Wi-Fi

The IEEE (Institute of Electrical and Electronics Engineers) has produced a
set of standards and specifications for wireless networks under the title IEEE
802.11 that define the formats and structures of the relatively short-range
signals that provide Wi-Fi service. The original 802.11 standard (without any
letter at the end) was released in 1997. It covers several types of wireless media:
two kinds of radio transmissions and networks that use infrared light.

The 802.11b standard provides additional specifications for wireless Ethernet
networks. A related document, IEEE 802.11a, describes wireless networks
that operate at higher speeds on different radio frequencies. Still other
802.11 radio networking standards with other letters are also available or
moving toward public release.

The specifications in widest use today are 802.11a, 802.11b, and 802.11g.
They’re the de facto standards used by just about every wireless Ethernet
LAN that you are likely to encounter in offices and public spaces and in most
home networks. It’s worth the trouble to keep an eye on the progress of those
other standards, but for the moment, 802.11a and 802.11g are the ones to
use for short-range wireless networks, especially if you’re expecting to connect
to networks where you don’t control all the hardware yourself.


The 802.11n standard is the next one in the pipeline, and when it’s
released, it will replace both 802.11b and 802.11g because it’s faster, more
secure, and more reliable. The older standards will still work, so new Wi-Fi
equipment will support all three (often along with 802.11a, which uses
different radio frequencies) and automatically match your network interface
to the signals it detects from each base station.


There are two more names in the alphabet soup of wireless LAN
standards that you ought to know about: WECA and Wi-Fi. WECA (Wireless
Ethernet Compatibility Alliance) is an industry group that includes all of the
major manufacturers of wireless Ethernet equipment. Their twin missions
are to test and certify that the wireless network devices from all of their
member companies can operate together in the same network, and to
promote 802.11 networks as the worldwide standard for wireless LANs.
WECA’s marketing geniuses have adopted the more friendly name of Wi-Fi
(short for wireless fidelity) for the 802.11 specifications.


Once or twice per year, the Wi-Fi Alliance conducts an “interoperability
bake-off ” where engineers from many hardware manufacturers confirm
that their hardware will communicate correctly with equipment from other
suppliers. Network equipment that carries a Wi-Fi logo has been certified
by the Wi-Fi Alliance to meet the relevant standards and to pass interoperability
tests. Figure 2-7 shows one version of the Wi-Fi logo.



Figure 2.7


Wi-Fi was originally intended to be a wireless extension of a wired LAN, so the distances between Wi-Fi base stations and the computers that communicate through them are limited to about 100 feet (35 meters) indoors or up to 300 feet (100 meters) outdoors, assuming there are no obstructions between the access point and the computer. When 802.11n equipment becomes available, it will support connections between computers and base stations at least as far apart as the older Wi-Fi versions. There are ways to extend the range of a Wi-Fi signal, but those techniques require special equipment and careful installation.






Because most Wi-Fi signals have such a limited range, you must find
new access point, or hot spot, and set up a new connection every time you move your computer to a new location. And because many Wi-Fi access points don’t permit strangers to connect through them, you may have to establish a separate account for each location. The Wi-Fi networks described in this book follow the 802.11a, b, and g standards, but much of the same information will also apply to the new 802.11n networks when they become available.