Bit Query Based M-ary Tree Protocol for RFID Tags Identification

The tag collision problem is considered as one of the critical issues in RFID system. Recently, bit tracking technology has been proposed for query tree (QT) based protocols to resolve tag collision efficiently. However, the performance of these protocols remain to be improved due to unused collided bits and idle slots. In this paper, a query method Bit query is presented, which requires the tag to respond a mapped bit string instead of its ID sequence. Compared with traditional ID query, it not only can eliminate idle queries, but also can separate collided tags into many small subsets and make full use of the collided bits as well. Based on this method, a novel query tree protocol Bit Query based M-ary Tree (BMQT) protocol is proposed, which recursively resolves collisions by forming a M-ary tree, and optimally switches from Bit query mode to ID query mode for quickly identifying the tags when tag is readable. Theoretical analysis and simulation results show that the system efficiency of BMQT is closed to 0.89, which outperforms the other existing QT-based and hybrid algorithms.