| In recent years,with the rapid development of Internet of Things(Io T)technology,there has been an increasing demand for accurate position information from sensing devices.Among them,Radio Frequency Identification(RFID)technology,as one of the short-range communication technologies in Io T,has been widely used in indoor positioning due to its low cost,non-contact,and high-precision advantages.To achieve high-precision and efficient positioning results,and overcome the shortcomings of existing RFID tag-based positioning methods,this thesis focuses on two signal characteristics of radio frequency signals,namely,Received Signal Strength Indication(RSSI)and Phase.From both parametric and non-parametric perspectives,a RFID-based positioning system is constructed.The main research contents of this thesis are as follows:To address the relative positioning problem for multiple RFID tags,this thesis proposes a multitag relative positioning system based on the RSSI sequence features from a radio frequency parametric perspective.Firstly,a uniformly moving antenna is used to obtain the RSSI time series corresponding to the multi-target tag array.Then,to address the issue of RSSI data interruption and missing values caused by tag occlusion,this thesis completes the RSSI sequence by considering the positional relationship of RFID tags in the array to fill in the missing data.Finally,relying on the tag RSSI sequences,a similarity measurement table based on RSSI cosine similarity is constructed,and a tag column and row adjustment algorithm is designed to achieve the relative positioning of multiple RFID tags.Through relative positioning tests on an indoor multi-tag array,the results demonstrate that the proposed method can achieve high precision and efficiency in multi-tag relative positioning tasks.To further improve the accuracy of RFID tag positioning in complex indoor scenarios,this thesis proposes an absolute positioning system for tag arrays based on signal feature fingerprints from the perspective of RF signal parametric analysis.Firstly,multiple fixed-position RFID antennas are used to acquire the RSSI and phase information of tags within the perception target area and construct an RFID signal feature fingerprint database.Then,a fuzzy clustering method is employed to generate the initial fuzzy similarity matrix of signals during the online positioning stage and complete the division of the fingerprint database.Finally,a fuzzy decision-based approach is used to generate the spatial coordinate information of multiple tags,enabling absolute positioning of RFID tag arrays.Experimental results from tag array positioning tests in indoor spaces demonstrate that the proposed system can achieve high precision and low-cost absolute positioning effects. |
