802.11be Nears Completion of Draft Standard

The ultimate approval of the 802.11be standard might only be slated for December 2024, but that has not hindered the Wi-Fi Alliance in developing a Wi-Fi 7 certification program.

Officially announced at the 2024 CES, the program has products based on silicon from Broadcom, Intel, Mediatek, and Qualcomm receiving the Wi-Fi CERTIFIED 7 label. Broadcom, Mediatek, and Qualcomm have already gone through two generations of Wi-Fi 7 products, and it is encouraging to finally see Wi-Fi 7 leave draft status. This also allows for faster adoption on the client side. The primary characteristics of Wi-Fi CERTIFIED 7 are derived from the efforts of the IEEE 802.11be EHT (Extremely High Throughput) working group.

The inclusion of 6 GHz support in Wi-Fi 6E in select regions has opened up channels that were previously unavailable for in-home wireless use. Wi-Fi CERTIFIED 7 introduces support for 320 MHz channels, which are only available in the 6 GHz band.

These channels are responsible for the high throughput promised in Wi-Fi CERTIFIED 7. However, the lack of 6 GHz in many regions has deterred client device vendors, as many of these companies do not want to invest extra for features that are not available across all geographies. It is likely that many client devices (especially on the smartphone side) will ship without support for 320 MHz channels initially.

Multi-Link Operation (MLO) is another technique to enhance available bandwidth for a single client. Wi-Fi CERTIFIED 7 permits clients to connect to the access point through multiple bands simultaneously, increasing the reliability of connections.

Wi-Fi 7 also introduces 4K QAM, enabling up to 12 bits to be encoded per symbol and representing a 20% increase in spectral efficiency over Wi-Fi 6 (which only required support for 1024 QAM).

Dense constellations require extremely advanced circuitry at both the transmitter (linear power amplifiers) and receiver ends to avoid symbol decoding errors. These are some of the advancements present in Wi-Fi CERTIFIED 7 devices.

Some of the other key updates in Wi-Fi CERTIFIED 7 include support for 512 compressed block acknowledgements, multiple resource units to a single station/client, and triggered uplink access.

802.11n introduced the concept of block acknowledgements at the MAC layer, where the receiver can acknowledge multiple wireless ‘frames’ (MAC Protocol Data Units or MPDUs) in one response. In Wi-Fi 6, the limit for the number of MPDUs per block acknowledgement was 256. In Wi-Fi 7, this has been increased to 512, allowing for better resource usage.

Wi-Fi 6 introduced the concept of resource units in the OFDMA scheme, where the radio channel is partitioned into smaller frequency allocations called RUs. These allow small packets to be transmitted to multiple users simultaneously. In Wi-Fi 6, each user could only get one RU. Wi-Fi 7 improves efficiency by enabling the allocation of non-contiguous RUs to a single user.

Benefits of Multiple RU Allocation to a Single User (Source: Mediatek)

Wi-Fi 6 introduced the concept of triggered uplink access, allowing clients to simultaneously transmit data back to the access point in an independent manner, synchronized by the AP sending out a trigger frame containing the resource unit allocation information for each client. Wi-Fi 7 further optimizes this scheme for QoS requirements and latency-sensitive streams.

In the meantime, the 802.11 working group has already begun the groundwork for Wi-Fi 8. 802.11bn (extremely high reliability or EHR) aims to bring more resilience to high-speed Wi-Fi networks by enabling multi-link operation distributed over multiple access points, coordination between multiple access points, and power saving features on the access point side.

Timeline for 802.11bn (EHR): Wi-Fi 8 Deployments in 2027 – 2028? (Source: What Will Wi-Fi 8 Be? A Primer on IEEE 802.11bn Ultra High Reliability [PDF])

The Wi-Fi Alliance anticipates a wide range of application scenarios for Wi-Fi 7 now that certification is in place.

These include mobile gaming, video conferencing, industrial IoT, automotive, multi-user AR/VR/XR, immersive e-training modules, and other use-cases. Wi-Fi 6 brought a number of technological advancements to Wi-Fi, and Wi-Fi 7 has built on that. Unfortunately, AR/VR/XR has been attempting to break into the mainstream for quite some time, but has experienced limited success. It is one of the primary single-client use-cases that can benefit from features like MLO in Wi-Fi 7.

Advancements in spectral efficiency over the last few generations have greatly aided enterprise deployments, where it is necessary to serve a large number of clients with a single access point while maintaining acceptable QoS. User experience in MDUs (multi-dwelling units/apartments) where multiple wireless networks compete with each other has also improved. Vendors are still in search of the ideal single-client scenario to realize the benefits of Wi-Fi 7, as wireline speeds have largely remained stagnant over the last decade, and there are very few ISPs offering gigabit speeds at reasonable prices or over a wide enough area. Both wireline and wireless technologies have to evolve in tandem to benefit consumers and attract them with appealing use-cases. As it stands, the pace of progress in Wi-Fi has mostly outpaced wired networks over the last couple of decades.

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