REFlex - RFID Real-Time Localization for Flexible Production Environments

Radio frequency identification is often seen as the successor of barcodes. RFID tags work without batteries, can store large amounts of data, are rewriteable, and need not be in line of sight of a reader to be detected. The dominating tags on the market, Electronic Product Code (EPC) tags, operate at 868/915 MHz and enable reading ranges of several meters. While the focus of industrial processes was on identification a few years ago, the localization of a tag gains more and more importance nowadays. Applications include the detection of item order on a conveyor belt, the localization of hand tools, or the determination of a tag’s movement direction.

The project REFlex investigates a new approach of measuring the distance between RFID reader and tag. The method is applicable to existing tags and circumvents accuracy limitations of existing systems by using time-of-flight based measurements. The ranging is implemented by superimposing an extremely low power broadband spread-spectrum signal onto the reader’s interrogation signal. This ensures that neither the RFID communication is influenced nor radio standards are violated.

The ranging method then separates the echo of the RFID tag from all other echoes of the environment by a novel algorithm, allowing for a direct measurement of the reader to tag distance. REFlex’s consortium investigates the applied methods with respect to their physical limits, required calibration techniques, and performance increase by using multiple antennas.

The research on distance measurement is complemented by investigating and modelling industrial processes which use RFID localization. This allows to determine accuracy requirements for the localization algorithms as well as to establish a feedback from industry to research. To pave the way for a successful industrial deployment of the localization technique, the consortium is also active in standardization bodies in parallel to research activities. Furthermore, the team of REFlex studies social and ethical aspects of possible consequences of the ranging technology, like indirect tracking of individuals, to achieve "responsible innovation".