21-01-2010, 12:23 PM
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ABSTRACT
RFID is an area of automatic identification that has quietly been gaining momentum in recent years and is now being seen as a radical means of enhancing data handling processes, complimentary in many ways to other data capture technologies such as barcoding. The object of any RFID system is to carry data in suitable transponders, generally known as tags, and to retrieve data, by machine-readable means, at a suitable time and place. Data within a tag may provide identification for an item in manufacture, goods in transit, a location, the identity of a vehicle, an animal or individual. RFID technology yields larger memory capacities, wider reading ranges, and faster processing.
An RFID system has the following components:
1. RFID DEVICE (tag or transponder) that contains data about an item.
2. RF TRANSCEIVER that generates RF signals.
3. An ANTENNA used to transmit RF signals between RFID DEVICE and READER.
4. READER that receives RF transmissions from an RFID DEVICE and passes the data to a host system for processing.
1. INTRODUCTION
RFID is an area of automatic identification that has quietly been gaining momentum in recent years and is now being seen as a radical means of enhancing data handling processes, complimentary in many ways to other data capture technologies such as bar coding. Developments in RFID technology continue to yield larger memory capacities, wider reading ranges, and faster processing. The object of any RFID system is to carry data in suitable transponders, generally known as tags, and to retrieve data, by machine-readable means, at a suitable time and place to satisfy particular application needs. Data within a tag may provide identification for an item in manufacture, goods in transit, a location, the identity of a vehicle, an animal or individual. A system requires, in addition to tags, a means of reading or interrogating the tags and some means of communicating the data to a host computer or information management system. A system will also include a facility for entering or programming data into the tags, if this is not undertaken at source by the manufacturer. Quite often an antenna is distinguished as if it were a separate part of an RFID system. Antenna is present in both readers and tags, essential for the communication between the two.
2. RFID SYSTEM
An RFID system includes the following components:
1. RFID device,that contains data about an item.
2. ANTENNA,used to transmit the RF signals between the reader and the RFID device .
3. RF transceiver that generates the RF signals.
4. READER ,that receives RF transmissions from the RFID device and passes the data to a host system for processing.
The tag, which does not have an own voltage supply (battery), is only activated when it is within the response range of the reader. Otherwise the tag is totally passive. The energy to activate the tag is supplied with the radio signal from the reader through the coupling unit. Also the timing pulse and data are transferred along with the signal.
The first function of the reader system is to activate the tags in its reading volume. To do this optimally, the reader must create an energizing electromagnetic field appropriate to the geometry of the reading volume and the most probable orientation of tags passing through the volume. The analog signal processing section of the reader performs detection of a very weak perturbation signal from a tag in the presence of a strong energizing field signal. Then it transforms the signal by filtering and amplification to a level appropriate to digitization and further processing in the digital domain.
The amplified signal from the tag modulation of the reader field is digitized and the resulting digital signal is analyzed to detect modulation patterns indicating a valid tag signal. 3. MODULATION To transfer data efficiently via the air interface or space that separates the two communicating components requires the data to be superimposed upon a rhythmically varying (sinusoidal) field or carrier wave. This process of superimposition is referred to as modulation, and various schemes are available for this purposes, each having particular attributes that favour their use. They are essentially based upon changing the value of one of the primary features of an alternating sinusoidal source, its amplitude, frequency or phase in accordance with the data carrying bit stream. On this basis one can distinguish amplitude shift keying (ASK), frequency shift keying (FSK) and phase shift keying (PSK).
Various schemes are available for modulation. Each type of modulation has advantages and disadvantages in terms of signal transmission rate, noise immunity and system complexity. They are based upon changing the value of amplitude, frequency or phase of an alternating sinusoidal source in accordance with the data carrying bit stream. On this basis one can distinguish amplitude shift keying (ASK), frequency shift keying (FSK) and phase shift keying (PSK):
Amplitude Shift Keying (ASK): The varying absorption of power (loading) at a sub-modulation frequency constitutes logical "1", the non-absorption of power constitutes a logical "0". ¢ Frequency Shift Keying (FSK): The loading varies at two different sub-modulation frequencies, corresponding to logical "0" and logical "1". Phase Shift Keying (PSK): The loading varies at a single sub- modulation frequency, but provides phase changes at specific time intervals to denote logical "0" and "1".
Both FSK and PSK are variants on ASK, using the principle of variable loading and superimposing extra frequencies or phase shifts by varying the "rhythm" of the loading sequence.
ASK can provide a high data rate but low noise immunity. FSK allows for a simple reader design, provides very strong noise immunity, but suffers from lower data rate than some other forms of modulation. PSK provides fairly good noise immunity, a moderately simple reader design, and a faster data rate than FSK.
4. ENCODING
The various encoding algorithms affect error recovery, cost of implementation, bandwidth, synchronization capability and other aspects of the system design. The algorithms include NRZ (Non-Return to Zero) Direct, Differential Biphase and Biphase L (Manchester). The waveforms of these data coding algorithms are presented.
The tag timing (clock signal) can be derived from the frequency of the excitation field of the reader. The fewer cycles per bit (i.e. shorter time length), the faster the message transmission will be. The more cycles per bit, the more reliable the message transmission will be. RF-ID tags generally transmit a message consisting of:
"PREAMBLE" or starting bits to indicate the beginning of the
message
"DATA" bits to transmit the ID information
"CHECKSUM" bits to insure the reliability of the transmitted data
The PREAMBLE field may also be used to define a particular type of tag and to allow reader timing synchronization. PREAMBLE field is often called the SYNC field. The DATA field may contain other information besides an ID code, for instance a country code or a manufacturer code. The CHECKSUM field may be a separate field at the end of the data transmission, or it may be distributed within the sequence of bits in the message.
5. WIRELESS COMMUNICATION AND THE AIR INTERFACE
Communication of data between tags and a reader is by wireless communication. Two methods distinguish and categorise RFID systems, one based upon close proximity electromagnetic or inductive coupling and one based upon propagating electromagnetic waves. Coupling is via Ëœantennaâ„¢ structures forming an integral feature in both tags and readers. While the term antenna is generally considered more appropriate for propagating systems it is also loosely applied to inductive systems.
Transmitting data is subject to the vagaries and influences of the media or channels through which the data has to pass, including the air interface. Noise, interference and distortion are the sources of data corruption that arise in practical communication channels that must be guarded against in seeking to achieve error free data recovery. Moreover, the nature of the data communication processes, being asynchronous or unsynchronised in nature, requires attention to the form in which the data is communicated. Structuring the bit stream to accommodate these needs is often referred to as channel encoding and although transparent to the user of an RFID system the coding scheme applied appears in system specifications. Various encoding schemes can be distinguished, each exhibiting different performance features.
6. COUPLING
There are various operating principles for RFID systems. The most important principles are:
Inductive coupling (close proximity coupling)
Backscatter coupling (propagation coupling)
Inductive Coupling
Inductively coupled tags are almost always passive. An inductively coupled tag usually comprises a single microchip and a large area coil that functions as an antenna. Inductively coupled systems operate at low or medium frequencies.
The principle of inductive coupling is illustrated in Figure 2. The reader's antenna coil generates a strong high frequency electro- magnetic field. A small part of the emitted field penetrates the antenna coil of the tag, which is some distance away from the coil of the reader. By induction, a voltage is generated in the tag's antenna coil. This voltage is rectified to supply power for the tag. The antenna coil of the tag and a capacitor form a parallel resonant circuit tuned to the transmission frequency of the reader. Inductive RFID tags communicate with the reader by shifting in and out of resonance. The equation for the resonance frequency of a circuit is: Where L is the inductance of the circuit and C is the capacitance of the circuit. The tag is in resonance when the resonance frequency of the circuit in the tag is very close to the frequency of the signal sent by the reader. A resonant tag within the alternating magnetic field of the reader's antenna draws energy from the magnetic field. This can be measured as voltage drop at the internal resistance in the reader antenna through the supply current to the reader's antenna. The amplitude of the voltage at the reader's antenna can be modulated by data controlled switching on and off the load modulator of the tag's resonant circuit. This type of data transfer is called load modulation. The voltage at the reader's antenna is measured and rectified to read the data. Backscatter Coupling
Backscatter coupled tags generally provide vastly increased ranges over inductively coupled ones. Rather than being limited to the ranges of the lines of force emitting from a magnetic field generator, they use the electric field propagation properties of radio signals to convey energy and data from the reader to the tag and data from the tag to the reader. Backscatter tags may be either passive (no battery) or active (battery powered). They reflect a small portion of the RF energy of the reader. The reflected signal is modulated or encoded with information stored in the tag. Backscatter tags can be programmed with varying amounts of information. Some tags may be reprogrammed by a reader, others have the ability to store additional data from readers to their internal memory.
Since electromagnetic waves are reflected by objects with dimensions greater than around half the wavelength of the wave, electric field propagation requires antenna systems that are typically half a wavelength of the operating frequency in size (150cm at 100MHz,15 cm at 1GHz, 5 cm at 2.5Ghz and 2.5cm at 5.8Ghz). Backscatter coupling is limited to high frequency systems due to the size of the antenna.
The reader's antenna emits power P1, of which a small proportion reaches the tags's antenna. This small portion (P1') supplies the antenna connections a HF voltage, which after rectification can be used as turn on voltage for the deactivation or activation of the power saving "power-down" mode (active tags). The voltage obtained may also be sufficient to serve as a power supply for short ranges (passive tags).
A proportion of the incoming power P1' is reflected by the antenna and returned as power P2. In order to transmit data from the tag to the reader, a modulation transistor across the resonant circuit formed by the antenna and a capacitor is switched on and off in time with the data stream to be transmitted. The amplitude of the power P2 reflected from the tag can thus be modulated A small proportion of the power P2 reflected from the tag is picked up by the reader's antenna. This signal is decoupled from the transmitted signal and transferred to the receiver input of a reader using a directional coupler
7. CARRIER FREQUENCIES
In wired communication systems the physical wiring constraints allow communication links and networks to be effectively isolated from each other. The approach that is generally adopted for radio frequency communication channels is to separate on the basis of frequency allocation. This requires, and is generally covered by government legislation, with different parts of the electromagnetic spectrum being assigned to different purposes. Allocations may differ depending on the governments concerned, requiring care in considering RFID applications in different countries. Standardisation efforts are seeking to obviate problems in this respect.
Three frequency ranges are generally distinguished for RFID systems, low, intermediate (medium) and high. The following table summarises these three frequency ranges, along with the typical system characteristics and examples of major areas of application. Table 1. Frequency Bands and Applications
Frequency Band
Characteristics Typical Applications
Low
100-500 kHz Short to medium read range
Inexpensive
low reading speed Access control
Animal identification
Inventory control
Car immobiliser
Intermediate
10-15 MHz
Short to medium read range
potentially inexpensive
medium reading speed Access control
Smart cards
High
850-950 MHz
2.4-5.8 GHz Long read range
High reading speed
Line of sight required
Expensive Railroad car monitoring
Toll collection systems
Frequency range
Applications and comments
Less than 135kHz
A wide range of products available to suit a range of applications, including animal tagging, access control and track and traceability. Transponder systems which operate in this band do not need to be licensed in many countries. 1.95 MHz, 3.25MHz, 4.75MHz, and 8.2MHz Electronic article surveillance
(EAS) systems used in retail stores Approx. 13 MHz, 13.56MHz EAS systems and ISM (Industrial, Scientific and Medical) Approx. 27 MHz ISM applications 430-460 MHz ISM applications specifically in Region 1 902-916 MHz ISM applications specifically in Region 2. In the USA this band is well organized with many different types of applications with different levels of priorities. This includes Railcar and Toll road applications. The band has been divided into narrow band sources and wide band (spread spectrum type) sources. In Region 1 the same frequencies are used by the GSM telephone network. 918-926 MHz RFID in Australia for transmitters with EIRP less than 1 watt 2350 - 2450 MHz
A recognized ISM band in most parts of the world. IEEE 802.11 recognizes this band as acceptable for RF communications and both spread spectrum and narrow band systems are in use.
8. DATA TRANSFER RATE AND BANDWIDTH
Choice of field or carrier wave frequency is of primary importance in determining data transfer rates. In practical terms the rate of data transfer is influenced primarily by the frequency of the carrier wave or varying field used to carry the data between the tag and its reader. Generally speaking the higher the frequency the higher the data transfer or throughput rates that can be achieved. This is intimately linked to bandwidth or range available within the frequency spectrum for the communication process. The channel bandwidth needs to be at least twice the bit rate required for the application in mind. Where narrow band allocations are involved the limitation on data rate can be an important consideration. It is clearly less of an issue where wide bandwidths are involved. Using the 2.4 - 2.5 GHz spread spectrum band, for example, 2 megabits per second data rates may be achieved, with added noise immunity provided by the spread spectrum modulation approach. Spread spectrum apart, increasing the bandwidth allows an increase noise level and a reduction in signal-to-noise ratio. Since it is generally necessary to ensure a signal is above the noise floor for a given application, bandwidth is an important consideration in this respect.
9. RANGE AND POWER LEVELS
The range that can be achieved in an RFID system is essentially determined by: The power available at the reader/interrogator to communicate with the tag(s)
The power available within the tag to respond The environmental conditions and structures, the former being more significant at higher frequencies including signal to noise ratio
Although the level of available power is the primary determinant of range the manner and efficiency in which that power is deployed also influences the range. The field or wave delivered from an antenna extends into the space surrounding it and its strength diminishes with respect to distance. The antenna design will determine the shape of the field or propagation wave delivered, so that range will also be influenced by the angle subtended between the tag and antenna.
In space free of any obstructions or absorption mechanisms the strength of the field reduces in inverse proportion to the square of the distance. For a wave propagating through a region in which reflections can arise from the ground and from obstacles, the reduction in strength can vary quite considerable, in some cases as an inverse fourth power of the distance. Where different paths arise in this way the phenomenon is known as "multi-path attenuation". At higher frequencies absorption due to the presence of moisture can further influence range. It is therefore important in many applications to determine how the environment, internal or external, can influence the range of communication. Where a number of reflective metal Ëœobstaclesâ„¢ are to encountered within the application to be considered, and can vary in number from time to time, it may also be necessary to establish the implications of such changes through an appropriate environmental evaluation.
The power within the tag is generally speaking a lot less than from the reader, requiring sensitive detection capability within the reader to handle the return signals. In some systems the reader constitutes a receiver and is separate from the interrogation source or transmitter, particularly if the Ëœup-linkâ„¢ (from transmitter-to-tag) carrier is different from the Ëœdown-linkâ„¢ (from tag-to-reader).
Although it is possible to choose power levels to suit different application needs is not possible to exercise complete freedom of choice. Like the restrictions on carrier frequencies there are also legislative constraints on power levels. While 100 - 500mW are values often quoted for RFID systems actual values should be confirmed with the appropriate regulatory authorities, in the countries where the technology is to be applied. The authorities will also be able to indicate the form in which the power is delivered, pulsed or continuous, and the associated allowed values.
Having gained some grasp of the data communication parameters and their associated values it is appropriate to consider, in a little more detail, the components of an RFID system.
10. RFID SYSTEM COMPONENTS
Transponders/Tags
The word transponder, derived from TRANSmitter/resPONDER, reveals the function of the device. The tag responds to a transmitted or communicated request for the data it carries, the mode of communication between the reader and the tag being by wireless means across the space or air interface between the two. The term also suggests the essential components that form an RFID system “ tags and a reader or interrogator. Where interrogator is often used as an alternative to that of reader, a difference is sometime drawn on the basis of a reader together with a decoder and interface forming the interrogator. The basic components of a transponder may be represented as shown below. Generally speaking they are fabricated as low power integrated circuits suitable for interfacing to external coils, or utilising "coil-on-chip" technology, for data transfer and power generation (passive mode). Basic features of an RFID transponder: The transponder memory may comprise read-only (ROM), random access (RAM) and non-volatile programmable memory for data storage depending upon the type and sophistication of the device. The ROM-based memory is used to accommodate security data and the transponder operating system instructions which, in conjunction with the processor or processing logic deals with the internal "house-keeping" functions such as response delay timing, data flow control and power supply switching. The RAM-based memory is used to facilitate temporary data storage during transponder interrogation and response.
The non-volatile programmable memory may take various forms, electrically erasable programmable read only memory (EEPROM) being typical. It is used to store the transponder data and needs to be non- volatile to ensure that the data is retained when the device is in its quiescent or power-saving "sleep" state. Data buffers are further components of memory, used to temporarily hold incoming data following demodulation and outgoing data for modulation and interface with the transponder antenna. The interface circuitry provides the facility to direct and accommodate the interrogation field energy for powering purposes in passive transponders and triggering of the transponder response. Where programming is accommodated facilities must be provided to accept the data modulated signal and perform the necessary demodulation and data transfer processes.
The transponder antenna is the means by which the device senses the interrogating field and, where appropriate, the programming field and also serves as the means of transmitting the transponder response to interrogation. A number of features, in addition to carrier frequency, characterise RFID transponders and form the basis of device specifications, including: Means by which a transponder is powered Data carrying options
Data read rates
Programming options
Physical form
Costs Powering tags - For tags to work they require power, even though the levels are invariably very small (micro to milliwatts). Tags are either passive or active, the designation being determined entirely by the manner in which the device derives its power. Active tags are powered by an internal battery and are typically read/write devices. They usually contain a cell that exhibits a high power-to-weight ratio and are usually capable of operating over a temperature range of -50° C to +70° C. The use of a battery means that a sealed active transponder has a finite lifetime. However, a suitable cell coupled to suitable low power circuitry can ensure functionality for as long as ten or more years, depending upon the operating temperatures, read/write cycles and usage. The trade-off is greater size and greater cost compared with passive tags. In general terms, active transponders allow greater communication range than can be expected for passive devices, better noise immunity and higher data transmissions rates when used to power a higher frequency response mode. Passive tags operate without an internal battery source, deriving the power to operate from the field generated by the reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime. The trade-off is that they have shorter read ranges than active tags and require a higher- powered reader. Passive tags are also constrained in their capacity to store data and the ability to perform well in electromagnetically noisy environments. Sensitivity and orientation performance may also be constrained by the limitation on available power. Despite these limitations passive transponders offer advantages in terms of cost and longevity. They have an almost indefinite lifetime and are generally lower on price than active transponders. Data carrying options - Data stored in data carriers invariable require some organisation and additions, such as data identifiers and error detection bits, to satisfy recovery needs. This process is often referred to as source encoding. Standard numbering systems, such as UCC/EAN and associated data defining elements may also be applied to data stored in tags. The amount of data will of course depend on application and require an appropriate tag to meet the need. Basically, tags may be used to carry: ¢ Identifiers, in which a numeric or alphanumeric string is stored for identification purposes or as an access key to data stored elsewhere in a computer or information management system, or ¢ Portable data files, in which information can be organised, for communication or as a means of initiating actions without recourse to, or in combination with, data stored elsewhere. In terms of data capacity tags can be obtained that satisfy needs from single bit to kilobits. The single bit devices are essentially for surveillance purposes. Retail electronic article surveillance (EAS) is the typical application for such devices, being used to activate an alarm when detected in the interrogating field. They may also be used in counting applications. Devices characterised by data storage capacities up to 128 bits are sufficient to hold a serial or identification number together, possibly, with parity check bits. Such devices may be manufacturer or user programmable. Tags with data storage capacities up to 512 bits, are invariably user programmable, and suitable for accommodating identification and other specific data such as serial numbers, package content, key process instructions or possibly results of earlier interrogation/response transactions.
Tags characterised by data storage capacities of around 64 kilobits may be regarded as carriers for portable data files. With increased capacity the facility can also be provided for organising data into fields or pages that may be selectively interrogated during the reading process.
Data read rate “ It has been mentioned already that data transfer rate is essentially linked to carrier frequency. The higher the frequency, generally speaking the higher the transfer rates. It should also be appreciated that reading or transferring the data requires a finite period of time, even if rated in milliseconds, and can be an important consideration in applications where a tag is passing swiftly through an interrogation or read zone.
Data programming options - Depending upon the type of memory a tag contains the data carried may be read-only, write once read many (WORM) or read/write. Read-only tags are invariably low capacity devices programmed at source, usually with an identification number. WORM devices are user programmable devices. Read/write devices are also user-programmable but allowing the user to change data stored in a tag. Portable programmers may be recognised that also allow in-field programming of the tag while attached to the item being identified or accompanied.
Physical Form - RFID tags come in a wide variety of physical forms, shapes sizes and protective housings. Animal tracking tags, inserted beneath the skin, can be as small as a pencil lead in diameter and ten millimetres in length. Tags can be screw-shaped to identify trees or wooden items, or credit-card shaped for use in access applications. The anti-theft hard plastic tags attached to merchandise in stores are also RFID tags, as are heavy-duty 120 by 100 by 50 millimetre rectangular transponders used to track inter-modal containers, or heavy machinery, trucks, and railroad cars for maintenance and tracking applications.
Costs - The cost of tags obviously depends upon the type and quantities that are purchased. For large quantities (tens of thousands) the price can range from less than a few tens of pence for extremely simple tags to tens of pounds for the larger and more sophisticated devices.
Increasing complexity of circuit function, construction and memory capacity will influence cost of both transponders and reader/programmers.
The manner in which the transponder is packaged to form a unit will also have a bearing on cost. Some applications where harsh environments may be expected, such as steel mills, mines, and car body paint shops, will require mechanically robust, chemical and temperature tolerant packaging. Such packaging will undoubtedly represent a significant proportion of the total transponder cost. Generally, low frequency transponders are cheaper than high frequency devices, passive transponders are usually cheaper than active transponders. The Reader/Interrogator The reader/interrogators can differ quite considerably in complexity, depending upon the type of tags being supported and the functions to be fulfilled. However, the overall function is to provide the means of communicating with the tags and facilitating data transfer. Functions performed by the reader may include quite sophisticated signal conditioning, parity error checking and correction. Once the signal from a transponder has been correctly received and decoded, algorithms may be applied to decide whether the signal is a repeat transmission, and may then instruct the transponder to cease transmitting. This is known as the "Command Response Protocol" and is used to circumvent the problem of reading multiple tags in a short space of time. Using interrogators in this way is sometimes referred to as "Hands Down Polling". An alternative, more secure, but slower tag polling technique is called "Hands Up Polling" which involves the interrogator looking for tags with specific identities, and interrogating them in turn. This is contention management, and a variety of techniques have been developed to improve the process of batch reading. A further approach may use multiple readers, multiplexed into one interrogator, but with attendant increases in costs. RF Transponder Programmers Transponder programmers are the means by which data is delivered to write once, read many (WORM) and read/write tags. Programming is generally carried out off-line, at the beginning of a batch production run, for example. For some systems re-programming may be carried out on-line, particularly if it is being used as an interactive portable data file within a production environment, for example. Data may need to be recorded during each process. Removing the transponder at the end of each process to read the previous process data, and to programme the new data, would naturally increase process time and would detract substantially from the intended flexibility of the application. By combining the functions of a reader/interrogator and a programmer, data may be appended or altered in the transponder as required, without compromising the production line. The range over which the programming can be achieved is generally less than the read range and in some systems near contact positioning is required. Programmers are also generally designed to handle a single tag at a time. However, developments are now satisfying the need for selective programming of a number of tags present within the range of the programmer. 11. RFID SYSTEM CATEGORIES RFID systems may be roughly grouped into four categories:
EAS (Electronic Article Surveillance) systems Portable Data Capture systems
Networked systems Positioning systems
Electronic Article Surveillance systems are typically a one bit system used to sense the presence/absence of an item. The large use for this technology is in retail stores where each item is tagged and a large antenna readers are placed at each exit of the store to detect unauthorised removal of the item (theft).
Portable data capture systems are characterised by the use of portable data terminals with integral RFID readers and are used in applications where a high degree of variability in sourcing required data from tagged items may be exhibited. The hand-held readers/portable data terminals capture data which is then either transmitted directly to a host information management system via a radio frequency data communication (RFDC) page link or held for delivery by line-linkage to the host on a batch processing basis.
Networked systems applications can generally be characterised by fixed position readers deployed within a given site and connected directly to a networked information management system. The transponders are positioned on moving or moveable items, or people, depending upon application. Positioning systems use transponders to facilitate automated location and navigation support for guided vehicles. Readers are positioned on the vehicles and linked to an on-board computer and RFDC page link to the host information management system. The transponders are embedded in the floor of the operating environment and programmed with appropriate identification and location data. The reader antenna is usually located beneath the vehicle to allow closer proximity to the embedded transponders. 12. APPLICATIONS Potential applications for RFID may be identified in virtually every sector of industry, commerce and services where data is to be collected. The attributes of RFID are complimentary to other data capture technologies and thus able to satisfy particular application requirements that cannot be adequately accommodate by alternative technologies. Principal areas of application for RFID that can be currently identified include: ¢ Transportation and logistics ¢ Manufacturing and Processing ¢
Security
A range of miscellaneous applications may also be distinguished, some of which are steadily growing in terms of application numbers. They include:
Animal tagging
Waste management
Time and attendance
Postal tracking
Airline baggage reconciliation ¢
Road toll management As standards emerge, technology develops still further, and costs reduce considerable growth in terms of application numbers and new areas of application may be expected. Some of the more prominent specific applications include:
Electronic article surveillance - clothing retail outlets being typical.
Protection of valuable equipment against theft, unauthorised removal or asset management. Controlled access to vehicles, parking areas and fuel facilities - depot facilities being typical. Automated toll collection for roads and bridges - since the 1980s, electronic Road-Pricing (ERP) systems have been used in Hong Kong.
Controlled access of personnel to secure or hazardous locations. ¢ Time and attendance - to replace conventional "slot card" time keeping systems.
Animal husbandry - for identification in support of individualised feeding programmes.
Automatic identification of tools in numerically controlled machines - to facilitate condition monitoring of tools, for use in managing tool usage and minimising waste due to excessive machine tool wear. ¢ Identification of product variants and process control in flexible manufacture systems. ]
Sport time recording ¢ Electronic monitoring of offenders at home
Vehicle anti-theft systems and car immobiliser A number of factors influence the suitability of RFID for given applications. The application needs must be carefully determined and examined with respect to the attributes that RFID and other data collection technologies can offer. Where RFID is identified as a contender further considerations have to be made in respect of application environment, from an electromagnetic standpoint, standards, and legislation concerning use of frequencies and power levels.
13. ADVANTAGES
1. Independent of line of sight.
2. Less response time.
3. Completely automated data recording.
4. Larger memory capacity.
5. Wider reading ranges.
6. faster processing.
14. DISADVANTAGES
Although tagging offers a wide variety of services, and we can easily tag domestic pets and livestock, there is a potentially dangerous ,slippery slope with respect to tagging people. The notion of attaching a permanent recording transponder to a human leads to a wide variety of ethical dilemmas.
15. CONCLUSION
In the near future, tags may become more than just identifiers of objects in space- they might also monitor status, history, and events, just as some boxes with fragile equipment now sport excess G -force tags that turn red when the box is dropped beyond a set distance. Electronic tags might well keep a continuously updated history of sensed events over time and, at read time ,may transfer not only their unique identifier but also an entire time-stamped history of events.
As tags become increasingly capable processors and require less and less power, tags will shortly begin to seem less like static bar code identifiers and more like active network nodes that are intermittently attached to the network.
16. REFERENCES
BOOKS
1. BARCODES AND OTHER AUTOMATIC IDENTIFICATION SCHEMES by ROBERT D.
LAMOREAUX. 2. RADIO FREQUENCY IDENTIFICATION FUNDAMENTALS AND APPLICATIONS by
KLAUS FINKENZELLER.
3. SMART TAGS “THE DISTRIBUTED MEMORY EVOLUTION by P. HEWKIN.
WEBSITES
1.aimglobal.org
2. iee.org
3.efy.com
4.howstuffworks.com
5.altavista.com
6.askgieves.com
7.ask.com
CONTENTS
1. INTRODUCTION
2. RFID SYSTEM 3. MODULATION
4. ENCODING
5. WIRELESS COMMUNICATION AND AIR INTERFACE
6. COUPLING
7. CARRIER FREQUENCIES
8. DATA TRANSFER RATE
9. RANGE AND POWER LEVELS
10. RFID SYSTEM COMPONENTS
11. RFID SYSTEM CATEGORIES 12. APPLICATIONS
13. ADVANTAGES 14. DISADVANTAGES
15. CONCLUSION
16. REFERENCES
