Research On Indoor Positioning Method Based On RFID

With the rapid development of Smarter Cities and Internet of Things technologies,the demand for indoor positioning information is increasing.Nowadays,as one of the core technologies of Internet of Things,Radio Frequency Identification(RFID)technology has become a hot entry point to study indoor positioning technology.The advantages of indoor positioning technology based on RFID lie in non-line of sight,non-contact,low power consumption,low cost and high positioning accuracy in the positioning process.However,in more complicated indoor environments,the process of the reader receiving signal strength indicator(RSSI)is vulnerable to multipath effects and ambient noise,so it is significant to study how to get better positioning results based on RFID technology.This thesis mainly focuses on algorithms of RFID indoor positioning.The main research contents are as follows:Firstly,the background and development of positioning technology at home and abroad were studied,and the advantages,disadvantages,and application scenarios of various positioning technologies were analyzed.The classification of RFID system structure,working principle and RFID positioning technology were introduced.The UHF RFID system link model is deduced,and the model formula for practical application is given.The multipath effects in the case of reflections and the effect of tag attachments on the RFID system link are theoretically analyzed.Secondly,the principle,advantages and disadvantages of the classic LANDMARC positioning algorithm are introduced in detail.The simulation experiments analyze the factors which affect LANDMARC algorithm performance such as the number of readers,the reference tag density,the number of neighbor tags,and the location of the tag to be positioned in the different set areas.In practical applications,the LANDMARC algorithm has a problem that the deployment restrictions of the reference tag in central region,a positioning algorithm which combines the RSSI ranging method and an improved LANDMARC algorithm is proposed.That is,no reference tag in the set central area,but arranged in a triangular manner on the edge region.The experimental results show that compared with the LANDMARC method,the proposed method respectively reduces the number of reference tags and the running time of the algorithm by 17.9%and 18.3%,while ensuring the positioning accuracy,which also provides a solution for the application scenarios of the center area's deployment of reference tag.Finally,facing with the problem that the traditional RFID indoor positioning method is susceptible to multipath effects and environmental noise,this thesis combined with the passive UHF RFID system link budget model,an RFID indoor location tracking method based on the segmented RTS smoothing algorithm is proposed.In the forward filtering stage of the RTS smoothing algorithm,the untracked Kalman filter(UKF)method is used to solve the non-linear problem existing in the RFID indoor location tracking.The reverse recursive process adopts a piecewise smoothing way to meet the demand of positioning accuracy and real-time performance.The simulation compares the localization effect of the segmented UKF-RTS algorithm with others from the perspective of open environment,multipath effects,and different label attachments.The results show that the segmented UKF-RTS algorithm has good positioning accuracy and real-time performance in indoor positioning applications,and also has good anti-interference ability.