Research On Anti-collision Technology Of RFID Multi-tag Parallel Identification

The Ratio Frequency Identification(RFID)is a non-contact automatic Identificat io n technology,and is an important supporting technology for the Internet of things.RFID implements automatic identification of items by exchanging electromagnetic signals(radio frequencies)between readers and tags.The technology has been widely used in smart cities,Internet of vehicles,environmental monitoring and smart logistics.As 5G technology's low latency and ultra-large bandwidth transmission rate provide a reliable guarantee for RFID transmission data,the 5G + IOT + AI model will set off a new generation of technologica l revolution.In RFID application systems,the detection and reading of large-scale RFID tags that send and receive signals at the same shared frequency constitute a great demand,and communication channel sharing technology is required.However,when multiple tags access such a channel,the problem of al ocating channel capacity to different users usual y occurs,which will cause signal overlap,which is commonly known as collision.The collision problem increases the identification delay while causing bandwidth and energy waste.If there is no appropriate processing mechanism,the normal operation of the entire system will be affected.Especially in the application of large-scale RFID system,the demand of using large-scale tag is increasing rapidly,so it is of great significance to efficiently solve the collision prevention algorithm of large-scale tags.For anti-collision technology,the current protocols standardized by ISO and EPCglobal1 are based mainly on two generic strategies,one is channel sharing by time(ALOHA algorithms)and tags identification by reader-machine questioning,generically cal ed “treebased protocols”.This thesis has made some innovations in tree-based algorithms.The main innovations are as follows:1.A RFID adaptive collision tree algorithm based on parallel matching(PMACT)This algorithm uses a parallel matching mechanism to reduce the number of query cycles.This mechanism only needs to send a query and perform label matching in parallel.The query used is called a parallel matching query,referred to as PMQ(Parallel Matching Query).At the same time,the number of conflict labels is used to adaptively select the search mode(twobranch collision tree or eight-branch collision tree).Theoretical analysis and simulation results show that compared with the existing tree-based algorithm,the proposed algorithm not only improves the efficiency of the system and the speed of label recognition,but also reduces the time complexity,especially in the case of large-scale tag recognition.The average system efficiency of PMACT is 0.61.Compared with QT,CT,ACT and OBTT have improved by 27%,11%,9%and 1.5%,respectively.2.A collision window tree algorithm based on parallel matching(PCwT)In the tree-based algorithms,the collision probability of tag response is very high at the beginning of identification process,and the transmission of the rest bits except prefix causes a long identification delay.Thus this thesis proposes a collision window tree algorithm based on parallel matching.This algorithm uses a parallel matching mechanism in the collis io n window tree algorithm(CwT),and uses a fixed window method to limit the length of the tag response.It aims to reduce the number of query cycles and the number of transmitted bits.3.A parallel-binary-based splitting collision tree algorithm(PSCT)The proposed algorithm combines the advantages of both locking and parallel binary splitting.The bit-locking mechanism al ows the rest of the search process to focus only on previously locked collision bits,greatly reducing redundant transmission of non-collision bits.The parallel binary splitting technology enables the length of the information returned by the reader and the tag response to be only 1 bit.At the same time,the tag can dynamically modify the response sequence in the response queue to implement tag self-transmission control.Theoretical analysis and simulation experiments show that the proposed PSCT algorithm is superior to the previous traditional anti-collision algorithms in terms of the number of transmission bits,recognition time,and the total number of time slots required.