC through a serial port for data processing.2. The research of static target localization algorithm. Due to that the RSS value is very sensitive in the practical measurement, and it's vulnerable to other same frequency electromagnetic wave, it's also vulnerable to the influence of objective factors such as temperature and humidity, the features make many DFL localization technologies based on RSS value result is not ideal. Aiming at this problem, this paper applies background learning algorithm which is based on mixture of Gaussian model to DFL positioning, distinguishing between background RSS effect and prospect target position through the study of background learning, what's reduces the RSS fluctuations affect on the positioning imaging Significantly.To achieve higher DFL positioning accuracy, this paper uses the frequency diversity technology, which improve the quality of imaging according to the multi-channel measurements.3. The research of moving target tracking algorithm. With the Zigbee modules' good performance of Sending and receiving, and modify the protocol stack to improve the software on its redundancy, this paper enables to reduce the time of a polling sampling in milliseconds level, so that fully meet the tracing sampling requirements for slow movement of people and things. Through research the Kalman filtering algorithm and the particle filter algorithm, this paper Integrates the two algorithm's advantages and improves the Particle degradation of normal Particle filter with the extended Particle filter based on the extended Kalman filter. This paper also overcome the problem of the reducing of the particle diversity which is caused by resampling of normal Particle filter with the linear resampling particle filter technology, what's makes the tracking performance improved significantly.Finally, this paper summarizes the defects of existing work,and puts forward the corresponding improvements for its insufficient, in order to make improvement in future research, this paper also prospects the future research direction.