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A Local Area Network allows computers at one geographical
location to share information and devices such as printers.
With a traditional LAN each computer physically connects to
the network via wires and a network port. A Wireless Local
Area Network (WLAN) provides the same services but without
the need physical connections between the computers and
the network.
 A WLAN typically uses radio waves which allow
network PC cards plugged into a PC/laptop to connect to a
traditional Ethernet LAN. WLANs can usually support data
rates of 11 Mbps (megabits per second), and have a range of
30-300 meters, with signals being able to pass through
walls. Most wireless LANs today use spread spectrum
technology, not because spread spectrum is the best radio
technology for wireless LANs but more as a result of FCC
rules (Federal Code of Regulations 15.247) that allow for
unlicensed operation in a number of radio bands, including
902 to 928 MHz, 2.400 to 2.483 GHz and 5.725 to 5.85 GHz.
These are the industrial, scientific and medical (ISM) bands
where unlicensed users are "secondary users" of the band and
must not interfere with licensed primary users. Fortunately
such interference has not been an issue because wireless
nodes are restricted to 1 watt of power for transmissions
and because the nature of spread spectrum is that it appears
as noise to all but intended receivers. The 2.4-GHz is the
band where most new wireless LAN products operate today. |
