IEEE 802.11

IEEE 802.11 also known by the brand Wi-Fi, denotes a set of Wireless LAN/WLAN standards developed by working group 11 of the IEEE LAN/MAN Standards Committee (IEEE 802). The term 802.11x is also used to denote this set of standards and is not to be mistaken for any one of its elements. There is no single 802.11x standard. The term IEEE 802.11 is also used to refer to the original 802.11, which is now sometimes called "802.11 legacy". For the application of these standards see Wi-Fi..

A 802.11b wireless Linksys router with a wired 4-port switch.

A Compaq 802.11b PCI card

The 802.11 family currently includes six over-the-air modulation techniques that all use the same protocol. The most popular techniques are those defined by the b, a, and g amendments to the original standard; security was originally included and was later enhanced via the 802.11i amendment. 802.11n is another modulation technique that has recently been developed; the standard is still under development, although products designed based on draft versions of the standard are being sold. Other standards in the family (c–f, h, j) are service enhancements and extensions or corrections to previous specifications. 802.11b was the first widely accepted wireless networking standard, followed (somewhat counterintuitively) by 802.11a and 802.11g.

802.11b and 802.11g standards use the 2.40 GHz (gigahertz) band, operating (in the United States) under Part 15 of the FCC Rules and Regulations. Because of this choice of frequency band, 802.11b and 802.11g equipment can incur interference from microwave ovens, cordless telephones, Bluetooth devices, and other appliances using this same band. The 802.11a standard uses the 5 GHz band, and is therefore not affected by products operating on the 2.4 GHz band.

The segment of the radio frequency spectrum used varies between countries, with the strictest limitations in the United States. While it is true that in the U.S. 802.11a and g devices may be legally operated without a licence, it is not true that 802.11a and g operate in an unlicensed portion of the radio frequency spectrum. Unlicensed (legal) operation of 802.11 a & g is covered under Part 15 of the FCC Rules and Regulations. Frequencies used by channels one (1) through six (6) (802.11b) fall within the range of the 2.4 gigahertz 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 allowing any commercial content or encryption.

Protocols

Summary

Protocol	Release Date	Op. Frequency	Thruput Rate (Typ)	Data Rate (Max)	Range (Indoor)	Range (Outdoor)
Legacy	1997	2.4-2.5 GHz	0.7 Mb/s	2 Mb/s	~25 meters	~75 meters
802.11a	1999	5.15-5.35/5.47-5.725/5.725-5.875 GHz	23 Mb/s	54 Mb/s	~30 meters	~100 meters
802.11b	1999	2.4-2.5 GHz	4 Mb/s	11 Mb/s	~35 meters	~110 meters
802.11g	2003	2.4-2.5 GHz	19 Mb/s	54 Mb/s	~35 meters	~110 meters
802.11n	2007 (unapproved draft)	2.4 GHz	74 Mb/s	540 Mb/s	~50 meters	~126 meters

802.11 legacy

Release Date	Op. Frequency	Thruput Rate (Typ)	Data Rate (Max)	Range (Indoor)	Range (Outdoor)
July 1997	2.4 GHz	1 Mb/s	2 Mb/s	?	?

The original version of the standard IEEE 802.11 released in 1997 specifies two raw data rates of 1 and 2 megabits per second (Mbit/s) to be transmitted via infrared (IR) signals or by either Frequency hopping or Direct-sequence spread spectrum in the Industrial Scientific Medical frequency band at 2.4 GHz. IR remains a part of the standard but has no actual implementations.

The original standard also defines Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) as the medium access method. A significant percentage of the available raw channel capacity is sacrificed (via the CSMA/CA mechanisms) in order to improve the reliability of data transmissions under diverse and adverse environmental conditions.

At least six different, somewhat-interoperable, commercial products appeared using the original specification, from companies like Alvarion (PRO.11 and BreezeAccess-II), BreezeCom, Lucent, Netwave Technologies (AirSurfer Plus and AirSurfer Pro), Symbol Technologies (Spectrum24), and Proxim (OpenAir). A weakness of this original specification was that it offered so many choices that interoperability was sometimes challenging to realize. It is really more of a "beta-specification" than a rigid specification, allowing individual product vendors the flexibility to differentiate their products. Legacy 802.11 was rapidly supplemented (and popularized) by 802.11b. Widespread adoption of 802.11 networks only occurred after 802.11b was ratified and as a result few networks ran on the 802.11-1997 standard.

802.11a

Release Date	Op. Frequency	Data Rate (Typ)	Data Rate (Max)	Range (Indoor)
October 1999	5 GHz	25 Mb/s	54 Mb/s	~30 meters (~98 ft)

The 802.11a amendment to the original standard was ratified in 1999. The 802.11a standard uses the same core protocol as the original standard, operates in 5 GHz band, and uses a 52-subcarrier orthogonal frequency-division multiplexing (OFDM) with a maximum raw data rate of 54 MB/s, which yields realistic net achievable throughput in the mid-20 Mb/s. The data rate is reduced to 48, 36, 24, 18, 12, 9 then 6 Mb/s if required. 802.11a has 12 non-overlapping channels, 8 dedicated to indoor and 4 to point to point. It is not interoperable with 802.11b, except if using equipment that implements both standards.

Since the 2.4 GHz band is heavily used, using the 5 GHz band gives 802.11a the advantage of less interference. However, this high carrier frequency also brings disadvantages. It restricts the use of 802.11a to almost line of sight, necessitating the use of more access points; it also means that 802.11a cannot penetrate as far as 802.11b since it is absorbed more readily, other things (such as power) being equal.

Different countries have different regulatory support, although a 2003 World Radiotelecommunications Conference made it easier for use worldwide. 802.11a is now approved by regulations in the United States and Japan, but in other areas, such as the European Union, it had to wait longer for approval. European regulators were considering the use of the European HIPERLAN standard, but in mid-2002 cleared 802.11a for use in Europe. In the U.S., a mid-2003 FCC decision may open more spectrum to 802.11a channels.

Of the 52 OFDM subcarriers, 48 are for data and 4 are pilot subcarriers with a carrier separation of 0.3125 MHz (20 MHz/64). Each of these subcarriers can be a BPSK, QPSK, 16-QAM or 64-QAM. The total bandwidth is 20 MHz with an occupied bandwidth of 16.6 MHz. Symbol duration is 4 microseconds with a guard interval of 0.8 microseconds. The actual generation and decoding of orthogonal components is done in baseband using DSP which is then upconverted to 5 GHz at the transmitter. Each of the subcarriers could be represented as a complex number. The time domain signal is generated by taking an Inverse Fast Fourier transform (IFFT). Correspondingly the receiver downconverts, samples at 20 MHz and does an FFT to retrieve the original coefficients. The advantages of using OFDM include reduced multipath effects in reception and increased spectral efficiency.

802.11a products started shipping in 2001, lagging 802.11b products due to the slow availability of the 5 GHz components needed to implement products. 802.11a was not widely adopted overall primarily because the less-expensive 802.11b was already widely adopted, but also because of 802.11a's range disadvantage, some poor initial product implementations that further reduced its range, and in some cases the regulations. Manufacturers of 802.11a equipment responded to the lack of market success by improving the implementations (current-generation 802.11a technology has range characteristics much closer to those of 802.11b), and by making technology that can use more than one 802.11 standard. There are dual-band, or dual-mode or tri-mode cards that can automatically handle 802.11a and b, or a, b and g, as available. Similarly, there are mobile adapters and access points which can support all these standards simultaneously.

Data rate (Mb/s)	Modulation	Coding rate	Number of data bits per symbol	1472 byte transfer duration (µs)
6	BPSK	1/2	24	2012
9	BPSK	3/4	36	1344
12	QPSK	1/2	48	1008
18	QPSK	3/4	72	672
24	16-QAM	1/2	96	504
36	16-QAM	3/4	144	336
48	64-QAM	2/3	192	252
54	64-QAM	3/4	216	224

802.11b

Release Date	Op. Frequency	Data Rate (Typ)	Data Rate (Max)	Range (Indoor)
October 1999	2.4 GHz	5.5 Mb/s	11 Mb/s	~30 meters (~98 ft)

The 802.11b amendment to the original standard was ratified in 1999. 802.11b has a maximum raw data rate of 11 Mb/s and uses the same CSMA/CA media access method defined in the original standard. Due to the CSMA/CA protocol overhead, in practice the maximum 802.11b throughput that an application can achieve is about 5.9 Mb/s using TCP and 7.1 Mb/s using UDP.

802.11b products have appeared on the market very quickly, since 802.11b is a direct extension of the DSSS (Direct-sequence spread spectrum) modulation technique defined in the original standard. Technically, the 802.11b standard uses Complementary code keying (CCK) as its modulation technique. Hence, chipsets and products were easily upgraded to support the 802.11b enhancements. The dramatic increase in throughput of 802.11b (compared to the original standard) along with substantial price reductions led to the rapid acceptance of 802.11b as the definitive wireless LAN technology.

802.11b is usually used in a point-to-multipoint configuration, wherein an access point communicates via an omni-directional antenna with one or more clients that are located in a coverage area around the access point. Typical indoor range is 30 m (100 ft) at 11 MB/s and 90 m (300 ft) at 1 MB/s. With high-gain external antennas, the protocol can also be used in fixed point-to-point arrangements, typically at ranges up to 8 kilometers (5 miles) although some report success at ranges up to 80–120 km (50–75 miles) where line of sight can be established. This is usually done in place of costly leased lines or very cumbersome microwave communications equipment. Designers of such installations who wish to remain within the law must however be careful about legal limitations on effective radiated power.

802.11b cards can operate at 11 Mb/s, but will scale back to 5.5, then 2, then 1 Mb/s (also known as Adaptive Rate Selection), if signal quality becomes an issue. Since the lower data rates use less complex and more redundant methods of encoding the data, they are less susceptible to corruption due to interference and signal attenuation. Extensions have been made to the 802.11b protocol (for example, channel bonding and burst transmission techniques) in order to increase speed to 22, 33, and 44 Mb/s, but the extensions are proprietary and have not been endorsed by the IEEE. Many companies call enhanced versions "802.11b+". These extensions have been largely obviated by the development of 802.11g, which has data rates up to 54 Mb/s and is backwards-compatible with 802.11b.

802.11g

Release Date	Op. Frequency	Data Rate (Typ)	Data Rate (Max)	Range (Indoor)
June 2003	2.4 GHz	24 Mbps	54 Mbps	~50 meters

In June 2003, a third modulation standard was ratified: 802.11g. This flavor works in the 2.4 GHz band (like 802.11b) but operates at a maximum raw data rate of 54 Mb/s, or about 24.7 Mb/s net throughput (like 802.11a). 802.11g hardware is compatible with 802.11b hardware. Details of making b and g work well together occupied much of the lingering technical process. In older networks, however, the presence of an 802.11b participant significantly reduces the speed of an 802.11g network.

The modulation scheme used in 802.11g is orthogonal frequency-division multiplexing (OFDM) for the data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mb/s, and reverts to (like the 802.11b standard) CCK for 5.5 and 11 Mb/s and DBPSK/DQPSK+DSSS for 1 and 2 Mb/s. Even though 802.11g operates in the same frequency band as 802.11b, it can achieve higher data rates because of its similarities to 802.11a. The maximum range of 802.11g devices is slightly greater than that of 802.11b devices, but the range in which a client can achieve the full 54 Mb/s data rate is much shorter than that of which a 802.11b client can reach 11 Mb/s.

The 802.11g standard swept the consumer world of early adopters starting in January 2003, well before ratification. Corporate users held back - Cisco and other big equipment makers waited until ratification. By summer 2003, announcements were flourishing. Most of the dual-band 802.11a/b products became dual-band/tri-mode, supporting a, b, and g in a single mobile adapter card or access point. Despite its major acceptance, 802.11g suffers from the same interference as 802.11b in the already crowded 2.4 GHz range. Devices operating in this range include microwave ovens, Bluetooth devices, and cordless telephones.

802.11n

Release Date	Op. Frequency	Data Rate (Typ)	Data Rate (Max)	Range (Indoor)
Unfinished	2.4 GHz or 5 GHz	100-210 Mbps	700 Mbps	~70 meters

Timeline

In January 2004, IEEE announced that it had formed a new 802.11 Task Group (TGn) to develop a new amendment to the 802.11 standard for wireless local-area networks. The real data throughput is estimated to reach a theoretical 540 Mbit/s (which may require an even higher raw data rate at the physical layer), and should be up to 50 times faster than 802.11b, and up to 10 times faster than 802.11a or 802.11g.

In late July 2005, previous competitors TGn Sync, WWiSE, and a third group, MITMOT, said that they would merge their respective proposals as a draft which would be sent to the IEEE in September; a final version will be submitted in November. The standardization process is expected to be completed by the second quarter of 2009.

802.11n builds upon previous 802.11 standards by adding MIMO (multiple-input multiple-output). MIMO uses multiple transmitter and receiver antennas to allow for increased data throughput via spatial multiplexing and increased range by exploiting the spatial diversity, perhaps through coding schemes like Alamouti coding.

The Enhanced Wireless Consortium (EWC) was formed to help accelerate the IEEE 802.11n development process and promote a technology specification for interoperability of next-generation wireless local area networking (WLAN) products.

On 19 January 2006, the IEEE 802.11n Task Group approved the Joint Proposal's specification, based on EWC's specification as the confirmed 802.11n proposal.

At the March 2006 meeting, the IEEE 802.11 Working Group sent the 802.11n Draft to its first letter ballot, allowing the 500+ 802.11 voters to review the document and suggest bugfixes, changes and improvements.

On 2 May 2006, the IEEE 802.11 Working Group voted not to forward Draft 1.0 of the proposed 802.11n standard for a sponsor ballot. Only 46.6% voted to accept the proposal. To proceed to the next step in the IEEE process, a majority vote of 75% is required. This letter ballot also generated approximately 12000 comments -- much more than anticipated.

In November 2006, TGn voted to accept draft version 1.06, incorporating all accepted technical and editorial comment resolutions prior to this meeting. An additional 800 comment resolutions were approved during the November session which will be incorporated into the next revision of the draft. As of this meeting, three of the 8 comment topic ad hoc groups chartered in May have had completed their work and 88% of the technical comments had been resolved with approximately 370 remaining.

On 19 January 2007, the IEEE 802.11 Working Group unanimously (100 yes, 0 no, 5 abstaining) approved a request by the 802.11n Task Group to issue a new Draft 2.0 of the proposed standard. Draft 2.0 was based on the Task Group's working draft version 1.10. There were two required vote "hurdles" before the March meeting: First, a 15-day procedural vote asking the question, "Should 802.11n Draft 1.10 be forwarded to Working Group letter ballot as Draft 2.0?.", a prerequisite for the second, "Should 802.11n Draft 2.0 be forwarded to Sponsor Ballot?" Both letter ballots required 75% "Yes" votes to pass.

On 7 February 2007, the results of Letter Ballot 95, the 15-day Procedural vote, were announced. The result was a pass with 97.99% approval and 2.01% disapproval. On the same day, 802.11 Working Group leadership announced the opening of Letter Ballot 97. It invited detailed technical comments and closed on 9 March 2007.

On 9 March 2007, Letter Ballot 97, the 30-day Technical vote to approve Draft 2.0, closed. They were announced by IEEE 802 leadership during the Orlando Plenary on 12 March 2007. The ballot passed with an 83.4% approval, well above the 75% approval threshold. There were approximately 3,076 unique comments, which will be examined for incorporation into the next minor revision of Draft 2.

According to the IEEE 802.11 Working Group Project Timelines, the estimated 802.11n publish date is now September 2008.

An 802.11 access point may operate in one of three modes:

1. Legacy (only 802.11a, b, and g)
2. Mixed (both 802.11a, b, g, and n)
3. Greenfield (only 802.11n) - maximum performance

See also: 802.11 non-standard equipment § Pre-802.11n equipment

Channels and international compatibility

See also: Wi-Fi § Technical information

802.11b and 802.11g -- as well as 802.11n when using the 2.4 GHz band -- divide the 2.4 GHz spectrum into 14 overlapping, staggered channels whose center frequencies are 5 megahertz (MHz) apart. The 802.11b, and 802.11g standards do not specify the width of a channel; rather, they specify the center frequency of the channel and a spectral mask for that channel. The spectral mask for 802.11b requires that the signal be attenuated by at least 30 dB from its peak energy at ±11 MHz from the center frequency, and attenuated by at least 50 dB from its peak energy at ±22 MHz from the center frequency.

Since the spectral mask only defines power output restrictions up to ±22 MHz from the center frequency, it is often assumed that the energy of the channel extends no further than these limits. In reality, if the transmitter is sufficiently powerful, the signal can be quite strong even beyond the ±22 MHz point. Therefore, it is a misconception that channels 1, 6, and 11 do not overlap. It is more correct to say that, given the separation between channels 1, 6, and 11, the signal on any channel should be sufficiently attenuated to minimally interfere with a transmitter on any other channel. However, this is not universally true; for example, a powerful transmitter can easily overwhelm a weaker signal on a non-overlapping channel. In some lab tests, throughput on a file transfer on channel 11 decreased slightly when a similar transfer began on channel 1, indicating that even channels 1 and 11 can interfere with each other to some extent.

Although the statement that channels 1, 6, and 11 are "non-overlapping" is incomplete, the 1-6-11 guideline has merit. If transmitters are closer together than channels 1, 6, and 11 (for example, 1, 4, 7, and 10), overlap between the channels will probably cause unacceptable degradation of signal quality and throughput.

The channels that are available for use in a particular country differ according to the regulations of that country. In the United States, for example, FCC regulations only allow channels 1 through 11 to be used. In Europe channels 1-13 are licensed for 802.11b operation but only allow lower transmitted power (only 100 mW) to reduce the interference with other users of the band. In Japan, all 14 channels are licensed for 802.11 operation.

Standard and Amendments

Within the IEEE 802.11 Working Group, the following IEEE Standards Association Standard and Amendments exist:

• IEEE 802.11 - THE WLAN STANDARD was original 1 Mbit/s and 2 Mb/s, 2.4 GHz RF and IR standard (1997), all the others listed below are Amendments to this standard, except for Recommended Practices 802.11F and 802.11T.
• IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001)
• IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mb/s (1999)
• IEEE 802.11c - Bridge operation procedures; included in the IEEE 802.1D standard (2001)
• IEEE 802.11d - International (country-to-country) roaming extensions (2001)
• IEEE 802.11e - Enhancements: QoS, including packet bursting (2005)
• IEEE 802.11F - Inter-Access Point Protocol (2003) _{Withdrawn February 2006}
• IEEE 802.11g - 54 Mb/s, 2.4 GHz standard (backwards compatible with b) (2003)
• IEEE 802.11h - Spectrum Managed 802.11a (5 GHz) for European compatibility (2004)
• IEEE 802.11i - Enhanced security (2004)
• IEEE 802.11j - Extensions for Japan (2004)
• IEEE 802.11k - Radio resource measurement enhancements _{(proposed - 2007?)}
• IEEE 802.11l - _{(reserved and will not be used)}
• IEEE 802.11m - Maintenance of the standard; odds and ends. _(ongoing)
• IEEE 802.11n - Higher throughput improvements using MIMO (multiple input, multiple output antennas) _{(pre-draft - 2009?)}
• IEEE 802.11o - _{(reserved and will not be used)}
• IEEE 802.11p - WAVE - Wireless Access for the Vehicular Environment (such as ambulances and passenger cars) _{(working - 2009?)}
• IEEE 802.11q - _{(reserved and will not be used, can be confused with 802.1Q VLAN trunking)}
• IEEE 802.11r - Fast roaming _{Working "Task Group r" - 2007?}
• IEEE 802.11s - ESS Extended Service Set Mesh Networking _{(working - 2008?)}
• IEEE 802.11T - Wireless Performance Prediction (WPP) - test methods and metrics Recommendation _{(working - 2008?)}
• IEEE 802.11u - Interworking with non-802 networks (for example, cellular) _{(proposal evaluation - ?)}
• IEEE 802.11v - Wireless network management _{(early proposal stages - ?)}
• IEEE 802.11w - Protected Management Frames _{(early proposal stages - 2008?)}
• IEEE 802.11x - _{(reserved and will not be used, can be confused with 802.1x Network Access Control)}
• IEEE 802.11y - 3650-3700 Operation in the U.S. _{(early proposal stages - ?)}

There is no standard or task group named "802.11x". Rather, this term is used informally to denote any current or future 802.11 amendment, in cases where further precision is not necessary. (The IEEE 802.1x standard for port-based network access control, is often mistakenly called "802.11x" when used in the context of wireless networks.)

802.11F and 802.11T are stand-alone documents, rather than amendments to the 802.11 standard and are capitalized as such.

Standard or Amendment?

Both the terms "standard" and "amendment" are used when referring to the different variants of IEEE 802.11. Which is correct?

As far as the IEEE is concerned there is only one standard - IEEE 802.11. This standard is continuously updated by means of amendments such as IEEE 802.11a, IEEE 802.11b etc. Periodically a new version of the IEEE 802.11 standard is produced combining the previous version of the standard and all amendments published up to that date. For example, there is a 2003 edition of the standard available for purchase that incorporates the IEEE 802.11a, IEEE 802.11b, and IEEE 802.11d amendments. It is possible that at some point, only this version will be made available for free download replacing the six year old version of the base standard and the first three amendments.

So the correct term for the base standard called "802.11 legacy" on this page would in fact be 802.11-1999. But outside the working group that produces IEEE 802.11 such accuracy is probably unnecessary. 130.13.221.0 19:06, 7 April 2007 (UTC)rxc130.13.221.0 19:06, 7 April 2007 (UTC)

Nomenclature

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 IEEE 802.1D bridge, but need not actually run the 802.1D protocol. A Portal provides access to the WLAN by non-802.11 LAN STAs.

Community networks

With the proliferation of cable modems and DSL, there is an ever-increasing market of people who wish to establish small networks in their homes to share their high speed Internet connection.

Wireless office networks are often unsecured or secured with WEP, which is said to be easily broken. These networks frequently allow anyone within range, including passersby on the street outside, to connect to the Internet. There are also efforts by volunteer groups to establish wireless community networks to provide free wireless connectivity to the public.

Security

In 2001, a group from the University of California, Berkeley presented a paper describing weaknesses in the 802.11 Wired Equivalent Privacy (WEP) security mechanism defined in the original standard; they were followed by Fluhrer, Mantin, and Shamir's paper entitled "Weaknesses in the Key Scheduling Algorithm of RC4". Not long after, Adam Stubblefield and AT&T publicly announced the first verification of the attack. In the attack they were able to intercept transmissions and gain unauthorized access to wireless networks.

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). The Wi-Fi Alliance announced an interim specification called Wi-Fi Protected Access (WPA) based on a subset of the then current IEEE 802.11i draft. These started to appear in products in mid-2003. IEEE 802.11i (also known as WPA2) itself was ratified in June 2004, and uses the Advanced Encryption Standard, instead of RC4, which was used in WEP and WPA.

In January 2005, IEEE set up yet another task group TGw to protect management and broadcast frames, which previously were sent unsecured. See IEEE 802.11w

Non-standard 802.11 extensions and equipment

Many companies implement wireless networking equipment with non-IEEE standard 802.11 extensions either by implementing proprietary or draft features. These changes may lead to incompatibilities between these extensions.

Further information: 802.11 non-standard equipment

See also

• Bluetooth, another wireless protocol primarily designed for shorter range applications.
• Ultra-wideband
• Wibree
• WiMAX (also known as 802.16), another wireless protocol designed for MANs.
• Spectral efficiency comparison table

External links

• Get IEEE 802
• Download the 802.11 standards from IEEE
• Official IEEE 802.11 Work Plan predictions
• 802.11 Protocol Map/Poster
• Status of the 802.11n standard
• IEEE 802.11 working group
• "Using the Fluhrer, Mantin, and Shamir Attack to Break WEP" (2001), paper by Stubblefield (PDF)
• 802.11 Protocol Map O'Reilly Network article by Matthew Gast that includes a map outlining the relationship between the various 802.11 protocols, standards and regulatory bodies.
• Chapter 15: A Peek Ahead at 802.11n: MIMO-OFDM 802.11 Wireless Networks: The Definitive Guide, Second Edition (PDF)

References

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