The Research On Tag Anti-collision Algorithm For RFID Systems

RFID(radio frequency identification)is a non-contact automatic identification technology,which can identify the target object automatically and read the relevant data stored in the RFID tag through full-duplex data communication by radio frequency signals.Due to its identification procedure needs no human intervention and it can work in harsh environments,RFID has been widely used in many fields including the production process,the logistics,the security and the traffic management,etc.The issue in RFID systems is the tag collision problem as tags always exist in the same radio frequency channel,and multiple tags simultaneously request the same time slot.Therefore,research on tag anti-collision algorithm to improve the identification efficiency in RFID system is a crucial problem.This paper describes the development of RFID,the composition and working principle of the RFID system briefly.Then the paper analyzes several existing tag anti-collision algorithms in detail.The following two points are the main work of this paper:(1)An Improved dynamic framed slotted ALOHA Anti-collision algorithm(IAA)based on estimation method for RFID systems has been proposed.Based on the time slot distribution information,the algorithm estimates the average number of tags in each collision slot and then dynamically sets the frame size for unrecognized tags due to the collision between multiple tags.Simulation results demonstrate that IAA outperforms other existing algorithms in the literature in terms of the identification efficiency and the total number of time slots used.(2)A Hybrid Collision Tree protocol(HCT)has been proposed in this thesis.This protocol firstly determines a reasonable frame length based on the estimated number of tags by the estimation method.Then the reader queries each selected slot to identify tags.If there is a collision problem,CT(Collision Tree)algorithm is used.CT algorithm is a binary tree protocol based on the principle of collision tracking to solve the colliding tags one by one.Simulation results show that HCT algorithm has effectively improved the identification efficiency compared with CT algorithm.And the stability of HCT is better in comparison with other algorithms in the literature.