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electromagnetic radiation emitted from the read-
ers. Passive tags can operate over longer periods of
time, but can only transmit signals over a shorter
range. Active tags, however cannot function once
their embedded power source runs out, but can
transmit signals over longer distances. RFID tags
are composed of various materials, have different
capabilities, come in many shapes and are available
in different sizes ranging from as small as a grain
of rice to as big as a six-inch ruler. These tags can
be applied on to any item like boxes, cases and
pallets or embedded in identification documents
or even human and animal tissue for the purpose
of tracking or identification.
An RFID reader is an active device that is
used to read information stored in tags or transmit
information to a tag. The reader consists of an
antenna, either internal or external which continu-
ously emits radio waves so that the RFID tag can
respond to it by sending back their embedded in-
formation. This information is generally known as
the Electronic Product Code (EPC) and is usually
the identifier of the object, person or animal onto
which the tag is applied. The readers also have a
processor to decode the signals and the identity
information received from the tags. RFID readers
can either be stationary - positioned at a specific
point like at the entrance/exit of a gate or they can
be integrated into handheld computers making
them handy and portable. There are several RFID
readers today in the market with varying reading
ranges. Many RFID readers can even read up to
2000 tags per second simultaneously. Most new
readers also have Ethernet, Wi-Fi or USB ports.
RFID system architecture is incomplete with-
out middleware. Middleware is the software that
resides between the RFID readers and enterprise
applications. It takes the raw data from the reader,
filters the data (since a reader might read the same
tag 100 times per second) and then passes the useful
data to the backend systems. Middleware plays
an important role in the RFID system by getting
the right information and then sending it to the
right application at the right time. The market is
filled with many RFID middleware products - all
perform some basic filtering and might also do
some additional functions (Thornton, 2006, p.16).
The main goal of an RFID system is to carry
information on a tag and retrieve it with a reader
through a wireless connection. As shown in Figure
1, the antenna on the tag and reader continuously
emits RF signals at a given frequency. When a
reader comes into contact with these signals, the
tag is activated and it communicates wirelessly
with the reader through the modulation of the
transmittance frequencies and then the tag sends
the data to the reader. The capabilities of an RFID
system depend on the carrier frequency at which
the information is transported. These frequency
allocations are generally managed through legis-
lations and regulations set by individual govern-
ments. Due to government regulations, different
parts of the electromagnetic spectrum are assigned
for different purposes, as a result of which, a
number of bands are used around the world for
RFID applications (Roberts, 2006, p.20). Table
1 of this chapter shows the commonly used fre-
quency ranges for RFID. Different frequencies
Table 1. Frequency Bands and Applications
Frequency Band
Read Range
Typical Applications
LF
<135 KHz
~10 cm
Access control, animal identification, inventory control, car
immobilizer
HF
10 - 13.56 MHz
~1 m
Access control, smart cards, library control
UHF
860 - 960 MHz
~2 - 5 m
Railway vehicle monitoring, toll collection systems, pallet
and container tracking, vehicle tracking
Microwaves
2.4 - 5.8 GHz
~100 m
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