The Optimization for Hyperbolic Positioning of UHF Passive RFID Tags

This paper presents a fine-grained positioning method for radio frequency identification (RFID). The proposed method applies hyperbolic positioning to locate ultrahigh frequency passive RFID tags. In our design, finding the tagged object's location is formulated as an optimization problem. Phase values, collected by the moving antenna, are exploited to achieve the optimal solution. The intuition of hyperbolic positioning lies in that the difference of distances from a target tag to two antennas can be inferred from phases. When integrating hyperbola curves together, optimization method can be performed to achieve the object's location. Particle swarm optimization is then applied to enhance computational ability. For random phases, polynomial regression is employed to model the relationship between phase values and distances. We implement a prototype of hyperbolic positioning optimization to pinpoint the RFID tag's location and evaluate its performance in our laboratory environment. Compared with other RFID localization methods, i.e., received signal strength indicator based and phase-based approaches, our design shows greater tolerance to tag diversity and tag orientation.