Wi-Fi 6

IEEE 802.11ax, officially marketed by the Wi-Fi Alliance as Wi-Fi 6 (2.4 GHz and 5 GHz)[4] and Wi-Fi 6E (6 GHz),[5] is an IEEE standard for wireless local-area networks (WLANs) and the successor of 802.11ac. It is also known as High Efficiency Wi-Fi, for the overall improvements to Wi-Fi 6 clients under dense environments.[6] It is designed to operate in license-exempt bands between 1 and 7.125 GHz, including the 2.4 and 5 GHz bands already in common use as well as the much wider 6 GHz band (5.925–7.125 GHz in the US).[7]

Wi-Fi Generations
Generation IEEE
Standard		 Maximum
Linkrate
(Mbit/s)		 Adopted Radio
Frequency
(GHz)[1]
Wi‑Fi 7 802.11be 40000 TBA 2.4/5/6
Wi‑Fi 6E 802.11ax 600 to 9608 2020 2.4/5/6
Wi‑Fi 6 2019 2.4/5
Wi‑Fi 5 802.11ac 433 to 6933 2014 5
Wi‑Fi 4 802.11n 72 to 600 2008 2.4/5
(Wi-Fi 3*) 802.11g 6 to 54 2003 2.4
(Wi-Fi 2*) 802.11a 6 to 54 1999 5
(Wi-Fi 1*) 802.11b 1 to 11 1999 2.4
(Wi-Fi 0*) 802.11 1 to 2 1997 2.4
*: (Wi-Fi 0, 1, 2, 3, are unbranded common usage.[2][3])

The main goal of this standard is enhancing throughput-per-area[lower-alpha 1] in high-density scenarios, such as corporate offices, shopping malls and dense residential apartments. While the nominal data rate improvement against 802.11ac is only 37%,[6]: qt  the overall throughput improvement (over an entire network) is 300% (hence High Efficiency).[8]: qt  This also translates to 75% lower latency.[9]

The quadrupling of overall throughput is made possible by a higher spectral efficiency. The key feature underpinning 802.11ax is orthogonal frequency-division multiple access (OFDMA), which is equivalent to cellular technology applied into Wi-Fi.[6]: qt  Other improvements on spectrum utilization are better power-control methods to avoid interference with neighboring networks, higher order 1024‑QAM, up-link direction added with the down-link of MIMO and MU-MIMO to further increase throughput, as well as dependability improvements of power consumption and security protocols such as Target Wake Time and WPA3.

The IEEE 802.11ax standard was finalised on September 1, 2020 when Draft 8 received 95% approval in the sponsor ballot and received final approval from the IEEE Standards Board on February 1, 2021.[10]

Rate set
Modulation and coding schemes
MCS
index[lower-roman 1]		 Modulation
type		 Coding
rate		 Data rate (Mbit/s)[lower-roman 2]
20 MHz channels40 MHz channels80 MHz channels160 MHz channels
1600 ns GI[lower-roman 3]800 ns GI1600 ns GI800 ns GI1600 ns GI800 ns GI1600 ns GI800 ns GI
0BPSK1/288.61617.23436.06872
1QPSK1/21617.23334.46872.1136144
2QPSK3/42425.84951.6102108.1204216
316-QAM1/23334.46568.8136144.1272282
416-QAM3/44951.698103.2204216.2408432
564-QAM2/36568.8130137.6272288.2544576
664-QAM3/47377.4146154.9306324.4613649
764-QAM5/68186.0163172.1340360.3681721
8256-QAM3/498103.2195206.5408432.4817865
9256-QAM5/6108114.7217229.4453480.4907961
101024-QAM3/4122129.0244258.1510540.410211081
111024-QAM5/6135143.4271286.8567600.511341201

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 the previous amendment of 802.11 (namely 802.11ac), multi-user MIMO has been 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 at the same time. With 802.11ax, a similar multiplexing is introduced in the frequency domain, namely OFDMA. With this technique, multiple clients are assigned with 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. In order to have enough subcarriers to support the requirements of OFDMA, four times as many subcarriers are needed than by the 802.11ac standard. In other words, for 20, 40, 80 and 160 MHz channels, there are 64, 128, 256 and 512 subcarriers in the 802.11ac standard, but 256, 512, 1,024 and 2,048 subcarriers in the 802.11ax standard. 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, which introduces four times longer OFDM symbols: for 802.11ac the duration of an OFDM symbol is 3.2 microseconds, and for 802.11ax it is 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.[11] 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 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 or not. 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 device to different TWT period 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.[12]

Notes
  1. Throughput-per-area, as defined by IEEE, is the ratio of the total network throughput to the network area.[6]

Comparison
IEEE 802.11 network PHY standards
Frequency
range, or type		 PHY Protocol Release date[13] Frequency Bandwidth Stream data rate[14] Allowable
MIMO streams		 Modulation Approximate range
Indoor Outdoor
(GHz) (MHz) (Mbit/s)
1–6 GHz DSSS/FHSS[15] 802.11-1997 Jun 1997 2.4 22 1, 2 N/A DSSS, FHSS 20 m (66 ft) 100 m (330 ft)
HR-DSSS[15] 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][16] ? ?
802.11p Jul 2010 5.9 ? 1,000 m (3,300 ft)[17]
802.11y Nov 2008 3.7[A] ? 5,000 m (16,000 ft)[A]
ERP-OFDM 802.11g Jun 2003 2.4 38 m (125 ft) 140 m (460 ft)
HT-OFDM[18] 802.11n
(Wi-Fi 4)		 Oct 2009 2.4/5 20 Up to 288.8[B] 4 MIMO-OFDM 70 m (230 ft) 250 m (820 ft)[19]
40 Up to 600[B]
VHT-OFDM[18] 802.11ac
(Wi-Fi 5)		 Dec 2013 5 20 Up to 346.8[B] 8 MIMO-OFDM 35 m (115 ft)[20] ?
40 Up to 800[B]
80 Up to 1733.2[B]
160 Up to 3466.8[B]
HE-OFDMA 802.11ax
(Wi-Fi 6)		 Feb 2021 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[21] 802.11ad Dec 2012 60 2,160 Up to 6,757[22]
(6.7 Gbit/s)		 N/A OFDM, single carrier, low-power single carrier 3.3 m (11 ft)[23] ?
802.11aj Apr 2018 45/60[C] 540/1,080[24] Up to 15,000[25]
(15 Gbit/s)		 4[26] OFDM, single carrier[26] ? ?
EDMG[27] 802.11ay Est. March 2021 60 8000 Up to 20,000 (20 Gbit/s)[28] 4 OFDM, single carrier 10 m (33 ft) 100 m (328 ft)
Sub-1 GHz IoT TVHT[29] 802.11af Feb 2014 0.054–0.79 6–8 Up to 568.9[30] 4 MIMO-OFDM ? ?
S1G[29] 802.11ah Dec 2016 0.7/0.8/0.9 1–16 Up to 8.67 (@2 MHz)[31] 4 ? ?
2.4 GHz, 5 GHz WUR 802.11ba[E] Oct 2021 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 2022 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
802.11-2020 Dec 2020 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. 802.11ac only specifies operation in the 5 GHz band. Operation in the 2.4 GHz band is specified by 802.11n.
  2. Kastrenakes, Jacob (2018-10-03). "Wi-Fi now has version numbers, and Wi-Fi 6 comes out next year". The Verge. Retrieved 2019-05-02.
  3. "Wi-Fi Generation Numbering". ElectronicNotes. Retrieved November 10, 2021.
  4. "Generational Wi-Fi® User Guide" (PDF). www.wi‑fi.org. October 2018. Retrieved 22 March 2021.
  5. "Wi-Fi 6E expands Wi-Fi® into 6 GHz" (PDF). www.wi‑fi.org. January 2021. Retrieved 22 March 2021.
  6. E.Khorov, A. Kiryanov, A. Lyakhov, G. Bianchi (2019). "A Tutorial on IEEE 802.11ax High Efficiency WLANs". IEEE Communications Surveys & Tutorials. IEEE. 21 (in press): 197–216. doi:10.1109/COMST.2018.2871099.{{cite journal}}: CS1 maint: uses authors parameter (link)
  7. "FCC Opens 6 GHz Band to Wi-Fi and Other Unlicensed Uses". www.fcc.gov. 24 April 2020. Retrieved 23 March 2021.
  8. Aboul-Magd, Osama (17 March 2014). "802.11 HEW SG Proposed PAR" (DOCX). www.ieee.org. Archived from the original on 7 April 2014. Retrieved 22 March 2021.
  9. Goodwins, Rupert (3 October 2018). "Next-generation 802.11ax wi-fi: Dense, fast, delayed". www.zdnet.com. Retrieved 23 March 2021.
  10. "IEEE 802.11, The Working Group Setting the Standards for Wireless LANs". www.ieee802.org. Retrieved 2022-01-07.
  11. Aboul-Magd, Osama (2014-01-24). "P802.11ax" (PDF). IEEE-SA. Retrieved 2017-01-14.
  12. Porat, Ron; Fischer, Matthew; Venkateswaran, Sriram; et al. (2015-01-12). "Payload Symbol Size for 11ax". IEEE P802.11. Retrieved 2017-01-14.
  13. "Official IEEE 802.11 working group project timelines". January 26, 2017. Retrieved 2017-02-12.
  14. "Wi-Fi CERTIFIED n: Longer-Range, Faster-Throughput, Multimedia-Grade Wi-Fi® Networks" (PDF). Wi-Fi Alliance. September 2009.
  15. Banerji, Sourangsu; Chowdhury, Rahul Singha. "On IEEE 802.11: Wireless LAN Technology". arXiv:1307.2661.
  16. "The complete family of wireless LAN standards: 802.11 a, b, g, j, n" (PDF).
  17. Abdelgader, Abdeldime M.S.; Wu, Lenan (2014). The Physical Layer of the IEEE 802.11p WAVE Communication Standard: The Specifications and Challenges (PDF). World Congress on Engineering and Computer Science.
  18. Wi-Fi Capacity Analysis for 802.11ac and 802.11n: Theory & Practice
  19. Belanger, Phil; Biba, Ken (2007-05-31). "802.11n Delivers Better Range". Wi-Fi Planet. Archived from the original on 2008-11-24.
  20. "IEEE 802.11ac: What Does it Mean for Test?" (PDF). LitePoint. October 2013. Archived from the original (PDF) on 2014-08-16.
  21. "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.
  22. "802.11ad - WLAN at 60 GHz: A Technology Introduction" (PDF). Rohde & Schwarz GmbH. November 21, 2013. p. 14.
  23. "Connect802 - 802.11ac Discussion". www.connect802.com.
  24. "Understanding IEEE 802.11ad Physical Layer and Measurement Challenges" (PDF).
  25. "802.11aj Press Release".
  26. Hong, Wei; He, Shiwen; Wang, Haiming; Yang, Guangqi; Huang, Yongming; Chen, Jixing; Zhou, Jianyi; Zhu, Xiaowei; Zhang, Nianzhu; Zhai, Jianfeng; Yang, Luxi; Jiang, Zhihao; Yu, Chao (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.
  27. "IEEE 802.11ay: 1st real standard for Broadband Wireless Access (BWA) via mmWave – Technology Blog". techblog.comsoc.org.
  28. Sun, Rob; Xin, Yan; Aboul-Maged, Osama; Calcev, George; Wang, Lei; Au, Edward; Cariou, Laurent; Cordeiro, Carlos; Abu-Surra, Shadi; Chang, Sanghyun; Taori, Rakesh; Kim, TaeYoung; Oh, Jongho; Cho, JanGyu; Motozuka, Hiroyuki; Wee, Gaius. "P802.11 Wireless LANs". IEEE. pp. 2, 3. Archived from the original on 2017-12-06. Retrieved December 6, 2017.
  29. "802.11 Alternate PHYs A whitepaper by Ayman Mukaddam" (PDF).
  30. Lee, Wookbong; Kwak, Jin-Sam; Kafle, Padam; Tingleff, Jens; Yucek, Tevfik; Porat, Ron; Erceg, Vinko; Lan, Zhou; Harada, Hiroshi (2012-07-10). "TGaf PHY proposal". IEEE P802.11. Retrieved 2013-12-29.
  31. Sun, Weiping; Choi, Munhwan; Choi, Sunghyun (July 2013). "IEEE 802.11ah: A Long Range 802.11 WLAN at Sub 1 GHz" (PDF). Journal of ICT Standardization. 1 (1): 83–108. doi:10.13052/jicts2245-800X.115.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.