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New Technique Could Help Advance RFID Adoption

SARFID offers a low-cost, easily deployable solution for accurately determining the locations of moving tagged objects.
By Alice Buffi
Sep 19, 2016

Nowadays, the full adoption of ultrahigh-frequency (UHF) RFID technology to manage luggage in airport baggage-handling systems (BHS) is being discussed. For example, in April 2016, Delta Air Lines announced plans to use RFID to track 120 million bags annually (see Delta Gives Green Light to RFID Baggage Tracking), with 99.9 percent accuracy. Bill Lentsch, Delta's senior VP of airport customer service and cargo operations, said, "With a $50 million investment in RFID at 344 stations around the globe, we aim to reliably deliver every bag on every flight."

For the industry as a whole, the primary concerns related to adoption center on the cost-benefit ratio of using an RFID-enabled BHS compared with the bar-code technology currently in use. The advantages of employing RFID have been described in "RFID for Baggage Tagging," a white paper posted by Impinj in 2010, and RFID Journal's editor and publisher, Mark Roberti, discussed the return on investment in 2013 (see Airlines Could Benefit From RFID-Enabled Baggage Handling).

Efforts to adopt RFID technology for baggage-handling systems could be aided by the application of accurate and efficient phase-based localization methods, such as the SARFID (Synthetic Aperture Radar approach for RFID tag localization) technique that I and several colleagues at the University of Pisa developed and patented (see "Method for determining the location of a moving RFID tag," EP2533173B1, Applicant: University of Pisa, Authors: P. Nepa, F. Lombardini, A. Buffi).

SARFID is a smart technique able to simultaneously localize multiple RFID-tagged items moving along conveyor belts, in real time, by analyzing phase changes in the RF signal transmitted by a tag. The technique works with off-the-shelf readers, antennas and tags. If an RFID gate already exists at a belt section, the SARFID technique can be simply implemented either as an upgrade to the reader firmware or as ad-hoc middleware, without any modification necessary to the BHS infrastructure. SARFID is fully automatic and can significantly reduce labor costs and human errors. Experimental results in real scenarios demonstrated that UHF RFID tags can be correctly sorted and localized with centimeter-order accuracy.

The SARFID technique can work with only a single reader antenna, not requiring the simultaneous detection of a tagged object by a set of spatially separated antennas. Moreover, it works with any bag tags compliant with the EPC Gen 2 RFID protocol. Additionally, in a tag-dense scenario, an extension of the SARFID technique can be used to discriminate among tagged objects on the selected conveyor line and any other tagged object, either static or not, located in the reader antenna's coverage area.

SARFID is a low-cost, easy-to-deploy solution that can be employed in any system, including automatic conveyor lines (belts, rails and so forth), to achieve accurate spatial localization of tagged objects in motion.

The technique can also find applications in any scenario for which there is relative movement between a reader antenna and tagged objects: automation production lines, handling systems on rails, overhead cranes, automatic storage system in warehouses, etc. Indeed, SARFID can also be used to localize tagged objects on a shelf if the reader antenna can be moved in front of that shelf using a proper mechanical system.

Further details regarding the SARFID technique and measurement results in various real scenarios can be found at www.mrlab.it/wireless/sarfid-localization.

Alice Buffi is a researcher at the University of Pisa's Microwave and Radiation Laboratory.

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