Wi-Fi 6

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Short description: Wireless networking standard

Wi-Fi 6, or IEEE 802.11ax, is an IEEE standard from the Wi-Fi Alliance, for wireless networks (WLANs). It operates in the 2.4 GHz and 5 GHz bands,[1] with an extended version, Wi-Fi 6E, that adds the 6 GHz band.[2] 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 6 GHz band.[3]

This standard aims to boost data speed (throughput-per-area[lower-alpha 1]) in crowded places like offices and malls. Though the nominal data rate is only 37%[4] better than 802.11ac, the total network speed increases by 300%,[5] making it more efficient and reducing latency by 75%.[6] The quadrupling of overall throughput is made possible by a higher spectral efficiency.

802.11ax Wi-Fi has a main feature called OFDMA, similar to how cell technology works with Wi-Fi.[4] This brings better spectrum use, improved power control to avoid interference, and enhancements like 1024‑QAM, MIMO and MU-MIMO for faster speeds. There are also reliability improvements in power usage and security protocols like 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.[7]

Rate set

Modulation and coding schemes
MCS
index[lower-roman 1] 		Modulation
type 		Coding
rate 		Data rate (Mbit/s)[lower-roman 2]
20 MHz channels 40 MHz channels 80 MHz channels 160 MHz channels
1600 ns GI[lower-roman 3] 800 ns GI 1600 ns GI 800 ns GI 1600 ns GI 800 ns GI 1600 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

  1. ↑ MCS 9 is not applicable to all combinations of channel width and spatial stream count.
  2. ↑ Per spatial stream.
  3. ↑ GI stands for guard interval.

OFDMA

In 802.11ac (802.11's previous amendment), multi-user MIMO was introduced, which is a spatial multiplexing technique. MU-MIMO allows the access point to form beams towards each 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 domain: OFDMA. With OFDMA, multiple clients are assigned to different Resource Units in the available spectrum. By doing so, an 80 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 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 intervals).

Technical improvements

The 802.11ax amendment brings several key improvements over 802.11ac. 802.11ax addresses frequency bands between 1 GHz and 6 GHz.[8] Therefore, unlike 802.11ac, 802.11ax also operates in the unlicensed 2.4 GHz band. To meet the goal of supporting dense 802.11 deployments, the following features have been approved.

Feature 802.11ac 802.11ax Comment
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 kHz bandwidth. Therefore, bandwidth occupied by a single OFDMA transmission is between 2.03125 MHz and ca. 80 MHz bandwidth. OFDMA segregates the spectrum in time-frequency 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 (MU-MIMO) Available in Downlink direction Available in Downlink and Uplink direction With downlink MU-MIMO an AP may transmit concurrently to multiple stations and with uplink MU-MIMO an AP may simultaneously receive from multiple stations. Whereas OFDMA separates receivers to different RUs, 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 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 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.
NAV Single NAV Two NAVs In dense deployment scenarios, NAV 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.
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 µs or 0.8 µs 0.8 µs, 1.6 µs or 3.2 µs Extended guard interval durations allow for better protection against signal delay spread as it occurs in outdoor environments.
Symbol duration 3.2 µs 12.8 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.[9]
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

  1. ↑ Throughput-per-area, as defined by IEEE, is the ratio of the total network throughput to the network area.[4]

Comparison

IEEE 802.11 network PHY standards
Frequency
range,
or type 		PHY Protocol Release
date[10] 		Frequency Bandwidth Stream data rate[11] Allowable
MIMO streams 		Modulation Approximate
range[citation needed]
Indoor Outdoor
(GHz) (MHz) (Mbit/s)
1–6 GHz DSSS/FHSS[12] 802.11-1997 Jun 1997 2.4 22 1, 2 N/A DSSS, FHSS 20 m (66 ft) 100 m (330 ft)
HR-DSSS[12] 802.11b Sep 1999 2.4 22 1, 2, 5.5, 11 N/A DSSS 35 m (115 ft) 140 m (460 ft)
OFDM 802.11a Sep 1999 5 5/10/20 6, 9, 12, 18, 24, 36, 48, 54
(for 20 MHz bandwidth,
divide by 2 and 4 for 10 and 5 MHz) 		N/A OFDM 35 m (115 ft) 120 m (390 ft)
802.11j Nov 2004 4.9/5.0[D][13][failed verification] ? ?
802.11p Jul 2010 5.9 ? 1,000 m (3,300 ft)[14]
802.11y Nov 2008 3.7[A] ? 5,000 m (16,000 ft)[A]
ERP-OFDM(, etc.) 802.11g Jun 2003 2.4 38 m (125 ft) 140 m (460 ft)
HT-OFDM[15] 802.11n Oct 2009 2.4/5 20 Up to 288.8[B] 4 MIMO-OFDM 70 m (230 ft) 250 m (820 ft)[16][failed verification]
40 Up to 600[B]
VHT-OFDM[15] 802.11ac Dec 2013 5 20 Up to 346.8[B] 8 MIMO-OFDM 35 m (115 ft)[17] ?
40 Up to 800[B]
80 Up to 1733.2[B]
160 Up to 3466.8[B]
HE-OFDM 802.11ax September 2019 [18] 2.4/5/6 20 Up to 1147[F] 8 MIMO-OFDM 30 m (98 ft) 120 m (390 ft) [G]
40 Up to 2294[F]
80 Up to 4804[F]
80+80 Up to 9608[F]
mmWave DMG[19] 802.11ad Dec 2012 60 2,160 Up to 6,757[20]
(6.7 Gbit/s) 		N/A OFDM, single carrier, low-power single carrier 3.3 m (11 ft)[21] ?
802.11aj Apr 2018 45/60[C] 540/1,080[22] Up to 15,000[23]
(15 Gbit/s) 		4[24] OFDM, single carrier[24] ? ?
EDMG[25] 802.11ay Est. May 2020 60 8000 Up to 20,000 (20 Gbit/s)[26] 4 OFDM, single carrier 10 m (33 ft) 100 m (328 ft)
Sub-1 GHz IoT TVHT[27] 802.11af Feb 2014 0.054–0.79 6–8 Up to 568.9[28] 4 MIMO-OFDM ? ?
S1G[27] 802.11ah Dec 2016 0.7/0.8/0.9 1–16 Up to 8.67 (@2 MHz)[29] 4 ? ?
2.4 GHz, 5 GHz WUR 802.11ba[E] Est. Sep 2020 2.4/5 4.06 0.0625, 0.25 (62.5 kbit/s, 250 kbit/s) N/A OOK (Multi-carrier OOK) ? ?
Light (Li-Fi) IR 802.11-1997 Jun 1997 ? ? 1, 2 N/A PPM ? ?
? 802.11bb Est. Jul 2021 60000-790000 ? ? N/A ? ? ?
802.11 Standard rollups
  802.11-2007 Mar 2007 2.4, 5 Up to 54 DSSS, OFDM
802.11-2012 Mar 2012 2.4, 5 Up to 150[B] DSSS, OFDM
802.11-2016 Dec 2016 2.4, 5, 60 Up to 866.7 or 6,757[B] DSSS, OFDM
  • A1 A2 IEEE 802.11y-2008 extended operation of 802.11a to the licensed 3.7 GHz band. Increased power limits allow a range up to 5,000 m. (As of 2009), it is only being licensed in the United States by the FCC.
  • B1 B2 B3 B4 B5 B6 Based on short guard interval; standard guard interval is ~10% slower. Rates vary widely based on distance, obstructions, and interference.
  • C1 For Chinese regulation.
  • D1 For Japanese regulation.
  • E1 Wake-up Radio (WUR) Operation.
  • F1 F2 F3 F4 For single-user cases only, based on default guard interval which is 0.8 micro seconds. Since multi-user via OFDMA has become available for 802.11ax, these may decrease. Also, these theoretical values depend on the link distance, whether the link is line-of-sight or not, interferences and the multi-path components in the environment.
  • G1 The default guard interval is 0.8 micro seconds. However, 802.11ax extended the maximum available guard interval to 3.2 micro seconds, in order to support Outdoor communications, where the maximum possible propagation delay is larger compared to Indoor environments.

References

  1. ↑ "Generational Wi-Fi® User Guide" (PDF). Wi-Fi Alliance. October 2018. https://www.wi-fi.org/file/generational-wi-fi-user-guide. 
  2. ↑ "Wi-Fi 6E expands Wi-Fi® into 6 GHz" (PDF). Wi-Fi Alliance. January 2021. https://www.wi-fi.org/file/wi-fi-6e-highlights. 
  3. ↑ "FCC Opens 6 GHz Band to Wi-Fi and Other Unlicensed Uses". 24 April 2020. https://www.fcc.gov/document/fcc-opens-6-ghz-band-wi-fi-and-other-unlicensed-uses-0. 
  4. ↑ 4.0 4.1 4.2 Khorov, Evgeny; Kiryanov, Anton; Lyakhov, Andrey; Bianchi, Giuseppe (2019). "A Tutorial on IEEE 802.11ax High Efficiency WLANs". IEEE Communications Surveys & Tutorials 21 (1): 197–216. doi:10.1109/COMST.2018.2871099. 
  5. ↑ Aboul-Magd, Osama (17 March 2014). "802.11 HEW SG Proposed PAR" (DOCX). https://mentor.ieee.org/802.11/dcn/14/11-14-0165-01-0hew-802-11-hew-sg-proposed-par.docx. 
  6. ↑ Goodwins, Rupert (3 October 2018). "Next-generation 802.11ax wi-fi: Dense, fast, delayed". https://www.zdnet.com/article/next-generation-802-11ax-wi-fi-dense-fast-delayed/. 
  7. ↑ "IEEE 802.11, The Working Group Setting the Standards for Wireless LANs". https://www.ieee802.org/11/Reports/802.11_Timelines.htm. 
  8. ↑ Aboul-Magd, Osama (2014-01-24). "P802.11ax". IEEE-SA. https://development.standards.ieee.org/get-file/P802.11ax.pdf?t=81645500003. "2 page PDF download" 
  9. ↑ Porat, Ron; Fischer, Matthew; Venkateswaran, Sriram; Nguyen, Tu; Erceg, Vinko; Stacey, Robert; Perahia, Eldad; Azizi, Shahrnaz et al. (2015-01-12). "Payload Symbol Size for 11ax". IEEE P802.11. https://mentor.ieee.org/802.11/dcn/15/11-15-0099-04-00ax-payload-symbol-size-for-11ax.pptx. 
  10. ↑ "Official IEEE 802.11 working group project timelines". January 26, 2017. http://grouper.ieee.org/groups/802/11/Reports/802.11_Timelines.htm. Retrieved 2017-02-12. 
  11. ↑ "Wi-Fi CERTIFIED n: Longer-Range, Faster-Throughput, Multimedia-Grade Wi-Fi® Networks". Wi-Fi Alliance. September 2009. http://www.wi-fi.org/register.php?file=wp_Wi-Fi_CERTIFIED_n_Industry.pdf. [|permanent dead link|dead link}}]
  12. ↑ 12.0 12.1 Banerji, Sourangsu; Chowdhury, Rahul Singha. "On IEEE 802.11: Wireless LAN Technology". arXiv:1307.2661.
  13. ↑ "The complete family of wireless LAN standards: 802.11 a, b, g, j, n". https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_news_from_rs/183/n183_lan.pdf. 
  14. ↑ Abdelgader, Abdeldime M.S.; Wu, Lenan (2014). "The Physical Layer of the IEEE 802.11p WAVE Communication Standard: The Specifications and Challenges". World Congress on Engineering and Computer Science. http://www.iaeng.org/publication/WCECS2014/WCECS2014_pp691-698.pdf. 
  15. ↑ 15.0 15.1 Wi-Fi Capacity Analysis for 802.11ac and 802.11n: Theory & Practice
  16. ↑ Belanger, Phil; Biba, Ken (2007-05-31). "802.11n Delivers Better Range". Wi-Fi Planet. http://www.wi-fiplanet.com/tutorials/article.php/3680781. 
  17. ↑ "IEEE 802.11ac: What Does it Mean for Test?". LitePoint. October 2013. http://litepoint.com/whitepaper/80211ac_Whitepaper.pdf. 
  18. ↑ "Wi-Fi 6 Routers: What You Can Buy Now (and Soon) | Tom's Guide". https://www.tomsguide.com/amp/us/best-wifi-6-routers,review-6115.html. 
  19. ↑ "IEEE Standard for Information Technology--Telecommunications and information exchange between systems Local and metropolitan area networks--Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 3: Enhancements for Very High Throughput to Support Chinese Millimeter Wave Frequency Bands (60 GHz and 45 GHz)". IEEE Std 802.11aj-2018. April 2018. doi:10.1109/IEEESTD.2018.8345727. https://ieeexplore.ieee.org/document/8345727. 
  20. ↑ "802.11ad - WLAN at 60 GHz: A Technology Introduction". Rohde & Schwarz GmbH. November 21, 2013. p. 14. https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ma220/1MA220_2e_WLAN_11ad_WP.pdf. 
  21. ↑ "Connect802 - 802.11ac Discussion". https://www.connect802.com/802-11ac-discussion. 
  22. ↑ "Understanding IEEE 802.11ad Physical Layer and Measurement Challenges". https://www.keysight.com/upload/cmc_upload/All/22May2014Webcast.pdf. 
  23. ↑ "802.11aj Press Release". https://mentor.ieee.org/802.11/dcn/18/11-18-0698-01-0000-802-11aj-press-release.docx. 
  24. ↑ 24.0 24.1 Hong, Wei; He, Shiwen; Wang, Haiming; Yang, Guangqi; Huang, Yongming; Chen, Jixing; Zhou, Jianyi; Zhu, Xiaowei et al. (2018). "An Overview of China Millimeter-Wave Multiple Gigabit Wireless Local Area Network System". IEICE Transactions on Communications E101.B (2): 262-276. doi:10.1587/transcom.2017ISI0004. https://www.jstage.jst.go.jp/article/transcom/E101.B/2/E101.B_2017ISI0004/_pdf. 
  25. ↑ "IEEE 802.11ay: 1st real standard for Broadband Wireless Access (BWA) via mmWave – Technology Blog". https://techblog.comsoc.org/2018/06/15/ieee-802-11ay-1st-real-standard-for-broadband-wireless-access-bwa-via-mmwave/. 
  26. ↑ Sun, Rob; Xin, Yan; Aboul-Maged, Osama; Calcev, George; Wang, Lei; Au, Edward; Cariou, Laurent; Cordeiro, Carlos et al.. "P802.11 Wireless LANs". IEEE. pp. 2,3. Archived from the original. Error: If you specify |archiveurl=, you must also specify |archivedate=. https://web.archive.org/web/20171206183820/https://mentor.ieee.org/802.11/dcn/15/11-15-1074-00-00ay-11ay-functional-requirements.docx. Retrieved December 6, 2017. 
  27. ↑ 27.0 27.1 "802.11 Alternate PHYs A whitepaper by Ayman Mukaddam". https://www.cwnp.com/uploads/802-11alternatephyswhitepaper.pdf. 
  28. ↑ Lee, Wookbong; Kwak, Jin-Sam; Kafle, Padam; Tingleff, Jens; Yucek, Tevfik; Porat, Ron; Erceg, Vinko; Lan, Zhou et al. (2012-07-10). "TGaf PHY proposal". IEEE P802.11. https://mentor.ieee.org/802.11/dcn/12/11-12-0809-05-00af-tgaf-phy-proposal.docx. Retrieved 2013-12-29. 
  29. ↑ Sun, Weiping; Choi, Munhwan; Choi, Sunghyun (July 2013). "IEEE 802.11ah: A Long Range 802.11 WLAN at Sub 1 GHz". Journal of ICT Standardization 1 (1): 83–108. doi:10.13052/jicts2245-800X.115. http://riverpublishers.com/journal/journal_articles/RP_Journal_2245-800X_115.pdf. 

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