Efficient collision-slot utilization for missing tags identification in RFID system

Abstract

Radio Frequency Identification (RFID) technology has become one of the most promising building blocks in future IoT-enabled applications, including supply chain management, intelligent logistics, inventory control, etc.. This paper studies the fundamental problem of completely identifying missing tags in RFID systems. The most important measure for missing tag identification is to minimize the execution time. Most of the existing missing tag identification schemes compare the singleton slot in the expected mapping vector with the actual mapping vector observed by a reader to determine whether the corresponding tag is missing or not. However, they are of low efficiency because the useless collision slots account for a large proportion of the slots in a time frame. This paper proposes a Collision Unfolding-based Missing tag Identification (CUMI) protocol, which applies a novel indicator vector and Manchester coding techniques for transforming parts of abandoned collision-slots into valuable slots, thereby the utilization of slots in a time frame gets a promotion. However, CUMI requires transmitting long indicator vectors to tags, which incurs too much communication overhead. To address this problem, we propose an Enhanced Collision Unfolding-based Missing tag Identification (ECUMI) protocol to further compress the length of indicator vectors at the expense of longer tag responses. Throughout the simulation, we find that ECUMI has a higher time efficiency in missing tag identification than CUMI does. Extensive simulation results reveal that CUMI and ECUMI outperform the state-of-the-art missing tag identification protocols by at least 1.02× and 1.8× in the single-reader scenario, respectively.