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RADIO FREQUENCY IDENTIFICATION (RFID)

WILLIAM MCCOMBIE

BRUCE A. WELT

Packaging Science Program,

Agricultural and Biological

Engineering Department,

University of Florida/IFAS,

Gainesville, Florida

INTRODUCTION

Radio-frequency identiﬁcation (RFID) is a method for

automatic identiﬁcation that relies on storing and retriev-

ing data from transponder ‘‘tags.’’ RFID systems require

readers equipped with one or more antennas connected to

back-end computer systems. Tags are equipped with

power generation and regulation, control circuitry, data

memory, and communications capability. Readers activate

tags to initiate data transfer via radio signals. Proponents

expect RFID technology to replace conventional barcode

technologies. To date, RFID has been evaluated and im-

plemented in a number of applications including supply

chain tracking, animal identiﬁcation, and toll collection.

Opponents to RFID suggest that the technology does,

however, have some drawbacks, including cost of imple-

mentation, reliability, performance, and potential for priv-

acy misuse issues.

HISTORY

RFID has roots in several technologies. One such technol-

ogy dates back to World War II, when Great Britain

implemented a system known as ‘‘Identity Friend or

Foe’’ to identify incoming planes as either friendly or

enemy. A ground transmitter would send a signal to a

plane, and a transponder on the plane would respond with

an encrypted message indicating whether the plane was

friendly. Modern RFID works on the same basic principle.

The ﬁrst patent for a passive RFID-type system was

ﬁled in 1970 (U.S. Patent 3,713,148). The term RFID was

ﬁrst used in U.S. Patent 4,384,288 entitled, ‘‘Portable radio

frequency emitting identiﬁer.’’ Since then and particularly

within the last decade, many RFID-related patents have

been issued. Signiﬁcant patent holding companies include

Internic, Motorola, Alien Technology, and IBM. Modern

technology has been able to produce microchips with RFID

capability, allowing RFID to be used in many applications

at relatively low cost. However, the question remains as to

whether the costs are or will be low enough to replace

barcodes.

Proponents of RFID technology envision a future in

which any object can be wirelessly tracked. One vision

involves the smart, automated supermarket. This vision

has customers exiting supermarkets without stopping at

the cashier. Instead, embedded RFID tags in merchandise

packaging would automatically interface with readers

located on the shelves and at the exit of the store.

Payments would be processed with RFID-enabled pay-

ment cards. Simultaneously, ‘‘smart shelves’’ would detect

those items removed for purchase to provide real-time

inventory reporting allowing optimal logistics and supply,

merchandizing, and therefore optimizing sales while and

minimizing out-of-stock items.

This vision continues into the home. Purchased gro-

ceries would interface with smart appliances. A smart

refrigerator would alert consumers to expired or ﬁnished

merchandise and order new products as required in

accordance with consumer deﬁned rules. Smart ovens

would properly cook foods by retrieving detailed cooking

instructions tags embedded in packaging. Such devices

have already been developed in numerous academic and

corporate laboratories. One such device, already devel-

oped by Samsung, uses 2D barcodes printed on product

packaging rather than RFID tags (1). Finally, when

packages are disposed of or recycled, tags might be used

to facilitate automated sorting in order to route materials

for optimal recycling, energy conversion, or disposal.

Such technologies are in developmental stages today.

The Metro Extra Future Store in Rheinberg, Germany

performed an experiment with RFID in which certain

items in the store were individually tagged. Several items

were placed on ‘‘smart shelves,’’ which detect removed

items and signal back-end systems to request more stock.

Some items had tags attached to the packaging, while

1058 RADIO FREQUENCY IDENTIFICATION (RFID)

other items, such as Gillette razors, had tags embedded at

the factory.

Digital video disks (DVDs) stocked by the store also

contained RFID tags and were used in conjunction with

interactive kiosks, allowing shoppers to watch movie pre-

views. The store also embedded RFID tags in its customer

loyalty cards, but this was later discontinued after privacy

advocates protested the practice (2).

Currently, RFID tags cost as low as about 7b per tag

when purchased in multimillion unit quantities. Manu-

facturing costs continue to be relatively high as manufac-

turing processes are improved and scaled. However,

failure rates of RFID tags continue to be unsustainably

high. Defective tag rates, postapplication tag failure rates,

and overall tag longevity are not well known as manufac-

turers are reluctant to share such data. However, experi-

ence with various tag types suggest defective rates in the

range of 30% and postapplication failure rates in the

5–20% range within one year of application. Rigorous,

third-party studies are needed to more fully understand

RFID tag failure modes and rates.

Alien Technology and Symbol Technologies (now Moto-

rola) are both attempting to reduce this cost with Fluidic

Self-Assembly (FSA) and Parallel Integrated Chip Assem-

bly (PICA), respectively (3, 4). Table 1 summarizes these

technologies.

INDUSTRY STANDARDS FOR AUTOMATIC

IDENTIFICATION

Barcodes

Barcodes have been around for many years, and there are

many standards. One of the most common in the United

States is the Universal Product Code, which retailers use

to identify merchandise. Other standards exist, many of

them proprietary. Most barcodes, however, do not un-

iquely identify an item, but rather an item type (e.g.

‘‘case of super-widgets’’ versus ‘‘this case is the 82nd case

of widgets.’’)

UID

Universal Identiﬁcation is a method used by the United

States Department of Defense (DOD) to identify assets

(5). DOD describes its needs for unique identiﬁcation

capabilities as follows (6):

The Department must, of necessity, uniquely identify the

items to which it takes title to provide for better asset

accountability, valuation and life cycle management. Unique

identiﬁcation provides the Department the opportunity to

differentiate an individual item from all others. Unique iden-

tiﬁcation of items provides the Department with the source

data to facilitate accomplishment of the following:

. Improve the acquisition of equipment- and performance-

based logistics services for the warﬁghter,

. Capture timely, accurate, and reliable data on items (i.e.,

equipment, reparables, materials, and consumables),

. Improve life-cycle asset management.

. Track items in the department and industry systems for

operational, logistic, and ﬁnancial accountability purposes.

While DoD’s UID mandate requires physical marking

of all items with a unique code, RFID is being used as a

means to transfer UID information. UID is primarily

implemented using two-dimensional ‘‘DataMatrix’’ style

barcodes.

EPC Global

The Electronic Product Code (EPC) is a set of standards

initiated by the Massachusetts Institute of Technology

(MIT) Auto ID Labs and eventually overseen by EPC

Global Inc. The EPC protocols intend to ensure that all

tags, RFID or otherwise, are coded with unique values.

EPC Global deﬁnes a set of standards for hardware,

software, and the codes themselves. An EPC can contain

a preexisting standard, such as Global Trade Identiﬁca-

tion Number (GTIN), Serial Shipping Container Code

(SSCC), Global Location Number (GLN), Global Return-

able Asset Identiﬁer (GRAI), or Global Individual Asset

Identiﬁer (GIAI), and provides speciﬁcations for imple-

menting such codes within an EPC (7).

The EPC standard dictates how data should be stored

on tags, in addition to translating codes from one format to

another. An example of how UPC/GTIN is implemented as

a unique and serialized EPC SGTIN code follows.

Global Trade Identiﬁcation Number (GTIN) is one

method of identifying objects with an automated data

capture system. GTIN, like UPC, does not, however,

uniquely identify items. The EPC system includes a

serialized GTIN, known as Serialized Global Trade

Table 1. Summary of RFID Technologies

Method Company Description Progress

Fluidic self-assembly Alien Technology Chips are attached by ﬂowing in a

special ﬂuid over holes shaped

to catch the chips.

Alien claims that prices will

continue to drop as FSA

production increases.

PICA (parallel integrated chip

assembly)

Symbol Technologies Attaches RFID chips to inlays

(antennas) in parallel.

Expected to be online in 2006;

however, this is not the case.

Conventional methods Various companies Tags are manufactured by

attaching each chip to each

antenna individually.

RADIO FREQUENCY IDENTIFICATION (RFID) 1059

Identiﬁcation Number. The code includes a header (used

to identify the encoding to the reader, whether it is SGTIN

or another standard, and the size of the tag in bits); a ﬁlter

to separate loads by pallet, case, or item; a company

identiﬁcation number; a product identiﬁcation number,

and a serial number. This information can be used to

query a database to ﬁnd out more information about

tagged items. The 64- and 96-bit EPC compliant tags are

currently available; however, 64-bit tags are being phased

out. Table 2 shows an example of SGTIN-96 encoding.

It is worth noting that although EPC was developed to

be used with RIFD, industry is realizing that serialized

codes can also be implemented with other identiﬁcation

methods, including barcodes.

Hardware. EPC Global standards deﬁne operational

characteristics for hardware, including frequency and wire-

less communication protocols. These standards provide for

common communications methods and interfaces that al-

low components from different companies to work together.

Software. RFID middleware is software used to inter-

face between RFID readers and other components, includ-

ing user interfaces, databases, and other applications. The

main purpose of middleware is to simplify interfacing back

end systems with new RFID hardware. As RFID gains

acceptance, RFID software and backend systems are being

developed to more easily integrate, thus putting into

question the long-term need for middleware applications.

There are several commercial and open source packages

available on the market, including solutions from Micro-

soft, Inc., ConnecTerra, Inc. (now BEA Systems, Inc.),

GlobeRanger, Inc., IBM, Inc., and Sun Microsystems, Inc.

Middleware packages are capable of interfacing di-

rectly with RFID devices and can translate information

from the reader(s) into formats that can be used by other

applications. An EPC Global encoded tag, for example, can

be broken down into speciﬁc values for company, item, and

serial number, while the middleware performs one action

for carton tags and another for pallet tags. Another

advantage of using middleware is compatibility with

different brands and models of RFID readers.

It is worth noting that middleware is not necessarily

limited to RFID technology. Most packages are compatible

with conventional barcode systems and other systems as

well.

RFID devices are being offered with increasing levels of

middleware functionality built in. These are capable of

doing basic middleware operations without the need for

additional software. Alternatively, for some applications,

such as those where only a single reader is used, custom

software can be written to interpret tag information.

APPLICATIONS

One of the largest applications of RFID is supply chain

management. This industry has used conventional bar-

codes for years with great success. RFID initiated serial-

ization offers potential to greatly enhance supply chain

visibility and enables suppliers and retailers to track

goods from the point of manufacture to the store shelf

and beyond.

The lowest level of RFID tracking is known as ‘‘item

level’’ tagging and consists of placing RFID tags on

individual items, in a manner similar to UPC labels on

most grocery products. Item level tagging has been tested

and implemented in several retail environments, such as

at Wal-Mart stores and Metro Group’s Extra Future Store

initiative in Germany. Most modern implementations,

however, have been limited to case and pallet levels.

Wal-Mart is one of the largest backers of the technology

and has put it to use to in an effort to improve supply

chain efﬁciency, reduce labor costs, and reduce shelf out-

of-stocks, apparently resulting in increased sales (8, 9).

Electronics retailer Best Buy Co. Inc. (Richﬁeld, Minne-

sota) also experimented with item level RFID on DVDs

and video games. The initial trial was linked to increased

DVD sales due to reductions in out-of-stock merchandise

(10).

The supply chain is not the only place where RFID has

been implemented. Toll booths have used RFID to auto-

matically collect tolls using transponders carried by mo-

torists. Examples include SunPass (a toll collection system

used in Florida) and EZ-Pass (a toll collection system used

in the northeastern United States).

A primitive form of RFID is Electronic Article Surveil-

lance (EAS). A major supplier of EAS systems is Tyco,

Inc.’s (Pembroke, Bermuda) ADT Division (formerly Sen-

sormatic of Boca Raton, FL). Instead of using a chip to

store information, EAS tags use simple tuned circuits that

respond to particular radio frequencies. Such systems are

commonly used in retail stores to deter shoplifting, and

they are also used in libraries to prevent removal of

articles that have not been checked out. Such tags are

either removed or deactivated at check-out to prevent

Table 2. Example of SGTIN-96 Encoding

Field Header Filter Partition Company Item Serial

Number of

bits

8 3 3 20-40 (dependant

on partition size)

24-4 (dependant

on partition size)

Description Set to 0 30

to indicate

SGTIN-96

encoding

Determines

the type of

item, such as

a pallet,

carton, or

item

Determines

the size of the

company and

Item ﬁelds

Identiﬁes the

company that

produced the

item

Identiﬁes the

item the tag is

attached to, such

as a box of

detergent

Serial number to

uniquely identify

a product (i.e.,

which box of

detergent)

1060 RADIO FREQUENCY IDENTIFICATION (RFID)

them from triggering alarms when removed from

the premises. Figure 1 shows Checkpoint Systems Inc.

(Thorofare, NJ) EAS antennas at the entrance to the

University of Florida bookstore. Upon removing an unpaid

item (or an item that has not been deactivated properly),

such as a textbook, an alarm will sound, alerting store

staff. Checkpoint also manufacturers EPCGlobal compa-

tible RFID products and produces a line of EAS devices

that may be upgraded for use with RFID systems. Other

applications of RFID include ExxonMobil’s (Irving, Texas)

SpeedPass, ﬁrst used in 1997. It was a system that allowed

cashless payments at Mobil/Exxon fueling stations, and

also at McDonald’s fast food restaurants with a simple

keychain attachment (11).

Credit card manufacturers have also recently started

embedding RFID chips within credit cards for cashless

payments, and many cities have used RFID for transport

payments. Examples include Visa’s payWave, Master-

Card’s PayPass, and American Express’s ExpressPay.

Animal tracking is another application of RFID. Do-

mesticated pets and livestock can be injected with a

subdermal RFID chip, improving herd management and

allowing lost animals to be identiﬁed.

TYPES OF RFID

Passive RFID

Passive RFID is a type of RFID tagging in which tags are

not self-powered. Passive tags are designed to harvest

power from radio signals transmitted by an RFID reader

at a particular frequency. When within the electromag-

netic ﬁeld emitted by the reader, passive tags activate and

respond as required to interrogation. The two most com-

mon passive technologies involve high-frequency (HF) and

ultra-high-frequency (UHF) energy. The HF mode uses

the magnetic component of the ﬁeld and has a very short

read range. HF tags typically need to be within a few

centimeters of a reader. UHF tags offer greater read

ranges that are typically on the order of a 2–10 ft. UHF

tags are more common for supply chain applications,

whereas HF tags are ﬁnding greater use in asset manage-

ment and other applications that require more intimate

proximity between reader and tag (e.g., hospital patient

bracelets for drug distribution). UHF tags communicate

using the principle of backscatter radiation. Essentially,

the tag reﬂects a portion of reader’s energy back to the

reader with a superimposed modulated signal (12). Tag

performance depends upon antenna size and geometry.

Tag size is mainly due to the antenna. Larger antennas

tend to provide longer read ranges. Current technology

has enabled tags to be embedded in paper or under the

skin. Hitachi’s mChip, for example, is 7.5 mm thick (13).

Passive RFID tags have been used for tracking pallets of

goods, contactless ‘‘smart cards,’’ and machine readable

passports. Figure 2 shows some passive RFID tags.

Active RFID

Active RFID involves tags with an internal power source,

such as a battery. One common application of active RFID

technology is electronic toll collection. Active RFID tags

may also be paired with one or more different types of

sensors, such as temperature sensors. Toll collection de-

vices may include some form of feedback, alerting the user

when a toll is collected. Active RFID tags are much more

expensive than passive RFID tags and are typically in the

$5to$100 range. Figure 3 shows an active RFID sensor

developed at the University of Florida to assist in mon-

itoring food freshness (14).

Semiactive/Semipassive

Semiactive/semipassive RFID tags, like active tags, also

contain a power supply, but this power supply is only used

to power the circuitry. The radio signal is transmitted

using power from the incoming radio signal. Semiactive/

semipassive RFID technology is being developed primarily

for ‘‘smart’’ reusable containers and pallets.

Frequencies

Many RFID systems can interface with tags from other

systems if the frequencies and protocols are the same.

There are some standards to frequencies, and lower-

frequency tags are generally less expensive but have a

shorter range (Table 3) (15).

ADVANTAGES AND DISADVANTAGES OF RFID

Advantages

Unlike barcodes, which require a line of sight between

reader and barcode, RFID tags interface with readers using

radio signals. RFID chips are tiny while storing hundreds

or thousands of bits of information, which allows tags

to be hidden from view. By comparison, barcodes require

clearly visible area on items or packaging, and this area

requirement generally increases with the amount of data

stored.

Figure 1. Checkpoint EAS antennas use special one-bit tags to

detect unauthorized removal of products from premises.

RADIO FREQUENCY IDENTIFICATION (RFID) 1061

Data collection rate is the primary advantage of RFID.

Since barcodes require line-of-sight for data collection,

barcode read rates depend upon rates at which barcodes

can be presented to readers. RFID tags communicate

without line of sight and at high frequency allowing tens

or hundreds of tags to be read each second. However, this

inherent advantage of RFID is mitigated by the rates at

which items such as containers, pallets, cases and items

can be physically moved through the supply chain. Since

barcode readers are capable of reading data on items at

the highest speeds attainable within the supply chain, this

RFID advantage may not be fully exploitable.

Another advantage of RFID is that it helped to intro-

duced standards and serialization to industry. With con-

ventional UPC/EAN barcodes, each package of an item

contains an identical product code. They identify only the

manufacturer and the product type. A serialized RFID

tag, on the other hand, contains a serial number, allowing

a reader to determine which package of a product is being

scanned. This information can be queried into a database

to determine the source, expiration date, and other useful

information about a particular item.

Disadvantages

Data Transmission. In theory, radio signals can be read

without direct line of sight between tags and readers. In

practice, however, something close to line of sight is often

necessary due to dielectric properties of tagged items.

Many products are good absorbers of electromagnetic

energy used for RFID, which interferes with low power

RFID transmissions. Additionally, many products contain

metals or metal packaging. Metals shield, scatter, and

reﬂect radio signals, resulting in unpredictable RFID

performance. Therefore, maximum, or at least predictable,

RFID performance is often obtained when the least mate-

rial is placed between tag and reader, practically negating

the purported ‘‘no line of sight’’ beneﬁt.

Reliability. As with any electronic device, RFID tags

have a tendency to fail. Most passive RFID tags consist of

an integrated circuit connected to an antenna. Should the

chip, antenna, or the connection between the chip and

Figure 2. Assorted passive UHF RFID tags.

Figure 3. Active RFID freshness monitoring tag developed at

the University of Florida.

1062 RADIO FREQUENCY IDENTIFICATION (RFID)

antenna become damaged, the tag will no longer function

properly. Unlike barcodes, RFID tags are more dependent

on the environment. One problem facing RFID implemen-

tation is difﬁculty reading tags attached to metals or

liquid containers.

Additionally, some consumers have devised methods to

detect and ‘kill’ RFID tags. One such example is the RFID

Zapper, created using an off-the-shelf single-use camera

and a coil of wire. The device uses the capacitor in the

camera (normally used to power the ﬂash) to pass a high

voltage through the coil, overpowering the RFID tag and

causing the circuit to overload (16). RFID tags can also be

disabled by placing them in a microwave oven; however,

this can be dangerous and can cause damage to the tagged

item and the microwave oven as well as the RFID tag (17).

In either case, the impact of disabled tags on supply chain

peformance remains unmeasured.

Cost. RFID tags are extremely costly in comparison to

barcodes, even at the industry’s current target rate of 5

cents per RFID tag. In addition to direct costs, RFID

tags cannot be produced in the ﬁeld. Therefore, commit-

ment to RFID technology requires a related commitment

to actively managed RFID tag inventory. Unexpected

shortages of tags could seriously disrupt operations. Alter-

natively, barcodes may be printed as required on virtually

any substrate using a variety of well-established printing

or marking techniques. By comparison, barcodes are 100

to 1000 times less expensive than RFID tags that contain

similar data.

Disposable tags are not the only investment in imple-

mentation. RFID implementation requires RFID-enabled

label printers, readers, and antennas, software, middle-

ware, computers, and network infrastructure that are

compatible with a particular generation of RFID tags.

Currently, the switch to ‘‘Generation 2’’ tags quickly

rendered ﬁrst generation technology obsolete. It is likely

that improvements in RFID technologies will result in

required costly hardware upgrades that were similar to

other computer networking products. Recall networking

technology migrating from 1200 bps telephone modems to

56k modems to ISDN, T1, ADSL, and so on. While costly

upgrades in networking technologies were quickly offset

by productivity increases and new revenue generating

opportunities, such immediate and apparent rewards are

probably not awaiting capital expenditures for upgraded

RFID hardware for basic supply chain management

functionality.

Consumers

Privacy and Security. One obstacle in deploying RFID is

consumer privacy. Advocacy organizations, such as Con-

sumers Against Supermarket Privacy Invasion and Num-

bering (CASPIAN) and FoeBud, a German group of RFID

and privacy activists, strongly oppose item level tracking,

since these technologies may allow for undisclosed wire-

less customer tracking. One controversial example in-

volves a system that collects photos of customers as

products are removed from shelves (18). While the system

was promoted as a means to reduce shoplifting, consumer

advocacy groups fear that such technologies violate con-

sumer rights.

While some retailers, including the Metro Extra Future

Store, claim that RFID tags are useless once they leave

the store, privacy advocates claim that the tags are still

‘‘live’’ and can be tracked by other readers beyond the

store of purchase.

Opponents envision a ‘‘1984’’-type society in which all

people and objects are tracked using microchips embedded

under the skin. In fact, such systems are now widely used

for pets (19). The VeriChip or VeriPay (20) is a type of

RFID chip that is designed to be implanted under the skin.

While it may only contain a 16-digit serial number, this

information is linked to a database and can also be picked

up by any compatible reader. One such use of the VeriChip

is at the Baja Beach Club, in Barcelona, Spain, which

experimented with implanting chips in people to allow

them to pay for drinks and obtain VIP beneﬁts without the

need to carry a wallet. Human-implantable chips have

also been used in medical settings for patient identiﬁca-

tion, though they are not without health and privacy risks

of their own (21). Religious groups have even linked such

Table 3.

Technology Frequencies

Read Range

(Approximate) Characteristics Applications

Low frequency o135 KHz o1 ft Coiled antennas Can

work around ﬂuids

and metals

Animal identiﬁcation

Automation Access control

High frequency 13.56 MHz W3 ft Common around the

world Poor

performance around

metals

Payment and loyalty cards

Access control Item level

tracking People

identiﬁcation

Ultra-high frequency 433 MHz W10 ft Interference from

liquids and metals

Supply chain

860 MHz-930 MHz

(depending on region)

100’s of feet for some

active systems

Microwave 2.45 GHz, 5.8 GHz Similar to UHF Fast data transfer

rates.

Access control

May be active or

passive

Toll collection Industrial

automation

RADIO FREQUENCY IDENTIFICATION (RFID) 1063

chips to the book of Revelation, which apparently de-

scribes a time in which people are required to take a

mark in order to buy or sell (17).

Disposal. A signiﬁcant, yet little publicized, challenge

facing RFID is the issue of disposal. Passive RFID tags

have been designed to be discarded, and electronic waste

is a growing problem in the United States (21). RFID

tagging may contribute to the problem because RFID tags

are fabricated in ways that make them difﬁcult to recycle;

and because they are designed to be attached to or part of

other items, RFID tags interfere with established recy-

cling technologies. One study on the impact of RFID tags

on corrugated recycling found that (1) laminated copper

antennas do not readily break down and are removed

early in the pulping process as a nonrecyclable solid waste

and (2) conductive silver inks used as an alternative to

copper on nonlaminated labels remain with paper sub-

strates and are not easily extractable from ﬁnished paper

(22).

Interference and Spurious Reads. As with any radio-fre-

quency device, RFID systems are susceptible to electromag-

netic interference. Interference may interrupt, obstruct, or

degrade performance of RFID systems. There are many

sources of interference, particularly in industrial settings.

The Packaging Science Laboratory at the University of

Florida has relied upon a hand-held spectrum analyzer to

identify and mitigate potential sources of interference

(Figure 4).

The EPC Global RFID air operating protocol requires

that complying RFID reader manufacturers use frequency

hopping spread spectrum (FHSS) to mitigate electromag-

netic interference issues (23).

RFID systems are also quite susceptible to spurious

reads. Spurious reads involve reading tags that are not

intended to be read. Spurious read may occur for many

reasons including tags that become separated from packa-

ging. Figure 5 shows an example of a tag that may

interfere with normal RFID operation.

Spurious reads are a particular problem in multireader

environments. Also, manual handling of tagged items in

reader environments can also be problematic because

items might be carried through read zones in directions

opposite to expected ﬂow. Spurious reads could also be a

serious problem in automatic checkout and payment

applications in retail outlets, where items from one cus-

tomer’s cart are charged to another customer.

IMPLEMENTATION OF RFID IN THE INDUSTRY

Mandates by Companies

Wal-Mart. Wal-Mart, Inc. made a big push into RFID

primarily as a way to reduce labor costs and occurrences of

out-of-stock merchandise. In 2003, Wal-Mart announced

that it would require its top 100 suppliers to use ultra-

high-frequency RFID tags conforming to EPC Global

standards on pallets and cases destined to speciﬁc dis-

tribution test centers by January 2005. Additionally, Wal-

Mart insisted that no price increases to cover RFID

investments would be tolerated. This requirement was

later eased to 65% of pallets and cartons due to issues with

reading tags on metal and liquid (15). Wal-Mart then

extended the requirement to other suppliers, expecting

all suppliers to use RFID by December 2006.

Wal-Mart RFID speciﬁcations stated an expectation to

be able to read 100% of pallet tags in the pallet/portal

conﬁguration and 100% of case tags for cases in any

Figure 4. Handheld spectrum analyzer at the University of

Florida Packaging Lab.

Figure 5. RFID tag that fell from palletized product. (Photo by

Bruce Welt, University of Florida.)

1064 RADIO FREQUENCY IDENTIFICATION (RFID)

orientation moving at up to 600 ft/min on conveyor equip-

ment (24). These speciﬁcations led to considerable anxiety,

confusion, and capital expenditure as companies scram-

bled to acquire limited quantities of ﬁrst-generation RFID

hardware. Additionally, RFID testing laboratories began

to sprout all over the United States where work focused on

equipment performance comparisons, tag read rates, tag

placement on cases and pallets, read ranges, product

interference issues, and so on (12). Of particular note is

the amount of work devoted to improving read rates of

palletized cases moving through RFID portals even

though Wal-Mart’s speciﬁcations did not require case

tags to be read in this conﬁguration (25, 26). The practical

result of this work, however, was the realization that line-

of-site was practically necessary in order to be sure that

the pallet tags and case tags could be read as required.

Wal-Mart and RFID proponents generally supported

use of nonproprietary, EPC Global standards in order to

allow the industry to quickly grow to a necessary critical

mass to ensure survival. Several years of effort went into

development of ‘‘Generation 2’’ technology, which elimi-

nated issues related to incompatible tags and equipment.

Ultimately, Generation 2 technology was to be freely

available to all participants. However, once these stan-

dards were ratiﬁed, Intermec, Inc. (Everett, Washington)

caused a stir by indicating that its intention to make its

patents available did not mean that they would be avail-

able without cost. Intermec’s RFID patent portfolio cur-

rently covers critical aspects of RFID as ratiﬁed in the

Generation 2 standard. To avoid prolonged legal wran-

gling, Intermec devised an apparently effective plan to

properly reward its shareholders while allowing the RFID

industry to move forward. Its plan involved offering access

to its complete patent portfolio under a preferred royalty

plan, but only for a limited time of 90 days. Companies

that did not sign up within the 90-day period would be

required to negotiate terms on a patent-by-patent basis as

well as face patent infringement actions. Intermec’s plan

was apparently successful; and even archrival and sole

holdout, Symbol Technologies, Inc. (now part of Motorola),

ultimately acquiesced and arrived at an agreement with

Intermec, albeit after the 90-day window closed.

US DoD. The United States Department of Defense

(DoD) has a large number of assets; and at any time, many

of these assets are in transit. The DoD needed a way to

track these assets. It assigned each asset with a Unique

Identiﬁer (UID), and uses RFID to read UID values from

objects. It mandated all shipments to be equipped with

RFID tags (5, 7). The DoD uses standard EPCglobal

compliant tags. As with other RFID applications, adoption

has been slow, but the DoD attributes this to its necessary

focus on current intensive military operations (27).

ALTERNATIVES TO RFID

RFID has provided industry with two potentially valuable

advances. First, RFID made code serialization feasible

and accessible. By serializing identiﬁcation codes, each

tagged item can be independently tracked through the

supply chain. This realization has helped to create new

opportunities for improving supply chain logistics. Second,

RFID brought people and companies together to create

standards and operating procedures that provide for more

efﬁcient data transfer and collaboration.

While RFID might be credited for helping to bring

these advances, the cruel irony is that many are starting

to realize that all of the beneﬁts from these advances may

be realized without RFID. Ultimately, RFID is simply a

means to collect data via radio waves. Other well-estab-

lished technologies are also available that are useful for

collecting data, and these may be simpler and cheaper to

implement than RFID. Barcodes and image processing are

two promising alternative methods for collecting data.

Technological advances in electronics have been increas-

ing the power, speed, and capabilities of barcode and

image processing systems while reducing costs.

Chipless RFID

Chipless RFID is a recent innovation that combines RFID

and barcodes. Unlike conventional RFID tags, chipless

RFID does not rely on a central integrated circuit to

transmit and receive information and instead uses a series

of chemicals, each tuned to resonate at a certain frequency

when excited by incoming radio waves. Each chemical

represents a bit, with a chemical’s presence representing a

1 and its absence representing a 0. Such a system can be

printed relatively inexpensively onto an item, similar to

how barcodes are printed. The developers of such a

technology intend for chipless RFID to assist in anti-

counterfeiting and anti-copying measures (28). Unlike

conventional RFID, however, chipless RFID does not

provide features commonly found on RFID chips, such as

error and interference detection and avoidance.

1D Barcodes

Barcodes were invented shortly after World War II in

response to a need to manage grocery inventory. In

September 1969 the Grocery Manufacturers of America

(GMA) and the National Association of Food Chains met to

express a need for an ‘‘inter-industry product code.’’ The

effort of an ad hoc committee resulted in an 11-digit code

now commonly known as the Universal Product Code

(UPC) (Figure 6). After considerable time and develop-

ment, on June 6, 1974 a pack of Wrigley’s gum was

checked out of Marsh’s Supermarket in Troy, OH using a

barcode scanner developed by NCR, formerly National

Cash Register Company (29, 30).

Figure 6. UPC barcode example for (123456789012).

RADIO FREQUENCY IDENTIFICATION (RFID) 1065

While UPC barcodes served the grocery industry well,

other code standards were developed for other industries.

Today there are barcode standards that can include

numbers, letters, and the special characters that make

up the complete ASCII character set. Table 4 summarizes

these barcode standards. The UPC code standard has been

widely adopted throughout the world as a slightly mod-

iﬁed barcode known as European Article Numbering

(EAN). The 11-digit UPC code actually presents 12 digits

because the last digit serves as a checksum digit to ensure

reading accuracy. The EAN-13 symbology is a superset of

the UPC symbology and contains 13 digits in order to

accommodate country identiﬁcation codes, which are re-

quired in Europe and other parts of the world. The UPC

and EAN contain a string of numbers indicating the

source or company associated with the item as well as a

code identifying the item type. The UPC, however, does

not store a serial number, which means that each choco-

late bar has an identical UPC.

UPC/EAN codes can also be represented as Global

Trade Identiﬁcation (GTIN) numbers, which is the current

basis for identifying goods in transit throughout the

world. RFID added unique serial numbers to GTIN, which

are now known as serialized global identiﬁcation numbers

(S-GTIN). The EPC Global, Inc. electronic product code

(EPC) is a superset of S-GTIN and contains additional

information about the nature of the particular type of

RFID tag that is used, which are not needed for non-radio-

based systems. The important question at this time is

whether RFID is the appropriate technology to carry

serialization forward.

The main problem with adding serial numbers to linear

barcodes is that they require signiﬁcant amounts of print-

ing area, which most companies would rather devote to

informational or promotional content. One promising tech-

nology that is squeezing more data into smaller areas was

originally known as reduced space symbology (RSS). RSS is

actually a family of symbologies, each developed for some

marketplace efﬁciency such as speed, size, or readability.

The name ‘‘RSS’’ created confusion due to another unre-

lated technology for syndicating web content (‘‘really sim-

ple syndication’’), which was also known as RSS. Therefore,

the term RSS is being rebranded as GS1 Databart (31).

Currently, a GS1 Databar version of the UPC code requires

about 1/3 of the area currently consumed by the UPC/EAN

barcode (32). This provides ample opportunity to include

serialization and/or other useful data in the future. GS1

Databar will likely prove to be a serious challenger to RFID

technology in the near future as GS1 Databar technology is

scheduled to sunrise in 2010 (Figure 7).

OCR

Optical Character Recognition (OCR) is a technology in

which a computer or machine is used to read standard

text. Such technology is in use by postal services, for

example, to read address labels and direct mail to correct

destinations. A variation, Magnetic Ink Character Recog-

nition (MICR), is commonly used by banks and retailers to

process checks. Figure 8 shows human readable version of

EPC data being captured by a Cognex, Inc. vision system.

Figure 9 shows both the 2D barcode and human-readable

text being interpreted by the camera software.

OCR algorithms are not currently as robust as barcode

readers at this time; however, technological improvements

in hardware and software along with cost reductions will

likely open opportunities for human-readable data in the

future.

2D Barcodes

Two-dimensional barcodes are a relatively new technology

that store more data than conventional linear barcodes.

While they carry the same advantages and disadvantages

of linear barcodes, the ability to store more data makes it

more practical to store information such as a serial

number. 2D barcodes have been used by UPS for package

tracking, by state governments for Driver Licenses/ID

cards, and by NASA for part identiﬁcation.

One of the most common 2D barcode standards is

DataMatrix (Figure 10). It is designed such that it can

be printed or engraved on objects as small as the head of a

pin (5) or as large as several feet across. The symbols

themselves can hold up to 2335 alphanumeric characters,

and they include error detection and correction algorithms

that produce a valid read even if a signiﬁcant portion of

the symbol is damaged or absent. DataMatrix codes, like

RFID, can be used to store serialized EPC and UID codes.

Figure 11 shows a 2D barcode with some damage. Even

though some data are missing, some or all of the data can

still be read.

Figure 12 shows 2D barcode information used to store

digital sound data on a roll of movie ﬁlm in two different

formats.

Another advantage of tracking using 2D barcodes is

backward compatibility. 2D barcode equipment can print

and read linear barcodes without the need for additional

hardware.

PRACTICAL TESTING AND IMPLEMENTATION

Universal tracking of items in rapidly moving supply

chains requires robust systems. To successfully implement

such systems, testing is required to understand basic

performance characteristics, weaknesses, and limitations.

Such evaluations can be extensive, complex, and tedious.

RFID Hardware

A simple RFID system consists of a tag, a reader, and an

antenna. The reader transmits and receives signals to and

from the tag through the antenna.

RFID Printer. While RFID tags can be programmed

at the factory or by readers, it may be desirable to

program RFID tags using a specially designed label

printer

. Such printers

print onto labels with em-

bedded RFID tags. The printer contains an RFID

device that programs tags as labels are printed. This

method allows easy mass encoding of RFID tags.

Currently, however, encoding RFID tags while print-

ing tags signiﬁcantly slows the printing process.

1066 RADIO FREQUENCY IDENTIFICATION (RFID)

Table 4. Summary of Barcode Standards

Standard Description Applications Sample

Plessey Two bar widths with white space,

easy to print using dot-matrix

printers. Does not include built-in

error checking.

Libraries, some

retailers

UPC Robust barcode algorithm for retail

use. Stores numbers only with

manufacturer and product. Last

digit is used as a check digit.

Retail in the

United States

Codabar Capable of being printed with dot-

matrix printers. Self checking.

Stores numbers and can store

some letters.

Libraries, air-

bills, blood

banks.

Code 39 Compatible with many readers;

however, data density is low.

Contains alphanumeric

characters and some symbols.

Code 93 Higher density and more robust

than Code 39. Two check

characters.

Canadian Post

Ofﬁce

Code 128 High density, can store any

character.

Shipping and

packaging

industries

EAN-13 Superset of UPC symbology with

additional country code.

Worldwide retail

GS1-128 (UCC/

EAN-128)

Implementation of Code 128 used

for storing various types of data

such as a Global Trade Item

Numbers or an Expiration Date.

GS1 DataBar

(RSS)

Can encode 14-digit GTIN values.

Smaller than conventional UPC/

EAN barcodes.

Healthcare

industry,

intended for

retail

(Continued)

RADIO FREQUENCY IDENTIFICATION (RFID) 1067