802.11 This early wireless standard provides speeds of up to 2 Mbps.
Because 802.11 supports two entirely different methods of encoding—Frequency Hopping
Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS)—there is often
incompatibility between equipment. 802.11 has also had problems dealing with
collisions and with signals reflected back from surfaces such as walls.
802.11a This is an extension of the 802.11 standard and uses a
different band than 802.11b and 802.11g—the 5.8-GHz band called Unlicensed National
Information Infrastructure (U-NII) in the United States. Because the U-NII band has
a higher frequency and a larger bandwidth allotment than the 2.4-GHz band, the 802.11a
standard achieves speeds of up to 54 Mbps.
802.11b This extension of the original 802.11 standard boosts wireless
throughput from 2 Mbps to 11 Mbps. It can transmit up to 328 feet (100 m) under good
conditions, although this distance may be reduced considerably by obstacles such as
walls. This upgrade has dropped FHSS in favor of the more reliable DSSS. Settling on
one method of encoding eliminates the problem of having a single standard that
includes two kinds of equipment that aren’t compatible with each other. 802.11b
devices are compatible with older 802.11 DSSS devices but are not compatible with
802.11 FHSS devices. 802.11b is currently the most widely used wireless standard.
802.11g 802.11g is an extension to 802.11b and operates in the same
2.4-GHz band. It brings data rates up to 54 Mbps using Orthogonal Frequency-Division
Multiplexing (OFDM) technology. Because 802.11g is backward compatible with 802.11b,
an 802.11b device can interface directly with an 802.11g access point. You may even
be able to upgrade some newer 802.11b access points to be 802.11g compliant via
relatively easy firmware upgrades.
802.11i 802.11i addresses many of the security concerns that come with
a wireless network by adding Wi-Fi Protected Access (WPA) and Robust Security Network
(RSN) to 802.11a and 802.11b standards. WPA uses Temporal Key Integrity Protocol (TKIP)
to improve the security of keys used with WEP, changing the way keys are derived and
adding a message-integrity check function to prevent packet forgeries. RSN adds a layer
of dynamic negotiation of authentication and encryption algorithms between access points
and mobile devices. 802.11i is backwards compatible with most 802.11a and 802.11b devices,
but loses security if used with non-802.11i devices.
802.11n The next standard in development is IEEE 802.11n. This new
standard offers far higher speeds than current standards. Speed projections are at
least 100 Mbps, but they could go up to 320 Mbps. The standard isn’t expected to be
ratified until November 2006.
802.11X This refers to the general 802.11 wireless standard—b, g, or
i. It is not to be confused with 802.1X, a security standard.
802.15 This specification covers how information is conveyed over
short distances among a Wireless Personal Area Network (WPAN). This type of network
usually consists of a small networked group with little direct connectivity to the
outside world. It is compatible with Bluetooth 1.1.
802.16 IEEE 802.16, was ratified in January 2001. It enables a single
base station to support many fixed and mobile wireless users. It is also called the
Metropolitan Area Network (MAN) standard. 802.16 aims to combine the long ranges of
the cellular standards with the high speeds of local wireless networks. Intended as
a “last-mile” solution, this standard could someday provide competition for hard-wired
broadband services such as DSL and cable modem. 802.16 operates in the 10- to 66-GHz
range and has many descendants.
802.16d This recent standard—also called the IEEE 802.16-2004
standard or WiMax—can cover distances of up to 30 miles. Theoretically, a single
base station can transmit hundreds of Mbps with each customer being allotted a portion
of the bandwidth. 802.16d may use either the licensed 2.6- and 3.5-GHz bands or the
unlicensed 2.4- and 5-GHz bands. .
802.16e This is based on the 802.16a standard and specifies mobile
air interfaces for wireless broadband in the licensed bands ranging from 2 to 6 GHz.
802.20 Specifies mobile air interfaces for wireless broadband in
licensed bands below 3.5 GHz.
802.1X 802.1X is not part of the 802.11 standard. It is a sub-standard
designed to enhance the security of an 802.11 network. It provides an authentication
framework that uses a challenge/response method to determine if a user is authorized.
Access Point (AP) A hardware device that acts as a wireless
communication hub that connects a network to wireless devices.
Ad Hoc Mode A hardware device that acts as a wireless communication
hub that connects a network to wireless devices.
Advanced Encryption Standard (AES) AES is the federal next-generation
cryptography algorithm, which replaces DES and 3DES. AES uses 128-, 192-, and 256-bit
keys and is part of the 802.11i specification.
Antenna Gain The ability of the antenna to focus or direct radio
waves (or energy) in a particular direction. Gain measures how well an antenna sends
or picks up radio signals. Gain is noted in decibels-isotropic (dBi). Higher figures
mean higher gain.
Base Station See Access Point (AP).
Bluetooth A short-range wireless standard used as a substitute for
cable or infrared connections in portable devices such as cellular phones, PDAs, and
laptop computers. Bluetooth operates in the 2.4-GHz range.
Client Devices Hardware such as PC Cards, mini-PCI modules, mobile
computing equipment, and PCI/ISA bus Wi-Fi radios. They usually communicate via an
Access Point to other devices on the network.
Direct Sequencing Spread Spectrum (DSSS) The most common kind of
wireless transmission, sending data redundantly over a 2.4-GHz bandwidth range
between transmitters and receivers, using the same spreading pattern to decode the
data for security. Not compatible with Frequency Hopping Spread Spectrum.
EAP Extensible Authentication Protocol (EAP) is an optional IEEE
802.1x security feature. It is an authentication protocol and is often used in large
organizations to enable access to an EAP-enabled Remote Authentication Dial-In User
Service (RADIUS) server. EAP works on wireless LANs, as well as wired Ethernet and
Token Ring networks. It uses a central server to authenticate each user. EAP requires
centralized administration, and is not completely hacker-proof. See 802.1X.
Encryption A security feature that changes data so it can be read only
by the intended receiver.
Frequency Hopping Spread Spectrum A wireless transmission method
operating in the 2.4-GHz band. It divides the available bandwidth into 78 1-MHz
channels, broadcasting in short, 400-ms bursts over 1 channel before hopping to the
next. Transmitters and receivers are synchronized to the same hopping pattern to
ensure security. Any data lost to interference is simply retransmitted on a subsequent
hop at a different frequency. Not compatible with Direct Sequencing Spread Spectrum.
Hotspot A public place in which an access point provides wireless
broadband network services to wireless-equipped visitors through a WLAN. Hotspots are
often found in restaurants, hotels, and airports and may be free or charge a fee.
Infrared Laser Infrared laser wireless transmission offers wireless
connections with speed rivaling fiber optic cable—up to 155 Mbps. It’s an ideal
technology to provide emergency backup for fiber. Laser connections are protocol
independent, so they’re adaptable not only to Ethernet but also to any other network
protocol, including Fast Ethernet and ATM.
Infrastructure Mode A wireless network topology in which devices pass
data through a wireless access Point (AP). The AP mediates all communication between
wireless devices and may also link to a wired network. Contrast with Ad Hoc Mode.
Omnidirectional Describes an antenna that can transmit radio waves in
a 360 degree pattern. Use this type of antenna when coverage in all directions is
Orthogonal Frequency-Division Multiplexing (OFDM) OFDM is a
multicarrier modulation method for sending a large amount of digital data over a radio
wave. As with any multiplexing function, OFDM splits the medium (the radio wave) into
multiple, narrower subsignals that are transmitted simultaneously at different
Quality of Service (QoS) Quality of Service describes network device
capabilities that provide some guarantee of performance such as throughput, priority,
speed, latency, etc. It is specified by IEEE 802.11e for wireless LANs and is still
RADIUS Remote Authentication Dial-In User Service (RADIUS) is an
authentication, authorization, and accounting protocol maintained by the Internet
Engineering Task Force (IETF) that can increase security dramatically. RADIUS is used
by many Internet Service Providers (ISPs) because it provides centralized management
of authentication data, such as passwords, and performance accounting. RADIUS servers
are available from many vendors. GNU RADIUS is a noncommercial version.
Roaming The ability to move seamlessly from one access point coverage
area to another with no loss in connectivity.
Root Bridge The physical connection to the main hard-wired LAN. It
is the top of the pyramid in wireless networking. It accepts associations from
nonroot bridges, access points, and other client devices, however, it can’t associate
with other root bridges.
Spread Spectrum A wireless method that provides transmission over the
license-free 902- to 928-MHz radio band. Spread spectrum is highly resistant to
interference because it sends data over more than one frequency at a time. Because
EMI/RFI interference rarely affects the entire available bandwidth, data still gets
through even if one or two frequencies have interference. Two major kinds of spread
spectrum are direct sequencing spread spectrum and frequency hopping spread spectrum.
Super G Super G is a proprietary extension of the 802.11g standard
that doubles throughput to 108 Mbps. Super G is not an IEEE approved standard. If you
use it, you should use devices from one vendor to ensure compatibility. Super G is
generally backwards compatible with 802.11g.
TKIP The Temporal Key Integrity Protocol (TKIP), pronounced tee-kip,
is an enhancement to Wired Equivalency Protocol (WEP) security. It is part of the
IEEE 802.11i encryption standard for wireless LANs. TKIP is designed to improve
security for 802.11 equipment, particularly legacy hardware, already in use. TKIP
adds four algorithms to WEP: per-packet key mixing function, message integrity code
(MIC), rekeying mechanism, and an IV sequencing discipline to remove replay attacks.
Voltage Standing Wave Ratio (VSWR) This is a measurement of mismatch
in a circuit, cable, waveguide, or antenna system. In a standing wave system, it is
the ratio between the incident and the reflection voltage waves.
Wi-Fi Protected Access (WPA) This protocol increases the level of
security in 802.11 wireless standards. It works with WEP-enabled existing Wi-Fi
devices. When compared to WEP, WPA offers improved data encryption through TKIP. It
also provides user authentication through EAP.
Wireless Application Protocol (WAP) An open architecture that
describes how information is displayed on the limited capacities common to handheld
wireless devices. WAP enables programmers to work with the limited memory; tiny CPU
size; small, monochrome screens; low bandwidth; and erratic connections often found
in devices such as cellular phones and PDAs.
Wired Equivalency Protocol (WEP) A basic security method defined in
802.11. It was designed to provide the same link integrity as that of wired LANs. It
does this by encrypting data transmitted over radio waves between 802.11 wireless
devices. Because WEP uses the two lowest layers of the OSI model, the data link and
physical layers, it does not offer end-to-end security.
Wireless Internet Service Provider (WISP) An Internet provider that
specializes in providing wireless Internet access, often in hotspots in public areas
such as airports.
Wireless IP Wireless IP (Internet Protocol) is the packet protocol
standard for sending wireless data over the Internet.
Wireless LAN (WLAN) A local area network that incorporates wireless
transmission—usually using one of the 802.11 Ethernet standards—in place
of cable. Wireless Ethernet standards, such as 802.11, differ from standard 802.3
wired Ethernet only at OSI Layers 1 and 2, making them interoperable with standard
wired Ethernet. Because these wireless standards are real Ethernet standards and look
like Ethernet to your applications, they’re perfectly compatible with Microsoft®
Windows®, Macintosh® OS, and Linux®.