Adaptive couple-resolution blocking protocol for repeated tag identification in RFID systems

RFID applications such as monitoring an object for a long time need to identify tags repeatedly within the scope of the reader. Re-identification process can be improved using the information obtained from the previous tag identification process. Couple-resolution blocking (CRB) protocol utilizes the blocking technique that prevents staying tags from being collided by newly arriving tags. Staying tags can be efficiently re-identified by utilizing the retained information. After staying tags are separately all identified, arriving tags are identified. In this paper, we argue that CRB may work more poorly than other protocols which do not consider the repeated tag identification, such as query tree (QT) and collision tree (CT) protocol, when only few tags stay. To tackle the problem, we propose an adaptive CRB (ACRB) protocol. In ACRB, the reader estimates the tag staying ratio during the re-identification process for staying tags. If the estimated ratio is lower than a certain threshold, the blocking technique is immediately abandoned. Instead, staying tags and arriving tags are identified together without considering the retained information. In addition, we propose to improve CRB further using CT protocol, instead of QT protocol. Through computer simulation, we show that ACRB improves the identification efficiency of CRB, especially when the tag staying ratio is low.