IEEE 802.11

IEEE 802.11 is a set of media access control (MAC) and physical layer (PHY) specifications for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6, 5, and 60 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). The base version of this standard was released in 1997 with amendments to it continuing into the future. The original design and the amendments to follow it have laid the groundwork for the Wi-Fi band.

General Description

The standards of the 802.11 family consist of a series of half-duplex over-the-air modulation techniques that use the same basic protocol. While 802.11-1997 was the first wireless networking standard in the family, 802.11b was the first standard to be widely used. Following 802.11b, the standards 802.11a, 802.11g, 802.11n, and 802.11ac became popular. Other standards are service amendments and extensions or corrections to the previous specifications.

802.11b and 802.11g both use the 2.4 GHz ISM band, operating in the United States under Part 15 of the U.S. Federal Communications Commission Rules and Regulations. Unfortunately, these two standards occasionally suffer from interference from microwave ovens, cordless telephones, and Bluetooth devices. Both of these standards control their interference and susceptibility to interference by using direct-sequence spread spectrum (DSSS) and orthogonal frequency-division multiplexing (OFDM) signalling methods.

On the other hand, 802.11a uses the 5 GHz U-NII band, which for most of the world offers at least 23 non-overlapping channels rather than the 2.4 GHz ISM frequency band, where adjacent channels overlap. Of note, the channels allowed for use in each of these standards varies depending on the country. In the United States for instance, regulations due to the FCC may restrict or require special licensing for certain transmissions.

Wi-Fi Basic Information

IEEE 802.11: Wi-Fi Basic Information

Wi-Fi Alliance

The Wi-Fi Alliance is a trade association that promotes Wi-Fi technology and certifies Wi-Fi products if the conform to certain standards of interoperability. It is important to note that not every IEEE 802.11-compliant device is submitted for certification to the Wi-Fi Alliance. This may be because of the costs associated with the certification process. Note that the lack of the Wi-Fi logo does not necessarily imply a device is incompatible with Wi-Fi devices.

The Wi-Fi Alliance owns the Wi-Fi trademark and manufacturers may use the trademark on their products if they have been tested for interoperability.

Modulation Formats

IEEE 802.11: Modulation Formats

Standards and Amendments

IEEE 802.11: Standards and Amendments

IEEE 802.11: n

Channels

IEEE 802.11: Channels

Frames

IEEE 802.11: Frames

Nomenclature

Various terms in 802.11 are used to specify aspects of wireless local-area netowrking operating, and may be unfamiliar to some readers. For example, Time Unit (usually abbreviated TU) is used to indicate a unit of time equal to 1024 microseconds. Numerous time constants are defined in terms of TU (rather than the nearly equal millisecond). Also, the term "Portal" is used to describe an entity that is similar to an 802.1H bride. A Portal provides access to the WLAN by non-802.11 LAN STAs.

Community Networks

With the proliferation of cable modems and DSL, there is an ever-increasing market of people who wish to establish small networks in their homes to share their broadband Internet connection. Many hotspot or free networks frequency allow anyone within range, including passerby outside, to connect to the internet. There are also efforts by volunteer groups to establish wireless community networks to provide free wireless connectivity to the public.

Security

IEEE 802.11: Security

802.11 Non-Standard

802.11 non-standard equipment is equipment that seeks to extend the Wi-Fi standard 802.11 by implementing proprietary features. Examples of non-standard equipment is listed below.

Super G: Chipmaker Atheros sells this proprietary channel bonding feature for manufacturers of access points and client cards. The feature can boost network speeds up to 108 Mbit/s by using channel bonding. The range is also increased to 4x the range of 802.11g and 20x the range of 802.11b. This feature may interfere with other networks and may not support all b and g client cards.
"125 High Speed Mode" or Linksys "SpeedBooster:" Developed by Broadcom, this frame-bursting feature is another proprietary development.
MAXg: U.S. Robotics developed this line of wireless products boasting 125 Mbit/s (actual throughput 35 Mbit/s) and about a 75% increase in signal range from the 802.11g standard. Based on tests performed by KeyLabs on March 23, 2005, the MAXg series consistently outperformed the equivalent proprietary solutions and some of the "Draft 802.11n" solutions from other developers.

Descriptions

802.11b and 802.11g use the 2.4 GHz ISM Band. They both occasionally suffer interference from microwave ovens, cordless telephones, and bluetooth devices.
802.11 technology had origins in 1985 when the US Federal Communications Commission released the ISM band for unlicensed use.
In 1991 NCR Corporation / AT&T invented the precursor to 802.11 in Nieuwegein, The Netherlands. These devices were intended for use in cashier systems and featured data rates of 1 to 2 Mbit/s.