A Summary of RFID Standards

One option the Auto-ID Center had was to develop the numbering system and network infrastructure and use ISO protocols as the standard for the air interface. Earlier, EAN International and the Uniform Code Council had merged their efforts to create the Global Tag (GTAG), with ISO's UHF protocol. But the Auto-ID Center rejected this, because the ISO UHF protocol was too complex and would increase the cost of the tag unnecessarily.

The Auto-ID Center developed its own UHF protocol. Originally, the center planned to have one protocol that could be used to communicate with different classes of tags. Each successive class of tags would be more sophisticated than the one below it. The classes changed over time, but here is what was originally proposed.

• Class 1: a simple, passive, read-only backscatter tag with one-time, field-programmable non-volatile memory.
• Class 2: a passive backscatter tag with up to 65 KB of read-write memory.
• Class 3: a semi-passive backscatter tag, with up to 65 KB read-write memory; essentially, a Class 2 tag with a built-in battery to support increased read range.
• Class 4: an active tag that uses a built-in battery to run the microchip's circuitry and to power a transmitter that broadcasts a signal to a reader.
• Class 5: an active RFID tag that can communicate with other Class 5 tags and/or other devices.

Eventually, the Auto-ID Center adopted a Class 0 tag, which was a read-only tag that was programmed at the time the microchip was made. The Class 0 tag used a different protocol from the Class 1 tag, which meant that end users had to buy multiprotocol readers to read both Class 1 and Class 0 tags.

In 2003, the Auto-ID Center transitioned into two separate organizations. Auto-ID Labs at MIT and other universities around the world continued primary research on EPC technologies. EPC technology was licensed to the Uniform Code Council, which set up EPCglobal as a joint venture with EAN International, to commercialize EPC technology. In September 2003, the Auto-ID Center handed off the Class 0 and Class 1 protocols to EPCglobal, and EPCglobal's board subsequently approved Class 0 and Class 1 as EPC standards.

Class 1 and Class 0 have a couple of shortcomings, in addition to the fact that they are not interoperable. One issue is that they are incompatible with ISO standards. EPCglobal could submit them to ISO for approval as an international standard, but it is likely that ISO would want to revise them to bring them into line with ISO RFID standards. Another issue is that they cannot be used globally. Class 0, for instance, sends out a signal at one frequency and receives a signal back at a different frequency within the UHF band; this is prohibited in Europe, according to some experts (European Union regulations are open to interpretation).

In 2004, EPCglobal began developing a second-generation protocol (Gen 2), which would not be backward compatible with either Class 1 or Class 0. The aim was to create a single, global standard that would be more closely aligned with ISO standards. Gen 2 was approved in December 2004. RFID vendors that had worked on the ISO UHF standard also worked on Gen 2.