cellular tower

Network makers promise next-generation mobile phones will download data faster than fibre.

The original goal for 5G cellular was 10 Gbps downloads. Now engineers say 20 Gbps.

Without getting deep into electromagnetic physics and radio engineering, this was an ambitious goal. Ambitious, but as the evidence so far shows, realistic.

Yet there are challenges.

Carriers can’t push wireless data through the air at 20 Gbps using the existing mobile radio spectrum.

More spectrum please

Which means carriers need to find new spectrum to deliver the promised 5G performance.

Or, to be more accurate, governments need to reorganise spectrum allocations. They get to decide who can use which parts of the spectrum.

Spectrum is an important resource. It isn’t only used by mobile phone companies. So governments must weigh up the needs of mobile phone companies against other spectrum users.

In part it does this is by putting a price on spectrum. Chunks of ratio frequencies are sold to the highest bidder. Usually, but not always, this involves an auction.

New Zealand’s Radio Spectrum Management, part of the Ministry of Business, Innovation and Employment, is already working on plans to put frequencies aside for 5G cellular.

Meanwhile, the Commerce Commission is working on regulatory aspects of the move to 5G.

Telecommunications Commissioner Dr Stephen Gale says:

“We believe the power to regulate remains an important competition safeguard, especially with 5G networks and potential new entrants on the horizon”.

Money go round

In the past government spectrum auctions work by dividing available frequencies into blocks. Bigger blocks give carriers more bandwidth to play with. In simple terms more bandwidth can mean faster data speeds.

Spectrum auctions can make a lot of money for governments. Past auctions have poured gold into the public sector. The recent UK 5G spectrum raised £1.3 billion, around NZ$2.5 billion.

It may look like a windfall. Governments often treat the money that way. But it is more about moving money from one place to another. When telcos pay a lot for spectrum the cost is passed onto customers.

Risks

If they overpay, they may spend money that would otherwise be used to build towers and extend the network’s reach. Overpaying often means a network roll-out is slower.

Given the value of cellular communications to the wider economy, squeezing out the maximum amount of cash in a spectrum auction can be counterproductive in the long term.

New Zealand’s last spectrum auction took a more sensible approach.

The government realised the economy could be better served in the long term by a good mobile network than by a windfall. So carriers were offered a fixed price well below what it might have made in a competitive auction.

Not everything sold so one remaining block of spectrum was then auctioned off.

In the past different cellular services have run in different frequency bands.

This can still happen. Yet one of the features of 5G is that carriers are able to mash together greater amounts of bandwidth from different bands. Or to use an engineer’s language: they can aggregate spectrum.

While this already happens a little with 4G, Spectrum aggregation is central to 5G. How that works in practice will be interesting. It will be a challenge for phone makers.

Higher frequency

Most people in the telecoms business expect 5G to use higher frequencies than today’s mobile phones. Depending on who you talk to, the options go all the way up to 95GHz.

This brings us to another challenge carriers face. Radio waves have different properties in different bands.

Low frequencies are useful for communicating with submarines or in mines. Shortwave radio is good for broadcasting over long distances. And so on.

Dealing with this is an engineering problem. There are also political challenges. In some cases existing spectrum users may have to give up their rights or move services to different frequencies. It can be disruptive.

Compared with some other countries, New Zealand is well placed to deal with these challenges.

UHF – ultra-high frequency

Almost all of today’s mobile telephone traffic takes place in what is known as the ultra high-frequency band or UHF. This is the spectrum from 300 MHz to 3GHz.

Some of the spectrum that will be used for 5G is in the next band up: super high frequency or SHF. That runs from 3 to 30 GHz.

UHF and SHF frequencies are microwaves. Which means the band is used by microwave ovens. It’s also used by Wi-Fi and other home wireless devices, satellite communications, radar and radio astronomy.

As you move into higher spectrum bands radio signals run into a different set of physical problems. At 5GHz and above signals get absorbed by solid objects.

The signals don’t propagate so well. So antennae cover shorter distances. In other words, you need to build more towers to give carpet coverage.

Bluetooth

Bluetooth devices operate in part of this frequency band.

The devices have low signal power levels compared with cellular phones. They are only designed to work over a short distance.

Even so, you a taste of what to expect from a 5G cell site operating at this frequency by thinking about Bluetooth’s limitations around your house. The signals may pass through wooden walls, masonry can block them. So can metal frames.

When outdoors, microwave signals don’t tend to pass through mountains or hills. In effect, they only work in line-of-sight. A cell site operating at higher microwave frequencies that works for a customer in winter might struggle in summer when there are leaves on the trees.

Rain fade

Go beyond 30GHz and radio signals are affected by water molecules. That means rain — satellite TV users will already know about rain fade. From about 60GHz oxygen molecules get in the way.

Some engineers overseas want to use frequencies as high as 95 GHz for their 5G networks. There’s a military weapon that works at this frequency.

This tells you something about the risks, although the power used for cellular phones would be many times lower than any weapon.

Payoff

To keep things simple, let’s leave it at this: higher frequency radio waves are harder to use. On the other hand, they offer much more bandwidth and that means higher potential data speeds.

As a rough rule of thumb, higher frequencies mean faster data, but over shorter distances. Typically higher frequency sites will be in densely populated areas and will be only a few dozen metres apart.

When cell sites are a few dozen metres apart, you need a lot of them. They don’t need to be big. You could put them on existing telephone or power poles.

In New Zealand

For now, talk of higher frequencies and the problems using them is largely academic. Most of the planned 5G action here in New Zealand is in or around frequency bands already used by mobile phones.

When Spark managing director Simon Moutter outlined his companies plans he called for more spectrum below 1 GHz.

He says it will be needed to provide 5G services in rural areas. This will almost certainly mean the 600 MHz band, which is already in the government’s sights. Signals in this frequency band can travel over long distances.

Moutter also identified the “two most likely spectrum bands”. Spark wants the mid-frequency C-band and high-frequency mmWave band to be ready as soon as possible so it can put its 5G network in place in time for the 2020-21 America’s Cup in Auckland.

This shouldn’t be difficult in principle.

Is there enough for 5G?

There should be enough usable spectrum in the 600 MHz band and the C-band to give New Zealand’s three big mobile carriers all they need to build viable 5G networks.

Yet they are not the only possible bidders for 5G spectrum. Wisps — wireless internet service providers — do a fine job filling in the gaps in regional broadband coverage.

Wisps could also make good use of more spectrum. And the spectrum of most use to them happens to be the spectrum the carriers are keenest to buy.

Small regional service providers lack the financial clout of the mobile carriers, but they can argue the service they offer is as deserving. Maybe more, after all, wisps service New Zealand’s exporters.

Elsewhere, Callplus founder Malcolm Dick’s Blue Reach project is likely to show interest in 5G spectrum. Blue Reach plans what it calls a 5G wholesale service. Presumably, the wisps would be among Blue Reach’s customers.

Economic logic says a competitive auction is a way of ensuring spectrum goes to the bidder who stands to gain the most. This, the argument goes, means the most economically efficient use is made of each block of spectrum.

In practice, some bidders sit on unused spectrum. The last NZ auction made that unlikely as it included a use-it-or-lose-it clause.

Some less well-heeled organisations find it hard to buy the spectrum they need. How these issues will be addressed will become clearer when the auction terms are formally announced.

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