Definition: 802.11

The Wi-Fi standards. The IEEE 802.11 standards cover every version of Wi-Fi, and the Wi-Fi Alliance certifies products. Wi-Fi is the wireless counterpart to "wired" Ethernet, and Wi-Fi and Ethernet co-exist in every home and business.

The first 802.11 specification was introduced in 1997 (Wi-Fi 0), and several incompatible products became available. In 1999, 802.11b became the first Wi-Fi standard widely supported.

All versions of 802.11 use OFDM encoding except for 802.11b, which uses DSSS (see OFDM and spread spectrum). For details about each standard, see below and 802.11 versions.

Infrastructure and Ad Hoc Modes
In "infrastructure" mode, Wi-Fi devices transmit to an "access point" (base station), which may be a stand-alone unit or built into a wireless router. In "ad hoc" mode, two devices communicate peer-to-peer without an access point in between (see Wi-Fi Direct).

Throughput Varies
Speed is distance dependent. The farther away the device from the base station, the lower the speed. Also, the actual throughput is generally half of the rated speed because 802.11 uses collision "avoidance" (see CSMA/CA) rather than Ethernet's collision "detection" method (see CSMA/CD). For example, a 600 Mbps rating may yield 300 Mbps or less in real data throughput. For more about Wi-Fi networks, see wireless LAN and Wi-Fi. See Wi-Fi hotspot, 802.11 timeline, wireless router, ISM band, 802.16 and 802.15.


 802.11 SPECIFICATIONS

                  Max
 Wi-Fi    Bands  Speed   Channel Width
 #  IEEE  (GHz)  (Mbps)      (MHz)

 7  11be 2.4/5/6 46120   20/40/80/160/320

 6e 11ax 6        9608   20/40/80/160

 6  11ax 2.4/5    9608   20/40/80/160

 5  11ac 5        6933   20/40/80/160

 4  11n  2.4/5     600   20/40

 3  11g  2.4        54   20

 2  11a  5          11   20

 1  11b  2.4         2   20

 0  11   2.4         1   20

Stand-Alone Access Points

Wi-Fi access points (APs) are central base stations with antennas. Stand-alone models come in ceiling mounted (middle) and desktop (bottom) versions. They are often not found in homes because an AP is built into the router (see wireless router).

Wi-Fi Adapters

The adapter (top) adds Wi-Fi to any computer via USB, while the card on the bottom plugs into a PCI slot inside a desktop computer. (Images courtesy of D-Link Corporation and TP-LINK Technologies Co., Ltd.)

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Definition: 802.11