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IEEE 802.11

IEEE 802.11 is part of the IEEE 802 set of local area network (LAN) technical standards, and specifies the set of medium access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) computer communication. The standard and amendments provide the basis for wireless network products using the Wi-Fi brand and are the world's most widely used wireless computer networking standards. IEEE 802.11 is used in most home and office networks to allow laptops, printers, smartphones, and other devices to communicate with each other and access the Internet without connecting wires. IEEE 802.11 is also a basis for vehicle-based communication networks with IEEE 802.11p.

"IEEE 802.11x" redirects here. Not to be confused with IEEE 802.1X.

The standards are created and maintained by the Institute of Electrical and Electronics Engineers (IEEE) LAN/MAN Standards Committee (IEEE 802). The base version of the standard was released in 1997 and has had subsequent amendments. While each amendment is officially revoked when it is incorporated in the latest version of the standard, the corporate world tends to market to the revisions because they concisely denote the capabilities of their products. As a result, in the marketplace, each revision tends to become its own standard. 802.11x is a shorthand for "any version of 802.11", to avoid confusion with "802.11" used specifically for the original 1997 version.


IEEE 802.11 uses various frequencies including, but not limited to, 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz frequency bands. Although IEEE 802.11 specifications list channels that might be used, the allowed radio frequency spectrum availability varies significantly by regulatory domain.


The protocols are typically used in conjunction with IEEE 802.2, and are designed to interwork seamlessly with Ethernet, and are very often used to carry Internet Protocol traffic.

General description[edit]

The 802.11 family consists of a series of half-duplex over-the-air modulation techniques that use the same basic protocol. The 802.11 protocol family employs carrier-sense multiple access with collision avoidance (CSMA/CA) whereby equipment listens to a channel for other users (including non 802.11 users) before transmitting each frame (some use the term "packet", which may be ambiguous: "frame" is more technically correct).


802.11-1997 was the first wireless networking standard in the family, but 802.11b was the first widely accepted one, followed by 802.11a, 802.11g, 802.11n, 802.11ac, and 802.11ax. Other standards in the family (c–f, h, j) are service amendments that are used to extend the current scope of the existing standard, which amendments may also include corrections to a previous specification.[8]


802.11b and 802.11g 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. 802.11n can also use that 2.4-GHz band. Because of this choice of frequency band, 802.11b/g/n equipment may occasionally suffer interference in the 2.4-GHz band from microwave ovens, cordless telephones, and Bluetooth devices. 802.11b and 802.11g control their interference and susceptibility to interference by using direct-sequence spread spectrum (DSSS) and orthogonal frequency-division multiplexing (OFDM) signaling methods, respectively.


802.11a uses the 5 GHz U-NII band which, for much of the world, offers at least 23 non-overlapping, 20-MHz-wide channels. This is an advantage over the 2.4-GHz, ISM-frequency band, which offers only three non-overlapping, 20-MHz-wide channels where other adjacent channels overlap (see: list of WLAN channels). Better or worse performance with higher or lower frequencies (channels) may be realized, depending on the environment. 802.11n and 802.11ax can use either the 2.4 GHz or 5 GHz band; 802.11ac uses only the 5 GHz band.


The segment of the radio frequency spectrum used by 802.11 varies between countries. In the US, 802.11a and 802.11g devices may be operated without a license, as allowed in Part 15 of the FCC Rules and Regulations. Frequencies used by channels one through six of 802.11b and 802.11g fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators may operate 802.11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not commercial content or encryption.[9]

History[edit]

802.11 technology has its origins in a 1985 ruling by the U.S. Federal Communications Commission that released the ISM band[8] for unlicensed use.[12]


In 1991 NCR Corporation/AT&T (now Nokia Labs and LSI Corporation) invented a precursor to 802.11 in Nieuwegein, the Netherlands. The inventors initially intended to use the technology for cashier systems. The first wireless products were brought to the market under the name WaveLAN with raw data rates of 1 Mbit/s and 2 Mbit/s.


Vic Hayes, who held the chair of IEEE 802.11 for 10 years, and has been called the "father of Wi-Fi", was involved in designing the initial 802.11b and 802.11a standards within the IEEE.[13] He, along with Bell Labs Engineer Bruce Tuch, approached IEEE to create a standard.[14]


In 1999, the Wi-Fi Alliance was formed as a trade association to hold the Wi-Fi trademark under which most products are sold.[15]


The major commercial breakthrough came with Apple's adoption of Wi-Fi for their iBook series of laptops in 1999. It was the first mass consumer product to offer Wi-Fi network connectivity, which was then branded by Apple as AirPort.[16][17][18] One year later IBM followed with its ThinkPad 1300 series in 2000.[19]

Protocol Version: Two bits representing the protocol version. The currently used protocol version is zero. Other values are reserved for future use.

Type: Two bits identifying the type of WLAN frame. Control, Data, and Management are various frame types defined in IEEE 802.11.

Subtype: Four bits providing additional discrimination between frames. Type and Subtype are used together to identify the exact frame.

basic service set

More Fragments: The More Fragments bit is set when a packet is divided into multiple frames for transmission. Every frame except the last frame of a packet will have this bit set.

Retry: Sometimes frames require retransmission, and for this, there is a Retry bit that is set to one when a frame is resent. This aids in the elimination of duplicate frames.

Power Management: This bit indicates the power management state of the sender after the completion of a frame exchange. Access points are required to manage the connection and will never set the power-saver bit.

More Data: The More Data bit is used to buffer frames received in a distributed system. The access point uses this bit to facilitate stations in power-saver mode. It indicates that at least one frame is available and addresses all stations connected.

Protected Frame: The Protected Frame bit is set to the value of one if the frame body is encrypted by a protection mechanism such as (WEP), Wi-Fi Protected Access (WPA), or Wi-Fi Protected Access II (WPA2).

Wired Equivalent Privacy

Order: This bit is set only when the "strict ordering" delivery method is employed. Frames and fragments are not always sent in order as it causes a transmission performance penalty.

: The WLAN standard was originally 1 Mbit/s and 2 Mbit/s, 2.4 GHz RF and infrared (IR) standard (1997), all the others listed below are Amendments to this standard, except for Recommended Practices 802.11F and 802.11T.

IEEE 802.11-1997

: 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001)

IEEE 802.11a

: 5.5 Mbit/s and 11 Mbit/s, 2.4 GHz standard (1999)

IEEE 802.11b

: Bridge operation procedures; included in the IEEE 802.1D standard (2001)

IEEE 802.11c

: International (country-to-country) roaming extensions (2001)

IEEE 802.11d

: Enhancements: QoS, including packet bursting (2005)

IEEE 802.11e

: Inter-Access Point Protocol (2003) Withdrawn February 2006

IEEE 802.11F

: 54 Mbit/s, 2.4 GHz standard (backwards compatible with b) (2003)

IEEE 802.11g

: Spectrum Managed 802.11a (5 GHz) for European compatibility (2004)

IEEE 802.11h

: Enhanced security (2004)

IEEE 802.11i

: Extensions for Japan (4.9-5.0 GHz) (2004)

IEEE 802.11j

IEEE 802.11-2007: A new release of the standard that includes amendments a, b, d, e, g, h, i, and j. (July 2007)

: Radio resource measurement enhancements (2008)

IEEE 802.11k

: Higher Throughput WLAN at 2.4 and 5 GHz; 20 and 40 MHz channels; introduces MIMO to Wi-Fi (September 2009)

IEEE 802.11n

: WAVE—Wireless Access for the Vehicular Environment (such as ambulances and passenger cars) (July 2010)

IEEE 802.11p

: Fast BSS transition (FT) (2008)

IEEE 802.11r

: Mesh Networking, Extended Service Set (ESS) (July 2011)

IEEE 802.11s

IEEE 802.11T: Wireless Performance Prediction (WPP)—test methods and metrics Recommendation cancelled

: Improvements related to HotSpots and 3rd-party authorization of clients, e.g., cellular network offload (February 2011)

IEEE 802.11u

: Wireless network management (February 2011)

IEEE 802.11v

: Protected Management Frames (September 2009)

IEEE 802.11w

: 3650–3700 MHz Operation in the U.S. (2008)

IEEE 802.11y

: Extensions to Direct Link Setup (DLS) (September 2010)

IEEE 802.11z

IEEE 802.11-2012: A new release of the standard that includes amendments k, n, p, r, s, u, v, w, y, and z (March 2012)

IEEE 802.11aa: Robust streaming of Audio Video Transport Streams (June 2012) - see

Stream Reservation Protocol

: Very High Throughput WLAN at 5 GHz[g]; wider channels (80 and 160 MHz); Multi-user MIMO (down-link only)[102] (December 2013)

IEEE 802.11ac

: Very High Throughput 60 GHz (December 2012) — see also WiGig

IEEE 802.11ad

IEEE 802.11ae: Prioritization of Management Frames (March 2012)

: TV Whitespace (February 2014)

IEEE 802.11af

IEEE 802.11-2016: A new release of the standard that includes amendments aa, ac, ad, ae, and af (December 2016)

: Sub-1 GHz license exempt operation (e.g., sensor network, smart metering) (December 2016)

IEEE 802.11ah

: Fast Initial Link Setup (December 2016)

IEEE 802.11ai

: China Millimeter Wave (February 2018)

IEEE 802.11aj

IEEE 802.11ak: Transit Links within (June 2018)

Bridged Networks

IEEE 802.11aq: Pre-association Discovery (July 2018)

IEEE 802.11-2020: A new release of the standard that includes amendments ah, ai, aj, ak, and aq (December 2020)

: High Efficiency WLAN at 2.4, 5 and 6 GHz;[h] introduces OFDMA to Wi-Fi[75] (February 2021)

IEEE 802.11ax

: Enhancements for Ultra High Throughput in and around the 60 GHz Band (March 2021)

IEEE 802.11ay

IEEE 802.11az: Next Generation Positioning (March 2023)

: Wake Up Radio (March 2021)

IEEE 802.11ba

: Light Communications (November 2023)

IEEE 802.11bb

IEEE 802.11bc: Enhanced Broadcast Service (February 2024)

: Enhancements for Next Generation V2X (see also IEEE 802.11p) (March 2023)

IEEE 802.11bd

Nomenclature[edit]

Various terms in 802.11 are used to specify aspects of wireless local-area networking operation 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 bridge. A portal provides access to the WLAN by non-802.11 LAN STAs.

802.11 frame types

Comparison of wireless data standards

Fujitsu Ltd. v. Netgear Inc.

a term used by some trade press to refer to faster versions of the IEEE 802.11 standards

Gi-Fi

LTE-WLAN Aggregation

OFDM system comparison table

Passive Wi-Fi

Reference Broadcast Infrastructure Synchronization

TU (time unit)

TV White Space Database

Ultra-wideband

White spaces (radio)

Wi-Fi operating system support

or Bluetooth low energy

Wibree

WiGig

– another wireless protocol primarily designed for shorter-range applications

Wireless USB

IEEE 802.11 working group

Official timelines of 802.11 standards from IEEE

– Including historical timeline of mergers and acquisitions

List of all Wi-Fi Chipset Vendors