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Wireless Fidelity
Wi-Fi (short for "wireless fidelity") is a term for certain types of wireless
local area network (WLAN) that use specifications in the 802.11 family. The term Wi-Fi was
created by an organization called the Wi-Fi Alliance, which oversees tests that certify
product interoperability. A product that passes the alliance tests is given the label
"Wi-Fi certified" (a registered trademark).
Originally, Wi-Fi certification was applicable only to products using the 802.11b
standard. Today, Wi-Fi can apply to products that use any 802.11 standard. The 802.11
specifications are part of an evolving set of wireless network standards known as the
802.11 family. The particular specification under which a Wi-Fi network operates is called
the "flavor" of the network. Wi-Fi has gained acceptance in many businesses,
agencies, schools, and homes as an alternative to a wired LAN. Many airports, hotels, and
fast-food facilities offer public access to Wi-Fi networks. These locations are known as
hot spots. Many charge a daily or hourly rate for access, but some are free. An
interconnected area of hot spots and network access points is known as a hot zone.
Unless adequately protected, a Wi-Fi network can be susceptible to access by unauthorized
users who use the access as a free Internet connection. The activity of locating and
exploiting security-exposed wireless LANs is called war driving. An identifying
iconography, called war chalking, has evolved. Any entity that has a wireless LAN should
use security safeguards such as the Wired Equivalent Privacy (WEP) encryption standard,
the more recent Wi-Fi Protected Access (WPA), Internet Protocol Security (IPsec), or a
virtual private network (VPN).
History
Wi-Fi logoWi-Fi uses both single carrier direct-sequence spread spectrum radio technology
and multi-carrier OFDM radio technology. Unlicensed spread spectrum was first authorized
by the Federal Communications Commission in 1985 and these FCC regulations were later
copied with some changes in many other countries enabling use of this technology in all
major countries. These regulations then enabled the development of Wi-Fi, its onetime
competitor HomeRF, and Bluetooth. The precursor to Wi-Fi was invented in 1991 by NCR
Corporation/AT&T (later Lucent & Agere Systems) in Nieuwegein, the Netherlands. It
was initially intended for cashier systems; the first wireless products were brought on
the market under the name WaveLAN with speeds of 1 Mbit/s to 2 Mbit/s. Vic Hayes, who was
the primary inventor of Wi-Fi and has been named the 'father of Wi-Fi,' was involved in
designing standards such as IEEE 802.11b, 802.11a and 802.11g.
How it works ?
A typical Wi-Fi setup contains one or more APs and one or more clients. An AP broadcasts
its SSID via packets that are called beacons, which are usually broadcast every 100 ms.
The beacons are transmitted at 1 Mbit/s, and are of relatively short duration and
therefore do not have a significant effect on performance. Since 1 Mbit/s is the lowest
rate of Wi-Fi it assures that the client who receives the beacon can communicate at least
1 Mbit/s. Based on the settings (e.g. the SSID), the client may decide whether to connect
to an AP. If two APs of the same SSID are in range of the client, the client firmware
might use signal strength to decide which of the two APs to make a connection to. The
Wi-Fi standard leaves connection criteria and roaming totally open to the client. This is
a strength of Wi-Fi, but also means that one wireless adapter may perform substantially
better than the other. Since Wi-Fi transmits in the air, it has the same properties as a
non-switched ethernet network. Even collisions can therefore appear as in non-switched
ethernet LAN's.
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