A Time-Efficient Protocol for Unknown Tag Identification in Large-Scale RFID Systems

Abstract

In radio-frequency identification (RFID) applications, RFID tags attached to new, misplaced, or counterfeited commodities sometimes may not be timely registered and are unknown for readers. In applications like inventory management and product tracking, these unknown tags pose several challenges for fast tag identification. A simple method to identify unknown tags is to first deactivate the registered known tags, and then collect IDs of the unknown ones. However, this is a nontrivial task. In fact, unknown tags cause interference with the deactivation of known tags. Moreover, the unknown tag collection methods used in existing protocols either suffer severe tag collisions or generate many empty slots, which increases the final execution time. In this article, we propose an efficient unknown tag identification (EUTI) protocol. First, EUTI builds a vector-based filter to exclude the tags that are not expected to reply in each slot, so that EUTI can use both predicted collision slots and singleton slots for unknown tag deactivation and avoid collisions caused by unknown tags. Second, EUTI adopts a reservation mechanism to reduce collision slots and guide each unknown tag to skip empty slots when replying, thus saving execution time. Moreover, we provide a theoretical analysis of EUTI to minimize execution time and extend EUTI to multi-reader scenarios. Numerical results show that EUTI outperforms the state-of-the-art solutions by reducing up to 44.12% in deactivation time, 26.47% in collection time, and 27.75% in total time.