The truth about broadband

Posted on 20 Oct 2008 at 10:39

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Gallery

How fast is it really? What are the best deals? We answer your Internet access questions based on one of the biggest ever surveys of UK users.

If you're reading this magazine, you almost certainly have broadband Internet in your home. Like electricity and gas, it's a service that most of us have come to take for granted. But, as with other utilities, it doesn't pay to get complacent and forget to shop around. Even if you're happy with your provider, you should be aware how they compare with their rivals. By taking a fresh look at the deals available, you could save money, improve your connection speed, get better service and support, or all of the above.

What makes choosing broadband tricky is assessing the two key factors: what speed you're going to get and which deal will work out the best value. In this article we'll try to help you on both of those counts. Based on data supplied to us by users, we've picked out 15 of the top ISPs in the UK and rated their performance and value. We can also reveal what speeds their customers are actually getting, as opposed to what's advertised.

'Up to' no good

There's been a lot of publicity about the difference between the nominal speed of today's broadband connections - 2, 8, 16, 20 or 24 megabits per second (Mbit/sec) - and the speed that users actually get. You'll have noticed that every Internet service provider (ISP) is now careful to describe the speed available as 'up to' whatever it may be. The main reason for the uncertainty is not any kind of skulduggery by the ISPs, but the nature of the technology that delivers high-speed Internet to most homes in the UK via the telephone network.

Pushing a given medium, such as an old bit of copper wire, to carry more data is a complex technical challenge. This whole area of technology pretty much originated in a 1948 scientific paper by the American mathematician Claude Shannon, 'A Mathematical Theory of Communication'. Armed with Shannon's theory, engineers set about figuring out how to transmit digital data over the existing telephone lines. It was only in 1988, though, that they came up with an effective way to use higher frequency bands, above the 'baseband' already used for analogue voice calls, to transmit more data at once. This kicked off the steady increase in bandwidth that's brought us to the relatively huge speeds available today.

Referred to as DSL, which rather meaninglessly stands for 'digital subscriber line', this technology is effective but stupendously complex. One reason why we didn't all have broadband in the mid 1990s, when the Internet first became popular, was that the processing power required to get the data in and out wasn't available then.

What's stopping you?

The limitations of the system are partly imposed by Shannon's maths, and partly by the more mundane physical properties of the infrastructure. The quality of the wiring affects how high the frequencies can be pushed without transmission failing, and the further you get from the originating point, the weaker the signal. This is known as 'line attenuation'. In practical terms, a subscriber more than 2km from the telephone exchange will see a significant reduction in bandwidth compared to the theoretical maximum. But someone who lives right next door might never hit that maximum either. They'll just have a better chance.

All this means that setting up a broadband connection between a given exchange and a given subscriber is largely a matter of 'suck it and see'. The provider's equipment - normally still owned and maintained by BT's wholesale division, but sometimes installed in the exchange by an ISP - creates and tests communication channels over the connection at higher and higher frequencies until they stop working. Then the usable channels are grouped into 'virtual circuits', one for downstream (from the exchange to the user) and one for upstream (from the user to the exchange).