IEEE 802.11ax

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, with an extended version, Wi-Fi 6E, that adds the 6 GHz band. 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 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.

This standard aims to boost data speed (throughput-per-area) in crowded places like offices and malls. Though the nominal data rate is only 37% better than 802.11ac, the total network speed increases by 300%, making it more efficient and reducing latency by 75%. 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 . 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.

Rate set

''Notes''

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. 802.11ax addresses frequency bands between 1 GHz and 6 GHz. Therefore, unlike 802.11ac, 802.11ax also operates in the unlicensed 2.4 GHz band. Wi-Fi 6E introduces operation at frequencies of or near 6 GHz, and superwide channels that are 160 MHz wide, the frequency ranges these channels can occupy and the number of these channels depends on the country the Wi-Fi 6 network operates in. To meet the goal of supporting dense 802.11 deployments, the following features have been approved.

Comparison

Notes

References

External links

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

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