Chapter 3 • Telecommunications and Networking 67cordless telephones, cellular telephones, wireless LANs,
and microwave transmission of voice and data.
Acordless telephoneis a portable device which
may be used up to about 1,000 feet from its wired
telephone base unit. This permits the user to carry the
telephone to various rooms in a house or take it outdoors
on the patio. By contrast, a cellular telephonemay be
used anywhere as long as it is within range—about eight to
ten miles—of a cellular switching station. At present, these
cellular switching stations are available in all metropolitan
areas of the United States and most rural areas. The
switching stations are low-powered transmitter/receivers
that are connected to a cellular telephone switching office
by means of conventional telephone lines or microwave
technology. The switching office, which is computer-
controlled, coordinates the calls for its service area and
links the cellular system into the local and long-distance
telephone network. Today’s smartphones, such as a
BlackBerry or an iPhone, combine a cell phone with a
handheld computer and have the ability to access the
Internet over the so-called 2G (second generation) or
3G (third generation) networks operated by the cellular
carriers. The 3G networks provide much faster data trans-
mission rates—typically from 500 kbps to 2 mbps—than
the 2G networks, which are often in the 20 kbps range.
4G networks, with even higher data transmission rates, are
on the horizon.
Wireless LANsare growing in popularity. They
have the obvious advantage of being reasonably easy to
plan and install. A wireless system provides networking
where cable installation would be extremely expensive or
impractical, such as in an old building. A wireless LAN
also permits users of mobile devices such as handheld or
laptop computers to connect to the LAN (and thus the
Internet) whenever they are within range of a wireless
access point (WAP), such as in a coffee shop or an airport
terminal. A wireless LAN is less secure than a wired LAN
and more susceptible to interference, which might increase
the error rate and force the wireless LAN to operate at a
slower data rate. Most wireless LANs operate in the range
of 6 to 100 mbps, with some of the newer wireless LANs
operating at speeds up to 300 mbps.RFID Signals Growing Slowly
Radio frequency identification (RFID)has been around since World War II, but it didn’t gain public
attention until 2003 when Walmart announced that it would require its 100 top suppliers to begin
using RFID for selected applications by January 2005. At the time, there was an expectation that RFID
would change retailing forever, but that hasn’t happened. In fact, even Walmart has pulled back on its
original mandate. While it still uses RFID in stores and distribution centers, Walmart does not require its
suppliers to use RFID. Only about 600 of Walmart’s 20,000 suppliers have joined the movement to RFID.
Nevertheless, RFID has blossomed in areas other than retailing, and the sales of RFID tags, readers, soft-
ware, and services have grown to $6 billion a year. The biggest use of RFID is in smart cards, including
passports, ID cards, and prepaid transportation cards. The military is using RFID to keep track of equip-
ment and supplies, and governments are using RFID to tag livestock to help stop the spread of diseases
such as mad cow disease.
There are actually two flavors of RFID, passive and active. Both types of RFID are built around an
RFID tag, which is a small piece of hardware—often the size of a postage stamp or smaller—that uses
radio-transmitted codes to uniquely identify itself. A passive RFID tag combines a tiny chip with an
antenna; it does not have an internal power source. Instead, a passive tag relies on the minute electrical
current induced in the antenna by an incoming radio signal, providing enough power for the tag to
send a brief response, typically just an ID number. An active RFID tag contains its own power supply and
can transmit identifying information either continuously, on request, or on a predetermined schedule.
Active tags are much more expensive, usually over $1.00, while the prices of passive tags have dropped
to the $0.05 to $0.10 level. At present, most of the RFID action involves passive RFID tags because of
their lower cost. Passive RFID tags include those used on smart cards and livestock, as well as on an
increasing number of consumer items. Active RFID tags are commonly found in cell phones, aircraft
transponders, and other specialized applications such as the tracking of medical equipment. RFID is not
creating a retailing revolution, but it is slowly and surely becoming important for identifying people,
products, equipment, and even livestock.
[Based on Khermouch and Green, 2003; Ohlhorst, 2005; and Weier, 2009]