Guy Kewney

How many neighbours do you have within 100 feet of your desk at home? How many of those have a PC? And in the next 12 months, how many will have a wireless network? And do you care?

You should care, because the figures are scary. My friend Jon lives in an apartment at the top of the Archway hill in north London. From there, he can look down on a truly vast acreage of real estate, and he can broadcast his wireless Lan to all he sees.

Being a bit of a technical experimenter, he's boosted his 802.11 signal to the legal limit; he reckons he can pick up his home network from pubs, bars and restaurants as much as a mile away, and he does. Well, that is to say, he used to.

These days, it tends to be hard to do. He showed me the output of Netstumbler around December last year. His own access point was the strongest signal, but he could also see another 30-odd access points listed. And, most of the time, despite his super-antenna, they drown out his signal due to the sheer weight of numbers.

Most of us don't live on top of a hill, but if we live in a typical urban or suburban neighbourhood we're probably within wireless range of at least a dozen buildings. In my street each house is about 20 feet wide, and most of them contain two flats with three or even five rooms each.

A Wifi access point in my upper storey window can pump out a signal into the street, reaching two houses on either side, plus about eight buildings across the road, and five on the terrace behind.

There are roughly 30 homes in range and, at the moment, only six of us have our own access points. That's twice as many as we can tolerate, because 802.11b and 802.11g have only three channels that don't overlap.

In theory, of course, there are 13 channels. If you play around in a congested area, you'll quickly find that channels 1, 6, and 13 (or channel 11 in the US) are non-interfering. Channel 3 interferes with 1 and 6, and channel 9 with 6 and 13. But this doesn't stop it working, as the software can pick up the transmitter it wants.

Does it work properly, though? Not even a bit. I was alerted to the problem when I found that I shared channel 6, the default, with three neighbours. My high-speed 802.11g network was running at an average of about 10Kbits/sec instead of 20Mbits/sec. Not only that, but it was hiccupping, stalling, dropping out, and generally pretending to be absent.

Proof came when I switched to channel 1 and everything was fine again for two days. Then two of my neighbours did the same thing, because two new channel 6 networks started up. Chaos.

It is time to trial a neighbourhood mesh. Not only will this get around the problem of spectrum congestion, but it will extend my own wireless network into areas of the town it can't reach.

The mesh concept is best illustrated at Locustworld, and you can experiment with it for nothing by downloading a bootable disk image onto a spare PC. To do it seriously, you buy a small mini-ITX PC and (this is the tricky part) go and introduce yourself to your wireless neighbours.

With a little luck, I expect to be able to sign up at least one of my more tech-savvy neighbours immediately, and create a two-node mesh. Each of us will be able to have (secure) access to our own home network, over the mesh, from either node. Then we move on and extend the network up and down the street, and across the terrace, and into the next street and so on.

The idea is that if we all have the same wireless network, congestion goes away. The Locustworld software makes sure nobody accidentally prints out Miss February on my colour printer or reads my invoices file.

And the network shares broadband around, so if any of us is using a particularly high download speed, the capacity is there. Best of all, my own network should reach the pub, the greasy spoon and the library.

Yes, frankly, I'm nervous about trying it. I expect my neighbours to be suspicious, especially the ones who haven't a clue what a wireless network is, or why anybody would want one. And there will be questions about who pays, and how much. Some kind of co-operative will have to be created.

But one thing is clear: we can't go on like this. Even if we switch to 802.11a, which has more channels - or 802.11h, which is a legal form of 11a, which I still haven't seen in the real world - it only takes a few more 'clever' innovations, such as LG Electronics and its Wifi television (three hours of battery life is clever?), and the level of interference and bandwidth use will make the whole thing a no-no.

The writing is on the wall. Two days after we got to eight local Wifi nodes, two of them were switched off. I'm betting that the buyers took them back to the supplier, saying they were broken.

This time next year, the local PC store will be fired by the network vendors for returning too many wireless devices, and sales of Homeplug mains-cable network devices will be booming. We have to do something before it gets that bad.

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