The Research And Improvement Of ALOHA Anti-Collision Algorithm

RFID(Radio Frequency Identification) is a non-contact automatic identification technology, which has been developed rapidly in recent years. In RFID systems, when a number of tags simultaneously communicate with the reader, it's a key problem that how to prevent collision.The paper introduces the development of RFID system, expounds the basic principles of RFID system. Then several common ALOHA anti-collision algorithms are analyzed in detail. The paper introduces the principles of these ALOHA anti-collision algorithms and compares the system efficiency of them with Matlab. It is proved that when the frame length equals to the number of tags in the system, the efficiency of the algorithm will be best. So it is important that how to estimate the number of tags in the system. A improved algorithm is introduced, with a few parameters the performance of the improved algorithm in different cases of frame length is analyzed.The group DFSA algorithm is studied. With the mathematical model of it, the paper deduces the best method of grouping, and analyzes the system efficiency of it. Aiming at the problem of group DFSA algorithm, a improved algorithm is introduced. This improved algorithm solves the problem that the group DFSA algorithm cannot identify tags in other groups before finishing the identification of one group. In order to keep better system efficiency, the improved algorithm estimates the number of tags in the system in every circle. So that it simplifies the process of circles in a single group of group DFSA algorithm. With the simulation of Matlab, it is proved that the improved algorithm has better system efficiency than the group DFSA algorithm, and it takes less time slots to complete the identification of all tags in system.For the limitation of hardware, the anti-collision algorithm is not perfect. With the development of chip technology, more and more improved anti-collision algorithm will be come up with.