CTHp1-7: Prefix-Length Adaptation for PRQT Protocol in RFID Systems

Prefix-randomized query-tree (PRQT) protocol has been proposed for multiple tag identification in RFID systems. The optimal performance of PRQT can be achieved with a proper choice of the initial prefix length according to the tag set size. In this paper, we propose an initial prefix length adaptation algorithm for PRQT protocol when the tag set size is unknown before identification. The algorithm starts with the setting of a small initial prefix length l followed by the polling of all 2^l prefixes. The initial prefix length is then increased repeatedly until the collision ratio satisfies a prescribed condition. We derive the optimal increment step size and the respective sequence of decision thresholds. Simulation results show that PRQT with initial prefix length adaptation can significantly reduce the expected tag read time for all range of tag set size when compared to the use of query-tree protocol.