The ABCs of RFID
Understanding what RFID devices are and how they work is critical to an analysis of the policy issues surrounding this technology. Generic references to “RFID technology” may be applied incorrectly to a wide range of devices or capabilities. For example, RFID by itself is not a location-tracking technology. At sites where readers are installed, RFID may be used to track tagged objects, but this static readability differs from technology such as global positioning systems, or GPS, which uses a network of satellites to pinpoint the location of a receiver. And RFID technology itself can be used for a variety of applications, from contactless identification cards that can be scanned no farther than inches away from a reader, to highway systems utilizing “active” RFID tags that can initiate communication with a scanner 100 feet away.
A. Primary Components of RFID Devices
RFID devices have three primary elements: a chip, an antenna, and a reader. A fourth important part of any RFID system is the database where information about tagged objects is stored.
- The chip, usually made of silicon, contains information about the item to which it is attached. Chips used by retailers and manufacturers to identify consumer goods may contain an Electronic Product Code (“EPC”). The EPC is the RFID equivalent of the familiar universal product code (“UPC”), or bar code, currently imprinted on many products. Bar codes must be optically scanned, and contain only generic product information. By contrast, EPC chips are encrypted with a unique product code that identifies the individual product to which it is attached, and can be read using radio frequency. These codes contain the type of data that product manufacturers and retailers will use to track the authenticity and location of goods throughout the supply chain.
An RFID chip may also contain information other than an EPC, such as biometric data (a digitized image of a fingerprint or photograph, for example). In addition, some chips may not be loaded with information uniquely identifying the tagged object at all; so-called “electronic article surveillance systems” (“EAS”) may utilize radio frequency communication to combat shoplifting, but not to uniquely identify individual items.
- The antenna attached to the chip is responsible for transmitting information from the chip to the reader, using radio waves. Generally, the bigger the antenna, the longer the read range. The chip and antenna combination is referred to as a transponder or, more commonly, as a tag. Participants at the workshop brought samples of tags currently in use. The pictures below show a common EPC tag that can be affixed to an object (Figure A) and a paper hang-tag that can be attached to individual articles of clothing (Figure B13).
The reader, or scanning device, also has its own antenna, which it uses to communicate with the tag. Readers vary in size, weight, and power, and may be mobile or stationary. Although anyone with access to the proper reader can scan an RFID tag, RFID systems can employ authentication and encryption to prevent unauthorized reading of data. “Reading” tags refers to the communication between the tag and reader via radio waves operating at a certain frequency. In contrast to bar codes, one of RFID’s principal distinctions is tags and readers can communicate with each other without being in each other’s line-of-sight. Therefore, a reader can scan a tag without physically “seeing” it. Further, RFID readers can process multiple items at one time, resulting in a much-increased (again as compared to UPC codes) “speed of read.”
The pictures on the opposite page show various RFID readers: a stationary reader that could be used to track tagged cases of goods entering a warehouse (Figure C19); a mobile reader used to monitor inventory on a retail store floor (Figure D20); and a prototype of a glove embedded with a scanner used to track daily domestic living activities (Figure E21).
- The database, or other back-end logistics system, stores information about RFIDtagged objects. Access to both a reader and its corresponding database are necessary before information stored on an RFID tag can be obtained and understood. In order to interpret such data, RFID readers must be able to communicate with a database or other computer program.
One protocol being developed for product manufacturers uses chips embedded with a 96-bit EPC code – a number – that includes several fields identifying the manufacturer (“ABC Company”), the product (“cola”), its size or its packaging (“24-pack of cola cans”), and a unique identifier. This system, the “EPCglobal Network,” calls for a secure network of servers that will share information obtained from tagged objects moving through the supply chain. According to the network’s architect, EPCglobal, the data will be stored on EPCglobal member company databases, access to which will be controlled by those individual companies. In order to interpret what these fields mean, a directory, or “object naming service” (“ONS”), will direct the reader to the appropriate server(s) where the data from the tag and associated information are stored. The ONS will function much like a reverse telephone directory or an Internet browser, which translates a URL into a Web site. In the RFID context, the ONS will identify what server has information about the tagged item, allowing an RFID user to interpret the meaning of the particular code on a particular tag. The database information will vary with the context. For example, with automatic highway toll payment systems, databases will link account numbers stored on a tag to the appropriate prepaid account for billing purposes.
Although all RFID systems have these essential components, other variables affect the use or set of applications for which a particular tag is appropriate. As discussed further below, key factors include whether the tag used is “active” or “passive”; what radio frequency is used; the size of the antennas attached to the chip and to the reader; what and how much information can be stored on a tag; and whether the tag is “read/write” or “read-only.” These factors affect the read ranges of the systems as well as the kind of object that can usefully be tagged. They also impact the cost, which is an especially important commercial consideration when tagging a large volume of items.
B. Passive v. Active Tags
There are three types of RFID tags, differentiated by how they communicate and how that communication is initiated:
- Passive tags have no onboard power source – meaning no battery – and do not initiate communication. A reader must first query a passive tag, sending electromagnetic waves that form a magnetic field when they “couple” with the antenna on the RFID tag.” Consistent with any applicable authorization, authentication, and encryption, the tag will then respond to the reader, sending via radio waves the data stored on it. Currently, depending on the size of the antenna and the frequency, passive tags can be read, at least theoretically, from up to thirty feet away. However, real-world environmental factors, such as wind and interference from substances like water or metal, can reduce the actual read range for passive tags to ten feet or less. Passive tags are already used for a wide array of applications, including building-access cards, mass transit tickets, and, increasingly, tracking consumer products through the supply chain. Depending on the sophistication of the chip, such as how much memory it has or its encryption capability, a passive tag currently costs between 20 cents and several dollars.
• Semi-passive tags, like passive tags, do not initiate communication with readers, but they do have batteries. This onboard power is used to operate the circuitry on the chip, storing information such as ambient temperature. Semi-passive tags can be combined, for example, with sensors to create “smart dust” – tiny wireless sensors that can monitor environmental factors. A grocery chain might use smart dust to track energy use, or a vineyard to measure incremental weather changes that could critically affect grapes.30 Devices using smart dust, also known as “motes,” currently cost about $100 each, but, in a few years, reportedly could drop to less than $10 apiece.
• Active tags can initiate communication and typically have onboard power. They can communicate the longest distances – 100 or more feet. Currently, active tags typically cost $20 or more. A familiar application of active tags is for automatic toll payment systems, like the Northeast’s “E-ZPass,” that allow cars bearing active tags to use express lanes that don’t require drivers to stop and pay.
C. Radio Frequency
Communication between RFID tags and readers is also affected by the radio frequency used, which determines the speed of communications as well as the distance from which tags can be read. Higher frequency typically means longer read range. Low-frequency (“LF”) tags, which operate at less than 135 kilohertz (KHz), are thus appropriate for short-range uses, like animal identification and anti-theft systems, such as RFID-embedded automobile keys. Systems that operate at 13.56 megahertz (MHz) are characterized as high frequency (“HF”). Both low-frequency and high-frequency tags can be passive. Scanners can read multiple HF tags at once and at a faster rate than LF tags. A key use of HF tags is in contactless “smart cards,” such as mass transit cards or building-access badges.35
The third frequency, Ultra-High Frequency (“UHF”), is contemplated for widespread use by some major retailers, who are working with their suppliers to apply UHF tags to cases and pallets of goods. These tags, which operate at around 900 MHz, can be read at longer distances, which outside the laboratory environment range between three and possibly fifteen feet. However, UHF tags are more sensitive to environmental factors like water, which absorb the tag’s energy and thus block its ability to communicate with a reader.
D. Read/Write Capacity
Finally, another important feature of RFID tags is their “read/write” capacity, or “read only” status. These terms refer to a tag’s ability to have data added to it during its lifetime. The information stored on a “read-only” tag cannot be altered, but a writeable tag (with read/write capacity) can receive and store additional information. Read/write applications are most prevalent when tags are re-used. They are usually more sophisticated and costly than read-only applications. In addition, read/write applications have shorter read ranges. Read only tags are well-suited to applications like item-level tagging of retail goods, since they are less expensive and, as part of a networked system, can provide a great deal of information by directing the reader to the associated database(s) where information about the tagged item is maintained.
FTC Releases Radio Frequency Identification Workshop Report, FTC 3/9/2005
- NIST Advises on RFID Security Risks, eweek 5/1/2007
- Radio Frequency Identification: Opportunities and Challenges in Implementation, NTIA 5/17/2005
- COMMERCE TO HOST RFID WORKSHOP WITH INDUSTRY, Wednesday, April 6, 2005., TA DOC 2/22/2005
- FTC Releases Radio Frequency Identification Workshop Report, FTC 3/9/2005
- FCC'S OFFICE OF ENGINEERING AND TECHNOLOGY ANNOUNCES PANELISTS AND AGENDA FOR WORKSHOP ON RADIO FREQUENCY IDENTIFICATION, OCTOBER 7, 2004. News Release. News Media OET. Contac, FCC 9/30/2004
- FCC ANNOUNCES RADIO FREQUENCY IDENTIFICATION (RFID) WORKSHOP. The FCC will convene a Radio Frequency Identification (RFID) Workshop to take place October 7, 2004, at the Federal Communications Commission. News Release. News MediaFCC 9/17/2004
- "From RFID to Smart Dust: The Expanding Market for Wireless Sensor Technologies" U.S. Department of Commerce April 1, 2004 Panelist Bios Agenda
- Revisiting Smart Dust with RFID Sensor Networks PDF
- When Safety Matters: Using Active RFID Down the Mines RFID technology can help businesses in many ways. But the greatest promise may lie in enhanced security, access control, and safety for workers in dangerous environments. The RFID system Watcher-ATS has proven particularly useful in mining and offshore oil platform applications. Feb 1, 2004 By: Sven Haagensen, Ph.D.
- Passive Tags (range 20 feet)
- Active Tags (contains a battery)
Webcasts & Podcasts
- 10/7/04 Radio Frequency Identification Workshop
- Panelists and Agenda: Word | Acrobat
- News Release: Word | Acrobat
- Consumers Against Supermarket Privacy Invasion and Numbering (CASPIAN)
- the Privacy Rights Clearinghouse
- CSTB: Radio Frequency Identification (RFID) Technologies: A Workshop Summary, CSTB 2/1/2005
- Radio Frequency Identification Reduces Workplace Privacy, RAND 2/18/2005
- Boss, R. W. (2004, May 14). RFID Technologies for Libraries.
- Consumers Against Supermarket Privacy Invasion and Numbering. (2003, November 20).
- RFID Position Statement of Consumer Privacy and Civil Liberties Organizations.
- Eschet, G. (2004). Adapting Fair Information Practices to Radio Frequency Technology (Draft). SSRN
- Harper, J. (2004, June 21). RFID Tags and Privacy: How Bar-Codes-On-Steroids Are Really a 98-Lb. Weakling. CEI OnPoint.