The IEEE 802.11 wireless Ethernet standards come from the Institute of Electrical and Electronics Engineers, Inc. (IEEE). This organization only sets the specifications for the standards—it doesn’t test individual wireless products for compliance to these standards. Because the IEEE 802.11 standards are real Ethernet standards that look like Ethernet to your applications, compatibility with wired Ethernet is seldom an issue.
You may notice that “Wi-Fi” is sometimes used interchangeably with the 802.11 standards, particularly with 802.11g, however, this is not quite correct. Wi-Fi simply refers to a product that’s certified by the Wi-Fi Alliance, an organization that has a program to guarantee compliance to the IEEE wireless standards and ensure interoperability between Wi-Fi products. All Wi-Fi products meet IEEE standards, but all IEEE wireless products are not necessarily Wi-Fi.
IEEE 802.11-1997—the first wireless Ethernet.
IEEE 802.11 was introduced in 1997. It was a beginning, but the standard had serious flaws. 802.11 only supported speeds of up to 2 Mbps. It supported two entirely different methods of encoding—Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS)—leading to confusion and incompatibility between equipment. It also had problems dealing with collisions and with signals reflected back from surfaces such as walls. These defects were soon addressed, and in 1999, the IEEE 802.11b Ethernet standard arrived.
IEEE 802.11-2007.
This 2007 release of 802.11 updated the standard by merging amendments a, b, d, e, g, h, i, and j into the base standard ratified in 1997.
IEEE 802.11b.
Ratified in 1999, the 802.11b extension of the original 802.11 standard boosts wireless throughput from 2 Mbps up to 11 Mbps. 802.11b can transmit up to 200 feet (61 m) under good conditions, although this distance may be reduced by the presence of obstacles such as walls. 802.11b uses the popular 2.4-GHz band. The 802.11b upgrade dropped FHSS in favor of DSSS. DSSS has proven to be more reliable than FHSS, and settling on one method of encoding eliminates the problem of having a single standard that includes two equipment types that aren’t compatible with each other. 802.11b devices are compatible with older 802.11 DSSS devices, but they’re not compatible with 802.11 FHSS devices.
IEEE 802.11a.
Also ratified in 1999, 802.11a uses a different band than 802.11b—the 5.8-GHz band called U-NII (Unlicensed National Information Infrastructure) in the United States. Because the U-NII band has a higher frequency and a larger bandwidth allotment than the 2.4-GHz band, the 802.11a standard achieves speeds of up to 54 Mbps.
IEEE 802.11g.
802.11g is an extension of 802.11b and operates in the same 2.4-GHz band as 802.11b. It brings data rates up to 54 Mbps using Orthogonal Frequency-Division Multiplexing (OFDM) technology. Because 802.11g is backward compatible with 802.11b, an 802.11b device can interface directly with an 802.11g access point. 802.11g wireless Ethernet was the most popular standard for many years and is still in common use, however, the newer 802.11n standard is rapidly taking over as the most popular wireless standard because it offers far greater speed and range.
IEEE 802.11n.
802.11n, which operates in both the 2.4- and 5-GHz bands, is today’s wireless standard. It’s not just a step up from the common 802.11g standard, it’s so much better in throughput, coverage, and reliability that it can be said to be revolutionary. This new wireless standard can theoretically achieve wireless throughput of up to 300 Mbps. As a practical matter, 802.11n supports Fast Ethernet throughput of 100 Mbps. Additionally, its effective range is also dramatically larger than earlier 802.11 standards.
802.11n achieves this remarkable performance by using multiple wireless signals and antennas instead of one and by using channel bonding. The technique of using multiple wireless signals and antennas is called Multiple-Input/Multiple-Output (MIMO). Because MIMO transmits multiple data streams simultaneously, it increases wireless capacity while also increasing network reliability and coverage. This wireless transmission method takes advantage of a radio transmission characteristic called multipath, which means that radio waves bouncing off surfaces such as walls and ceilings will arrive at the antenna at fractionally different times. This characteristic has long been considered to be a nuisance that impairs wireless transmission, but MIMO technology actually exploits it to
enhance wireless performance.
MIMO uses a transmission technique called spatial multiplexing to send a high-speed data stream across multiple antennas by breaking it into several lower-speed streams and sending the streams simultaneously. Each signal travels multiple routes for redundancy.
To pick up these multipath signals, MIMO uses multiple antennas and compares signals many times a second to select the best one. A MIMO receiver makes sense of these signals by using a mathematical algorithm to reconstruct the signals. Because it has multiple signals to choose from, MIMO achieves higher speeds at greater ranges than conventional wireless hardware does.
Although 802.11n supports very high speeds, real-world throughput may not be up to advertised speeds and depends on conditions, distance, and type of encryption used.
To operate at maximum speed, 802.11n must operate in channel bonding mode. Channel bonding combines two adjacent 20-MHz channels into a single 40-MHz channel, effectively doubling bandwidth. Channel bonding increases the chances of difficulties when 802.11n is operated in the same space as older “dumb” wireless networks. Even though 802.11n is backwards compatible, the one network mistake that most frequently slows 802.11n is to have 802.11n clients share a 802.11n router with 802.11b/g clients. This interferes with its operation and forces the 802.11n to slow down to deal with the older standards, resulting in significant network slowdowns.
IEEE 802.11s.
This proposed amendment to the 802.11 standard defines how wireless devices negotiate a mesh network both in static topologies and in an ad-hoc network. IEEE 802.11s operates at Layer 2—the Data Link Layer—relying on MAC addresses for its operation. It relies on 802.11a, 802.11b, 802.11g, or 802.11n to carry the actual traffic, with the newer 802.11n in most common use.
IEEE 802.11u.
This amendment, ratified in 2011, simplifies the process of adding mobile users to the wireless network, enabling devices such as laptop computers and smartphones to quickly select an appropriate network by viewing information about available networks. Devices that are not previously authorized to join a network can become authorized based on rules set by the network administrator. These rules may be quite sophisticated and may require new devices to complete an on-line enrollment. This standard has not yet been widely adopted but promises to simplify wireless network connections in congested areas where a wireless device may have access to dozens of competing wireless networks.
IEEE 802.11i.
IEEE 802.11i, also called WPA2, addresses many of the security concerns that come with a wireless network by adding Wi-Fi Protected Access (WPA) and Robust Security Network (RSN) to 802.11a and 802.11b standards. It makes use of the Advanced Encryption Standard (AES) block cipher, an improvement over the RC4 stream cipher used by WEP and WPA. AES is secure enough to meet the FIPS 140-2 specification.
WPA uses Temporal Key Integrity Protocol (TKIP) to improve the security of keys used with Wired Equivalent Privacy (WEP), changing the way keys are derived and adding a message-integrity check function to prevent packet forgeries. RSN adds a layer of dynamic negotiation of authentication and encryption algorithms between access points and mobile devices. 802.11i is backwards compatible with most 802.11x devices, but it loses security if used with non-802.11i devices.
IEEE 802.21
This 2008 standard manages the handoff when mobile devices travel between networks of the same type or between networks of different types. This results in a seamless user experience when, for instance, a smartphone moves out of the range of an 802.11n network and switches to a 3G cellular network.
IEEE 802.15.
This specification covers how information is conveyed over short distances among a Wireless Personal Area Network (WPAN or PAN). This type of network usually consists of a small networked group with little direct connectivity to the outside world.
IEEE 802.16.
IEEE 802.16, was ratified in January 2001 and enables a single base station to support many fixed and mobile wireless users.
It’s also called the Metropolitan Area Network (MAN) standard. 802.16 aims to combine the long ranges of the cellular standards with the high speeds of local wireless networks. Intended as a “last-mile” solution, this standard could someday provide competition for hard-wired broadband services such as DSL and cable modem. 802.16 operates in the 10- to 66-GHz range and has many descendants.
IEEE 802.16d.
This recent standard, also called IEEE 802.16-2004 or WiMax, can cover distances of up to 30 miles. Theoretically, a single base station can transmit hundreds of Mbps, with each customer being allotted a portion of the bandwidth. 802.16d uses either the licensed 2.6- and 3.5-GHz bands or the unlicensed 2.4- and 5-GHz bands.
IEEE 802.16e.
This is based on the 802.16a standard and specifies mobile air interfaces for wireless broadband in the licensed bands ranging from 2 to 6 GHz.
IEEE 802.20.
A proposed specification for a wireless standard for IP-based services. This standard is expected to operate in licensed bands below 3.5 GHz and will be used for mobile broadband wireless networks.
IEEE 802.11x.
This refers to the general 802.11 wireless standard—b, g, or a. Don’t confuse it with 802.1x, a security standard.
IEEE 802.1x. 802.1x is not part of the 802.11 standard. It’s a sub-standard designed to enhance the security of an 802.11 network. It provides an authentication framework that uses a challenge/response method to check if a user is authorized.
