Mar 14, 2012Manufacturers of the microchips used in passive ultrahigh-frequency (UHF) radio frequency identification transponders based on GS1's Electronic Product Code (EPC) standard are having informal discussions in an effort to reach an agreement regarding an industry-wide approach to encoding unique serial numbers in EPC tags using the Tag ID (TID), a serial number hard-coded into RFID chips during manufacture. The goal would be to ensure that end users could use chip-based serialization—numbers generated from the TIDs—without worrying that tags provided by different vendors would contain duplicate serial numbers.
GS1 US set up a U.S.-based working group in April 2011 to look into the issue of serialization, working with Gena Morgan, GS1 US' program manager, and Ken Traub, a consultant for GS1 US, as the group's facilitators. The team comprised roughly 30 stakeholders, including label converters, brand owners, retailers and chipmakers.
"Everyone agreed that it would be nice to have a global standard," Traub says, "but in the end, everybody agreed that suppliers need the flexibility to develop their own serialization plans, whether managing serial numbers themselves, using the Tag ID, or using a combination of methods."
At present, there are a small number of suppliers tagging a large volume of apparel items for retailers, so the chances of an EPC being duplicated are not large, and the problems caused by duplication would be minimal. But that could change, according to Patrick Ervin, Alien Technology's VP of worldwide marketing and sales.
"There are several approaches to serialization," Ervin explains. "Having a pre-encoded serial numbers is one way. Using software to create serial numbers, or having a service bureau do it, are other ways. What we want to do is try to make it less complex for the end users to use whatever method they want, or mix several methods without the risk of duplication."
The industry is looking to utilize Tag IDs to create EPCs. Every TID is unique, since each includes 12 bits to identify the chip manufacturer, as well as 12 bits for the model, plus a serial number. The EPC Gen 2 standard specifies two different formats for the TID bank, both of which lead to a globally unique identifier, and there is a global registry to ensure the uniqueness of TIDs for Gen 2 tags complying with the Gen 2 / ISO 18000-6C standard.
If the EPC is based on a unique TID, then no duplication would be possible. The problem is that the TID's serial number includes 24 bits to identify the manufacturer and model, plus a 48- to 144-bit serial number, and the 96-bit EPC format used for consumer products has just 38 bits assigned for the serial number portion of the EPC (the other 58 bits are utilized to identify the type of product being tagged, so that the combination of product identifier and serial number is unique across all tags). As such, there is insufficient room to include the full TID, which ranges from 72 to 168 bits in size when all three components (the chipmaker ID, the model ID and the serial number) are combined. What's more, there is currently no simple way for a goods manufacturer tagging items at multiple locations worldwide to ensure that it does not duplicate EPCs.
GS1 US' serialization working group examined several options for using parts of the TID, but could not agree on an approach that would meet the needs of all involved parties. Several retailers and goods suppliers have already begun serializing products, and did not want to have to switch to a different schema. Other stakeholders expressed concerns regarding how to employ only a portion of the TID and still guarantee uniqueness.
The IC companies, however, still believe that they can agree on a system that would guarantee uniqueness, while offering end users flexibility. NXP Semiconductors has proposed a system of assigning each chipmaker a six-bit number, or several numbers if necessary for different chip models. Each serial number would consist of six bits identifying the chipmaker, as well as 32 bits from the TID. These 38 bits could be encoded into the serial number portion of each tag's EPC. The end user would then add its Company Prefix (thereby indicating the manufacturer of the item being tagged) and the product identifier, after which the full EPC would be a Serialized Global Trade Identification Number (SGTIN), as defined by an existing GS1 standard, which most companies currently use as their EPC.
NXP plans to introduce a serialization method called FastEPC at the RFID Journal LIVE! 2012 conference and exhibition, being held on Apr. 3-5, 2012, in Orlando, Fla., and will demonstrate the solution at its booth, as part of the Coolest RFID Demo Contest (see RFID Journal Introduces 'Coolest RFID Demo' Contest). With FastEPC, the company will preprogram a 38-bit unique number based on the TID into the serial number section of each chip's EPC memory. A customer can either add its Company Prefix and product number to create an SGTIN, or encode a completely new EPC containing its own serial number.
"The process is much more streamlined for the end user," says Victor Vega, NXP Semiconductors' director of RFID solutions. "NXP ICs have always included a unique TID, lending them to be easily used as a basis for the TID-based EPC serialization," he states, "but with FastEPC, there are no look-up tables, and no need to read and extract information from the TID. This reduces both programming content and processing time, whereby only the Company Prefix and product information need be encoded into the tag."
Another advantage of this approach, according to Vega, is that the reader can communicate with multiple tags prior to programming (if tag EPC numbers are not unique, however, the reader will recognize multiple tags as a single tag, and will be able to communicate with them only if they are isolated in the read field). Preprograming also allows a retailer or brand owner to scan the bar code of a product being tagged, in order to extract that item's Universal Product Code (UPC), and to then convert it to a GTIN by writing the Company Prefix and stock-keeping unit (SKU) from the bar code to the relevant tag fields—or to use a fixed reader to bulk-encode GTINs in the event that all of the items have the same SKU, thereby resulting in automated SGTIN serialization.
Alien, Impinj and NXP will each offer its own serialization approach to customers, but Vega is confident that the three chipmakers can still work together to offer chip-based serialization, while ensuring that EPCs are not duplicated. "The approach we've put forward [FastEPC] is simple and flexible, and will not add to the cost of the IC," he says. "Without a common approach, managing serialization will be more complex for the end user, and there will be a greater risk of duplication. Alien, Impinj and NXP have made good strides in the past few weeks toward an aligned approach. We continue working together toward a unified solution."
