Electronic Product Code - EPC

Many companies are investing in RFID systems today to get the advantages they offer. These investments are usually made in closed-loop systems - that is, when a company is tracking goods that never leave its own control. That way, they don't have to worry about their tags being read by other companies. But most companies don't have close-loop systems. Since all existing RFID technology is proprietary (meaning there are no standards), if Company A tags a widget and sends it to Company B, Company B can't identify the product unless it has invested in the same technology from the same vendor as Company A.

Creating one, open global network for RFID means that companies can invest in systems and have confidence that the tags they put on their products can be read by retailers and other business partners. It means companies can share information about products and develop systems that automate many of today's labor-intensive operations. For example, when shipments arrive at a store from a factory, the computer systems of both companies can be updated automatically and an invoice can automatically be sent. It also means that manufacturers of RFID equipment can make equipment in vast quantities, since it will work with anyone's system, which will help bring down the price of both tags and readers.

How do you distinguish between one can of Coke and another? There are a number of ways, but the best solution found is to give each item a unique number - a license plate, if you will. The Auto-ID Center has proposed a universal standard for product "license plates" - the Electronic Product Code. Like a bar code, the EPC is divided into numbers that identify the manufacturer, product, version and serial number. But the EPC uses an extra set of digits to identify unique items. The EPC is the only information stored on the RFID tag's microchip. This keeps the cost of the tag down and provides flexibility, since an infinite amount of dynamic data can be associated with the serial number in a database.

How do you track the item using the license plate?  The answer is to create a network of RFID readers (sometimes called interrogators). In a warehouse for example, there could be readers around the doors on a loading dock and on every bay. When a pallet of goods arrives, the reader on the dock door picks up its unique license plate. Inventory systems are alerted to its arrival. When the pallet is put in bay A, that reader sends a signal saying item 1-2345-67890 is in bay A.

The Auto-ID Center has proposed a new Electronic Product Code as the next standard for identifying products. The goal is not to replace existing bar code standards, but rather to create a migration path for companies to move from established standards for bar codes to the new EPC. To encourage this evolution, was adopted the basic structures of the Global Trade Item Number - GTIN, an umbrella group under which virtually all existing bar codes fall. There's no guarantee that the world will adopt the EPC, but this proposal already has the support of the Uniform Code Council - UCC, and EAN International, the two main bodies that oversee international bar code standards. 

The EPC is a number made up of a header and three sets of data, as show in the above figure. The header identifies the EPC's version number - this allows for different lengths or types of EPC later on. The second part of the number identifies the EPC Manager - most likely the manufacturer of the product the EPC is attached to - for example "The Coca-Cola Company". The third, called object class, refers to the exact type of product, most often the Stock Keeping Unit -SKU - for example "Diet Coke 330ml can, US version. The fourth is the serial number, unique to the item - this tells us exactly which 330ml can of Diet Coke we are referring to. This makes it possible, for example, to quickly find products that might be nearing their expiration date.

The Auto-ID Center has proposed EPCs of 64-bits, 96-bits, and 256-bits (see tables below). The 96-bit number is the one that should be most common. Selecting the 96-bit was a compromise between the desire to ensure that all objects have a unique EPC and the need to keep the cost of the tag down. The 96-bit EPC provides unique identifiers for 268 million companies. Each manufacturer can have 16 million object classes and 68 billion serial numbers in each class, more than enough to cover all products manufactured worldwide for years to come. Since there is no need for that many serial numbers at this time, was proposed an interim 64-bit code. The smaller code will help keep the price of the RFID chips down initially, while providing more than enough unique EPCs for current needs.

Types of Tags

• EPC UHF Class 0 : specifies a factory-programmed (non-rewriteable) tag that operates in the 860-930 MHz frequency range.

• EPC UHF Class 1: tags are one-time programmable (OTP, which means data on the tag can be updated one time in the supply chain after the tag is initially programmed) and operate in the 860-930 MHz range.

• EPC HF Class 1: tags operate at 13.56 MHz and have the same data and programming characteristics as the UHF version.

(see also RFID information)

EPC Headers

EPC Structures (bits)

For more information about the EPC, visit the website of the Auto-ID Center - Massachusetts Institute of Technology -MIT (www.autoidcenter.org).