(networking, standard)
An IEEE wireless local area network (WLAN) standard protocol, expected to be approved in June 2003. 802.11g offers wireless transmission over relatively short distances at up to 54 megabits per second (Mbps).

802.11g operates in the 2.4 GHz range and is thus compatible with 802.11b (11 Mbps Wi-Fi).
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The Wi-Fi standards. 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.

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 rated 54 Mbps may yield 27 Mbps 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    Indoor  ChannelWi-Fi   Bands Speed   Range*   Width No.    (GHz) (Mbps)  (ft)     (MHz)1 11b  2.4      11    150  20
 2 11a       5   54     95  20
 3 11g  2.4      54    170  20
 4 11n  2.4, 5  150**  230  20/40
 5 11ac      5  433*** 230  20/40/80/160
 6 11ax 2.4, 5  600*** 230  20/40/80/160

  ** = Per antenna at 40 MHz channels.
 *** = Per antenna at 80 MHz channels.

Stand-Alone Access Points
Wi-Fi access points (APs) are central base stations with antennas. These examples are stand-alone APs (ceiling mounted and desktop). They are generally not found in homes because an AP is already built into the wireless router.

Stand-Alone Access Points
Wi-Fi access points (APs) are central base stations with antennas. These examples are stand-alone APs (ceiling mounted and desktop). They are generally not found in homes because an AP is already built into the 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.)

802.11 versions

Following is a summary of the IEEE 802.11 Wi-Fi standards, from newest to oldest. If devices with different versions communicate, the transmission will be at the highest common speed between them. See 802.11 and Wi-Fi.

11ax (2019) - Highest Speed (Wi-Fi 6)
802.11ax operates in both the 2.4 GHz and 5 GHz bands with data rates in the multi-gigabit range (see 802.11ax). More multiuser modes to support higher user density. Branded as Wi-Fi 6.

11ac (2012) - High Speed
802.11ac operates in the 5 GHz band with data rates into the gigabit range (see 802.11ac). Very valuable when multiple users are online at the same time. Retroactively branded as Wi-Fi 5.

11n (2009) - High Speed
802.11n uses multiple antennas for speeds up to 450 Mbps. 11n operates in both 2.4 GHz and 5 GHz spectrum bands and is compatible with previous 11b/g and 11a standards (see 802.11n). More than enough speed for the casual user. Retroactively branded as Wi-Fi 4.

11g (2003) - Medium Speed
Using orthogonal FDM (OFDM) transmission, 802.11g increased speed in the 2.4 GHz band to 54 Mbps. Both 11b and 11g are compatible, and equipment is often designated as 802.11b/g. See OFDM. Retroactively branded as Wi-Fi 3.

11a (1999) - Medium Speed
Using orthogonal FDM (OFDM), 802.11a transmits up to 54 Mbps. It uses the 5 GHz band and is not compatible with 11b. Retroactively branded as Wi-Fi 2.

11b (1999) - Slow Speed
Using DSSS and the 2.4 GHz band, 802.11b boosted speed to 11 Mbps while retaining the slower DSSS modes to accommodate weak signals. It was the first major wireless local network standard, and many laptops were retrofitted with 11b network adapters. Later, 11b was built into the laptop motherboard. Retroactively branded as Wi-Fi 1.

Very Slow (1997)
The first 802.11 specifications included two spread spectrum methods in the unlicensed 2.4 GHz band: 1 Mbps frequency hopping (FHSS) and 1 and 2 Mbps direct sequence (DSSS). It also included an infrared method. Both FHSS and infrared were dropped by the Wi-Fi Alliance, but 1 Mbps DSSS method is still used by access points to advertise themselves (see beaconing).
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