Here’s a guide to the standards in use now:802.11awas first out of the gate, at least on paper, and offered a great
deal of potential. It was fast, supported a bandwidth of as much as
54 mbps, and its radio frequency was far enough away from garage door
openers and other appliances to avoid interference. On the downside,
though, its transmission range— the distance its signal can carry — was
relatively short, about 60 feet or so. It works well within a room or house,
but not much farther. The standard works in the 5-GHz frequency range,
between 5.725–5.850 GHz, which is also used by some wireless phones.The higher a signal’s frequency and the more data it carries, the shorter
its effective range.
802.11bquickly supplanted -a for many users because of a tradeoff of
greater range over speed and lower cost. This standard sends signals in
the frequency range of 2.4–2.4835 GHz. This standard has a bandwidth of
about 11mbps but a signal range of about 300 feet, although in certain
settings the signal can be affected or stopped by household or business
appliances. Got a 2.4 GHz wireless phone in your house or office? Same
radio frequency. The same goes for microwave ovens, Bluetooth commu-
nication devices, and certain medical and scientific tools.And so early WiFi users had to choose between range and speed. Just
to make the decision more difficult, 802.11a and 802.11b use differentChapter 14: Feeling Up In the Air 205
Certification and compatibility
Any manufacturer can produce a device that
works within the unlicensed frequencies used
by the various WiFi standards. However, to
carry the official Wi-Fi Certified logo, a manu-
facturer has to be a member of an industry
association set up to grant that seal of approval.
While unofficial devices may work quite well,
only a product with the certification logo is
guaranteed to meet interoperability tests with
other standards and other manufacturers. WiFi
equipment works anywhere there is compatible
equipment, but a handful of countries have
either banned it or have not yet permitted its
use. Some European countries limit the number
of channels that can be used by a transceiver,
while some nations (including Italy) officially
require a license for use of the airwaves. A
handful of totalitarian regimes are very nervous
about all sorts of high-technology and may start
muttering something about CIA if they deter-
mine you are carrying a radio transmitter. When
in doubt, check with your country’s embassy or
local authorities.