Feb 01, 2012Every RFID project's first software design question should be: What unique identifier do the tags carry? The identifier is a number or code that identifies the physical object to which the tag is affixed. Choosing the right identification scheme keeps your application working the way you intend.
RFID readers must never encounter two objects carrying the same identifier, because the reader software can't tell them apart. To avoid this problem, you must first understand whether your application is "open loop," in which assets are tracked through the supply chain, or "closed loop," an RFID system employed within a single facility.
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In an open-loop application, a global identification standard is selected through industry consensus, and that determines what you do as a supply-chain participant. The supply chain for consumer products, for example, uses GS1's Serialized Global Trade Item Number (SGTIN), while the airline industry employs an International Airline Transport Association (IATA) standard to tag checked luggage.
In a closed-loop application, the identifier selection is up to you. In a controlled environment, in which the tags and readers are completely isolated from other applications, any identifier, such as a number preprogrammed by the tag manufacturer, will work. You don't need, for example a standards-based ID for short-range RFID tags that track parts through a factory machine with an embedded reader.
But in other closed-loop applications, readers may inadvertently capture information from "foreign" tags. Let's say, for instance, a dairy is tracking plastic totes using passive ultrahigh-frequency tags and doorway readers with a 15-foot range. The application wants to read only tote tags, but any UHF tag that gets close will be read. This could include tags employees unknowingly carry, such as those on ID badges or ski-lift tickets attached to jackets, or tags on unrelated RFID applications the dairy deploys. If one of these tags happens to carry the same code as one of the totes, the tote-tracking application will be plagued by false data.
To minimize this risk, use a global standard that ensures each identifier is truly unique worldwide. One example is GS1's Global Individual Asset Identifier (GIAI). This consists of a GIAI header, a unique "company prefix" assigned to you by GS1 and a serial number that you choose. Select a different serial number for each tag, and you get an identifier that is different from any other tag you or any other company creates. Your software application easily filters out foreign tags by rejecting any tag lacking a GIAI header or your assigned company prefix.
Identifier selection requires thought, but the right decision will help you avoid disaster down the road.
Ken Traub is the founder of Ken Traub Consulting, a Mass.-based firm providing services to software product companies and enterprises that rely on advanced software technology to run their businesses.