Research On Positioning Algorithm Of Rfid Tag Based On RSSI

With the rapid development of Internet of Things(IoT)technology,positioning technology,which is one of the core and key technologies of the Internet of Things,is attracting more and more attention.People's demand for outdoor positioning is increasing.In addition to GPS and Beidou technology,Long Range(LoRa)technology has become one of the popular outdoor positioning technologies due to its low power consumption,low cost and long transmission distance..This paper proposes a LoRa outdoor positioning method based on ranging,including data processing,establishing a ranging model and distance-based positioning.First,the RSSI is filtered based on Received Signal Strength Indication(RSSI)and Arrive of Time(TOA),and the weighted average of the filtered RSSI is used for ranging.Then,based on the method of pre-measurement samples,a corresponding ranging model of each positioning base station of a Gaussian distribution is constructed,and the distance between the device to be located and the location coordinate map of the positioning base station is obtained for positioning.Finally,the Taylor series expansion positioning algorithm is improved by the weighted triangular centroid algorithm,which effectively improves the performance of the Taylor positioning algorithm.The paper also developed a LoRa outdoor positioning verification platform based on STM32 microprocessor and SX1280 RF module,and carried out actual measurement.Matlab simulation and actual measurement results show that the LoSI outdoor positioning method based on RSSI proposed in this paper can effectively improve the positioning accuracy.The main work of the paper is as follows:(1)Introduce the category of LoRa positioning methods,explain the principles and characteristics of various positioning methods based on LoRa,and focus on the analysis of distance-based positioning methods.(2)Build a ranging model by measuring and merging the dynamic data processing methods of TOA and RSSI in advance.Through the dynamic statistical data of the sliding window method,combined with TO A to screen RSSI,using the weighted average method for data processing,effectively improve the accuracy of RSSI value.According to the distribution relationship between RSSI and distance,a Gaussian-like distance calculation model is proposed.By measuring the data in advance,the quasi-Newton iterative method is used to fit the model through the data to build a complete distance measurement model.RSSI value for distance calculation.Matlab simulation results show that the proposed data processing method can improve the accuracy of subsequent positioning results.(3)Based on the fusion triangle weighted centroid algorithm,an improved Taylor positioning algorithm is proposed.The Taylor series expansion positioning algorithm requires an initial position value,and then through continuous iterations,the gap between the real position and the actual position is reduced until the iteration stop condition is met.The selection of the initial value will cause the problems of non-convergence and too many iterations if it is far from the real position.Therefore,the position of the positioning device is estimated using the triangle weighted centroid algorithm.This position estimate is used as the initial position of the Taylor positioning algorithm value.Matlab simulation results show that the proposed improved Taylor positioning algorithm has better performance.(4)Design and implementation of LoRa outdoor positioning verification platform based on STM32 microprocessor and SX1280 as RF module.The platform includes a device to be located,multiple positioning base stations,a data collection terminal,and a PC terminal as a computing hub system.The positioning base station receives the signal from the device to be located,performs data processing and ranging,transmits the result to the data collection terminal,and the data collection terminal uploads the data to the PC terminal,where the proposed positioning algorithm is used by the Python program to achieve positioning.Design a transmission mechanism to ensure the balance between data transmission accuracy and effectiveness.The developed positioning system was measured on the Jiulonghu campus of Southeast University,and the proposed positioning algorithm was verified to have high positioning accuracy.