Research Of The Anti-Collision Algorithms In The Rfid System

RFID is a technology that transfers the information by the radio frequency signal and identifiesthe identity by the transferring information. Recently, RFID is applied and developed fast in manyfields, such as service, purchasing, storage, manufacture, circulation, etc, as RFID has theadvantages in abundant of data information, short identifying time and high security. Due to theexcellent prospects of its application, more and more corporations and research institutes areresearching it by investing much manpower and material resource.Currently, many sides in RFID system are still should be improved, such as anti-collision,security, high-cost and poor identifying distance, etc. And in this paper we mainly discuss in tagsanti-collision algorithm which is one of the most important problems in RFID system.Firstly, the origin of the anti-collision, some actual problems in the identifying process(such ascapture effect) and the idea of the anti-collision algorithm are be introduced in section 2, leading tothe two main types of the algorithm: the ALOHA based algorithm and the tree based algorithm.Moreover, some popular algorithms are introduced in detail without the capture effect, and thenanalyses their advantages and disadvantages.Secondly, HQT is analyzed without concerning the capture effect as well. And IHQT issuggested by improving the slot compensating mechanic of HQT, which the delay slots are decidedby the three lower bits of tags' ID which is matched the prefix and the new prefix which should betransfer later is decided by the information of the collision and current slot. In this way, not only theidle cycles can be avoided, but also do not sensitive by the distribution of the ID of tags which areamong the scope of the reader. The simulation performance disappears that IHQT is more stable andeffective than the QT and HQT.Finally, QT is discussed again to show the shortcoming concerning the influence of the captureeffect. According to the idea of how to prevent from the capture effect which is suggested in theGQT bring forward by Victor K.Y.Wu, the GHQT is suggested by improving IHQT. Though a littleidle cycles will be increased by the improvement, all the tags which among the scope of the readercan be identified even if the capture effect. The simulation performance disappears that GHQT canprevent the identifying process from capture effect, and is more effective than the GQT.