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Glossary

The following table lists the terms and their definitions used in this guide.

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.

access point (AP) An access point 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.

ad-hoc network A LAN or other small network, especially one with wireless or temporary

plug-in connections, in which some of the network devices are part of the

network only for the duration of a communications session or, in the case

of mobile or portable devices, while in some close proximity to the rest of

the network.

Table 56:

List of Terms

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