Research On Anti-collision Algorithms Of UHF RFID System

RFID(Radio Frequency Identification) is a non-contact automatic identification technology,which uses radio waves and electromagnetic coupling to realize communication between reader and tags. RFID technology has many advantages and is applied in many fields widely, including logistics management, industrial automation and transportation etc. With the large-scale application of RFID, tag collision problem affects the performance of RFID system seriously and the anti-collision algorithm is the key to solve the problem.According to the above problem, this thesis simply introduces the system composition,working principle, standard protocol of RFID system and some other relevant theoretical knowledge firstly. Secondly, this thesis introduces the traditional RFID anti-collision algorithm and its improved algorithm, as well as comparative analysis on the performance of these algorithms.Thirdly, due to the ALOHA algorithm have the features of a tag still cannot be identified, the improvement of Dynamic Frame-Slotted Aloha Algorithm is put forward in this thesis and Binary search algorithm is nested in it. This not only solves the fault of ALOHA algorithm can not guarantee 100% read rate, but also overcomes the shortcoming of Binary search algorithm needs long time to identify a large number of tags. Then, based on the query tree algorithm requires more times to identify all tags, an hybrid query tree anti-collision algorithm(HQT) for RFID system is presented in this thesis. The algorithm combines the advantages of binary query tree with quanternary query tree to identify tags and according to the information returned from tags to choose different query mechanism between binary query tree and quanternary query tree dynamically. So it can quickly identify all tags by reducing the number of query-responses and improves efficiency of identification.Finally, HQT algorithm is designed and simulated by using Verilog HDL language in the Quartus II 9.0 development environment. The simulation results show that the algorithm can identify tags efficiently and accurately. Moreover, with the increase of the number and bits of tags, HQT algorithm has more obvious advantages.