Concept Guide

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Term Definition
802.11 An evolving family of specifications for wireless LANs developed by a
working group of the Institute of Electrical and Electronics Engineers
(IEEE). 802.11 standards use the Ethernet protocol and CSMA/CA
(carrier sense multiple access with collision avoidance) for path sharing.
802.11a Provides specifications for wireless systems. Networks using 802.11a
operate at radio frequencies in the 5GHz band. The specification uses a
modulation scheme known as orthogonal frequency-division
multiplexing (OFDM) that is especially well suited to use in office
settings. The maximum data transfer rate is 54 Mbps.
802.11b WLAN standard often called Wi-Fi; backward compatible with 802.11.
Instead of the phase-shift keying (PSK) modulation method historically
used in 802.11 standards, 802.11b uses complementary code keying
(CCK), which allows higher data speeds and is less susceptible to
multipath-propagation interference. 802.11b operates in the 2.4 GHz
band and the maximum data transfer rate is 11 Mbps.
802.11g Offers transmission over relatively short distances at up to 54 Mbps,
compared with the 11 Mbps theoretical maximum of 802.11b. 802.11g
operates in the 2.4 GHz band and employs orthogonal frequency
division multiplexing (OFDM), the modulation scheme used in 802.11a,
to obtain higher data speed. Computers or terminals set up for 802.11g
can fall back to speeds of 11 Mbps, so that 802.11b and 802.11g devices
can be compatible within a single network.
802.11n Wireless networking standard to improve network throughput over the
two previous standards 802.11a and 802.11g with a significant increase
in the maximum raw data rate from 54 Mbps to 600 Mbps with the use
of four spatial streams at a channel width of 40 MHz. 802.11n operates
in the 2.4 and 5.0 bands.
AP An access point (AP) connects users to other users within the network
and also can serve as the point of interconnection between the WLAN
and a fixed wire network. The number of access points a WLAN needs is
determined by the number of users and the size of the network.
access point mapping The act of locating and possibly exploiting connections to WLANs while
driving around a city or elsewhere. To do war driving, you need a
vehicle, a computer (which can be a laptop), a wireless Ethernet card set
to work in promiscuous mode, and some kind of an antenna which can
be mounted on top of or positioned inside the car. Because a WLAN may
have a range that extends beyond an office building, an outside user
may be able to intrude into the network, obtain a free Internet
connection, and possibly gain access to company records and other
resources.
Table 88: List of Terms