View source for Wi-Fi 6

{{Short description|Wireless networking standard}}
{{Too technical|date=August 2023}}
'''Wi-Fi 6''', or '''IEEE 802.11ax''', is an IEEE standard from the [[Organization:Wi-Fi Alliance|Wi-Fi Alliance]], for wireless networks (WLANs). It operates in the 2.4 GHz and 5 GHz bands,<ref name="generational">{{cite web |date=October 2018 |title=Generational Wi-Fi® User Guide |url=https://www.wi-fi.org/file/generational-wi-fi-user-guide |access-date=22 March 2021 |publisher=[[Organization:Wi-Fi Alliance|Wi-Fi Alliance]] |format=PDF}}</ref> with an extended version, Wi-Fi 6E, that adds the 6 GHz band.<ref name="6e">{{cite web |date=January 2021 |title=Wi-Fi 6E expands Wi-Fi® into 6 GHz |url=https://www.wi-fi.org/file/wi-fi-6e-highlights |access-date=22 March 2021 |publisher=[[Organization:Wi-Fi Alliance|Wi-Fi Alliance]] |format=PDF}}</ref> It is an upgrade from Wi-Fi 5 (802.11ac), with improvements for better performance in crowded places. Wi-Fi 6 covers frequencies in license-exempt bands between 1 and 7.125 GHz, including the commonly used 2.4 GHz and 5 GHz, as well as the broader [[List of WLAN channels#6GHz|6&nbsp;GHz band]].<ref name="FCC Order 2020-04">{{cite web |date=24 April 2020 |title=FCC Opens 6 GHz Band to Wi-Fi and Other Unlicensed Uses |url=https://www.fcc.gov/document/fcc-opens-6-ghz-band-wi-fi-and-other-unlicensed-uses-0 |access-date=23 March 2021 |website=www.fcc.gov}}</ref>

This standard aims to boost data speed ([[Throughput|throughput]]-per-area{{efn|''Throughput-per-area'', as defined by IEEE, is the ratio of the total network throughput to the network area.<ref name="atutorial" />}}) in crowded places like offices and malls. Though the nominal data rate is only 37%<ref name="atutorial">{{cite journal |last1=Khorov |first1=Evgeny |last2=Kiryanov |first2=Anton |last3=Lyakhov |first3=Andrey |last4=Bianchi |first4=Giuseppe |year=2019 |title=A Tutorial on IEEE 802.11ax High Efficiency WLANs |journal=IEEE Communications Surveys & Tutorials |volume=21 |issue=1 |pages=197–216 |doi=10.1109/COMST.2018.2871099 |doi-access=free}}</ref> better than 802.11ac, the total network speed increases by 300%,<ref name="PAR">{{cite web |last=Aboul-Magd |first=Osama |date=17 March 2014 |title=802.11 HEW SG Proposed PAR |url=https://mentor.ieee.org/802.11/dcn/14/11-14-0165-01-0hew-802-11-hew-sg-proposed-par.docx |url-status=live |archive-url=https://web.archive.org/web/20140407080701/https://mentor.ieee.org/802.11/dcn/14/11-14-0165-01-0hew-802-11-hew-sg-proposed-par.docx |archive-date=7 April 2014 |access-date=22 March 2021 |website=www.ieee.org |format=DOCX}}</ref> making it more efficient and reducing latency by 75%.<ref name="Goodwins">{{Cite web |last=Goodwins |first=Rupert |date=3 October 2018 |title=Next-generation 802.11ax wi-fi: Dense, fast, delayed |url=https://www.zdnet.com/article/next-generation-802-11ax-wi-fi-dense-fast-delayed/ |access-date=23 March 2021 |website=[[ZDNet|www.zdnet.com]]}}</ref> The quadrupling of overall throughput is made possible by a higher [[Spectral efficiency|spectral efficiency]].

802.11ax Wi-Fi has a main feature called [[Orthogonal frequency-division multiple access|OFDMA]], similar to how [[Engineering:Cellular network|cell technology]] works with {{nowrap|Wi-Fi}}.<ref name="atutorial" /> This brings better spectrum use, improved power control to avoid interference, and enhancements like 1024{{nbh}}[[Quadrature amplitude modulation|QAM]], [[MIMO]] and MU-MIMO for faster speeds. There are also reliability improvements in power usage and security protocols like [[IEEE 802.11ah#Target Wake Time|Target Wake Time]] and WPA3.

The 802.11ax standard was approved on September 1, 2020, with Draft 8 getting 95% approval. Subsequently, on February 1, 2021, the standard received official endorsement from the IEEE Standards Board.<ref>{{Cite web|title=IEEE 802.11, The Working Group Setting the Standards for Wireless LANs|url=https://www.ieee802.org/11/Reports/802.11_Timelines.htm|access-date=2022-01-07|website=www.ieee802.org}}</ref>

== Rate set ==
{|class="wikitable mw-datatable"
|-
|+Modulation and coding schemes
|-
!rowspan="3" |MCS<br />index{{Efn-lr|MCS 9 is not applicable to all combinations of channel width and spatial stream count.}}
!rowspan="3" |Modulation<br />type
!rowspan="3" |Coding<br />rate
!colspan="8" |Data rate (Mbit/s){{Efn-lr|Per spatial stream.}}
|-
!colspan="2" |20&nbsp;MHz channels !!colspan="2" |40&nbsp;MHz channels !!colspan="2" |80&nbsp;MHz channels !!colspan="2" |160&nbsp;MHz channels
|-
!1600&nbsp;ns GI{{Efn-lr|''GI'' stands for ''guard interval''.}} !!800&nbsp;ns GI !!1600&nbsp;ns GI !!800&nbsp;ns GI !!1600&nbsp;ns GI !!800 ns GI !!1600&nbsp;ns GI !!800 ns GI
|-
|0 ||BPSK ||1/2 ||8 ||8.6 ||16 ||17.2 ||34 ||36.0 ||68 ||72
|-
|1 ||QPSK ||1/2 ||16 ||17.2 ||33 ||34.4 ||68 ||72.1 ||136 ||144
|-
|2 ||QPSK ||3/4 ||24 ||25.8 ||49 ||51.6 ||102 ||108.1 ||204 ||216
|-
|3 ||16-QAM ||1/2 ||33 ||34.4 ||65 ||68.8 ||136 ||144.1 ||272 ||282
|-
|4 ||16-QAM ||3/4 ||49 ||51.6 ||98 ||103.2 ||204 ||216.2 ||408 ||432
|-
|5 ||64-QAM ||2/3 ||65 ||68.8 ||130 ||137.6 ||272 ||288.2 ||544 ||576
|-
|6 ||64-QAM ||3/4 ||73 ||77.4 ||146 ||154.9 ||306 ||324.4 ||613 ||649
|-
|7 ||64-QAM ||5/6 ||81 ||86.0 ||163 ||172.1 ||340 ||360.3 ||681 ||721
|-
|8 ||256-QAM ||3/4 ||98 ||103.2 ||195 ||206.5 ||408 ||432.4 ||817 ||865
|-
|9 ||256-QAM ||5/6 ||108 ||114.7 ||217 ||229.4 ||453 ||480.4 ||907 ||961
|-
|10 ||1024-QAM ||3/4 ||122 ||129.0 ||244 ||258.1 ||510 ||540.4 ||1021 ||1081
|-
|11 ||1024-QAM ||5/6 ||135 ||143.4 ||271 ||286.8 ||567 ||600.5 ||1134 ||1201
|}

''Notes''
{{notelist-lr}}

== OFDMA ==
In 802.11ac (802.11's previous amendment), [[Multi-user MIMO|multi-user MIMO]] was introduced, which is a [[Spatial multiplexing|spatial multiplexing]] technique. MU-MIMO allows the access point to form beams towards each [[Station (networking)|client]], while transmitting information simultaneously. By doing so, the interference between clients is reduced, and the overall throughput is increased, since multiple clients can receive data simultaneously.

With 802.11ax, a similar multiplexing is introduced in the [[Frequency-division multiplexing|''frequency domain'']]: [[Orthogonal frequency-division multiple access|OFDMA]]. With OFDMA, multiple clients are assigned to different [[Resource Unit]]s in the available spectrum. By doing so, an 80&nbsp;MHz channel can be split into multiple Resource Units, so that multiple clients receive different types of data over the same spectrum, simultaneously.

To support OFDMA, 802.11ax needs four times as many subcarriers as 802.11ac. Specifically, for 20, 40, 80, and 160&nbsp;MHz channels, the 802.11ac standard has, respectively, 64, 128, 256 and 512 subcarriers while the 802.11ax standard has 256, 512, 1,024, and 2,048 subcarriers. Since the available bandwidths have not changed and the number of subcarriers increases by a factor of four, the subcarrier spacing is reduced by the same factor. This introduces OFDM symbols that are four times longer: in 802.11ac, an OFDM symbol takes 3.2 microseconds to transmit. In 802.11ax, it takes 12.8 microseconds (both without [[Guard interval|guard interval]]s).

== Technical improvements ==
The 802.11ax amendment brings several key improvements over 802.11ac. 802.11ax addresses frequency bands between 1&nbsp;GHz and 6&nbsp;GHz.<ref name="80211axPAR">{{cite web|url=https://development.standards.ieee.org/get-file/P802.11ax.pdf?t=81645500003|publisher=IEEE-SA|first=Osama|last=Aboul-Magd|date=2014-01-24|access-date=2017-01-14|title=P802.11ax|archive-url=https://web.archive.org/web/20141010000448/https://development.standards.ieee.org/get-file/P802.11ax.pdf?t=81645500003|archive-date=2014-10-10|url-status=live|quote=2 page PDF download}}</ref> Therefore, unlike 802.11ac, 802.11ax also operates in the unlicensed 2.4&nbsp;GHz band. To meet the goal of supporting dense 802.11 deployments, the following features have been approved.
{| class="wikitable"
! width="10%" | Feature
! width="20%" | 802.11ac
! width="20%" | 802.11ax
! width="60%" | Comment
|-
|[[Orthogonal frequency-division multiple access|OFDMA]]
|Not available
|Centrally controlled medium access with dynamic assignment of 26, 52, 106, 242(?), 484(?), or 996(?) tones per station. Each tone consists of a single subcarrier of 78.125&nbsp;kHz bandwidth. Therefore, bandwidth occupied by a single {{abbr|OFDMA|orthogonal frequency-division multiple access}} transmission is between 2.03125&nbsp;MHz and ca. 80&nbsp;MHz bandwidth.
|{{abbr|OFDMA|Orthogonal frequency-division multiple access}} segregates the spectrum in time-frequency [[Resource Unit|resource units (RUs)]]. A central coordinating entity (the AP in 802.11ax) assigns RUs for reception or transmission to associated stations. Through the central scheduling of the RUs, contention overhead can be avoided, which increases efficiency in scenarios of dense deployments.
|-
|[[Multi-user MIMO|Multi-user MIMO {{nowrap|(MU-MIMO)}}]]
|Available in [[Engineering:Telecommunications link#Downlink|Downlink]] direction
|Available in Downlink and [[Engineering:Telecommunications link#Uplink|Uplink]] direction
|With downlink MU-{{abbr|MIMO|multiple-input and multiple-output}} an AP may transmit concurrently to multiple stations and with uplink MU-MIMO an AP may simultaneously receive from multiple stations. Whereas {{abbr|OFDMA|orthogonal frequency-division multiple access}} separates receivers to different {{abbr|RUs|resource units}}, with MU-MIMO the devices are separated to different spatial streams. In 802.11ax, MU-MIMO and OFDMA technologies can be used simultaneously. To enable uplink MU transmissions, the AP transmits a new control frame (Trigger) which contains scheduling information (RUs allocations for stations, modulation and coding scheme (MCS) that shall be used for each station). Furthermore, Trigger also provides synchronization for an uplink transmission, since the transmission starts [[Short Interframe Space|SIFS]] after the end of Trigger. 
|-
|Trigger-based Random Access
|Not available
|Allows performing UL OFDMA transmissions by stations which are not allocated RUs directly.
|In Trigger frame, the AP specifies scheduling information about subsequent UL MU transmission. However, several RUs can be assigned for random access. Stations which are not assigned RUs directly can perform transmissions within RUs assigned for random access. To reduce collision probability (i.e. situation when two or more stations select the same [[Resource Unit|RU]] for transmission), the 802.11ax amendment specifies special OFDMA back-off procedure. Random access is favorable for transmitting buffer status reports when the AP has no information about pending UL traffic at a station.     
|-
|Spatial frequency reuse
|Not available
|Coloring enables devices to differentiate transmissions in their own network from transmissions in neighboring networks. Adaptive power and sensitivity thresholds allows dynamically adjusting transmit power and signal detection threshold to increase spatial reuse. 
|Without spatial reuse capabilities devices refuse transmitting concurrently to transmissions ongoing in other, neighboring networks. With basic service set coloring (BSS coloring), a wireless transmission is marked at its very beginning, helping surrounding devices to decide if a simultaneous use of the wireless medium is permissible. A station is allowed to consider the wireless medium as idle and start a new transmission even if the detected signal level from a neighboring network exceeds legacy signal detection threshold, provided that the transmit power for the new transmission is appropriately decreased. 
|-
|[[Network allocation vector|NAV]]
|Single NAV
|Two NAVs 
|In dense deployment scenarios, {{abbr|NAV|network allocation vector}} value set by a frame originated from one network may be easily reset by a frame originated from another network, which leads to misbehavior and collisions. To avoid this, each 802.11ax station will maintain two separate NAVs — one NAV is modified by frames originated from a network the station is associated with, the other NAV is modified by frames originated from overlapped networks.  
|-
|[[IEEE 802.11ah#Target Wake Time|Target Wake Time (TWT)]]
|Not available
|TWT reduces power consumption and medium access contention.
|TWT is a concept developed in 802.11ah. It allows devices to wake up at other periods than the beacon transmission period. Furthermore, the AP may group devices to different TWT periods, thereby reducing the number of devices contending simultaneously for the wireless medium.
|-
|Fragmentation
|Static fragmentation
|Dynamic fragmentation
|With static fragmentation, all fragments of a data packet are of equal size, except for the last fragment. With dynamic fragmentation, a device may fill available RUs of other opportunities to transmit up to the available maximum duration. Thus, dynamic fragmentation helps reduce overhead.
|-
|[[Guard interval]] duration
|0.4&nbsp;µs or 0.8&nbsp;µs
|0.8&nbsp;µs, 1.6&nbsp;µs or 3.2&nbsp;µs
|Extended guard interval durations allow for better protection against signal delay spread as it occurs in outdoor environments.
|-
|Symbol duration
|3.2&nbsp;µs
|12.8&nbsp;µs
|Since the subcarrier spacing is reduced by a factor of four, the OFDM symbol duration is increased by a factor of four as well. Extended symbol durations allow for increased efficiency.<ref name="LongerSymbolDuration">{{cite web|url=https://mentor.ieee.org/802.11/dcn/15/11-15-0099-04-00ax-payload-symbol-size-for-11ax.pptx|access-date=2017-01-14|title=Payload Symbol Size for 11ax|publisher=IEEE P802.11|date=2015-01-12|first1=Ron|last1=Porat|first2=Matthew|last2=Fischer|first3=Sriram|last3=Venkateswaran|first4=Tu|last4=Nguyen|first5=Vinko|last5=Erceg|first6=Robert|last6=Stacey|first7=Eldad|last7=Perahia|first8=Shahrnaz|last8=Azizi|first9=Po-Kai|last9=Huang|first10=Qinghua|last10=Li|first11=Xiaogang|last11=Chen|first12=Chitto|last12=Ghosh|first13=Rongzhen|last13=Yang|first14=Fei|last14=Tong|first15=Hyunjeong|last15=Kang|first16=Kaushik|last16=Josiam|first17=Mark|last17=Rison|first18=Rakesh|last18=Taori|first19=Sanghyun|last19=Chang|first20=Lei|last20=Wang|first21=Hongyuan|last21=Zhang|first22=Yakun|last22=Sun|first23=Liwen|last23=Chu|first24=Mingguan|last24=Xu|first25=Jinjing|last25=Jiang|first26=Yan|last26=Zhang|first27=Rui|last27=Cao|first28=Sudhir|last28=Srinivasa|first29=Saga|last29=Tamhane|first30=Mao|last30=Yu|first31=Edward|last31=Au|first32=Hui-Ling|last32=Lu|first33=Yasushi|last33=Takatori|first34=Yasuhiko|last34=Inoue|first35=Yusuke|last35=Asai|first36=Koichi|last36=Ishihara|first37=Akira|last37=Kishida|first38=Akira|last38=Yamada|first39=Fujio|last39=Watanabe|first40=Haralabos|last40=Papadopoulos|first41=Phillip|last41=Barber|first42=Peter|last42=Loc|first43=Le|last43=Liu|first44=Jun|last44=Luo|first45=Yi|last45=Luo|first46=Yingpei|last46=Lin|first47=Jiyong|last47=Pang|first48=Zhigang|last48=Rong|first49=Rob|last49=Sun|first50=David X.|last50=Yang|first51=Yunsong|last51=Yang|first52=Zhou|last52=Lan|first53=Junghoon|last53=Suh|first54=Jiayin|last54=Zhang|first55=Laurent|last55=cariou|first56=Thomas|last56=Derham|first57=Wookbong|last57=Lee|first58=Kiseon|last58=Ryu|first59=Jinyoung|last59=Chun|first60=Jinsoo|last60=Choi|first61=Jeongki|last61=Kim|first62=Giwon|last62=Park|first63=Dongguk|last63=Lim|first64=Suhwook|last64=Kim|first65=Eunsung|last65=Park|first66=HanGyu|last66=Cho|first67=Albert|last67=Van Zelst|first68=Alfred|last68=Asterjadhi|first69=Bin|last69=Tian|first70=Carlos|last70=Aldana|first71=George|last71=Cherian|first72=Gwendolyn|last72=Barriac|first73=Hemanth|last73=Sampath|first74=Menzo|last74=Wentink|first75=Richard|last75=Van Nee|first76=Rolf|last76=De Vegt|first77=Sameer|last77=Vermani|first78=Simone|last78=Merlin|first79=Tevfik|last79=Yucek|first80=VK|last80=Jones|first81=Youhan|last81=Kim|first82=James|last82=Yee|first83=Alan|last83=Jauh|first84=Chingwa|last84=Hu|first85=Frank|last85=Hsu|first86=Thomas|last86=Pare|first87=ChaoChun|last87=Wang|first88=James|last88=Wang|first89=Jianhan|last89=Liu|first90=Tianyu|last90=Wu|first91=Russell|last91=Huang |display-authors=3}}</ref>
|-
|Frequency bands
|5 GHz only
|2.4 GHz and 5 GHz
|802.11ac falls back to 802.11n for the 2.4 GHz band.
|}

==Notes==
{{notelist}}

== Comparison ==
{{802.11 network standards|state=mw-collapsed}}

==References==
{{Reflist}}

==External links==
* [https://www.researchgate.net/publication/327785405_A_Tutorial_on_IEEE_80211ax_High_Efficiency_WLANs Evgeny Khorov, Anton Kiryanov, Andrey Lyakhov, Giuseppe Bianchi. 'A Tutorial on IEEE 802.11ax High Efficiency WLANs', ''IEEE Communications Surveys & Tutorials'', vol. 21, no. 1, pp. 197–216, First quarter 2019]. {{doi|10.1109/COMST.2018.2871099}}
* {{cite journal
 | last1 = Bellalta | first1 = Boris
 | title = IEEE 802.11ax: High-Efficiency WLANs
 |arxiv=1501.01496
 | year = 2015
 | doi=10.1109/MWC.2016.7422404
 | volume=23
 | journal=IEEE Wireless Communications
 | pages=38–46| s2cid = 15023432
 }}
* Shein, Esther, ''[https://www.techrepublic.com/article/deloitte-dont-rule-out-wi-fi-6-as-a-next-generation-wireless-network/ Deloitte: Don't rule out Wi-Fi 6 as a next-generation wireless network]'', [[TechRepublic]], November 30, 2021

{{IEEE standards}}

[[Category:IEEE 802.11|ax]]

{{Sourceattribution|Wi-Fi 6}}