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Cable or wireless?

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Deciding which technologies to design into the buildings of the future is far from straightforward

Wired, wireless, optical fibre, satellite, infrared - there are already quite enough ways of shifting data around the office and home. But things are becoming seriously complicated - more complicated than your M&E engineer may want to you to know about, in fact. What's more, the implications of the new technologies are becoming increasingly important as designers seek to make all new buildings - including homes planned if John Prescott's department is really serious about connecting everybody - futureproof.

Down the wire Older, slower wired networks still use coaxial cable, aka BNC, although Cat 5 cabling using RJ45 connectors has become the standard as speeds have multiplied tenfold. Until recently, Cat5 was a data-only system. Now it can supply power to the peripherals to which its data links. This technology is known as PoE (power over ethernet) and it uses two unused pairs of wires in the standard 8-wire Cat5 cable. The effect is to eliminate mains connections to every bit of kit attached to a computer - except the computer itself. The upside is that peripherals would no longer need heavy power supplies.

The downside is that although peripherals would be cheaper - leading-edge PoE company PowerDsine talks of implementation costs in terms of pence - users would still have to re-equip.

Optical fibre cables were originally installed to carry signals for cable television. Now they also carry ADSL and voice signals. Recent developments by chip giant Intel may result in terabyte-fast optical links in a shift from electronic technology to the technology of light, photonics and optical fibre may become interesting once again. Meantime, old-fashioned copper phone cables used for voice, 56bps modems, ISDN and ADSL, now also carry interactive television signals - and in a curiously electro-incestuous move they now also carry the fast-growing-in-popularity always-on Internet telephony VoIP (voice over internet protocol), thus using the analogue telephone wires to carry digital computer data that happens to contain digitised voice signals.

An unlikely carrier of precise data, spiky mains cables are being tested as broadband carriers, and there are currently a number of experiments around the world, including the UK, over PLT (power line transmission, known in the US as broadband over power line). DOM (data over mains) refers to the in-office or in-house use of mains cables as telephone extensions and computer network cabling. As in PLT, the data signal is piggybacked on the mains frequency. But there are serious worries about its interference with short-wave radio transmissions: apparently the short vertical runs of cable in lamp posts can act as aerials radiating unwanted short-wave frequencies.

Hands off Infrared, built in to most laptops and palmtops, has limited purpose and is constrained by its need for a direct visual link as for television and hi-fi controller handsets. But last year a spin-off company from Warwick University, called Optical Antenna Solutions, said that it had developed a 'concentrator', a kind of optical aerial that, by bathing a room in IR, could deliver gigabytes per second. Because of the line-of-sight limitation with IR, the information remains securely only in that room.

This development apart, IR has been eclipsed by WiFi (Wireless Fidelity) which has taken off incredibly quickly: first as the relatively slow IEEE 802.11b network standard; and now, as 802.11g, twice as fast at 22Mbits/sec - although still less than half as fast as the 802.11a standard which is gaining popularity in the US. The shorter-range Bluetooth wireless, once expected to become the standard, has been too expensive and is only slowly emerging, still at too high a price. A cheap alternative, Zigbee, appeared last year but not a lot has been heard about it since.

So too with HomeRF, which operated in much the same way as WiFi. No one is absolutely sure about the future of 3G, the mobile-phone technology, licences for which the government auctioned so spectacularly to the private sector. It possibly offers global roaming for mobile computers whose technology is already converging with mobile telephony and may be fully integrated by the time 3G is implemented properly.

There is yet another development.

UWB is ultra wideband which is much faster than Bluetooth but also short range, in fact room-scale. The theory is that with so much wireless activity, and therefore interference, about (and you should include the ubiquitous wireless mice and keyboards in the tally), there is a need for low-power 'whispering' radio connections - especially when the current trend is for wireless connection of many domestic electronic products.

Needless to say, two groups of major manufacturers are arguing about how it should be implemented.

And then there is the implementation of the IEEE 802.16 standard Wimax, which BT is currently trialling in several locations. Wimax is a wireless broadband system with a likely usable range of up to five miles but possibly as much as 30 miles.

Initially it will probably be used for implementing broadband in remote locations but there is nothing to stop it being used in urban environments as, it is suggested, a link to mobile computers.

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