Opinion: A geographic split is the worst sharing option for upper 6 GHz

Despite recent international decisions, the fate of the upper 6 GHz band is still far from settled in many countries. Some regulators, and the European standardisation body CEPTCEPT stands for the European Conference of…, are considering a sharing approach that would allow both Wi-Fi and mobile to use the band.

Segregating a band geographically is inherently inefficient

Although both industries are sceptical, sharing could work in the 6 GHz band. However, deciding which form of sharing to adopt is critical. Various options have been proposed, including everything from an indoor-outdoor split to band segregation (which isn’t really sharing).

The worst option of them all, however, is a geographical split. This allows both Wi-Fi and mobile to use the band simultaneously but only in certain locations. Theoretically, this approach enables both industries to benefit from 6 GHz spectrum, depending on where they need it most. In reality, there are several flaws in the plan.

Risk of inefficient spectrum use

Most regulators strive to enable an efficient use of spectrum resources. Yet geographically segregating the band is inherently inefficient. By adopting geographical sharing, a regulator arbitrarily decides to exclude the Wi-Fi or the mobile industry from particular areas.

Instead of allowing these technologies to develop and deploy according to market needs, a regulator would need to decide that, for example, the mobile industry is better at providing coverage in stadiums, while excluding the Wi-Fi industry.

By adopting geographical sharing, a regulator is picking a winner

In reality, determining which technology would provide the most benefit in a particular area is difficult, and often depends on the specific situation.

For example, both industries could claim they are the best choice for providing connectivity in stadiums. Many arenas have robust Wi-Fi connectivity, while others benefit from good mobile coverage and lack sufficient Wi-Fi capacity. The best technology for each geography depends entirely on the local situation.

By adopting geographical sharing, a regulator is picking a winner. This is a notoriously difficult thing to do, particularly as both industries tend to want access to the same areas.

Lack of flexibility

There is no room for flexibility with geographic sharing. If for instance, the mobile industry gets access to the 6 GHz band in all urban areas, this would indefinitely lock Wi-Fi out of the band in major cities.

What happens if, for example, a mobile network operator (MNO) decides not to use the 6 GHz band in Birmingham because existing infrastructure and spectrum are deemed sufficient?

The Wi-Fi industry would still be shut out of Birmingham and the spectrum would remain unused until an MNO decides to deploy. If they never do, the spectrum simply lies fallow. It would be a real waste of valuable mid-band spectrum.

Simpler approaches also exist, like an indoor/outdoor spectrum split

Prolongs 6 GHz debate

Deciding where to draw the geographical borders of sharing is difficult, and would likely set off a new round of lobbying from both the Wi-Fi and mobile industries.

Although both industries want access to the band, their real need for 6 GHz is uncertain, and picking a geographical “winner” based on real-world evidence available today is nigh on impossible.

The mobile industry and the Wi-Fi industry would indeed both benefit from the increased capacity of 6 GHz. But growth in mobile data traffic consumption is slowing, and the mobile industry has already begun reducing spending on infrastructure. This raises the question of how urgently they need the band.

Meanwhile, there is little evidence that the Wi-Fi industry is facing an immediate capacity crunch. Spectrum available for Wi-Fi recently doubled when the lower part of the 6 GHz band was made available for unlicensed use in most jurisdictions.

Regulators who opt for geographical sharing will need to wade through a stream of forecasts and simulations from both industries explaining why they need the spectrum more urgently than anyone else in a given location. In the end, they will have to make their own predictions, and these are unlikely to be perfect.

A better alternative: flexible sharing

Despite protests from industry, sharing is probably possible in the 6 GHz band. Yet if regulators choose to embrace it, they need to adopt sharing regimes that are flexible and can react to the uncertain future spectrum needs of both Wi-Fi and mobile.

There are various ways to do this. The most complex of these are database or sensing-based systems like CBRS in the US. But simpler approaches also exist, like an indoor/outdoor spectrum split. This would take advantage of the different power levels of both technologies to restrict Wi-Fi to indoor use and mobile to outdoor use in areas where they are both present.

No solution will be perfect, and all will involve some level of compromise from both mobile and Wi-Fi. Yet a geographical sharing approach is by far the most divisive and least efficient method of sharing the upper 6 GHz band•