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.
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.
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.
Although IEEE 802.11 specifications list channels that might be used, the allowed radio frequency spectrum availability varies significantly by regulatory domain.
[9] 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.
In theory, 802.11a signals are absorbed more readily by walls and other solid objects in their path due to their smaller wavelength, and, as a result, cannot penetrate as far as those of 802.11b.
The dramatic increase in throughput of 802.11b (compared to the original standard) along with simultaneous substantial price reductions led to the rapid acceptance of 802.11b as the definitive wireless LAN technology.
It operates at a maximum physical layer bit rate of 54 Mbit/s exclusive of forward error correction codes, or about 22 Mbit/s average throughput.
[citation needed] The then-proposed 802.11g standard was rapidly adopted in the market starting in January 2003, well before ratification, due to the desire for higher data rates as well as reductions in manufacturing costs.
[citation needed] By summer 2003, most dual-band 802.11a/b products became dual-band/tri-mode, supporting a and b/g in a single mobile adapter card or access point.
[47][48] Prior to the final ratification, enterprises were already migrating to 802.11n networks based on the Wi-Fi Alliance's certification of products conforming to a 2007 draft of the 802.11n proposal.
[55][56] IEEE 802.11ad is an amendment that defines a new physical layer for 802.11 networks to operate in the 60 GHz millimeter wave spectrum.
Products implementing the 802.11ad standard are sold under the WiGig brand name, with a certification program developed by the Wi-Fi Alliance.
IEEE 802.11af, also referred to as "White-Fi" and "Super Wi-Fi",[61] is an amendment, approved in February 2014, that allows WLAN operation in TV white space spectrum in the VHF and UHF bands between 54 and 790 MHz.
802.11ah can be used for various purposes including large-scale sensor networks,[68] extended-range hotspots, and outdoor Wi-Fi for cellular WAN carrier traffic offloading, whereas the available bandwidth is relatively narrow.
The main use-cases include indoor operation and short-range communications due to atmospheric oxygen absorption and inability to penetrate walls.
This means that, typically, data frames pass an 802.11 (WLAN) medium and are being converted to 802.3 (Ethernet) or vice versa.
Due to the difference in the frame (header) lengths of these two media, the application's packet size determines the speed of the data transfer.
Each represents an average (UDP) throughput (please note that the error bars are there but barely visible due to the small variation) of 25 measurements.
Since the spectral mask defines only power output restrictions up to ±11 MHz from the center frequency to be attenuated by −50 dBr, it is often assumed that the energy of the channel extends no further than these limits.
[94][95] However, overlap between channels with more narrow spacing (e.g. 1, 4, 7, 11 in North America) may cause unacceptable degradation of signal quality and throughput, particularly when users transmit near the boundaries of AP cells.
[97] Domain codes are specified for the United States, Canada, ETSI (Europe), Spain, France, Japan, and China.
[citation needed] The regdomain setting is often made difficult or impossible to change so that the end-users do not conflict with local regulatory agencies such as the United States' Federal Communications Commission.
Current 802.11 standards specify frame types for use in the transmission of data as well as management and control of wireless links.
[dubious – discuss] Address 4 is only present in data frames transmitted between access points in an Extended Service Set or between intermediate nodes in a mesh network.
Some common 802.11 subtypes include: The body of a management frame consists of frame-subtype-dependent fixed fields followed by a sequence of information elements (IEs).
[108] The IEEE set up a dedicated task group to create a replacement security solution, 802.11i (previously, this work was handled as part of a broader 802.11e effort to enhance the MAC layer).
[citation needed] In January 2005, the IEEE set up yet another task group "w" to protect management and broadcast frames, which previously were sent unsecured.
[109] In December 2011, a security flaw was revealed that affects some wireless routers with a specific implementation of the optional Wi-Fi Protected Setup (WPS) feature.
[110][111] In late 2014, Apple announced that its iOS 8 mobile operating system would scramble MAC addresses during the pre-association stage to thwart retail footfall tracking made possible by the regular transmission of uniquely identifiable probe requests.
