Fast K-Reads in COTS RFID Systems

摘要

RFID has become fundamental to applications ranging from inventory management to indoor localization, where reliably reading each tag multiple times (K-reads) is critical for system reliability and robustness. While existing anti-collision protocols address general tag identification, they fail to guarantee deterministic K-reads completion due to the probabilistic nature of tag responses and physical-layer challenges like multipath fading and interference. This paper presents the first work that formally introduces and addresses the K-reads problem, which aims to ensure each tag is successfully read at least K times with minimal total inventory time. Our key insight stems from the observation that conventional approaches waste much interrogation time re-reading already-counted tags while persistently missing others. To solve this, we propose: 1) a novel power-tuned silence method that exploits channel asymmetry to selectively suppress easily detectable tags without transmission overhead; 2) a hybrid framework that intelligently combines: framed slotted ALOHA for bulk identification, power-tuned silence that selectively suppress easily detectable tags without transmission overhead, and targeted polling for remaining hard-to-read tags. Our approach dynamically optimizes the use of these techniques based on real-time tag response characteristics. Implemented on commercial RFID, the system achieves a 65.7% reduction in inventory time compared to the baseline.