Research Of Device-free Passive Localization Based On FPGA

Object Device-Free Localization is allowed to localize and track person or other things without carrying any electronic device or tag. And Object Device-Free Localization is easy to implement, and the cost is relatively low. Due to these advantages, Object Device-Free Localization is used in intrusion detection, border security, disaster relief and smart home, etc. Many of the current Object Device-Free Localization has used radio tomography algorithm and its improved algorithm. Radio tomography algorithm based on the received signal strength measurements use all wireless links RSS attenuation value in the monitored area to locate the target position. Localization effect in the outdoor environment is very good., because of the influence of the multipath effect in the indoor multipath environment, the orientation effect is not ideal.First, this paper studies the current Object Device-Free Localization algorithm. Aiming at the problem that the localization accuracy of radio tomographic imaging algorithm is not ideal in multipath environment, an improved algorithm based on bayesian background model is proposed. Firstly, the bayesian background model which is used to eliminate redundant links is established by combining the skew-laplace distribution with the bayesian theory. Then, the changes of received signal strength are weighted to reduce the multipath effect on localization accuracy. Finally, the target location is corrected by the posteriori estimate mean. The feasibility and availability of localization algorithm is verified by experiment.Second, Object Device-Free Localization based on radio tomographic imaging(RTI) algorithm takes a long time to solve the image of target position, which is difficult to meet the high real-time requirements, so a fast solving method for target localization based on field programmable gate array(FPGA) is designed in this paper. Firstly, the direct solving of target position is optimized and the direct calculating target position is converted into solving the linear equations of the positioning system. And then, the symmetric positive definiteness(SPD) of the coefficient matrix is proved. Finally, a fast coefficient updating method is applied to design the FPGA function block. By comparing with PC platform, the proposed system can improve the calculation speed greatly and satisfy the requirement of real-time.Finally, the overall design of the Object Device-Free Localization system is completed, mainly including wireless sensor node hardware and software design. The system also includes PC software design.