The Promise of 6 GHz

Last month, the Australian Communications and Media Authority (ACMA) opened the lower 500 MHz of the 6 GHz band for license-exempt (class license) use, opening the door for Wi‑Fi 6E in Australia. Australia is now the third country in the Asia Pacific region to open the band, with Malaysia also opening the lower 500 MHz in January of this year. South Korea, which was the first country in the region—and the third country globally—to open the 6 GHz band in October 2020, remains the only country in the region to open the full 1200 MHz.

The upper 700 MHz of the band is currently used in many countries for microwave and fixed satellite links. Numerous studies have focused on the ability of license-exempt technologies such as Wi-Fi to co-exist and interoperate with these incumbents, and regulators in countries like South Korea and the United States have proposed a directory mechanism, Automated Frequency Coordination (AFC), to avoid interference.

And while the ACMA does “recognise there is a sound case for making the upper band available for RLANs in the longer term”, they have opted for a two-phase approach, awaiting the outcome of further studies and other global developments.

A worthwhile question then is why the push for the full 1200 MHz? The lower 500 MHz provides the same bandwidth currently available in the 5 GHz band—and one could argue that it improves upon it. In the 6 GHz band, the allocated 500 MHz is completely contiguous and does not require Dynamic Frequency Selection (DFS) which forces us to limit the available channels to avoid impacting RADAR systems.

The answer lies in the ability of Wi-Fi to increase the available bandwidth through channel aggregation. Put simply, it allows devices to bond multiple 20 MHz channels into larger 40, 80 or even 160 MHz channels for greater throughput. With 500 MHz of spectrum, there are only six possible 80 MHz channels, which are simply insufficient for most typical wireless deployments. For 5 GHz today, most deployments are limited to 40 MHz channels in order to minimise co-channel interference and ensure devices experience optimal throughput, and we do not see that changing for 6 GHz where countries have only made available 500 MHz.

In contrast, the full 1200 MHz of spectrum will provide fourteen 80 MHz channels, allowing these wider channels to be used more generally, even in high density deployments. And for certain deployments, the seven available 160 MHz channels will also support a range of interesting use cases. Going forward, we expect Wi-Fi networks will be designed with the full 6 GHz band in mind. The emerging IEEE 802.11be standard—which will form the basis for Wi-Fi 7—is a case in point, being designed to support channel bandwidths of up to 320 MHz.

As customers begin to design and implement their next-generation wireless networks, Wi-Fi 6E is one of the considerations, particularly given that we are seeing many wireless refresh cycles extending to five to seven years. It is less about 6 GHz today and more about 6 GHz over the extended lifecycle. The focus is not simply on the wireless technology itself, but also on potential future applications which the network will need to support.

Augmented and virtual reality (AR and VR) are often called out as emerging technologies driving the need for Wi-Fi 6 (and 5G as well). Significant discussion is focused on their future potential, whether the full metaverse concept or a more focused starting point such as Webex Hologram.

However, those examples are predominantly focused on the enterprise.

It is interesting to note that within the industrial space we have seen aggressive early adoption of AR, together with remote and on-demand video capabilities.

From a technology perspective, these solutions require not just more bandwidth to support high-definition video, but also low latency. John Carmack, one of the founders of id Software and CTO at Oculus VR noted that:

“Human sensory systems can detect very small relative delays in parts of the visual or, especially, audio fields, but when absolute delays are below approximately 20 milliseconds, they are generally imperceptible.

If large amounts of latency are present in the VR system, users may still be able to perform tasks, but it will be by the much less rewarding means of using their head as a controller, rather than accepting that their head is naturally moving around in a stable virtual world. Perceiving latency in the response to head motion is also one of the primary causes of simulator sickness.”

Motion sickness is often caused by a “difference between actual and expected motion”. This extends to virtual environments as well, due to motion-to-photo latency, or the latency between the body’s movements and the user’s view as displayed on the headset. By keeping one-way latency to be less than 10 ms, VR or simulator sickness can be avoided. This represents an order of magnitude difference from the 100 ms latency requirement for which we design wireless networks today to maintain real-time voice and video quality.

Often, we view increased bandwidth as a requirement to move larger amounts of data—as one would expect with a move from HD video (1080p) to UHD (4K). But when we consider that wireless is a shared medium, increases in bandwidth also allow a client device to complete its transmissions more quickly, allowing other clients to gain access to the medium with shorter delays, thus reducing latency. For this reason, channel widths of 80 and 160 MHz are likely to be of critical importance to these emerging technologies.

The pilots and limited production environment deployments of these solutions today focus on specific job functions to leverage the technology. Wi-Fi 6E, with access to the full 1200 MHz of spectrum, is about designing for future scale—environments where AR and VR are as common as video conferencing is today when AR and VR headsets are as prevalent as smartphones and smartwatches.

In the same way, countries opening the 6 GHz for license-exempt use today are designing for the requirements of tomorrow. While we strongly encourage regulators to consider making the full 1200 MHz available from the start to minimise delays to innovation, we recognise that some countries may find a two-phase approach a simpler way to navigate the complexities of protecting incumbents and the requirements of systems like AFC. In that case, it will be important to ensure the work on the second phase is not forgotten once the first phase is complete.