Fast Tracking the Population of Key Tags in Large Large-Scale Scale Anonymous RFID Systems
Abstract: In large-scale scale radio frequency identification (RFID) (RFID)-enabled enabled applications, we sometimes only pay attention to a small set of key tags, instead of all. This paper studies the problem of key tag population tracking, which aims at estimating how many key tags in a given set exist in the current RFID system and how many of them are absent. Previous work is slow to solve this problem due to the serious interference replies ies from a large number of ordinary (i.e., non non-key) key) tags. However, time-efficiency efficiency is a crucial metric to the studied key tag tracking problem. In this paper, we propose a singleton slot slot-based based estimator, which is time-efficient, time because the RFID reader onl onlyy needs to observe the status change of expected singleton slots corresponding to key tags instead of the whole time frame. In practice, the ratio of key tags to all current tags is small, because key members are usually rare. As a result, even when the wh whole ole time frame is long, the number of expected singleton slots is limited and the running of our protocol is very fast. To obtain good scalability in large large-scale scale RFID systems, we exploit the sampling idea in the estimation process. A rigorous theoretical aanalysis nalysis shows that the proposed protocol can provide guaranteed estimation accuracy to end users. Extensive simulation results demonstrate that our scheme outperforms the prior protocols by significantly reducing the time cost.