Efficient tag reading protocol for large-scale RFID systems with pre-reading

In large-scale RFID systems, collecting all of the tag IDs is a time-consuming process. A protocol designated as Smart Trend-Traversal (STT) has been proposed to reduce collisions during the tag collection process and to dynamically construct the query strings used to interrogate the tags. In general, if the tag ID information is known to the reader from a previous tag collection round, the efficiency of the current round can be significantly improved. Various protocols have been proposed for scanning a known tag set based on the use of a hash function. Accordingly, the present study proposes an Enhanced STT scheme based on a blocking protocol and a Distributed Record Tag-Check (DRTC) mechanism. Compared to the conventional STT scheme, the proposed protocol adaptively adjusts the length of the query string depending on the response received to the previous query. Moreover, in the DRTC mechanism, the tags determine their transmission slot frame directly without the assistance of the reader, and thus the overall overhead of the tag-collection process is reduced. The simulation results show that the Enhanced STT scheme reduces the total number of queries required to collect the entire tag set compared to the conventional STT method. Moreover, the proposed DRTC mechanism yields an effective reduction in the total number of frame slots compared to existing protocols such as TPP/CSTR and ECRB.