Research On Anti-collision Algorithm In RFID System

Radio frequency identification (Radio Frequency Identification, RFID) is a kindof technology which makes use of a wireless radio frequency method to realizenon-touching automatic identification. This technology has been used widely in thefields of goods recognition and data collection, which has many advantages such ashigh recognition accuracy rate, rapid recognition speed, strong anti-interferenceability and long service life, and it can penetrate nonmetal materials and work inhostile environments. The Chinese government pays high attention and rapid promotionto the internet of things, as one of the terminal endings in the internet of things,RFID technology will be applied widely and have broad development prospects in thefuture.With the rapid development and requirement of application in RFID technology,the readers need identify a great number of tags efficiently and accurately in thelimited time. Signal collision is the key restriction to the performance of RFIDsystem, which becomes the research hotspot in the fields. In China, the traditionalanti-collision algorithm couldn’t solve the problems of signal collision very well.In view of some problems existed in the traditional anti-collision algorithms, thisthesis provides some improved methods and algorithm design, specific research workand innovation points as follows:(1) Study deeply on the traditional RFID anti-collision algorithms, and analyzeon the algorithm application background and deficiency.(2) An improvement is proposed to the regressive-style mechanism of theregressive-style binary search algorithm. In the regressive-style binary searchalgorithm, after identifying a tag successfully, the reader needs to send Active orderto activate dormancy tags, which increases the numbers of transmission orders, inaddition, the pre-jump could only deal with one collision prefix, and fails to makefull use of the information of collision nodes. Against the shortcomings ofregressive-style search algorithm, an anti-collision algorithm of adaptivemulti-tree is proposed. The optimizations of the new algorithm are as follows: thenew algorithm will modify the algorithm appoints, control communication state throughthe dormancy count, and remove the original activation order mechanism which can savehalf of the regressive search time; the new algorithm will adjust the length of instructions dynamically, and choose the appropriate number of forks flexiblyaccording to the continuous collision, which make full use of the information ofcollision nodes. What’s more, the new algorithm will reduce the send informationeffectively, so as to improve the transmission rate; direct identification when thereis only one collision bit, which will reduce the search times. The simulation resultsshow that, compared with regressive style search algorithm, the system efficiencyof the proposed algorithm is about 76.5%. Moreover, with the number of tags increasing,the superiority of the performance is more obvious.(3) The existing scheduling algorithms need to consume a lot of resources tomaintain the structure of the whole network realtimely, small changes in the systemwill cause the redistribution of network resources, and increase the cost of thesystem. A novel multi-reader algorithm anti-collision is proposed, which divides thereading process of RFID system into three stages including competition, appointmentand transmission. In the stage of competition, the cluster head occurs in thecompetition among readers; in the stage of reservation, cluster head sends anappointment command to the controlled readers within the group to appointmentcommunication order; in the stage of transmission, cluster head controls the readerswhich select the correct time slots to communicate by utilizing of the collision ofinformation from the stage of reservation, this way can avoid the signal collisionamong readers, the readers of no communication request are set to dormancy state,which will reduce the power consumption of the system. Compared with the existingscheduling algorithms, the new algorithm improves the reading efficiency, andmeanwhile reduces the power consumption.(4) Finally, in view of the problems existing in the reader anti-collisionalgorithms, which should be further improved, we propose modified plans anddescription, and prospect the future research direction of anti-collision algorithmsin RFID systems.