Wireless Sensor Networks : Technology, Protocols, and Applications

AVAILABLE WIRELESS TECHNOLOGIES 107
TABLE 4.6
(Continued)
Electronic article
surveillance
(EAS)
Electronic
product
code (EPC)
Error-correcting
code
Error-correcting
mode
Error-correcting
protocol
Excite
Factory
programming
Field
programming
GTAG (global tag)
High-frequency
tags
Inductive
coupling
Low-frequency
tags
Memory
Microwave tags
Multiple-access
schemes
Simple electronic tags that can be turned on or off. When an item
is purchased (or borrowed from a library), the tag is turned off.
When someone passes a gate area holding an item with a tag
that has not been turned off, an alarm sounds. EAS tags are
embedded in the packaging of most pharmaceuticals.
A 96-bit code created by the auto-ID center that will one day
replace bar codes. The EPC has digits to identify the manufacturer,
product category, and the individual item. It is backed by the
Uniform Code Council and the European Article Numbering
Association the two main bodies that oversee bar code standards.
A code stored on an RFID tag to enable a reader to determine the
value of missing or garbled bits of data. It is needed because a
reader might misinterpret some data from the tag and think
that a Rolex watch is actually a pair of socks.
A mode of data transmission between the tag and the reader in
which errors or missing data are corrected automatically.
A set of rules used by readers to interpret data correctly from
the tag.
A reader is said to ‘‘excite’’ a passive tag when the reader transmits
RF energy to wake up the tag and enable it to transmit back.
The process of writing the identification number into a silicon
microchip at the time the chip is made, as is necessary for some
read-only tags.
Tags that use EEPROM, or nonvolatile memory, can be
programmed after being shipped from the factory.
A standardization initiative of the Uniform Code Council and the
European Article Numbering Association for asset tracking and
logistics based on RFID. The GTAG initiative is supported by Philips
Semiconductors, Intermec, and Gemplus, three major RFID tag makers.
Tags that operate typically at 13.56 MHz. They can be read from
about 10 ft away and transmit data faster, but they consume
more power than do low-frequency tags.
A method of transmitting data between tags and readers in which
the antenna from the reader picks up changes in a tag’s antenna.
Tags that typically operate at 125 kHz. The main disadvantages of
low-frequency tags are that they have to be read from within 3 ft
and the rate of data transfer is slow. But they are less expensive
than high-frequency tags and less subject to interference.
The amount of data that can be stored on a tag.
Radio-frequency tags that operate at 5.8 GHz. They have very high
transfer rates and can be read from away as far as 30 ft, but they
use a lot of power and are expensive.
Methods of increasing the amount of data that can be transmitted
wirelessly within the same frequency spectrum. RFID readers
use time-division multiple access (TDMA), meaning that they
read tags at different times to avoid interfering with one another.
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