Deterministic blocker tag detection scheme by comparing expected and observed slot status in UHF RFID inventory management systems

Radio Frequency Identification (RFID) is largely used for UHF RFID inventory management system in the shop or warehouse. Recently, it is pointed out that Blocker Tag (BT), which is originally used to protect the privacy, jams RFID inventory management system and a BT detection scheme is proposed. The conventional BT detection scheme detects BT based on the anomaly of the observed number of collision slots. However, in the conventional scheme, a reader can detect BT neither accurately nor quickly since it has to observe at least one frame which consists of large slots. In this paper, we propose a deterministic BT detection by letting tags respond in the specified slots and comparing the expected and observed status of each slot. The response slot is determined by using a hash function, a random number, a frame length and tag's ID. This way enables the reader to predict the status of each slot. Our scheme immediately detects BT if the expected status is different from the observed status. Our scheme can also detect even though BT jams low-rate. Simulation results show that our scheme performs better than the conventional BT detections scheme in terms of the number of required slots to detect BT.