Nokia and Swedish telco Telia have completed a pilot deployment using the upper 6 GHz spectrum band, hoping to add capacity and coverage for future expansion. However, some regulators such as the UK's Ofcom think this band should be available for both mobile and Wi-Fi.

According to Nokia, the trials used a Massive MIMO (massive multiple-input multiple-output) antenna and demonstrated how the tech offers operators a path for upgrading when 5G-Advanced and 6G mobile networks are ready.

Specifically, Nokia used a 128TRX Massive MIMO radio based on its AirScale Habrok platform and a test terminal from MediaTek with integrated antennas. The field tests in the upper 6 GHz spectrum showed that it can add "massive capacity" in built-up areas, while high throughput can be achieved in suburban or rural areas, Nokia says.

Given the rate at which data traffic is increasing, most operators will need to up their mid-band spectrum allocation in the second half of the decade to keep up, the company argues. The upper 6 GHz spectrum was earmarked for mobile services at the World Radio Conference (WRC) 2023 last December, Nokia also claims, meaning a potential 200 MHz of mid-band spectrum per operator.

But it isn't that simple, of course. The upper 6 GHz band (6.425-7.125 GHz) was identified at WRC-23 as "the harmonized home for the expansion of mobile capacity for 5G-Advanced and beyond" in EMEA, the Americas, and Asia Pacific. However, the FCC in the US had already reserved the entire 6GHz band for Wi-Fi and other unlicensed operations back in 2020, so this doesn't apply in America.

The decision does not prevent national regulators from doing something different either, and Ofcom in the UK had already indicated last year that it was considering some way of sharing the upper 6 GHz band between Wi-Fi and mobile networks.

This still appears to be the case following a consultation process that Ofcom kicked off last year, which The Register reported at the time. Based on the responses to that, the regulator recently issued a new document [PDF] outlining its vision for this hotly contested part of the spectrum.

In it, Ofcom recognizes that both mobile operators and Wi-Fi kit makers want access to the band, and says that "an appropriate framework for sharing the band could open the possibility of combining the best of what mobile and Wi-Fi can offer."

Two possible solutions for sharing are explored: a variable spectrum split, and an indoor/outdoor split, supported by other mobile bands.

In the first, the upper 6 GHz band would be divided into a priority portion for Wi-Fi and a priority portion for mobile, where both systems would be free to expand into the other part of the band when the other service is not present.

For this to be possible, each would have to implement "sense and avoid" techniques for the other service, analogous to the carrier-sense, multiple access employed in early Ethernet implementations. Ofcom suggests that mobile and/or Wi-Fi could be modified to transmit a special signal that the other technology can sense easily, and stick to their own priority zone if detected.

The indoor/outdoor split method simply recognizes that Wi-Fi traffic is almost exclusively indoors, while mobile masts are located outdoors. The upper 6 GHz band is "not the most promising band for getting signals into or out of buildings," according to Ofcom, which states that this could prove to be an be an advantage in reducing the risk of the two services interfering with each other.

The comms regulator's document states that a better understanding of the trade-offs will be needed in this case, but suggests that mobile networks could rely on other, lower frequency bands to reach indoor mobile users.

An Ofcom spokesperson told us that the organization is working with industry to develop its hybrid sharing framework and the necessary coexistence solutions, and also with other European regulators. A technical report on this topic is scheduled to be published in 2025.

"The UK Government's Department for Science, Innovation and Technology (DSIT) is also funding several trials until March 2025 to explore new spectrum sharing techniques, which should provide insights for our work," the spokesperson told us.

"Next year, we'll set out further details on how we intend to make the upper 6 GHz band available in the UK, and will consult before making any decisions on future use of the band."

Until then, Wi-Fi kit will only be able to use the lower half of the 6 GHz band (5,925-6,425 MHz), which Ofcom made available for license-free use in 2020. ®

https://www.theregister.com//2024/06/05/nokia_upper_6_ghz_spectrum/