Research Of Tag Anti-Collision Algorithm In RFID Systems

Radio Frequency Identification (RFID) is an automatic identification technique(Auto-ID) which uses wireless technology to realize the contactless identification. In recent years, with its adventages in abundant of data information, short identifying time, high security, RFID has become very popular in many service industries, purchasing and distribution logistics, manufacturing companies and material flow systems. Its good prospect on applications makes many companies and institutes all over the world plough a great deal of energy into researching it.Currently, many technical problems are still unsolved in RFID systems, for example, tag collision problems, medial software design, network deployment. This thesis mainly focuses on the tag anti-collision problem in the UHF RFID systems.First of all, two main schemes of solving tag collision problems in RFID systems are introduced, including ALOHA based algorithm and tree based algorithm. The performances of the representative algorithms, say, Frame Slot ALOHA algorithm, Query Tree algorithm, Collision Tracking Tree algorithm are analyzed by simulation using Matlab.Second, the flaws of the existed algorithms are analyzed according to the simulation results. In order to overcome these disadvantages, a special data sequence is utilized, based on two novel algorithms, Grouping Based Bit-slot ALOHA algorithm and Bit Position Modulation Based Tree algorithm, are proposed. For the first algorithm, the use of special bit sequence and the grouping parameter Q promises the high efficiency and stability. For the second one, the truncated ID modulate the position of data-1 in the bit sequence, which realizes the M-ary tree and reduces the useless inventory, thus the reading time is shorten. Theoretical analysis of the proposed algorithms is given, simulation results testify the theoretical analysis and show that the efficiency and stability of the proposed ones significantly outperform others. Finally, thesis puts effort on the anti-collision mechanism in EPC Gen2 standard. Based on reasonable hypothesis and the air interface defined in the standard, A simulation platform is built under Matlab, and the impact of the grouping adjusting parameter on the performance of the anti-collision algorithm is investigated and Simulation of the Gen2 anti-collision algorithm is given under random error link. According to the above analysis and discussion, some useful suggestions are proposed for the practical deployment.