Most people have heard of broadband and many of them want it. But not everyone knows exactly what it is, what it can do for them, or how much it costs.

The commonly accepted meaning of broadband is that it's a way of providing high-speed internet access, at a speed of at least 512Mbits/sec. This is around 10 times the speed of a dial-up connection, so downloading web pages or receiving email is obviously a lot faster.

The other key thing about broadband is that it's 'always on'. This means you are permanently connected, so you don't have to dial up each time you want to use the internet. You just pay a monthly flat-rate fee, regardless of how much time you spend browsing, sending emails or doing anything else online.

For some people, always-on is the key. This means that if you want to check the news, talk to someone online, or even find out what's on TV, then the information is instantly available, so you don't have to wait while your computer dials up.

Others find that the increased speed is the most important thing, as it allows them to send and receive emails quickly, download music, watch movie trailers and look at graphics-intensive websites, without watching the clock or the pennies, as is often the case with a dial-up link.

But whether it's the speed, or the instant availability that interests you at first, once you have broadband, you'll almost certainly be hooked and start finding more ways to use the internet.

Defining broadband
To many people, broadband means ADSL (Asymmetric Digital Subscriber Line), the high-speed service that's provided over an existing telephone line, while still allowing it to be used for voice calls.

In fact, there are several other ways to deliver high-speed access. Cable television companies, for example, provide broadband using the same wires that deliver multi-channel TV to your home. Broadband can also be delivered wirelessly.

In fact, though the term is generally used to mean 'fast', technically it refers to particular methods of transmitting information, but here we'll use the common meaning of a fast connection, usually 512Kbits/sec or higher.

We say usually, because there are some alternatives. For example, an ISDN (Integrated Services Digital Network) connection can work at 128Kbits/sec and is referred to by some people as mid-band. Tiscali sells a 150Kbits/sec connection as broadband, although its competitors are at pains to say it's not really. It is, after all, only slightly faster than using dual-channel ISDN.

UK options
With some more simplification, we can say that essentially there are two main ways to get broadband: ADSL and cable modem. Cable is obviously only available in areas where you have cable TV and even there, because of the patchwork nature of the UK networks, not everyone who has cable TV can be connected, especially if you still have an old analogue service.

Since ADSL uses your existing telephone line, you might think that it would be available to everyone. However, that's not the case. First, the technology only works when the length of cable between you and the telephone exchange is less than about 6km (around 3.75 miles). Second, not all telephone exchanges have been equipped to offer the service. Lastly, your phone line has to be provided by BT, with a few exceptions.

That doesn't mean that an ADSL broadband service has to be provided by BT though. It operates a network, linking the individual ADSL lines in a telephone exchange to a central core, from which information is routed to and from other internet providers.

The upshot is that you can buy ADSL from more than 100 companies in the UK, although the final link between the exchange and your home or office is operated by BT. One of the practical benefits of this arrangement is that the range of offerings you'll find for ADSL is remarkably small, considering the number of companies in the market.

While some will package options like different numbers of email addresses or even web space, the upload and download speeds available - and the contention ratios, or traffic sharing - are set by BT.

Contention is a confusing issue; it's something people often think is exclusive to ADSL, but it's a part of all internet access. Essentially, it's a measure of the number of people who may be attempting to access a resource - like the internet, or an individual web page - at the same time.

BT offers ADSL with a contention ratio of 50:1 for home use, or 20:1 for business use. As a worst case, that means that for the 512Kbits/sec of bandwidth you think you have, there could be 49 other people trying to use it. If they're all downloading at the same time, it would take longer.

In practice though, the bandwidth is shared by many more people than that and the intermittent nature of much internet traffic means you're unlikely to notice it anyway.

Contention happens in dial-up too, where there may be more callers than modems, and in that case you can't even connect. Your ISP is unlikely to have a connection to the rest of the internet that's big enough to cope with all its users downloading at full speed simultaneously.

Remote web servers suffer too, since they don't have unlimited bandwidth. So while the ADSL contention figures are worth bearing in mind, other factors will have a far bigger effect on the speed of your internet access.

There's a small, but useful, exception to BT's control over ADSL, which is known by the catch name of LLU, or Local Loop Unbundling. Essentially, this means that some companies have put their own equipment in telephone exchanges, enabling them to transfer your ADSL connection to their network without involving BT.

That gives them more flexibility in the range of services they can offer, with some providing lines with speeds up to four times as fast as BT. But they tend to concentrate on areas with lots of business customers, so that they can recoup the cost of kitting out the exchange.

In other words, don't expect to find LLU facilities available in rural areas, or deprived inner cities. If it's not profitable for BT to equip an exchange, it's unlikely to be so for anyone else.

With the cable companies strapped for cash and not expanding their networks much at the moment, the expansion of broadband in the UK remains firmly linked to the plans of BT. Even if your service comes from another company, for most people availability is still dependent on whether or not BT has wired up your exchange.

A growing network
There are many campaigners who believe BT should be forced to provide ADSL everywhere, just as they have a universal service obligation for the telephone. That's unlikely to happen; BT is a private company, after all, and the investment in connecting up the most remote exchanges is considerable.

From a slow start, BT has been expanding availability of the service, however, and now a figure of 80 per cent of households is now claimed. Equally, there's a list of telephone exchanges that BT believes will never be viable, perhaps because they serve too few people over a large area, or they're simply too remote to connect effectively to the internet backbone.

If your exchange isn't yet enabled though, it's not necessarily all doom and gloom. First, you can check the current status at www.bt.com/broadband, which will tell you if it's available. If it's not, BT has a pre-registration scheme, in which target levels are set for an exchange.

Once the target number of people who have said they're interested in ADSL has been reached, work will be scheduled to convert the exchange.

So, all you need to do is persuade everyone else in your town or village that they need ADSL. BT actually has a dedicated area on its website to help those who want to campaign, and even offers leaflets that you can distribute.

It's also worth looking for independent sites, as well as contacting campaigners for help and advice - a Google search on the term 'broadband+4' will turn up a lot of them, and may even reveal a campaign near you.

One thing you should remember is that you don't have to commit yourself to taking ADSL from BT (or indeed anyone else) when you pre-register. It's enough to sign up and give your phone number to help your exchange reach its target, and then shop around for the best deal once the service is available.

Alternatives
But what can you do if you're in an area where BT doesn't think it will ever be viable to enable the exchange, or you're simply at the end of a long telephone cable that's never going to work?

All is not lost; a small number of companies, like Mesh Broadband, provide access via wireless networks, and there's a growing number of community networks doing the same.

Wireless access to the internet can be provided in a couple of ways. You can have a direct connection, via a two-way radio system or satellite, that links you to a service provider, although such systems can be expensive and often require that you have a clear line of sight to one of the provider's base stations.

Systems like Firstnet's WirelessDSL provide this, and some will even commit to installing a base station if there's a certain amount of interest in an area.

The alternative is a mesh network, where access is provided by a normal means, like a leased line, typically to a business location. From there it's shared around the community using a series of wireless base stations, which can pass traffic from one to the other, allowing the network to be extended using relatively cheap equipment.

Companies like Mesh do this on a commercial basis, while community groups like Consume.net help bring people together to form networks that can bring wireless access to people throughout a community.

Some, like the Kingsbridge Link, rely on a local company with an internet connection that can be shared in the evening, while others arrange for a connection themselves and form a company to collect money from those who use the service, effectively becoming a community-run internet provider.

There's obviously an investment in equipment involved but, if enough users are prepared to share the service, it can work out at only £10-£15 a month more than ADSL. If you want the benefits of broadband, but have no other options, then it's certainly worth considering, especially now that you can buy products like the Locust World Mesh Access Point designed specifically to create this sort of network.