| With the rapid development of the economy,society and information technology,the demand for high-precision,low-cost,and universally applicable indoor positioning applications is increasing in various industries.Indoor positioning technology has become a focus of research both domestically and internationally.Compared to outdoor environments,indoor channel environments are more complex.Due to the characteristics of building structures and the obstruction of indoor objects,electromagnetic wave signals will undergo phenomena such as refraction,reflection,and diffraction during propagation.Directly using traditional methods for positioning will result in non-line-of-sight(NLOS)errors and will also be affected by multipath effects,causing a decrease in positioning accuracy or even failure.Based on radio frequency identification(RFID),passive indoor positioning technology has broad application prospects due to its integration,low cost,and ease of deployment.In this thesis,we conducted research and design on key technologies and systems for ultra-high frequency RFID indoor passive positioning based on RSSI and PDOA,with the following main work:1.This thesis compared and analyzed the advantages and disadvantages of common indoor positioning methods and further studied the impact of NLOS and multipath effects on positioning accuracy and capability based on the comparison and research of multiple RFID classic positioning technology principles and core algorithms.2.This thesis systematically studied the propagation characteristics of indoor NLOS wireless signals and proposed a multi-hyperbolic positioning system based on SD-PDOA on a single reflection topology model.This method constructs multiple hyperbolic curves to solve the tag coordinates through antenna phase difference,corrects the coordinates obtained,and then uses the Kalman filter algorithm to estimate the results of multiple positioning.Simulation and experimental results show that the positioning accuracy under NLOS conditions with a single reflection is in the centimeter level.3.This thesis studied the multipath propagation effects and characteristics indoors.Based on the RSSI-based polygon positioning algorithm,we proposed a joint positioning method combining SD-PDOA and RSSI.The algorithm estimates the tag position using the RSSI polygon positioning algorithm,obtains a confidence interval through the Kalman filter algorithm,and then determines the positioning results obtained by SDPDOA according to the confidence interval.This algorithm fully combines the characteristics of RSSI and SD-PDOA positioning,significantly improving the indoor positioning accuracy under multipath interference.4.This thesis developed an upper computer software based on Octane SDK and C#language to drive the R420 reader to obtain the phase and intensity information of the UHF RFID tag’s backscatter signal.We built an indoor passive positioning experimental system based on SD-PDOA and RSSI and tested and verified the positioning performance under NLOS and multipath interference conditions.Simulation and experimental results show that the key technologies and systems for ultra-high frequency RFID indoor passive positioning based on NLOS and multipath interference environments have good positioning accuracy and can be widely used in Io T systems such as warehousing logistics and asset management. |
