Efficient Missing Tag Detection in a Large RFID System

Missing tag detection is an important problem for large RFID application systems (e.g., inventory control), and is drawing more and more attention from the research community in recent years. Li et al. proposed the Iterative ID-free Protocol (IIP) to identify the missing tags in a large RFID system, achieving high time efficiency. However, our analysis and experiments show that the time efficiency of IIP drops sharply when the missing rate increases. By exploiting information contained in the expected singleton slots, we propose IIPS to improve IIP, achieving high and steady time efficiency under both high and low missing rates. Furthermore, by identifying the missing tags in the expected collision slots and dynamically computing the missing rate through estimation of the present tags and statistics about the missing tags, we propose IIPS-CP and IIPS-CM, achieving higher time efficiency than IIPS under high missing rates. Our simulations show that, compared with IIP, when the number of total tags is 10000 and the missing rate is 80%, IIPS, IIPS-CP and IIPS-CM reduce the average time for identifying each tag by 84.8%, 88.9% and 89.3%, respectively.