Refarming 2G network brings mobile broadband services to rural Finland

Eetu Prieur: mobile broadband usage is ten times higher
than a year ago

One of the challenges for 3G operators is that in most of the world’s services are delivered on frequencies right at the top end of the mobile spectrum — yet they are the networks that are now expected to carry broadband internet at faster and faster speeds.

Yet frequencies in the 2,100 megahertz region don’t travel much beyond the horizon — so base stations have to be sited a few kilometres apart — and are terrible at getting into buildings.

Meanwhile, the old, more or less voice-only 2G services are carried on frequencies down at the bottom of the spectrum, around 800 or 900 megahertz. They bend around the horizon and are much better at getting through walls: ideal, if only we’d known in the early 1990s when the bands were being allocated, for mobile broadband.

As a result, many 3G operators are looking greedily at the 2G bands and wondering whether those frequencies can be “refarmed” — as they call it — for wireless broadband services.

Sometimes the answer is no, because the 2G operators are different, and have licences that do not allow them to use the bands for 3G. In some cases operators with both licences and frequencies on both bands can refarm.

Elisa in Finland is one of the first in Europe to refarm its 2G bands for 3G wireless broadband, but projects are likely in other parts of the world over the next few years.

“We’ve had nationwide GSM coverage since 1991, when we were the first in the world,” says Eetu Prieur, Elisa’s head of access networks.

And for some years the company has been rolling out 3G on 2,100 megahertz. By focusing on the biggest cities, Elisa achieved a population coverage of 80%, “but the area coverage is a lot smaller”.

Finland is huge: at 338,000 square kilometres it is just a shade smaller than Japan or Germany, but has only five million people, compared with Japan’s 127 million or Germany’s 82 million. Achieving rural coverage

Elisa, whose mobile business used to operate under the name Radiolinja, has several firsts in its history. It began the first commercial GSM service in the world in July 1991, carried the first commercial SMS in the world in 1993, and sold the first ringtone in 1998.

“Our mobile broadband growth has been huge,” says Prieur, a physicist who started his career in semiconductor wafer design. “We now have ten times higher usage than a year before. It is really fast exponential growth.”

At the same time, customer expectations are increasing. “All our customers now expect GSM reception wherever they are,” says Prieur, “but now they are disappointed when they can’t get mobile broadband.”

Yet more people are carrying smartphones or laptops that are designed to work with mobile broadband. A few years ago people would have been surprised — even grateful — to find a wifi hotspot. Now they want 3G wherever they go.

“We had to increase our geographical coverage of 3G,” he says. “We needed to build rural coverage, because of customer needs.”

The expensive answer was to continue building base stations operating on the 2,100 megahertz band, “but that would have been too expensive”.

Elisa already had a network of 2G base stations giving voice service on GSM throughout rural Finland, but Prieur estimates it would have needed up to four times the number of 3G stations to give the same level of coverage for broadband data.

So Elisa — with the help of its main vendor, Nokia Siemens Networks — is refarming its 900 megahertz 2G base stations to carry 3G as well as 2G. “This will give us huge cost savings, of 50-70%,” he says.

At the centre of the ree-engineered cell site Elisa is quoting a maximum speed of 14.4 megabits a second, though it is planning to move to HSPA Evolution in 2010, with speeds of 21 megabits, and then a further upgrade to 42 megs.

The company needed support from the Finnish telecoms regulator, Ficora, as the old licences from the early 1990s specified that the 900 megahertz band should be used for 2G GSM. But now the European Commission is trying to coordinate refarming across the 27 nations of the European Union, though some 2G operators are resolutely holding onto their bandwidth.

Elisa has not removed all the 2G capacity from its rural base stations, as many users rely on it — but the re-engineering has given the company the chance to make services more efficient than what was possible at the start of the last decade.

“We can use less bandwidth and optimisation tools,” says Prieur. “There are more features of 2G coverage and capacity now.”

By reusing existing sites, Elisa has been able to roll out 3G much faster than if it had had to build new sites, he notes. “And we have found that the coverage area of GSM voice is equal to the coverage for 3G data, so you have full mobile data speed in the GSM voice area.”

Actually, the data is slightly better, he adds. “When you’re at the cell edge and are just about to lose voice, you still have about one megabit of 3G data.”  GTB