Wi-Fi 6
Wireless networking standard
From Wikipedia, the free encyclopedia
IEEE 802.11ax-2021[5] or 802.11ax, is an IEEE standard from the Wi-Fi Alliance, for wireless networks (WLANs). The standard is marketed as Wi-Fi 6.[6] It operates in the 2.4 GHz and 5 GHz bands,[7] with an extended version, Wi-Fi 6E, that adds the 6 GHz band.[8] It is an upgrade from Wi-Fi 5 (IEEE 802.11ac), with improvements for better performance in crowded places. Wi-Fi 6 covers frequencies in license-exempt ISM bands, including the commonly used 2.4 GHz and 5 GHz, as well as the broader 6 GHz band (for WiFi 6E).[9]
Icon used by the Wi-Fi Alliance for Wi-Fi 6 | |
| Introduced | 1 September 2020 |
|---|---|
| Compatible hardware | Personal computers, gaming consoles, smart devices, televisions, printers, security cameras |
| Gen.[1] | IEEE standard |
Adopt. | Link rate (Mbit/s) |
RF (GHz) | ||
|---|---|---|---|---|---|---|
| 2.4 | 5 | 6 | ||||
| Wi‑Fi 1 | 802.11 | 1997 | 1–2 |  |
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| Wi‑Fi 2 | 802.11b | 1999 | 1–11 | |
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| Wi‑Fi 2G | 802.11a | 6–54 | |
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| Wi‑Fi 3 | 802.11g | 2003 | |
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| Wi‑Fi 4 | 802.11n | 2009 | 6.5–600 | |
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| Wi‑Fi 5 | 802.11ac | 2013 | 6.5–6,933 | [a] | |
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| Wi‑Fi 6 | 802.11ax | 2021 | 0.4–9,608 | |
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| Wi‑Fi 6E | |
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| Wi‑Fi 7 | 802.11be | 2024 | 0.4–23,059 | |
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| Wi‑Fi 8[2][3][4] | 802.11bn | TBA | |
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This standard aims to boost throughput[b] in crowded places like offices and malls. Though the nominal data rate is only 37%[10] higher than that of 802.11ac, the throughput increases by at least four times,[11] making it more efficient and reducing latency by 75%.[12] The quintupling of overall throughput is made possible by higher spectral efficiency.
802.11ax Wi-Fi has a main feature called OFDMA, similar to how cellular common-carrier networks work.[10] 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 such as lower power consumption 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.[13]
Rate set
| MCS index [i] |
Modulation type |
Coding rate |
Data rate (Mbit/s)[ii] | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Channel width (MHz) | ||||||||||
| 20 | 40 | 80 | 160 | |||||||
| Guard Interval (μs) | ||||||||||
| 1.6 | 0.8 | 1.6 | 0.8 | 1.6 | 0.8 | 1.6 | 0.8 | |||
| 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 | 288 |
| 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
MU-MIMO and 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-division multiplexing: 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, 1024, and 2048 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. While 802.11ac only uses the 5 GHz band, which is a bit over 700 MHz wide, 802.11ax also allows the use of the 2.4 GHz band of some earlier protocols, less than 100 MHz wide, and the larger 6 GHz band, about 1200 MHz wide.[14] Wi-Fi 6E adds to Wi‑Fi 6 the use of the 6 GHz band and, thereby, channels that are 160 MHz wide without the restrictions of Dynamic Frequency Selection that apply to all 160 MHz channels in the 5 GHz band.[15] The number and selection of channels available depends on the country a given Wi-Fi 6 network operates in.[16] 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, a single OFDMA transmission is between 2.03125 MHz and ca. 80 MHz wide. | 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 with 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 into different spatial streams. In 802.11ax, MU-MIMO and OFDMA can be used simultaneously. To enable uplink MU transmissions, the AP transmits a new control frame (Trigger) which contains scheduling information (RU allocations for stations, and the modulation and coding scheme (MCS) that shall be used for each station). Furthermore, a Trigger also provides synchronization for an uplink transmission, since the transmission starts SIFS after the end of a Trigger. |
| Trigger-based Random Access | not available | Allows performing UL OFDMA transmissions by stations which are not allocated RUs directly | In a 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 a 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 allow dynamically adjusting transmit power and signal detection threshold to increase spatial reuse. | Without spatial reuse capabilities devices refuse transmitting concurrently with transmissions in 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 idle and start a new transmission even if the detected signal level from a neighboring network exceeds the legacy signal detection threshold, provided that the transmit power for the new transmission is appropriately decreased. |
| NAV | Single NAV | Dual NAVs | In dense deployment scenarios, the NAV value set by a frame from one network may be easily reset by a frame 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 from a network the station is associated with, while the other NAV is modified by frames from overlapping 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 times other than the periodic beacon transmission time. Furthermore, the AP may group devices with various TWT periods, thereby reducing the number of devices contending simultaneously for the wireless medium. |
| Fragmentation | Static | Dynamic | 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 or 0.8 μs | 0.8, 1.6 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.[17] |
| Frequency bands | 5 GHz only | 2.4 and 5 GHz | 802.11ac falls back to 802.11n for the 2.4 GHz band. |
Comparison
| Frequency range, or type |
PHY | Protocol | Release date[18] |
Frequency band | Channel width | Stream data rate[19] |
Max. MIMO streams |
Modulation | Approx. range | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Indoor | Outdoor | |||||||||||
| (GHz) | (MHz) | (Mbit/s) | ||||||||||
| 1–7 GHz | DSSS[20], |
802.11-1997 | June 1997 | 2.4 | 22 | 1, 2 | N/a | DSSS, |
20 m (66 ft) | 100 m (330 ft) | ||
| HR/DSSS[20] | 802.11b | September 1999 | 2.4 | 22 | 1, 2, 5.5, 11 | N/a | CCK, DSSS | 35 m (115 ft) | 140 m (460 ft) | |||
| OFDM | 802.11a | September 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 | November 2004 | 4.9, 5.0 [B][21] |
? | ? | ||||||||
| 802.11y | November 2008 | 3.7[C] | ? | 5,000 m (16,000 ft)[C] | ||||||||
| 802.11p | July 2010 | 5.9 | 200 m | 1,000 m (3,300 ft)[22] | ||||||||
| 802.11bd | December 2022 | 5.9, 60 | 500 m | 1,000 m (3,300 ft) | ||||||||
| ERP-OFDM[23] | 802.11g | June 2003 | 2.4 | 38 m (125 ft) | 140 m (460 ft) | |||||||
| HT-OFDM[24] | 802.11n (Wi-Fi 4) |
October 2009 | 2.4, 5 | 20 | Up to 288.8[D] | 4 | MIMO-OFDM (64-QAM) |
70 m (230 ft) | 250 m (820 ft)[25] | |||
| 40 | Up to 600[D] | |||||||||||
| VHT-OFDM[24] | 802.11ac (Wi-Fi 5) |
December 2013 | 5 | 20 | Up to 693[D] | 8 | DL MU-MIMO OFDM (256-QAM) |
35 m (115 ft)[26] | ? | |||
| 40 | Up to 1,600[D] | |||||||||||
| 80 | Up to 3,467[D] | |||||||||||
| 160 | Up to 6,933[D] | |||||||||||
| HE-OFDMA | 802.11ax (Wi-Fi 6, Wi-Fi 6E) |
May 2021 | 2.4, 5, 6 | 20 | Up to 1,147[E] | 8 | UL/DL MU-MIMO OFDMA (1024-QAM) |
30 m (98 ft) | 120 m (390 ft)[F] | |||
| 40 | Up to 2,294[E] | |||||||||||
| 80 | Up to 5,500[E] | |||||||||||
| 80+80 | Up to 11,000[E] | |||||||||||
| EHT-OFDMA | 802.11be (Wi-Fi 7) |
Sep 2024 | 2.4, 5, 6 | 80 | Up to 5,764[E] | 8 | UL/DL MU-MIMO OFDMA (4096-QAM) |
30 m (98 ft) | 120 m (390 ft)[F] | |||
| 160 (80+80) |
Up to 11,500[E] | |||||||||||
| 240 (160+80) |
Up to 14,282[E] | |||||||||||
| 320 (160+160) |
Up to 23,059[E] | |||||||||||
| UHR | 802.11bn (Wi-Fi 8) |
May 2028 (est.) |
2.4, 5, 6 | 320 | Up to 23,059 |
8 | Multi-link MU-MIMO OFDM (4096-QAM) |
? | ? | |||
| WUR[G] | 802.11ba | October 2021 | 2.4, 5 | 4, 20 | 0.0625, 0.25 (62.5 kbit/s, 250 kbit/s) |
N/a | OOK (multi-carrier OOK) | ? | ? | |||
| mmWave (WiGig) |
DMG[27] | 802.11ad | December 2012 | 60 | 2,160 (2.16 GHz) |
Up to 8,085[28] (8 Gbit/s) |
N/a | 3.3 m (11 ft)[29] | ? | |||
| 802.11aj | April 2018 | 60[H] | 1,080[30] | Up to 3,754 (3.75 Gbit/s) |
N/a | single carrier, low-power single carrier[A] | ? | ? | ||||
| CMMG | 802.11aj | April 2018 | 45[H] | 540, 1,080 |
Up to 15,015[31] (15 Gbit/s) |
4[32] | OFDM, single carrier | ? | ? | |||
| EDMG[33] | 802.11ay | July 2021 | 60 | Up to 8,640 (8.64 GHz) |
Up to 303,336[34] (303 Gbit/s) |
8 | OFDM, single carrier | 10 m (33 ft) | 100 m (328 ft) | |||
| Sub 1 GHz (IoT) | TVHT[35] | 802.11af | February 2014 | 0.054– 0.79 |
6, 7, 8 | Up to 568.9[36] | 4 | MIMO-OFDM | ? | ? | ||
| S1G[35] | 802.11ah | May 2017 | 0.7, 0.8, 0.9 |
1–16 | Up to 8.67[37] (@2 MHz) |
4 | ? | ? | ||||
| Light (Li-Fi) |
LC (VLC/OWC) |
802.11bb | November 2023 | 800–1000 nm | 20 | Up to 9.6 Gbit/s | N/a | O-OFDM | ? | ? | ||
(IrDA) |
802.11-1997 | June 1997 | 850–900 nm | ? | 1, 2 | N/a | ? | ? | ||||
| 802.11 Standard rollups | ||||||||||||
| 802.11-2007 (802.11ma) | March 2007 | 2.4, 5 | Up to 54 | DSSS, OFDM | ||||||||
| 802.11-2012 (802.11mb) | March 2012 | 2.4, 5 | Up to 150[D] | DSSS, OFDM | ||||||||
| 802.11-2016 (802.11mc) | December 2016 | 2.4, 5, 60 | Up to 866.7 or 6,757[D] | DSSS, OFDM | ||||||||
| 802.11-2020 (802.11md) | December 2020 | 2.4, 5, 60 | Up to 866.7 or 6,757[D] | DSSS, OFDM | ||||||||
| 802.11-2024 (802.11me) | September 2024 | 2.4, 5, 6, 60 | Up to 9,608 or 303,336 | DSSS, OFDM | ||||||||
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