Share and enjoy: how to make the most of your 5G spectrum

23 November 2018 | Alan Burkitt-Gray

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Alan Burkitt-Gray

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As spectrum demands increase, some regulators are looking for ways to share it out. Some newcomers to the mobile industry, including wholesalers, look likely to win access to spectrum too

We’re seeing the beginnings of a radical change in the way the industry and regulators think of spectrum. All across the globe, operators wanting to improve their mobile data coverage have their eyes on bits of spectrum that are now used by other agencies. And regulators are starting to mutter “use it or lose it” to telcos about the spectrum they license.

It used to be the case that, once you’d got your hands on a chunk of spectrum, it was yours for the life of your licence – 20 years or more. Many operators that were granted free licences for 900MHz after a beauty contest in the 1980s are still sitting on that spectrum, having refarmed it to 2G, 3G and now 4G.

But demand for mobile data, and especially mobile video, continues to grow at a ridiculous rate. The supply of spectrum hasn’t increased – though engineers are finding ways to get commercial use out of frequencies that once were just used for lab tricks.

Back in my university days in Leeds I played with microwaves going through copper waveguides into prisms made of, what was it, polyethylene? Today, that would cause serious interference to most students’ mobile phones. And in the hills south of Bologna the curators of the Marconi museum demonstrate 100-year-old spark transmitters that would look really interesting on a spectrum analyser.

We’ve seen the mobile industry move up and down the spectrum from its original 900MHz or so like a hungry grizzly bear preparing for hibernation. It’s kicked the TV channels out of the top of the UHF bands and is looking further down, to 600MHz and lower. It long ago moved up to 1,800MHz, 1,900MHz and beyond.  Now the grizzly can sniff available spectrum at 3,500MHz and way beyond, up to the millimetre wave area of 26GHz or 28GHz.

In the US, the Navy uses a good chunk of the 3,500MHz band (that’s 3.5GHz, if you prefer) for radar to spot incoming missiles. Quite reasonably, the US Navy doesn’t see why it should give up spectrum that works extremely well at it what it wants it to do. If you remember any engineering or physics, the wavelength of 3,500MHz is about 8.5cm: missiles reflect those waves very well. But the industry’s lobbyists point out that the Navy operates off the coasts of the US and further out to sea, not inland. There’s a lot of the US that’s a long way from the sea.

And these days we have instantly accessible databases. The Navy knows where its ships are, even when they move, and it could populate a database to show, at any time, what frequencies are available for commercial users and what aren’t. Mobile phone masts don’t move and they could use only permitted frequencies – and shift to new frequencies when the USS Ronald Reagan appears on the horizon.

The industry has set up a lobbying and negotiating group called the Citizens Broadband Radio Service (CBRS) Alliance. Unfortunate name, I know: it brings to mind large hairy truckers moving slowly along the freeway saying “ten-four” to one another. The group has picked up 105 members, including all the US mobile operators, plus vendors such as Cisco, Ericsson and Nokia, and tower and infrastructure companies. Everyone seems to be in favour of the idea and the CBRS Alliance expects next year’s mobile phone generation will have chips that work with this shared spectrum.

Millimetre ranges

Now let’s come to those millimetre wave bands – literally, as the wavelength of 26/28GHz radio waves is about 11mm. They’re ideal for shared spectrum, because they don’t travel very far. Tony Lavender, Plum Consulting partner and CEO, puts the range at 100m or so, 200-300m in exceptional circumstances. That means you could have a small cell transmitting on a particular frequency in the 26 or 28GHz band, with another along the road on exactly the same frequency, and they would not interfere.

Just as with the 3,500MHz band, a database would help the industry to keep interference at bay, by identifying who’s using what and where. There are already licensed users of millimetre wave spectrum for fixed links, and they’d be on the database too.

The traditional role of the regulator was to license spectrum and then collect the fees – while the licence owners would use their spectrum or leave it empty. That’s not acceptable any more, regulators are starting to say. The days of buying spectrum and sitting on it are over. At Capacity Media’s Metro Connect conference in Amsterdam in September, the European Commission’s Kamila Kloc said shared spectrum is in the EU’s plans.

At another event in Munich the week before, Matthias Kurth, the former head of the German regulator, said Germany wants to reserve 100MHz of spectrum in the 3,500MHz band to share among industrial companies. Other regulators have told operators they will lose licensed spectrum if they don’t use it. Some are thinking of not charging for millimetre wave spectrum – allowing it to be shared by all – until the bands start to fill up.

Wholesale spectrum

Kloc – deputy head of cabinet for EU vice-president Andrus Ansip, who runs the digital single market programme – hinted that she and her colleagues are even thinking of making provisions for wholesale carriers: licensing spectrum that could be offered to a wide variety of users.

Spectrum licensing has been much of what regulators have done for a living for decades – but they’re recognising that allowing more use of spectrum, by more users, will benefit the industry and all of us.