ABSTRACT
Radio-frequency identification (RFID) is a promising technology for automated object identification that does not require line of sight, and accurate object identification is the primary objective of RFID. However, many factors such as object occlusions, metal/liquid opaqueness, and environmental conditions (e.g., radio noise) impede object detection, thus degrading the overall availability, reliability, and dependability of RFID systems. For example, a recent major study by Wal-Mart has shown that object detection probability can be as low as 66 percent. To improve the accuracy of object identification, we propose the tagging of objects with multiple tags. We show that this strategy dramatically improves the efficacy of RFID systems, even in the face of (radiopaque) metals and liquids, radio noise, and other interfering factors.We define different types ofmulti-tags and examine their benefits using analytics, simulations, and experiments with commercial RFID equipment.We investigate the effects of multi-tags on anticollision algorithms, and develop several techniques that enable multitags to enhance RFID security. We suggest new promising applications of multi-tags, ranging from improving patient safety to preventing illegal deforestation. We analyze the economics of multi-tag RFID systems and argue that the benefits of multi-tags can substantially outweigh the costs in many current applications, and that this trend will become even more pronounced in the future.
