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powered by a sensor reader. Conventional sensors are used in conjunc-
tion with a battery for tracking (and wireless transmission of) readings
such as ambient sound, temperature, light, videos, pressure, locations,
or other objects, which are then transmitted by the sensor itself. In
the case of RFID, the key is to identify specific information in the tag,
by powering it with a sensor reader. This specific information in the
tagisalsoknownas Electronic Product Identification Code (EPC) .The
uniqueness of identification code, and the cost-effectiveness of the tag,
allows the simultaneous tracking of a large number of objects, since the
presence of an object at a particular location can be associated with the
identification code on its tag.
While the core idea of RFID technology is not new, and dates back
to World War II for distinguishing between friendly and enemy aircrafts
[53, 50], recent years have seen the emergence of a new stripped down
version of the tag, which lacks a power source or antenna, and does
little more than provide a unique identifier. Unlike regular sensors, such
tags are extremely inexpensive , cost no more than a few cents each,
and can easily be constructed for large scale applications. Some of the
earliest discussions on the the rapid advancement of RFID technology
to such large scale applications may be found in [56, 71]. The trend
towards, smaller , unobtrusive ,and inexpensive tags is exemplified by
the following:
Zebra has developed a print engine, which can embed an RFID
transponder directly into a product label [16].
Hitachi has developed an extremely tiny RFID tag, known as the
μ -chip, which can be directly embedded into photocopier paper
[81]. This can be used for document tracking.
These different kinds of developments suggest the continuing minia-
turization of RFID technology across different domains. Furthermore,
these developments also suggest that the applications of RFID technol-
ogy go well beyond retail applications. It is important to note that the
complexity of an RFID tag can be fairly flexible, depending upon the
problem domain. If desired, it is possible to incorporate sensing into
RFID technology [71, 72] with the use of onboard sensors that generate
data dynamically. For example, an RFID tag may incorporate a tem-
perature sensor (for perishable goods), or a passive force sensor, which
can return information about the possible damage to a product, if it is
dropped. Such tags are typically active RFID tags (with an onboard
battery), and they are typically more expensive than passive tags, which
are powered by a sensor reader, and return only the EPC. The par-
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