Anticipative Wrap-Around Inquiry Method towards Efficient RFID Tag Identification

Abstract

One of the challenges in designing modern RFID systems is that when more than one tag exists in an RFID environment, it may occurs collisions so that the whole system becomes inefficient and increases the time for identifying RFID Tags. To simultaneously recognize multiple tags within a reader interrogation zone, an anti-collision algorithm should be applied. In this paper, we present an Anticipative Wrap-Around Inquiry (AWAI) method, which is an enhanced technique based on the query tree protocol. The main idea of the Anticipative Inquiry is to limit number of collisions at different level of a query tree. When number of collisions reaches a predefined ratio, it reveals that density in RF field is too high. To avoid sending unnecessary inquiries, the prefix matching will be moved to next level, alleviating the collision problems. Since the prefix matching is performed in level-ordered scheme, it may cause an imbalanced query tree on which the right sub-tree was not examined due to threshold jumping. By scanning the query tree from right sub-tree to left sub-tree in alternative levels, i.e., wrap-around, this flaw could be significantly ameliorated. The experimental results show that the method of setting frequency bound and wrap-around scan indeed improve the identification efficiency in high density and randomly deployed RFID systems.