IEEE 802.11 is part of the IEEE 802 set of LAN protocols, and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) Wi-Fi computer communication in various frequencies, including but not limited to 2.4, 5, and 60 GHz frequency bands. Wi-Fi technology has continually improved, with each generation bringing faster speeds, lower latency, and better user experiences in a multitude of environments and with a variety of device types.
IEEE 802.11ax, the newest release of the standard, marketed as Wi-Fi 6 by Wi-Fi Alliance, is one of the two Wi-Fi specifications standards of IEEE 802.11 expecting full deployment in late 2019; the other is IEEE 802.11ay. They can be thought of as High Efficiency Wireless.
802.11ax is designed to operate in all ISM bands between 1 and 6 GHz when they become available for 802.11 use, in addition to the 2.4 and 5 GHz bands already allocated.
Brief overview of previous versions of the standard
802.11 – 1997 (Legacy)
- First IEEE specification in 1997
- use of CCK (Complementary Code Keying) with DSSS (Direct –Sequence Spread Spectrum) or Frequency Hopping.
- CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) as the medium access method.
- Air data rate of 1 or 2 Mbps
- Specified for the 2.4 GHz band
- Air data rate includes error correction but not control and reference signals and channel overheads
802.11b
- Specification released in 1999
- Reached air data rate of 11 Mbps
- Further throughput increase, not possible using single carrier solutions.
- Symbol duration becoming shorter than the multipath spread.
802.11a
- Also in 1999 this amendment introduced the use of OFDM (Orthogonal Frequency Division Multiplexing), increasing air data rate up to 54 Mbps.
- Specified for use in the 5 GHz band only
802.11
- In 1999 the success of the 802.11b specification motivated the creation of WECA (Wireless Ethernet Compatibility Alliance), to solve interoperability issues between vendors
- WECA branded the technology Wi-Fi (trademark)
- WECA was later renamed to Wi-Fi Alliance, which focused on the interoperability between devices through its certification program
- In 2003 the amendment g extended the OFDM specification to 2.4GHz band
- In 2007 amendments a, b, d, e, g, h, i and j were merged with a comprehensive base specification
- Forming the then-current IEEE 802.11-2007 Standard
- In 2009 the amendment n (Enhancement for higher throughput) was released
- Claiming higher throughput by adding MIMO techniques to the specification
Amendments
- In 2012 amendments k, r, y, n, w, p, z, v, u and s were merged to the 802.11-2007 to form IEEE 802.11-2012 Standard (2,793 pages)
- IEEE 802.11ae (March 2012)
- Prioritization of Management Frames
- IEEE 802.11aa (June 2012)
- Robust streaming of Audio Video Transport Streams
- 11ad (December 2012)
- 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
- This frequency band has significantly different propagation characteristics than the 2.4 GHz and 5 GHz bands where Wi-Fi networks operate
- Products implementing the 802.11ad standard are being brought to market under the WiGig brand name
- The certification program is now being developed by the Wi-Fi Alliance instead of the now defunct WiGig Alliance.
- The peak transmission rate of 802.11ad is 7Gbit/s
- 11ac (December 2013)
- IEEE 802.11ac-2013 is an amendment to IEEE 802.11, published in December 2013, that builds on 802.11n
- Changes compared to 802.11n include wider channels (80 or 160 MHz versus 40 MHz) in the 5 GHz band, more spatial streams (up to eight versus four), higher order modulation (up to 256-QAM vs. 64-QAM), and the addition of Multi-user MIMO (MU-MIMO)
- As of October 2013, high-end implementations support 80 MHz channels, three spatial streams, and 256-QAM, yielding a data rate of up to 433.3 Mbit/s per spatial stream, 1300 Mbit/s total, in 80 MHz channels in the 5 GHz band; Vendors have announced plans to release so-called “Wave 2” devices with support for 160 MHz channels, four spatial streams, and MU-MIMO in 2014 and 2015
- 11af (February 2014)
- IEEE 802.11af, also referred to as “White-Fi” and “Super Wi-Fi”,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
- It uses cognitive radio technology to transmit on unused TV channels, with the standard taking measures to limit interference for primary users, such as analog TV, digital TV, and wireless microphones
- Access points and stations determine their position using a satellite positioning system such as GPS and use the Internet to query a geolocation database (GDB) provided by a regional regulatory agency to discover what frequency channels are available for use at a given time and position
- The physical layer uses OFDM and is based on 802.11ac
- The propagation path loss as well as the attenuation by materials such as brick and concrete is lower in the UHF and VHF bands than in the 2.4 and 5 GHz bands, which increases the possible range
- The frequency channels are 6 to 8 MHz wide, depending on the regulatory domain
- Up to four channels may be bonded in either one or two contiguous blocks
- MIMO operation is possible with up to four streams used for either space–time block code (STBC) or multi-user (MU) operation
- The achievable data rate per spatial stream is 26.7 Mbit/s for 6 and 7 MHz channels and 35.6 Mbit/s for 8 MHz channels
- With four spatial streams and four bonded channels, the maximum data rate is 426.7 Mbit/s for 6 and 7 MHz channels and 568.9 Mbit/s for 8 MHz channels
- 11mc (December 2015)
- Roll-up of 802.11-2012 + aa, ac, ad, ae & af to be published as 802.11-2015
- 11ai (November 2015)
- IEEE 802.11ai is an amendment to the 802.11 standard which will add new mechanisms for a faster initial link setup time
- 11ah (March 2016)
- IEEE 802.11ah defines a WLAN system operating at sub 1 GHz license-exempt bands, with final approval slated for March 2016
- Due to the favorable propagation characteristics of the low frequency spectra, 802.11ah can provide improved transmission range compared with the conventional 802.11 WLANs operating in the 2.4 GHz and 5 GHz bands
- 11ah can be used for various purposes including large scale sensor networks,extended range hotspot, and outdoor Wi-Fi for cellular traffic offloading, whereas the available bandwidth is relatively narrow
- 11aq (July 2016)
- IEEE 802.11aq is an amendment to the 802.11 standard which will enable pre-association discovery of services
- This extends some of the mechanisms in 802.11u that enabled device discovery to further discover the services running on a device, or provided by a network
