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Home > IEEE 802.11

IEEE 802.11 or Wi-Fi denotes a set of Wireless LAN standards developed by working group 11 of IEEE 802. The term is also used specifically for the original version; to avoid confusion that is sometimes called "802.11legacy".

The 802.11 family currently includes three separate protocols that focus on encoding (a, b, g); security was originally included, but is now part of other family standards (e.g., 802.11i). Other standards in the family (c–f, h–j, n) are service enhancement and extensions, or corrections to previous specifications. 802.11b was the first widely accepted wireless networking standard, followed, paradoxically, by 802.11a and 802.11g.

802.11b and 802.11g standards use the unlicensed 2.4 GHz band. The 802.11a standard uses the 5 GHz band. Operating in an unregulated frequency band, 802.11b and 802.11g gears can incur interference from microwave ovens, cordless phones, and other appliances using the same 2.4 GHz range.

1 Protocols

1.1 802.11legacy

The original version of the standard IEEE 802.11 released in 1997 and sometimes called "802.1y" specifies two data rates of 1 and 2 Megabits per second (M bit/s) to be transmitted via infrared (IR) signals or in the Industrial Scientific Medical frequency band at 2.4 GHz. IR has been dropped from later revisions of the standard, because it couldn't succeed against the well established IrDA protocol and has had no actual implementations. Legacy 802.11 was rapidly succeeded by 802.11b. At least five different, non-interoperable, commercial products appeared using this specification, from companies like Alvarion (PRO.11 and BreezeAccess-II) and Proxim (OpenAir and RangeLAN). A weakness of this original specification was that it offered so many choices that interoperability could not ever be realized. It is really more of a "meta-specification" than a rigid specification.

1.2 802.11b

802.11b has a raw throughput of 11 Mbit/s and uses Carrier Sense Multiple Access with Collision Avoidance ( CSMA/CA) as its media access method. A significant percentage of the available channel capacity is wasted because of the CSMA/CA. In practice the maximum throughput that an application can achieve is about 5.5 Mbit/s. Metal, water, and thick walls absorb 802.11b signals and decrease the range drastically. 802.11 runs in the 2.4 GHz spectrum.

With high-gain external antennas, the protocol can also be used in fixed point-to-point arrangements, typically at ranges up to eight kilometers (although some report success at ranges up to 80–120 km where line of sight can be established). This is usually done to replace costly leased lines, or in place of very cumbersome microwave communications equipment. Current cards can operate at 11 Mbit/s, but will scale back to 5.5, then 2, then 1, if signal strength becomes an issue.

Extensions have been made to the 802.11b protocol (e.g., channel bonding and burst transmission techniques) in order to increase speed to 22, 33, and 44 Mbit/s, but the extensions are proprietary and have not been endorsed by the IEEE. Many companies call enhanced versions "802.11b+".

The first widespread commercial use of the 802.11b standard for networking was made by Apple ComputerApple Computer, Inc. is a Silicon Valley company based in Cupertino, California, whose main business is computer technologies. Best known for its range of Macintosh computers and, more recently, its iPod personal audio ( MP3 and otherwise) player and iTun under the trademark AirPortAirPort is a wireless networking protocol from Apple Computer designed for their Macintosh computers. It is based on the IEEE 802. 11b (also known as Wi-Fi) standard and has been certified to be compatible with other 802. 11b devices. According to Apple,. On the non-Apple market, LinksysLinksys is a networking company founded in 1988. It sells wired and wireless products, routers, network cards and USB adapters. As an early adopter of the 802. 11g wireless standard Linksys became market leader on the Wintel platform. Most of the products could be considered the current leader.

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Topics: IEEE 802.11 802.11b 802.11a Mbit/s Standard Ghz 802.11g Ieee...

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