How white space brought broadband to a remote Scottish Isle

Standing in the sun, admiring the view of the sea along the southwest coast of the Scottish Isle of Bute, it was hard to imagine I was there for a broadband trial, but this small, sparsely inhabited island is home to a cutting edge experiment in rural connectivity.

In fact, perched along the roadside, overlooking seals to the right and a herd of cows to the left, is a large aerial, grabbing signal from unused TV spectrum to deliver a sturdy, if not fast, connection 6km from the nearest exchange.

BT has been for several months running a technical trial of white space broadband on the Isle of Bute, west of Glasgow. Ten farmers have been given connections this way, with a mast at Kilchattan Bay spitting out spectrum to five farms to the northeast and five to the northwest. That signal is picked up via modified TV aerials, and to the farmers and their families appears just as any other broadband would at point of use.

BT hails the trial as a technical success, but its engineers, working alongside experts from the University of Strathclyde, continue to work out the finer details, while the telco giant’s executives ponder whether it can make sense commercially.  Here’s how it all works — and a picture of some cows.

White space

White space is the bits of the UHF spectrum — what’s used to air television channels and what will be used to provide LTE mobile networks — that isn’t being used. Data can be sent in these gaps, and there’s more and more space being freed up by the digital switchover. Such unused channels can be used to provide broadband, assuming they aren’t being used for something else. A database has been set up that can be polled for allocation rights, as public services, for example, could take over a channel in case of a natural disaster, so that database is key to allowing broadband services to keep checking they have the right to use the space.

There’s a few handy aspects to this spectrum. First, the places with the most free spectrum are the rural parts of the country, those that need different ways to deliver broadband. Sometimes things just work our rather nicely, don’t they?

And, if that weren’t enough, it’s free to use. Unlike the spectrum being auctioned off by regulator Ofcom for 4G services later this year, the TV space won’t cost billions of pounds. That fact led to the most effusive praise of Ofcom I’ve ever heard from the mouth of a BT spokesperson.

Another convenient feature of this spectrum is — at the right frequency — it doesn’t need line of sight between the transmitter and receiver, and can cut through obstacles such as trees, houses and sheep. (Even sending it over water doesn’t interfere too much, despite the tides apparently being a challenge, as the depth of water alters how the radio signal is bounced around.) Different frequencies work better in different places, as lower frequencies offer more coverage but slower speeds, while higher frequencies offer less coverage but faster speeds — which might sound vaguely familiar from school physics classes.

Wireless but not mobile

BT’s trial isn’t about mobile broadband, even though it is technically wireless and uses spectrum in a similar way. Instead, the white space is being treated as cabling, offering point-to-multi-point connections, just as you would run a cable from the exchange to a cabinet, or from the cabinet to a home. It is essentially the last mile (or three) of cable, without the cables.

It all sounds fantastic, but there are downsides. It can’t support too many users. BT suggests it’s for the “tens” of homes, not the hundreds or thousands, but points out that many exchanges in Scotland actually serve fewer than 100 lines (more on that later). Channels can also be bonded together — using two slices of 8MHz channel to double speeds — or use multiple separate channels to keep the load down.

Speeds aren’t superfast, BT admits. The connections on Bute peak at 10Mbits/sec using modified TV aerials, or 15Mbits/sec on specialised equipment brought in from the US (BT is testing both, as the former works better for longer distances, while the latter is better for short hops).

This being broadband, those are “up to” speeds. BT said speeds on the former are up to 8Mbits/sec, but that falls to 4Mbits/sec at a point 6km from the mast — however, those aren’t the speeds I saw.

At BT’s trial centre — the Kingarth Hotel pub, which is as fine a location to test broadband as anyone could find — the best speed I picked up was 6.7Mbits/sec, not too shabby for a pair of winding car rides and a ferry trip away from anywhere I’d consider urban.

Another testing area, Seal Point, is 6km down the curvy road — as someone who gets carsick, I was happy the BBC folks wanted the window open, even if the blasts of refreshing sea air were now and then overcome by a whiff of cow manure.

That far out, BT has claimed speeds of 3.5Mbits/sec; mine didn’t top 1.5Mbits/sec, but the BBC managed a Skype call, so it’s certainly better than nothing — which is exactly what the spot would get otherwise. While it’s 5km as the crow flies, along the roads where cables would have to run would be closer to 7.5km, far too long for ADSL.

Submarine backhaul

The trial isn’t only about white space access, however. There’s no point, BT notes, in setting up broadband access for end users if there’s a weak connection to the network. For this trial, BT has a microwave transmitter with a line-of-sight connection to the mainland 14km away– Law Hill, apparently — in order to provide a 100Mbits/sec backhaul connection. While that’s more than sufficient for the trial — indeed, only a quarter of capacity is even being used — Gibbs says Bute will need submarine fibre to get superfast broadband.

That microwave backhaul is picked up by a receiver perched on the roof of the local exchange, a small whitewashed shed, and run via cabling to the mast, which looks rather like those temporary basketball nets with blocks of concrete holding it in place. (It doesn’t look very stable, but we were assured it’s survived 100 mph winds.) It’s a cantilevered design, so engineers can easily lower the top down to access the transmitter, which is a modified WiMAX device.

A small aside to talk about the exchange. I’ve never been inside an exchange before (I know, I haven’t lived) but had a detailed tour from Malcolm Starke, who aside from being a BT engineer is also a PC Pro subscriber.

The Kilchattan Bay exchange serves 200 lines, which is tiny compared to the largest in the country — 60,000 at one in Manchester — but well above the smallest, another Scottish location with a whopping six. It features eight 2Mbit/sec ADSL connections for locals (normally those would be at least 8Mbit/sec but BT admits its an infill area, so it gets what it’s given), while the trial’s 100Mbit/sec box hums along feet away, used for testing, the pub and ten farms.

What’s the point?

The best connection some of the farmers could receive before the trial was satellite, and while that’s steadily improving, it apparently wasn’t good enough to access Defra’s website. Not being the sort to own cows, I’ve never tried to use Defra’s site before, but as one person put it, the site was clearly designed by a Londoner on a London network — if someone at Defra could create a version to use on slower broadband or even mobile connections, farmers of the UK would be joyful indeed. Animals, it would seem, have digital passports these days, and while some of the work can still be done on paper, that’s quickly being phased out.

Rural areas aren’t only about farming. The local pub and testing ground also found the faster connections to be a “game changer”, according to Malcolm Brew, who grew up in the area and conveniently happens to be an expert at rolling out telecoms in difficult situations. Now, it’s much easier to place orders with big breweries, making it possible to order a wider range of beer.

The social impact of this could be huge for a small community, allowing people to keep up with the world while continue to live locally, rather than move into Rothesay — the largest city on the island — or to the mainland. Brew said home owners have a harder time selling their house if it doesn’t have a decent connection.

The only farmer BT could pull from his field, Robert McAlister,  said online access let him watch his cattle sold at auction and helped his wife manage their books and look up pedigrees for breeding purposes — he kindly made it clear he meant ordering bull semen — but when asked if it had changed his life, said: “I wouldn’t say that.”

He added:  “I’m busy working during the day, and the last thing I want at night is to sit in front of the computer.”