802.11 - Computer Definition
The family of IEEE standards describing the over-the-air interfaces for a number of wireless local area networks (WLANs).Variously referred to in the vernacular as Wi-Fi (Wireless Fidelity) and Wireless Ethernet (the Ethernet CSMA/CA protocol is used in 802.11), 802.11 standards include infrared (IR) and radio frequency (RF) solutions, although there currently appear to be no practical applications for IR.The RF standards fall into the 2.4 GHz and 5 GHz ISM bands and offer theoretical bandwidth up to 54 Mbps. The original 802.11 standard (1997) operated in the 2.4 GHz band and supported theoretical data rates up to 2 Mbps. This early standard included a great number of options, which made interoperability of products difficult, or at least uncertain. As a result, 802.11 never gained any real traction in the market. Soon afterward, however, much improved extensions to 802.11 were finalized, and WLANs quickly gained in popularity. Current extensions include 802.11a, 802.11b, and 802.11g. Still under development is 802.11n. See also 802.11a, 802.11b, 802.11g, 802.11n, CSMA/CA, Ethernet, IEEE, ISM, RF, Wi-Fi, Wi-Fi5, and WLAN.
Commonly known as "Wi-Fi," the IEEE 802.11 standards provide the wireless counterpart to Ethernet, and the Wi-Fi Alliance certifies products. The versions have the suffixes 11a, 11b, 11g, 11n and 11ac; the latest being 802.11ac. The original 20 MHz channel was increased to 40 MHz in 11n and to 80 and 160 MHz in 11ac. For more details about each standard, see 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 wireless devices communicate peer-to-peer without an access point in between. Another direct connection mode is also available (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 data 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 rated 54 Mbps may yield 27 Mbps in real throughput. For more about Wi-Fi networks, see wireless LAN and Wi-Fi. See Wi-Fi hotspot, 802.11 timeline, wireless router, ISM band, CCK/OFDM, 802.16 and 802.15. 802.11 SUMMARY Max Indoor Bands Speed Range* Encoding (GHz) (Mbps) (ft) 11b DSSS 2.4, 5 11 150 11g OFDM 2.4 54 170 11a OFDM 5 54 95 11n OFDM 2.4, 5 150** 230 11ac OFDM 5 433*** 230 * = Up to 4x farther outdoors. ** = Per antenna at 40 MHz channels. *** = Per antenna at 80 MHz channels.