The simplest use is to connect your broadband box of tricks hanging off your phone jack, which is often somewhere useful like the downstairs hall, to your PC, which is likely to be anywhere but the hallway.

The widespread adoption of wireless modems has reduced the impact somewhat, but for networking your house it's a neat and simple solution. You've no problems with thick walls either: it'll run up to 300 metres and in theory you can add 254 devices (although more than 10 starts to slow things down).

Plus it all happens outside your PC (let's just say that the lack of Windows drivers is no bad thing). It's about as simple as networking gets. The technology goes under a lot of names, but we'll go with HomePlug.

Actually the basic idea is an old one: the power companies have been sending control signals over the mains since the 1920s - that's how electricity meters know to switch to the off-peak rate. And it's about much more than just networking computers and their peripherals: sending data over the power lines can be used to monitor and control everything connected to the mains.

Enter the internet fridge, and, we trust, more useful appliances.

The same, only faster

So why are we here again? New faster standards, that's why! The original HomePlug 1.0 standard accelerated out of the blocks at a somewhat pedestrian 14Mb/s, peaking at 85Mb/s a few releases down the line.

This was followed in 2005 by HomePlug AV, which could manage a peak rate of 200Mb/s and traded on the ability to cope with video and voice, hence 'AV'. The Technical Working Group of the HomePlug Alliance (both are just what they sound like they are) has now rustled up the HomePlug AV2 standard, which it claims "is expected to deliver a five times increase in performance". Big talk, as that'll be 600 Mb/s.

AV2 is fully interoperable with the older HomePlug AV standards and two other new formats: Green PHY and IEEE P1901. The Institute of Electrical and Electronics Engineers is the world's largest professional association dedicated to advancing technological innovation and excellence for the benefit of humanity (that's what it humbly says about itself anyway). These are the people behind the 802.3 Ethernet and 802.11 Wireless standards and they've outlined the P1901 standard, which offers 500Mb/s.

P1901 is based on HomePlug AV and is in the final stage of certification. There's also Green PHY, or HomePlug GP, which isn't aimed at PCs as such - it's a sort of green thing for the remote control of devices and part of the Smart Grid idea. It's basically a trimmed-down, low-bandwidth and low-power version of HomePlug, enabling you to monitor and turn things on and off remotely and whatnot.

Eventually you'll be able to sit on the sofa and control all the electrical devices in the house. But is the emergence of two new higher-speed standards a problem?

Not at all: they will work with each other and P1901 is really just another layer of standardisation and ratification for HomePlug, a base standard to work from. If things go to plan, just about all the versions should talk to each other and you'll be able to mix and match, buying on price and performance rather than being tied to any one standard (backward compatibility for version 1.0 aside - that's technically possible, but economically unfeasible).

This is important for the whole industry, so we're sure they won't muck it all up by splitting the market. We don't want any more incompatibilities such as that between the 200Mb/s NetGear and Devolo kit. Right, guys?

Real-world speeds

HomePlug AV2's top speed of 600Mb/s is a theoretical maximum of course. Add encryption, fluctuations in the mains, interference, distance, various overheads and so forth and well, we shall see.

The 200Mb/s AV version returns about 190Mb/s under ideal conditions in a simple speed test across about 10 feet. In the real world this'll mean it'll be more like 150Mb/s or so, dropping to under 100Mb/s if you really push the parameters. We won't get 600Mb/s, sigh.

We should easily see over 400Mb/s or so though, which is fast enough for lots of HD video, which is what everybody seems to insist on pushing across links now. It's no Gigabit LAN, sure, but it has to do much more work in a hostile environment.

Sounds great, but there's a good reason why everybody doesn't use HomePlug: it's not cheap. A basic two plug starter system goes for around £50 for version 1.0 and £80-odd for HomePlug AV. Adding another device adds another £25 or more.

When you start to explore what's going on inside a HomePlug unit, it becomes clear why they cost what they do: there's some serious electrical trickery involved. A lot of the current kit is beautifully built: Devolo in particular knows how to produce good looking, family friendly kit.

We recently tested its dLAN 200 AVSmart+ Starter Kit and were most impressed - it was built like a tank. The other big player is Netgear: its kit isn't quite as accomplished, but it's cheaper. Then there are Belkin, Cisco, Sharp and a few other big names: not a lengthy list yet, but growing.

MULTI-ROOM AUDIO: The Collage system from Russound features natty remote controls with which you can access all areas

HomePlug isn't the only network you'll need. Wireless is still, well, wireless, and if you want the fastest possible connection then using a Ethernet cable is still the way to go, and always will be; you can't beat a direct wired connection. But the idea has grown from a curious approach to a solid standard for houses that aren't fully-cabled expensive new builds.

There's also the technology to go the whole hog and use the mains to deliver your broadband too, no phone socket required. With Broadband over Power Lines (BPL), your modem can be plugged into any socket in the house. This one does require a spot of infrastructure investment in mains wiring, though - repeaters and filters and whatnot. It's currently one of those 'It's technically possible, should we give it a proper go commercially?' ideas that are currently floating around.

You'll be seeing a lot more of HomePlug and similar technologies in the future. Electrical devices are going to start talking to each other through the power lines - a network of wires that makes the internet look meagre in comparison.

Computers started life in isolation. Networking and then the internet brought a whole new dimension. Now every electrical device you plug into the wall can join in. Hyperbole? Yes, but you get the picture.

Meanwhile, HomePlug is a very workable and neat system. At the moment it's expensive, but it will soon get fast enough to be very interesting. What we need now is volume to lower the cost of the kit.

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First published in PC Format Issue 249

Liked this? Then check out How to choose the best home networking option

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