Report on RFID
At A Glance
Radio-frequency identification, or more widely known as RFID, is a system where a reader reads tag(s) via radio frequency waves and interprets the content with a predefined format. The technologies that RFID system uses have been here for a while, but only recently the usage has become widespread that now many are not aware that they are using items that contain RFID tags in it.
Various RFID systems are in the market for different purposes and the cost for each system vary greatly, but their functionality, as well the technology employed, are essentially the same.
History of RFID
In 1888, German physicist Heinrich Rudolf Hertz first proved the existence of electromagnetic radiation; then in 1901 Guglielmo Marconi sent the first wireless long-distance transmission. These created a new era in mankind history.
The first RFID implementation happened in World War II when British military installed “Identification, Friend or Foe” (IFF) on their aircraft, which enabled them to identify the incoming aircraft’s identity – a signal would be transmitted to the aircraft’s transponder which would return an encrypted code. Such technology enabled them to reduce friendly fires among Allied forces. Modern technologies are still essentially the same.
The first RFID patent was awarded by United States Patent and Trademark Office in 1973 to Mario W. Cardullo.[1] Also in the 1970s, Los Alamos National Laboratory was developing a system to track nuclear materials. The system was commercialized in 1980s when the scientists who worked on the project left the laboratory and set up a business.
Between 1999 and 2003, two air interface protocols (Class 1 and Class 0), the Electronic Product Code (EPC) numbering scheme, and a network architecture for looking up data associated on an RFID tag on the Internet, were developed by the Auto-ID Center. Uniform Code Council obtained the license for the technology in 2003, and EPCglobal was created, as a joint venture with EAN International, to commercialize EPC technology. EPCglobal ratified a second-generation standard in December 2004, as a way to anticipate broader adoption.
Basic Usages and Applications of RFID
The simplest form of a RFID system contains three major components: a tag, a reader, and a predefined format to transfer information. RFID tags transfer information in its memory to the reader via radio frequency waves.
Many of us use RFID-enabled devices daily without realizing its existence. Some of the more notable examples of RFID applications are:
Passports – Malaysians got the world’s first biometric passport in 1998, when IRIS Corporation developed the technology using RFID. Many other countries have since begun to issue similar passports.
Digital Currency - Hong Kong’s Octopus Card, and Japan’s Suica, both based on Sony’s FeliCa RFID smart card system, as well as other equivalent cards, let commuters skip the queues in front of ticket vending machines, and is also a form of payment in convenient stores and at vending machines.
Toll Payments – Systems like Singapore’s Electronic Road Pricing (ERP) use RFID systems to eliminate the need to stop the vehicle completely to pay the toll charges.
Libraries – The usage of RFID tags on books as well as other materials facilitate checkouts as well as aid patrons to pinpoint its location.
Animal Tracking – Pets, livestock, and endangered species can be tagged with RFID chips, and then be tracked to observe its movements as well as to store data such as vaccination records, ownership details, birth date and even temperature.
RFID Technology
RFID Tags
Several designs of RFID tags are available in the market, each with its own characteristics which make one suitable for a particular application while totally impractical to be used on other circumstances.
Regardless of designs, each RFID tag has the following essential components:
Antenna – primarily for transmitting and receiving radio frequencies to communicate with the readers. Passive tags also use the antennas to collect energy.
Integrated Circuit (IC) – An essential part of a tag, its job is to transmit the tag’s unique identifier, and also as a master controller for more complex tags.
Printed Circuit Board (PCB) – Holds the tag together. Depending on the purpose, it can be rigid or flexible, as well as being made of different materials.
Two major classifications of RFID tags, active tags and passive tags are in the market today. An active tag has its own power source, typically battery. Such tags have greater ranges compared to passive counterparts and also can be read through impenetrable materials, but they are larger and more expensive, mostly due to batteries, and the batteries limits its lifespan, depending on its beacon rate, which is the interval of the signal being sent. At up to 8MB, active tags also have larger amount of memory.
Passive tags, on the other hand, are cheap to manufacture, much smaller, and therefore, more common on the market. Passive tags collect energy through its antenna. They, however, have comparatively limited range, and may not be read through impenetrable materials. Furthermore, passive tags are notably lower in memory, often not exceeding 64KB.
RFID Readers
In order to read and understand the content of RFID tags, appropriate readers are needed for the purpose. Essentially there are at least two components needed for any reader:
Antennas are needed to receive and transmit radio frequency. The effectiveness of RFID deployments largely depend on the selection of appropriate antennas.
Integrated Circuit (IC) board handles necessary information to communicate with the tag. Each board contains a microprocessor, memory and a radio frequency transponder.
In some setups it is necessary to have multiple readers set up.
EPC Standards
Electronic Product Code (EPC) is the standard for the RFID system developed by MIT’s Auto-ID Center in 2000. Like Barcode’s Universal Product Code, it identifies an item. However, RFID tags with EPC can identify a particular item, compared to Barcodes, which can only identify an item’s type.
An EPC code contains the following fields:
Header – it tells the reader the format of the code.
EPC Manager Number – it contains the manufacturer’s information.
Object Class – identifies a class of objects.
Serial Number – identifies a particular item.
Depending on the application, the length of the code can be from 32-bit to 256-bit.
RFID Frequencies
Depending on usages, different RFID frequency range caters different needs for a system. It is particularly important to choose an appropriate frequency range or it may cause interference to other electromagnetic waves such as television signals. Also different countries have different regulations on the RFID’s radio frequencies. The table below summarises frequency ranges available for RFID readers. (Content obtained from http://rfid-handbook.de/rfid/frequencies.html)
Frequency-ranges used for RFID-systems shown with the corresponding field strength and power levels.
Algorithms for RFID
Several algorithms exist for RFID systems to provide required functionalities, but two most important algorithms for RFID are cryptography algorithm and anti-collision algorithm.
While most RFID tags, for example tags found on groceries, do not contain security-sensitive contents other than its EPC codes, some other RFID implementations, for example passports and digital cash systems, require sufficient encryption to protect the user from security risks. Encryptions techniques such as DES, 3DES, AES and proprietary KEELOQ® are used to secure sensitive information that could be exploited to expose privacy and security issues.
When two or more RFID tags are being read simultaneously, or two or more RFID readers read the same tag at the same time, collisions can occur. Such collisions affect accuracy of the RFID data being read, as well as overall performance of the readers.
Readers utilize multiple access communication type to communicate with several tags at the same time. For readers three multi-access procedures exist – Space Division Multiple Access (SDMA), Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA). SDMA reuses resources such as channel capacity of devices that are spatially separated. The usage of a directional antenna causes the reader to communicate only with a tag in its range. SDMA however is complex and expensive, thereby limits its usefulness. Meanwhile, FDMA divides an RF bandwidth into several smaller frequency bands, enabling tags to communicate in different channels. Like SDMA, FDMA’s usefulness is limited due to its implementation cost. TDMA, on the other hand, divides the available channel capacity into unique time slots that are allocated within each channel. It restricts when and how much a tag can transmit data. TDMA is the most widely implemented reader anti-collision procedures, and is also the most widely used anti-collision for tags as well.[2]
The most notable tag anti-collision algorithm is based on ALOHA, which was first developed in 1970s for a packet radio network at University of Hawaii. Data is sent whenever a station has some. The sender station listens to the broadcast to determine if the transmission is successful or has suffered a collision. If a packet fails to be delivered due to collision, the sender waits for a random period before resending the data. RFID works similarly by listening to the radio before transmitting data. An improvement to ALOHA algorithm, known as slotted ALOHA, divide the time intervals between data transmission, further reducing collision wait time. Further improvement, known as frame-slotted ALOHA, is proposed to alleviate problems associated with collisions when multiple RFID tags are simultaneously present in a reader’s field.[3]
Collision and Multiple Access Protocol
Conclusion
RFID is increasingly widespread in daily applications and while it has come concerns, its benefit cannot be denied. However there is also a constant need to improve the existing system to suit the requirements better for one application. Increasing scale of economics to reduce per unit cost is also an important factor in order to make the application more widespread in the future.
[1] http://www.rfidjournal.com/article/view/1338/1/129
[2] Banks, Jerry et al. RFID Applied. 2007 ISBN 978-0-471-79365-6
[3] Anti-Collision Algorithm for RFID Tags, Selwyn Piramuthu, Information Systems and Operations Management, University of Florida, 2008, http://tifac.velammal.org/CoMPC/articles/24.pdf
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