Research On Anti-collision Algorithm Of UHF Band In RFID System

Radio frequency Identification (RFID) is a kind of technology which makes useof a wireless radio frequency method to realize non-touching automatic identification.This technology has been used widely in the fields of goods recognition and datacollection, which has many advantages such as high recognition accuracy rate, rapidrecognition speed, strong anti-interference ability and long service life, and it canpenetrate nonmetal materials and work in hostile environments. The Chinesegovernment pays high attention and rapid promotion to the internet of things，RFIDtechnology as one of the key technologies in the Internet of things, RFID technologywill be applied widely and have broad development prospects in the future.Ultra High Frequency (UHF) RFID system is a new technology developed inrecent years, Because it has far distance recognition, recognition accuracy, recognitionof high speed characteristics, so it is widely used in the automatic recognition ofpersonnel, animal, goods, etc, which becomes the research hotspot in the fields. Withthe rapid development and requirement of application in RFID technology, the readersneed identify a great number of tags efficiently and accurately in the limited time, andsignal collision is the key restriction to the performance of RFID system, this paper isstudy about the anti-collision problem which is restricting the development of RFIDsystem, and put forward the improvement algorithm and design ideas, the mainresearch work is as follows:(1)Briefly introduced ISO/IEC18000-6protocol which is widely used in theUHF band RFID system, and from the coding, modulation, anti-collision mechanism,data transmission command and different label state etc, the type C protocol in theISO/IEC18000-6protocol are analyzed.(2)Analysis the three kinds of anti-collision algorithm for UHF band RFIDsystem protocol: Aloha algorithm，binary tree anti-collision algorithm and the timeslot of stochastic anti-collision algorithm, and compared them by simulation, throughexperiments, we know that the binary tree algorithm and the dynamic binaryalgorithm find a tag required an average search times is log27V+1, regressive-stylebinary tree anti-collision algorithm to identify N tags need only2N-1search. For theALOHA algorithm, The DFSA algorithm for type A protocol and slot randomanti-collision algorithm for type C protocol is difference, in the DFSA algorithm，changes the slot number N after each round identification, and the slotted randomanti-collision algorithm through the Q parameter transmitted between the reader andtag, real-time dynamic changes the slot number N in each round of recognition, so relatively flexible, and high safety. But one thing is, because Q values are integers, Qvalue adjustment, which limits the number of frame slots in {1，2，4，8，16，32，...，256}，so it is limited the adjustments of frame slot number.(3)Make a further analysis on the anti-collision algorithm which is used inISO/IEC18000-6C protocol. When a frame time slots number is equal to the labelnumber, system throughput rate up to0.3679, and that in turn, when the systemthroughput is the highest, frame length is also approximate equal to the identificationtag number. It is based on the above consideration, we can get an improved algorithm，this algorithm takes the system throughput maximum oriented, provides thetheoretical basis for adjusting the frame slot number fast. By using the Matlabsoftware, from the system efficiency and time slot occupied two aspects, comparedthe original slotted random anti-collision algorithm and improved algorithm，Show theperformance of the new algorithm in the two aspects is better.(4)Finally, in view of the problems existing in the new improved anti-collisionalgorithms, which should be further improved, we propose modified plans anddescription, and prospect the future research direction of anti-collision algorithms inRFID systems.