Tuesday, April 26, 2005 - AIM Global
With all the publicity about the submission of UHF Gen2 to ISO and, more significantly, the announcement by RFID vendors of Gen2 tags and readers, it's time to review what UHF Gen2 actually represents in terms of technology.
While UHF Gen2 was developed within EPCglobal™, the document submitted to ISO is a standard for UHF systems operating in the 860-960 MHz frequency band. It is not a specification designed exclusively for EPC use. This opens up the use of UHF Gen2 to applications outside the supply chain and will help move development forward at a rapid pace.
The need for UHF Gen2 grew out of the first implementation of EPC UHF systems as well as the need to accommodate some international regulatory and registration authority issues prior to ISO submission. It represents a major step forward in establishing a globally acceptable UHF RFID standard. (A globally acceptable standard already exists for 915 MHz RFID.)
The Gen2 specification represents some of the "best of all worlds" in RIFD and incorporates some significant technical advances over previous UHF offerings.
Specifically, UHF Gen2:
Offers increased range over Gen1;
Includes Write Once Read Many (WORM) and read/write tags with user memories up to 256 bits (up from 96 bits);
Mandates three different modulation schemes (for local regulatory compliance);
Offers the potential for significantly higher data transfer rates;
Offers a solution to spurious or unintended reads where multiple readers are in operation in close proximity ("dense reader mode");
Provides a standard command set but allows optional proprietary commands;
Provides for the optional use of ISO Application Family Identifiers (AFIs).
While this is a major improvement over previous systems, there are some limitations.
The potential for increased data transfer rates may not improve throughput in "noisy" environments. Higher data transfer rates are more susceptible to interference from outside sources. This may lead to the need for multiple read attempts.
UHF Gen2 tags operate in an unregulated frequency band -- the ISM (Industrial, Scientific, Medical) band in the U.S. This frequency range is also used by wireless LANs, wireless telephones and other sources of RF. Similar situations exist in other countries as well. All of these other UHF devices may cause interference with Gen2 (as with Gen1).
"Dense reader mode" provides each reader the capability to operate at a slightly different frequency to help reduce interference. However, this is an optional feature. Not all reader manufacturers will immediately implement dense reader mode and existing readers will not have this feature (although it may be available as a firmware upgrade). Additionally, tags will respond to any valid interrogation attempt -- whether on the intended frequency for that reading location or not. Tags have no way of being informed of the "correct" frequency for interrogation or response. Thus, while this is a good first step towards reducing unwanted reads from, say, an adjacent loading door, it is not foolproof and reader placement and location design will still play an important role in achieving the potential of Gen2.
Even with these limitations, Gen2 is still a significant improvement. It establishes a single, global foundation on which manufacturers can base future technological enhancements.