22-02-2011, 03:12 PM
presented by:
Kishore Kumar
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RADIO-FREQUENCY IDENTIFICATION
INTRODUCTION
RFID stands for radio-frequency identification. The acronym refers to small electronic devices that consist of a small chip and an antenna. The chip typically is capable of carrying 2,000 bytes of data or less.
The RFID device serves the same purpose as a bar code or a magnetic strip on the back of a credit card or ATM card; it provides a unique identifier for that object. And, just as a bar code or magnetic strip must be scanned to get the information, the RFID device must be scanned to retrieve the identifying information.
RFID is only one of numerous technologies grouped under the term automatic identification (auto id), such as bar code, magnetic inks, optical character recognition, voice recognition, touch memory, smart cards, biometrics etc. Auto id technologies are a new way of controlling information and material flow, especially suitable for large production networks.
The RFID technology is a means of gathering data about a certain item without the need of touching or seeing the data carrier, through the use of inductive coupling or electromagnetic waves. The data carrier is a microchip attached to an antenna (together called transponder or tag), the latter enabling the chip to transmit information to a reader (or transceiver) within a given range, which can forward the information to a host computer. The middleware (software for reading and writing tags) and the tag can be enhanced by data encryption for security-critical application at an extra cost, and anti-collision algorithms may be implemented for the tags if several of them are to be read simultaneously.
COMPONENTS:
A basic RFID system consists of three components:
• An antenna or coil
• A transceiver (with decoder)
• A transponder (RF tag) electronically programmed with unique information
• The antenna emits radio signals to activate the tag and to read and write data to it.
• The reader emits radio waves in ranges of anywhere from one inch to 100 feet or more, depending upon its power output and the radio frequency used. When an RFID tag passes through the electromagnetic zone, it detects the reader's activation signal.
• The reader decodes the data encoded in the tag's integrated circuit (silicon chip) and the data is passed to the host computer for processing.
APPLICATIONS OF RFID
Asset management
Production tracking
Inventory control
Pricing and promotion
Shipping & receiving
Regulatory compliance
Returns & recall management
Transportation
Service and warranty authorizations
ADVANTAGES OF THE TECHNOLOGY
Though RFID is not likely to entirely replace commonly used barcodes in the near future, the following advantages suggest to additionally apply RFID for added value of identification:
• Tag detection not requiring human intervention reduces employment costs and eliminates human errors from data collection.
• As no line-of-sight is required, tag placement is less constrained.
• RFID tags have a longer read range than, e. g., barcodes.
• Tags can have read/write memory capability, while
barcodes do not,
• An RFID tag can store large amounts of data additionally to a unique identifier.
• Unique item identification is easier to implement with RFID than with barcodes.
• Tags are less sensitive to adverse conditions (dust, chemicals, physical damage etc.),
• Many tags can be read simultaneously,
• RFID tags can be combined with sensors,
• Automatic reading at several places reduces time lags and inaccuracies in an inventory,
• Tags can locally store additional information; such distributed data storage may increase fault tolerance of the entire system,Reduces inventory control and provisioning costs,
• Reduces warranty claim processing costs.
LIMITATIONS OF THE TECHNOLOGY
Although many RFID implementation cases have been reported, the widespread diffusion of the technology and the maximum exploitation of its potential still requires technical, process and security issues to be solved ahead of time. Today’s limitations of the technology are foreseen to be overcome and specialists are already working on several of these issues.
1. Standardization
Though the characteristics of the application and the environment of use determine the appropriate tag, the sparse standards still leave much freedom in the choice of communication protocols and the format and amount of information stored in the tag. Companies transcending a closed-loop solution and wishing to share their application with others may encounter conflicts as cooperating partners need to agree in standards concerning communication protocols, signal modulation types, data transmission rates, data encoding and frames, and collision handling algorithms. Currently, two major groups of standards are competing worldwide: one is EPC created by the Auto-ID Center and receiving the support of UCC (Uniform Code Council) and EAN (European Article Numbering), the other is the ISO-specified (International Standards Organization) set of standards.
2. Cost
The cost of tags depends on their type. In the 2003 report ‘RFID Systems in the Manufacturing Supply Chain.’
This predicted decrease is still deemed insufficient, as economic use of tags—taking the associated 5–35% decrease of labor costs and zero tag information generation costs into account as well—would require a maximum of 25 cents per tag for high-end products, and 5 cents for common item-level tagging.
Prices of active or semi-passive tags (at least $1 per tag) are even more of a hindrance, allowing their economic application only for scanning high-value goods over long ranges.
3. Collision
Attempting to read several tags at a time may result in signal collision and ultimately to data loss. To prevent this, anti-collision algorithms (most of them are patented or patent pending) can be applied at an extra cost. The development of these methods, aimed at reducing overall read time and maximizing the number of tags simultaneously read, still goes on.
4. Frequency
The optimal choice of frequency depends on several factors, such as:
a.) Transmission mode. RFID tags basically use two kinds of data transmission, depending on the behaviour of electromagnetic fields at the frequency used. In lower frequencies (such as 125–134kHz in the LF band or 13.56MHz in the HF band), inductive coupling is used, while in frequency bands above (UHF with typical frequency ranges of 433MHz, 865–956MHz and 2.45GHz), wave backscattering is the main means of transmission. This also affects the safe reading range, as it is easier to build direction-selective devices with a longer read range in higher frequencies. This may restrict design freedom if either reading range or spatial selectivity are an important issue.
b.) Behaviour of tagged goods and environment. Properties of some materials may be an obstacle to RFID application at a given frequency, as they may corrupt data transmission either by absorption or by ambient reflection of the signals. Typically, conductive materials such as goods containing water, or metal surfaces may be the source of problems. However, absorption and reflection being frequency-dependent, failure at one frequency does not rule out applicability at other frequencies. Electromagnetic disturbance can also have external sources, which is also a common—though also frequency-dependent—problem in an industrial environment.
c.) International standards in frequency allocation. Due to historic reasons, the world is divided into three large regions of frequency allocation for various purposes, region 1 containing Europe, Africa, the Middle East and former SU member states, region 2 with North and South America and the part of the Pacific east of the date line, and region 3 with Asia, Australia and the Pacific west of the date line. The industry exerts pressure towards an uniformization of frequencies allowed for RFID, yet there still are notable differences between the three regions, forcing companies planning to employ tags in several regions to restricting themselves to bands shared by all regions concerned. A compromise for tags only modulating the reader signal without actively producing a carrier wave on their own may be their ability to work in a wider frequency range than nominally specified, allowing their usage even in regions where RFID bands are ‘close enough’.
5. Faulty or deficient detection of tags
a.) Tags may be damaged during usage. A wide range of application challenges can be answered by the multitude of suitable tags, yet none of them is completely invulnerable and the causes of damage may vary from type to type. The result is a read failure which is, in many cases difficult to detect, as is the fact of the damage itself for a hidden tag. This becomes a business issue when, for example, the payment for goods is calculated by the number of detected tags and no measures are taken to compensate for read failures.
b.) Adverse conditions of the environment and improper placement may corrupt reading. As mentioned before, absorption, ambient reflection of the signal and external signal sources (such as security systems, cordless phones, barcode scanners) may introduce read errors. Similarly, improper orientation of tags may impair reading efficiency as most antennas used in tags are direction-sensitive.
c.) Registration of data from tags which pass within range of an RFID reader accidentally.
d.) Reader malfunction. This eventuality cannot be predicted or completely avoided, making alter-native fallback measures (such as barcodes) necessary for the case of reader failure.
6. Quick technology obsolescence
One of the common concerns of companies implementing RFID today is the rapid obsolescence of the technology, especially in view of the investment cost. Technology is continuously evolving and new protocol standards, faster and more fault-tolerant readers quickly outdate their predecessors.
7. Security and Privacy Issues
Depending on the field of application—and in some cases, prescribed by law—it may become necessary to prevent unauthorised persons from reading or writing data stored on or transmitted from tags. To this end, encryption must be ensured at all interfaces where data could be intercepted or transmitted (on the medium itself, as well as tag–reader and reader–host communication).
