Which broadband technology will win?

Predicting which of the four major kinds of broadband service will triumph in the battle to channel colossal streams of data into your homes and offices is currently exercising some of the finest of hi-tech minds.

Successful marketing will, as usual, be vital but, in the end, technology will tell.

Yet there is unlikely to be a single victor, according to Tony Morbin, editor-in-chief of Kagan Euromedia: "It will not be a question of winners and losers. It will be horses for courses and will be different from one country to another."

Users in large urban areas will harness the ability of fibre-optic cable to both receive and send huge amounts of data. People in less densely populated areas will rely on DSL technology and in remote areas and undeveloped parts of the world, data will be downloaded from satellites.

Wireless technologies will not only enable fast data delivery to those on the move, but also allow people to roam their homes and offices without tripping over tangled cables.

BBC News Online spoke to the movers and shakers in the broadband consultancy business to uncover the advantages and disadvantages of each of the four main broadband technologies: DSL, cable, satellite and terrestrial wireless.

Digital Subscriber Line (DSL)

"Asymmetric" DSL (ADSL) is with us now in the UK and other parts of the world. This broadband technology uses new ways of cramming data down existing telephone lines.

This is its key advantage, says Mark Cook, internet strategist at UUNet, who claim to be the world's largest internet service provider. "It's pretty much available to all - the infrastructure is there."

Current data download rates range from 512 thousand bits per second (Kbps) to two million bits per second (2Mbps) - between nine and 36 times faster than today's standard telephone rate of 56 kbps.

This could be improved to 4 Mbps, but not much more and crucially, the maximum rate that data can be sent back at is likely to be 512 Kbps - a marked asymmetry.

One of the difficulties is in passing the high frequency signals down the copper cables. The further away you get from the base station, the more likely it is to get degraded. However, installing more base stations, though expensive, could reduce the length of the cable runs and ramp up the speed.

A final plus of DSL is that the data transfer rate you are promised is very likely to be delivered as the technology in effect gives you a dedicated line to the exchange.

Cable

Fibre-optic cable's top selling point is its unparalleled capacity - a whopping 10 Mbps for both downloading and sending data is likely to be quite commonplace.

Tony Morbin says: "You won't just be able to download the latest movies, you'll be able to send Granny your latest home video too."

On the downside, laying the fibre-optic cable is expensive and only those who live or work in urban areas are likely to be within striking distance of a cable node. The "last mile" is usually made over copper wires.

Some new homes and offices are being built with ducts so that fibre-optic cable can be fed in at a later date, but the dream of having cable right into many homes is unlikely to be economic, analysts believe.

Luke Ireland is operations director for Evesham.com, who advise on and supply broadband services: "The disadvantage here is that you share a cable, so if everyone in your street is on at the same time, the data transfer rate is slowed."

However, the cable companies would say having too many customers is a nice problem and argue they would just add more nodes.

Satellite

Delivering data from space promises unrivalled coverage of the planet but is a one-way system - download only. To send data back, users have to plug into a phone or cable modem.

However, with interactive television, for example, where users may only need to respond with "yes", "no" and "I'll have six", a slow upload link may not be a problem.

And in large countries, such as South Africa, people are already taking advantage of the fact that no telephone or cable infrastructure is needed.

The data download rates can be very fast, up to 35 Mbps, but more common will be 4 to 6 Mbps per channel, which would be shared between users.

Wireless

Many analysts see wireless data transfer, based on radio frequencies, being of greatest use within homes or offices. You could use your laptop at up to 11 Mbps in any room in the house, without having to have phone or cable ports in every room.

Listed buildings, schools and hospitals could be given high-speed networks without any rewiring.

However, making wireless data access available over larger areas is more difficult, says Mark Cook.

"With 'line of sight' delivery, you need a man with a van to come and fit an aerial. However, you do get a good, focused beam delivering 512 Kbps to 2Mbps."

"With a local cellular packet system, you don't need an aerial, but signal quality may be lower."

Universal Mobile Telecommunication System (UMTS), the third generation mobile phone standard, will deliver much higher data download speeds than current mobile phones (9.6 Kbps).

But Mr Cook says: "By the time you get 2 Mbps to mobiles, that speed will be rather old hat on other networks."

However, boosting cellular access in specific areas where people on the move gather - hotel lobbies, airports - may make this technology attractive.

Power lines

One intriguing option which is not currently being developed is to use electricity cables to transfer data.

This has the advantage of having a ready-made network in virtually every home in the developed world and could deliver data at 1 Mbps.

Industry rumours suggest that the technology worked well but radio frequency tests showed that lampposts were acting as powerful transmitters and drowning surrounding areas with interference.