Research On LoRa Location Technology Based On RSSI And TDoA Fusion

As the rapid development of Internet of Things technology,wireless positioning technology has been used in all aspects of life.However,the current dominant outdoor positioning technology is limited by power consumption,communication distance and difficulty of achievement of service with relative low cost.To solve these problems,this thesis designs and implements a LoRa wireless positioning scheme based on the fusion algorithm,which takes the advantages in power consumption and communication distance of LoRa,and combines RSSI and TDoA positioning algorithms to obtain outdoor positioning.These methods realize the balance between low power consumption and high accuracy,providing technical support for outdoor complex environment positioning applications.The main work of this thesis is as follows:(1)Aiming at the problem of location accuracy,a location algorithm based on the fusion of Received Signal Strength Indication(RSSI)and Time Difference of Arrival(TDoA)is proposed,including data processing,model building and location based on ranging results.(2)The fusion algorithm based on RSSI and TDoA is simulated and analyzed by MATLAB,and study the influence of the filter window step size and the number of anchor nodes on the positioning error.According to results,as the increasing of the filter window step size and the number of anchor nodes,the average positioning errors of the three algorithms gradually decrease and finally become stable.The average location error of the fusion algorithm in this thesis is significantly reduced,compared with a single RSSI or TDoA location algorithm,(3)LoRa outdoor positioning system is built,based on STM32 microprocessor and SX1280 RF module.The system includes unknown nodes,multiple positioning anchor nodes,data collection gateway and PC terminal positioning software.The anchor node receives the signal of unknown nodes,performing data processing and ranging,and then transmits it to the data collection gateway which uploads the data to the PC based location software based on the fusion algorithm.(4)Field positioning tests were carried out in the south area of the campus by using the LoRa outdoor positioning system,which verified that the fusion algorithm based on RSSI and TDoA is superior to the single RSSI trilateral positioning algorithm or the Taylor expansion algorithm of TDoA random initial value in accuracy.Compared with two single algorithms,the accuracy of the fusion algorithm in this thesis is improved by 53.99% and8.10% respectively.