A New Slot-Count Selection Algorithm for RFID Protocol

EPCglobal RFID generation-2 (Gen-2) protocol [1] has been proposed for ultra-high frequency (UHF) passive tags and is being deployed. Gen-2 proposes a slotted random anti-collision algorithm, including an adaptive slot-count (Q) selection algorithm. The integer-valued parameter Q in Gen-2 plays a critical role in tag collision resolution. This adaptive algorithm dynamically adjusts value of Q based on the type of replies from tags. However, it modifies the value of Q the same way whether there is a "collided reply" or "no reply". This approach could lead to a slow tag identification speed, since it does not recognize the differences in duration between the "collided reply" and "no reply". This paper proposes a new slot-count selection algorithm which changes the parameter Q with different amounts depending on whether the reader receives a "collided reply" or there is "no reply" by a pre-specified waiting time. It is demonstrated, through analysis and simulations, that the new proposed algorithm achieves significantly faster tag identification speed compared to that of the existing Gen-2 adaptive Q algorithm.