The Case for Multi-Tag RFID Systems

Radio Frequency Identification (RFID) is a promis- ing technology for automated non-line-of-sight object identification. However, factors such as object occlu- sions, metal / liquid opaqueness, environmental con- ditions, and radio noise degrade the overall availabil- ity, reliability, and dependability of RFID systems. We show that simply increasing the number of read- ers does not adequately address these issues. Instead, we propose tagging each object with multiple tags, and provide definitive experimental data showing that this strategy dramatically improves the effectiveness of RFID systems in the face of radio noise and other in- terfering factors. We solidify the case for multi-tag RFID systems by addressing obstacles to reliable ob- ject detection, and analyzing how multi-tags improve tag detection, even in the presence of (radio-opaque) metals and liquids. We discuss applications that will benefit considerably from multi-tags, and propose care- ful RFID system design through the deployment of appropriate types of multi-tags and anti-collision al- gorithms. We also 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.