• Key building blocks of 802.11ax. Source: Qualcomm 2016, slide 11.
    image
  • Key parameters of 802.11ax compared against 802.11ac. Source: National Instruments 2017, table 1.
    image
  • OFDMA and MU-MIMO complement each other. Source: Qualcomm 2016, slide 18.
    image

IEEE 802.11ax

Summary

image
Key building blocks of 802.11ax. Source: Qualcomm 2016, slide 11.

IEEE 802.11ax standard is an evolution of 802.11ac. Unlike previous standards that focused mainly on increasing raw data rates, 802.11ax focuses on better efficiency, capacity and performance. This would translate to a 4x improvement in average throughput per user and better user experience. This is true even for dense indoor/outdoor deployments. It's able to do this due to a number of changes that include higher modulation, more OFDM sub-carriers, and longer OFDM symbol; multiplexing users via MU-MIMO, beamforming and OFDMA; scheduling uplink instead of contention; and mitigating co-channel interference via BSS colour codes.

While 802.11ac used only the 5 GHz band, 802.11ax addresses both 2.4 and 5 GHz bands, thus staying backward compatible and becoming the migration path for both 802.11n and 802.11ac devices.

IEEE 802.11ax is also called High Efficiency Wi-Fi (HEW).

Milestones

2014

Within the IEEE, High Efficiency WLANs (HEW) Task Group is formed to start the development of 802.11ax standard.

Oct
2016

Quantenna announces world's first 802.11ax chipset for APs. Named QSR10G-AX, it supports 8 streams at 5 GHz and 4 streams at 2.4 GHz.

Feb
2017

Qualcomm announces chips IPQ8074 (for routers/APs) and QCA6290 (for clients). It's expected that router devices will come out first (end 2017) followed by client devices (2018).

Aug
2017

Broadcom announces three chips as part of its 802.11ax family without support for MU-MIMO in the uplink.

Sep
2017

Draft 2.0 of 802.11ax is released. This may be incompatible with Draft 1.0 released in 2016 and mixing these two implementations within a Wi-Fi network might result in sub-optimal performance. By now, chipsets are already available from Broadcom, Qualcomm, and Quantenna. Meanwhile, Asus shows off an 802.11ax router that can deliver 4.8 Gbps but this is not yet in commercial availability.

Dec
2017

Marvell announces its SoC portfolio for 802.11ax.

Jan
2018

Intel announces that it will release 802.11ax chipsets some time this year. The chipsets will be for 2x2 and 4x4 home routers and gateways, supporting as many as 256 devices sharing bandwidth simultaneously.

Mar
2018

Draft 3.0 is expected to be released.

Jun
2018

Asus launches two 802.11ax routers, one of them capable of aggregate peak throughput of 11 Gbps to cater to high-bandwidth multiplayer gaming.

2019

IEEE 802.11ax is expected to be released. Certification of devices compliant to the standard is also likely to happen following the release.

Discussion

  • Why do we need 802.11ax?
    802.11ax overview. Source: Qualcomm 2017.

    IEEE 802.11ac increased raw data rates but left some problems unsolved. Uplink access is mainly based on contention. When there are many devices in a dense network, or multiple access points closely deployed, there can be collisions, backoffs and therefore reduced effective throughput. User experience is affected for all devices.

    The common use cases where this happens is at crowded public hotspots (airports) or event venues (football stadiums). It could also happen in apartment complexes, schools and educational campuses. Also, it's expected that by 2022 number as many as 50 Wi-Fi devices may be present in a smart home. This growth is mainly due to appliances and gadgets becoming IoT-enabled. IEEE 802.11ax aims to solves these problems from the perspective of overall network capacity utilization, efficiency, performance, user experience and reduced latency.

  • What are the main PHY changes 802.11ax brings compared to earlier 802.11 amendments?
    image
    Key parameters of 802.11ax compared against 802.11ac. Source: National Instruments 2017, table 1.

    802.11ax supports both 2.4 GHz and 5GHz bands. Therefore it's backward compatible with both 802.11n and 802.11ac, meaning that legacy clients can also connect to an 802.11ax AP, and vice versa. 802.11ax uses 4x larger FFT by increasing the number of subcarriers but also narrowing the subcarrier spacing, thus preserving channel bandwidth. OFDM symbol duration and cyclic prefix are increased for better performance in outdoor environments. For higher data rate for indoor environments, 1024-QAM and shorter cyclic prefix are introduced.

    While in 802.11ac Wave 2 only 4 simultaneous MU-MIMO streams were possible, this is increased to 8. MU-MIMO in the uplink is introduced while in 802.11ac Wave 2 this was possible only in the downlink. AP will send trigger frames to coordinate uplink MU-MIMO.

    OFDMA is introduced for the first time in Wi-Fi, similar to how it's done in 4G cellular. With OFDMA, multiple users can be transmitting at the same time, each using its allocated set of OFDM subcarriers. Subcarriers are grouped in Resource Units (RU), which are allocated.

  • What are the main MAC changes 802.11ax brings compared to earlier 802.11 amendments?

    Since 802.11ax is meant to solve the use case of high density networks, uplink access is scheduled and not based on contention. A new feature named Target Wake Time (TWT) is used to let stations sleep, save power and wake up at scheduled times. AP can thus do scheduling a way that minimizes contention among stations. This can also be seen as a load balancing technique to ease congestion.

    In dense networks, a neighbouring AP can cause cochannel interference. Stations on the overlapping areas will backoff excessively. This is alleviated in 802.11ax by a feature called BSS Color. This helps stations to identify if transmission is from another network and thereby take the right action.

  • For multiplexing users on the uplink path, we have both MU-MIMO and OFDMA. How are they different?
    image
    OFDMA and MU-MIMO complement each other. Source: Qualcomm 2016, slide 18.

    MU-MIMO increases overall capacity since multiple streams are transmitted at the same time. This is ideal for bandwidth-demanding applications. Transmission to each user is targeted via beamforming. OFDMA does not increase capacity but uses it more efficiently by allocating subcarriers to users based on their needs. With OFDM, a user would occupy all subcarriers for a given time even if that user doesn't have much to send. With OFDMA, multiple users can be multiplexed at the same time, each using different sets of subcarriers. This implies that OFDMA is suited for low-bandwidth applications. Users will also experience less latency with OFDMA. With OFDMA, multiple users with varying bandwidth needs can be scheduled at the same time.

    Thus, MU-MIMO and OFDMA complement each other. In typical deployments, performance of MU-MIMO in 802.11ac Wave2 was found to depend on distance between AP and clients, channel selection, antenna performance, presence and capability of other clients, etc. Some have noted that MU-MIMO may even result in lower throughput.

  • What are possible implementation challenges for 802.11ax?

    OFDM subcarrier spacing narrower at 78.125 kHz, which implies that oscillators must have better phase noise performance and RF frontends must have better linearity. Since 1024-QAM is possible, EVM requirements are tighter. Good performance requires tight frequency synchronization and clock offset correction. Stations must also maintain frame timing based on their clocks since their transmissions must be in coordinated precisely as noted in trigger frames.

References

  1. Artusi, Dan. 2017. "The Path to the Fastest Wi-Fi Speed: Three Things to Know about 802.11ax." IT Peer Network, November 30. Accessed 2018-03-08.
  2. Bellalta, Boris, Luciano Bononi, Raffaele Bruno, and Andreas Kassler. 2016. "Next generation IEEE 802.11 Wireless Local Area Networks: Current status, future directions and open challenges." Computer Communications, Elsevier, vol. 75, pp. 1-25, February 1. Accessed 2018-03-08.
  3. Business Wire. 2018. "ASUS Announces a Complete Lineup of 802.11ax Routers." Business Wire, June 04. Accessed 2018-06-06.
  4. Christiano, Marie. 2018. "A Look at IEEE 802.11ax-2019, the New Wi-Fi Standard for HEW (High-Efficiency Wi-Fi)." All About Circuits, January 30. Accessed 2018-03-08.
  5. Cunningham, Andrew. 2017. "Qualcomm’s new 802.11ax Wi-Fi chips will reduce congestion on next-gen networks." February 14. Accessed 2018-03-08.
  6. Higgins, Tim. 2017. "Why You Don't Need MU-MIMO." SmallNetBuilder, October 18. Accessed 2018-06-23.
  7. Kastrenakes, Jacob. 2018. "Here comes faster 802.11ax Wi-Fi." The Verge, January 6. Accessed 2018-03-08.
  8. Keysight Technologies. 2017. "OFDMA Introduction and Overview for Aerospace and Defense Applications." Application Note, December 01. Accessed 2018-06-22.
  9. Lilly, Paul. 2017. "Asus shows off ultra-fast 802.11ax router with a 4,804Mbps transfer speed." PC Gamer, September 4. Accessed 2018-03-08.
  10. Manz, Barry. 2018. "IEEE 802.11ax Will Save Wi-Fi from Itself." Mouser Electronics. Accessed 2018-03-08.
  11. Market Wired. 2016. "Quantenna Announces World's First 802.11ax Wi-Fi Solution." October 17. Accessed 2018-03-08.
  12. National Instruments. 2017. "Introduction to 802.11ax High-Efficiency Wireless." National Instruments White Papers, July 24. Accessed 2018-03-08.
  13. Qualcomm. 2016. "802.11ax: Transforming Wi-Fi to bring unprecedented capacity & efficiency." Accessed 2018-03-08.
  14. Qualcomm. 2017. "802.11ax bringing unprecedented capacity and efficiency to Wi-Fi." Qualcomm (on YouTube), January 18. Accessed 2018-03-08.
  15. Ross, Nick. 2016. "​WiFi review: Does MU-MIMO currently make a difference?" PC World, August 25. Accessed 2018-06-22.
  16. Tal, Doron. 2018. "Intel Announces 802.11ax Chipsets for Faster Wi-Fi." IT Peer Network, January 4. Accessed 2018-03-08.
  17. Urquidi, Julio. 2017a. "Broadcom Takes The 4x4 Road For 802.11ax." SNB Forums, August 17. Accessed 2018-03-08.
  18. Urquidi, Julio. 2017b. "Marvell Announces 802.11ax Device Family." SNB Forums, December 12. Accessed 2018-03-08.

Milestones

2014

Within the IEEE, High Efficiency WLANs (HEW) Task Group is formed to start the development of 802.11ax standard.

Oct
2016

Quantenna announces world's first 802.11ax chipset for APs. Named QSR10G-AX, it supports 8 streams at 5 GHz and 4 streams at 2.4 GHz.

Feb
2017

Qualcomm announces chips IPQ8074 (for routers/APs) and QCA6290 (for clients). It's expected that router devices will come out first (end 2017) followed by client devices (2018).

Aug
2017

Broadcom announces three chips as part of its 802.11ax family without support for MU-MIMO in the uplink.

Sep
2017

Draft 2.0 of 802.11ax is released. This may be incompatible with Draft 1.0 released in 2016 and mixing these two implementations within a Wi-Fi network might result in sub-optimal performance. By now, chipsets are already available from Broadcom, Qualcomm, and Quantenna. Meanwhile, Asus shows off an 802.11ax router that can deliver 4.8 Gbps but this is not yet in commercial availability.

Dec
2017

Marvell announces its SoC portfolio for 802.11ax.

Jan
2018

Intel announces that it will release 802.11ax chipsets some time this year. The chipsets will be for 2x2 and 4x4 home routers and gateways, supporting as many as 256 devices sharing bandwidth simultaneously.

Mar
2018

Draft 3.0 is expected to be released.

Jun
2018

Asus launches two 802.11ax routers, one of them capable of aggregate peak throughput of 11 Gbps to cater to high-bandwidth multiplayer gaming.

2019

IEEE 802.11ax is expected to be released. Certification of devices compliant to the standard is also likely to happen following the release.

Tags

See Also

Further Reading

  1. Bellalta, Boris, Luciano Bononi, Raffaele Bruno, and Andreas Kassler. 2016. "Next generation IEEE 802.11 Wireless Local Area Networks: Current status, future directions and open challenges." Computer Communications, Elsevier, vol. 75, pp. 1-25, February 1. Accessed 2018-03-08.
  2. Zemede, Martha. 2017. "IEEE 802.11ax: Physical Layer Overview." Keysight Technologies, via YouTube, October 2. Accessed 2018-03-08.
  3. National Instruments. 2017. "Introduction to 802.11ax High-Efficiency Wireless." National Instruments White Papers, July 24. Accessed 2018-03-08.
  4. Qualcomm. 2016. "802.11ax: Transforming Wi-Fi to bring unprecedented capacity & efficiency." Accessed 2018-03-08.

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Last update: 2018-09-10 05:02:29 by arvindpdmn
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Devopedia. 2018. "IEEE 802.11ax." Version 7, September 10. Accessed 2018-10-18. https://devopedia.org/ieee-802-11ax
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