What Is Next After 802.11ax?

Though 802.11ax (now also known as Wi-Fi 6) is only just beginning to hit the market, the IEEE 802.11 Working Group approved the formation of a new topic interest group called Extremely High Throughput (EHT) earlier this year to discuss the first steps toward developing the successor to 802.11ax. The complete task group that will work on the new standard is likely to be formed in May 2019, with an initial target completion date of two years. The primary objectives of EHT will be to increase peak throughput and improve network efficiency while better supporting higher throughput and low latency applications, including video, gaming, and Augmented Reality/Virtual Reality (AR/VR) applications.

Though there is still much being discussed behind the scenes, and everything has yet to be finalized, a rough shape is forming that highlights not only what the next generation of Wi-Fi will target but also how this will be achieved on a technical level. The main purpose of the standard will be to accomplish a significant (at least four-times) peak throughput and capacity increase over 802.11ax to better support applications (such as high-resolution video streaming, wireless AR/VR applications, and multiplayer gaming, among others) that demand high throughput and low latency. One of the major factors in the enhanced throughput for EHT will be its mandatory support for 6 GHz bands. ABI Research’s recent Executive Foresight discussed the importance of the Federal Communications Commission’s (FCC’s) recent vote to open up the 6 GHz band for Wi-Fi in more detail, and the 802.11ax working group is already determining how best to incorporate 6 GHz support into 802.11ax in anticipation of the spectrum becoming available. However, this expansion into the 6 GHz band will form much of the basis for EHT’s proposed

• Increased bandwidth:One proposed enhancement to EHT is the introduction of wider 320 MHz channels for increased peak throughput. However, while 160 MHz channels have been supported since 802.11ac, they have failed to gain much traction for a number of reasons. Instead, the 6 GHz band contains a possibility of adding seven new 160 MHz channels or three wider 320 MHz channels and one 160 MHz channel.
• MIMO enhancements:In contrast to 802.11ax, which supports a maximum of eight spatial streams, it has been proposed to extend the number of spatial streams to 16 in EHT to enhance peak throughput. Many initial 802.11ax Access Points (APs) are supporting 8x8 Multiple Input, Multiple Output (MIMO); however, the mainstream AP market to date has relied on either 2x2 or 4x4 configurations, with higher configurations reserved for high-end premium networking products. According to ABI Research forecasts, 8x8 solutions are forecast to be found in only 11% of networks and APs by 2022. Therefore, it remains to be seen whether 16 spatial streams will bring additional value and capacity to the majority of Wi-Fi end users. As a result, a key debate in the interest group is whether 16 spatial streams should be an optional, rather than mandatory, feature.
• Multi-AP transmissions:EHT is also discussing providing enhancements to multi-AP systems (mesh Wi-Fi) by enabling support for multi-AP transmissions and smart scheduling to improve efficiency and peak throughput.
• Multiband/multichannel aggregation:Full duplex over multiband has been proposed. This enables an AP to use multiple channels for both upload and download at the same time.
• Hybrid Automatic Repeat Request (HARQ): HARQ is a mechanism currently utilized in cellular and other wireless technologies thathelps improve the communication performance through detecting and correcting transmission errors.
• Increased Quadrature Amplitude Modulation (QAM):802.11ax introduced support for 1024 QAM as an optional feature, in contrast to the maximum 256 QAM supported in 802.11ac. For EHT, a further increase to support 4096 QAM is also being proposed, and this could increase throughput by about 20% over 802.11ax. However, it will be difficult to implement and requires beamforming to be used.

This list is by no means comprehensive, and it is not yet clear which of these standards will be mandatory and which will be optional. However, some current thinking among group members appears to divide features into the following segments.

While the 3rd Generation Partnership Project (3GPP) is aiming for a completion date of two years, there are some growing internal debates within the group around the slower speed of Wi-Fi standards versus 3GPP competition. Some in the industry believe that EHT should adopt a quicker phased approach, whereby a limited number of key features are supported to provide consistent improvements and speed up development cycles in a similar framework to that offered by the 3GPP for 5G. However, others believe that a quicker standard development process with a more limited feature set will not provide sufficient time to develop these major features effectively—resulting in a weakened or buggy standard that will only have time to implement more simple features instead of delivering greater leaps in performance. Further, it is argued that there would not be enough time to understand customer pain points and experiences to better inform the new standard, as the next amendment is being developed before the previous one has been rolled out or corrected sufficiently.

Ultimately, there will be strong debates around how best to use this additional bandwidth in the most effective manner. As EHT will likely form the basis of 6 GHz Wi-Fi for the next decade, it is critical that this is done well. This may eventually slow down the proposed two-year time line but may result in a better long-term outcome for the technology as well as ensuring that 6 GHz and EHT can better address some of the major challenges that Wi-Fi is currently facing. While 802.11ax will also support 6 GHz, it is EHT that will predominantly drive the shift toward 6 GHz Wi-Fi technologies and help build tri-band device adoption and installed base. However, 802.11ax’s early support may help in this eventual rollout process and speed up adoption when EHT does arrive.

However, some in the industry believe that simply adding more spectrum and bandwidth will not be enough in the long term. Wi-Fi networks will be increasingly required to accommodate different device types and heterogeneous services, each with their own quality of service requirements. One viewpoint is that the IEEE should focus more on better managing the spectrum resources and creating a sliced network capable of accommodating multiple services with different requirements rather than relying on the “best efforts” approach the technology is continuing to use today. While 6 GHz opens up considerable new high-performance capabilities, at some point, this band will also become congested, and Wi-Fi will eventually face the same or similar challenges that it is facing today to ensure that it can adequately support a huge range of different device types with different needs. In essence, Wi-Fi could eventually benefit by creating a similar framework to that offered by 5G technologies.