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Radio frequency identification (RFID) is a technology that is also referred to as automatic identification and data capture or AIDC. AIDC is used to help machines identify objects, and which include bar codes and smart cards. RFID specifically refers to automatic identification that uses radio waves to automatically identify people, animals and individual items.

RFID is not new, one of its original uses being the identification of friendly aircraft during the Second World War. Until recently, the technology was viewed as being too expensive and too limited in functionality for most commercial applications. Advances in technology have reduced the cost of individual system components and provided increased capabilities, to the point where numerous organizations are either using or considering using RFID technology. In fact, some organizations, notably Wal-Mart and the U.S. Defense Department, have mandated the use of RFID by their business partners.

RFID is made up of three components: a transponder or tag, a reader or interrogator and the necessary supporting infrastructure such a communications hardware and software.

The RFID tag in most cases consists of a chip and antenna mounted onto a substrate or an enclosure. In the chip is a processor, memory and radio transmitter. These transponders/tags communicate via radio frequency to a reader, which has its own antennas. The readers can interface through a wired or a wireless medium to a main computer. Transponders/tags are also known as smart or radio tags. The memory will vary depending on the manufacturer, from just a few characters to even kilobytes.

Transponders can either be read-only (R/O) that are pre-programmed with a unique identification or read-write (R/W) for applications that require data to be stored in the transponder and can be dynamically updated. Another type of transponder is write once read many times (WORM). This will allow for an identification number to be written to the transponder once. Here information is stored in the memory and while it cannot be changed, the transponder can be read many times.

The two primary types of RFID technologies are active and passive. Active RFID transponders are self-powered and are more expensive than passive. Self-powered active tags have greater communication distance and usually have a larger memory capacity than passive tags. A common application for active RFID is called automatic vehicle identification (AVI) and found on major toll highways.

Passive RFID transponders have no internal power source and require external power to operate (Figure 1). A transponder/tag is powered in one of two ways: inductive coupling or back-splatter. Low-frequency and high-frequency tags are powered using inductive coupling where an electromagnetic signal is transmitted from a reader. The signal received will charge an internal capacitor on the transponder, which in turn, will then supply the energy required to communicate with the reader.

Active or passive RFID are similar. For both:

• Transponders can be read from a distance and from any orientation and do not require line of sight to be read.

• Transponders are read/write capable, which allows for data to be added/changed dynamically at any time.

• Multiple tags can be quickly read all at one time.

• RF tags can be embedded into products and animals. This benefit allows the tag to work in harsh environments providing permanent identification for the life of the product.

Two organizations are most involved in drafting standards for RFID technology: the International Organization for Standardization (ISO) and EPCglobal. ISO represents global interests and has been involved with different RFID technologies for many years (Table 1). Most of the work has been through various subgroups of Joint Technical Committee One (JTC12), for drafting standards for information technology.

In 1999, several universities sponsored by the consumer product industry formed Auto Id Center with a mandate to advance RFID technology. In 2003, the Auto Id Center was reorganized to create EPCglobal under the UCC/EAN umbrella to manage the business side of the RFID market. The founding universities continue their research and development for the EPCglobal under newly formed Auto Id Labs. EPCglobal is responsible for defining specifications for all aspects of RFID technology including standardization. In addition to ISO and EPCglobal, there are many other global and regional organizations, as well as regulatory bodies that are involved in RFID standardization. Some examples include the Automotive Industry Action Group (AIAG) and the U.S. Food and Drug Administration (FDA) and Postal Service.

Low-frequency (LF) is the most mature RFID technology, having been primarily used in manufacturing and agriculture. In the agriculture sector, the ISO 11784 and 11785 standards are specifically designed for animal tracking. ISO 11784 defines the data structure of the animal tag, which includes country code and unique national ID. There are also provisions to use a manufacturer code in place of the country code. ISO 11785 is concerned with the technical aspects of reader-tag communication.

The ISO's 18000 series standards encompass all different frequencies. ISO 18000-2, for example, was finalized and published in 2004. It defines parameters for Air Interface Communications below 135 KHz, that is, the LF range. EPCglobal is also working toward creating standards and specifications for the LF RFID.

Of all the different RFID technologies, high frequency or HF has the most established and commonly used standards. This is partly because 13.56 MHz is a globally available frequency for RFID. JTC1/SC17/WG8, which is the working group for “contactless integrated circuit cards,” started the standardization process for HF RFID in 1995. Their efforts resulted in ISO 15693 and 14443, the most widely used RFID standards to date. Published in 2000, ISO 15693 defines parameters for vicinity RFID cards that are used in applications that require read ranges of more than 10 cm. The 15693 specifications are organized in three separate parts covering physical characteristic, air interface and communication protocol. ISO 14443 is the standard for proximity RFID cards with a read range limited to less than 10 cm. This standard is organized much the same way as the 15693 standard, defining similar parameters in different parts of the standard. The main difference between these two standards is their intended application. ISO 14443, because of its short read distance and encryption capabilities, is more suitable for applications where security is a serious concern such as electronic payment, banking and financial transactions. In addition to these two standards, SC17/WG8 has drafted several other standards pertaining to the use of RFID not covered in this discussion.

Standards are constantly evolving. ISO 15693 and 14443 are the established standards and work well. However, some industry experts feel they do not address all the issues. ISO, therefore, initiated a more focused process under the SC31 umbrella for RFID standardization. The ISO 18000-3 standard for 13.56 MHz RFID is built on the existing ISO 15693. It has two versions, with version one being similar to ISO 15693.

To date, the greatest energy and efforts have been directed at the ultrahigh-frequency or UHF (860 MHz to 956 MHz) band. Delays in developing widely accepted and uniform standards were initially blamed for the slower than expected UHF RFID deployment. These delays were partly due to restrictions in different regions of the world. Currently, there is no globally accepted frequency within the UHF band. The industry has come to terms with this reality and has developed products that are either region specific or able to work with different frequencies. In North America, UHF RFID uses 915 MHz. Europe and Japan use 860 MHz to 868 MHz and 950 MHz to 956 MHz respectively.

ISO's work in the 860 MHz to 956 MHz UHF band resulted in ISO 18000-6, a standard that defines parameters for air interface and communications. As in the case of other 18000 series standards, part 6 covers all technical aspects of RFID communications in great detail. As mentioned above, the 18000 series defines the air interface parameters for different frequencies in parts 2-7. Part 1 covers general parameters common to them. In addition, ISO/IEC 15961, 15962 and 15963 were finalized and published in the fall of 2004. ISO/IEC 15691 defines parameters and commands for communication with the application software, while ISO/IEC 15962 deals with the processing of data and its presentation to the RF tag, and the initial processing of data captured from the RF tag.

ISO/IEC 15963 deals with the unique identification code (UID) and describes the numbering scheme for tags.

EPCglobal's mission started with the vision to identify every item with a unique electronic product code (EPC). The plan is to have a global network implemented making every item visible throughout the supply chain. A great amount of research and development resources have been invested in creating specification and standardization of the EPC tags and the required infrastructure (Table 2). EPCglobal's efforts are primarily focused on UHF.

EPCglobal through its research wing, Auto ID-Labs, has defined specifications for different classes of EPC tags. Earlier class 0 and class 1 tags are being replaced by class 1 Gen 2 UHF tags or just Gen 2. Class 0 EPC tags had a factory-programmed 96-bit code, whereas class 1 allows for user-programmable codes. The Gen 2 interface addressed a number of problems that had been experienced with class 0 and class 1 tags. It was adopted with minor modifications as ISO 18000-6C in 2006.

EPCglobal has also ratified the low-level reader protocol (LLRP) standard. The LLRP standard enabled reader interoperability and created an open standard for technology providers. This new standard, produced by the EPCglobal Reader Operations Working Group, defines performance, flexibly and interface for operating network-connected RFID readers. The protocol was the result of collaboration between more than 90 companies including end users, RFID infrastructure vendors, middleware vendors, industry experts, and networking professionals. LLRP supplies the functionality around reader operations in compliance with the EPCglobal architecture framework. It is the first interface specification that provides comprehensive support for all control and data features of the EPCglobal Gen 2 UHF air interface protocol. The RFID industry is moving fast to enhance current standards and create the new ones required for the worldwide implementation of the technology. Considerable efforts have been channeled toward this goal and it is hoped that the standardization process can soon catch up with advancements in other aspects of the industry. ISO is the global authority for standardization and EPCglobal is a major force in the RFID market with the support of the consumer packaging industry.

In summary, it is important to have a good understanding of RFID technology and standards developments. This knowledge will enable engineers and businesses to use the technology, realize its functionality and understand its benefits.

The technical team of GAO RFID Inc. (www.GAORFID.com) is comprised of experienced design engineers and CompTIA RFID certified engineers who specialize in the development of solutions and integration services for various verticals.

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