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Can't Connect… Won't Connect

Bill Thompson

BBC technology correspondent Rory Cellan-Jones must be hoping that his near neighbours don't decide they want a larger family. He recently spent ages setting up a high-speed wireless network at home, documenting the whole tortuous process on the BBC Technology blog, but all his hard work could apparently be ruined by a single baby listener in the neighbourhood.

The intercoms sold to let parents listen in to every snuffle, sob and cry operate in the same frequency band as the wireless networks more and more of us are installing and can generate so much interference that they make them unusable.

The television rebroadcasters that many people use to watch satellite TV in the bedroom without having to install a second set-top box also use the same frequency, because it is one of the few areas of the radio spectrum that does not require a license, and they too can slow down wifi speeds or make it hard for a computer to make a connection to a local network.

These unwelcome findings about interference come from a detailed survey by Mass Consultants carried out on behalf of the telecoms regulator Ofcom as part of their investigation into how radio spectrum is currently used and should be allocated in future.

They found that in central London the number of overlapping networks attempting to use the same channel was a significant problem, and that in some areas nine-tenths of the available bandwidth was being used by wifi nodes advertising themselves or doing general 'housekeeping', with only one-tenth actually available for user data. Outside major metropolitan areas the real problem was interference from other devices using the same frequency ranges [also see Register's report on the survey].

As I write this in a café near Holborn I can see eighteen networks apart from the one I'm connected to, so I can vouch for the scale of the problem in London!

Wifi is far from robust in normal circumstances, as anyone who has wandered around a house with a laptop looking for a space that gets a decent signal will testify.

And back in 2006 consultants AirMagnet got some useful pre-Christmas publicity when they announced that reflections from tree baubles and tinsel could cut wireless signal strength by a quarter in well-decorated households.

But these findings reveal both the growing popularity and importance of wireless networks for home and business net use, and the urgent need to do something about it. Imagine how nice it would be if most wireless networks were suddenly five or even ten times faster and generally reliable.

There is, of course, a simple if somewhat radical solution to the problem of having to squeeze wifi, baby alarms and TV retransmitters into the same frequency range as remote controls, children's toys and many other devices. We could get rid of them — or at least the ones that cause trouble.

The problems largely arise because the devices are analogue and use a wider band of frequencies than digital versions of the same technology and their signals are much more variable than the relatively constrained digital signals expected by a wifi receiver, so if we made them all digital we could design them so as not to interfere.

Of course this won't happen, because owners won't accept that the analogue devices they've already paid for and used for years have to be sacrificed in the name of the bright shiny digital future.

I can see their point, even if part of me just wants to sweep their old technologies away in favour of an uncluttered wireless world.

Another solution would be to move wifi away from the currently unregulated 2.4 gigahertz frequency band it uses, but here we face much bigger issues than the objections of parents and sports fans.

Vast tranches of the radio spectrum from 9 kHz to 275 GHz is taken up by radio and television, both the older analogue transmissions that are currently being switched off and the newer digital services that replace them, DAB and digital terrestrial television.

If we got rid of the analogue and the digital services and replaced the whole thing with a high-bandwidth wireless network service then we would have more than enough room for laptops and baby listeners.

Yet even if Ofcom decided this was a good idea — and they won't — there is an international dimension to the issue as the International Telecommunication Union's Radiocommunication Sector has the task of ensuring that the many systems in use do not interfere with each other.

Much of the ITU's work is about balancing competing desires, but there are also real physical limits on what can be done. Some frequencies, for example, are used by remote sensing devices in satellites because they are characteristic of water or growing plants, and obviously these can't be changed by administrative fiat.

But as with so many established practices and procedures, from copyright law to the regulation of the financial markets, digital technologies both create new opportunities and challenge or undermine current practice. The ability to make perfect digital copies has lead to the crisis in the music and film industries, and the availability of digital communications channels is causing us to question the wasteful use of spectrum by analogue devices.

Unfortunately it seems unlikely that we'll see a wholesale rethink of the way spectrum is allocated, and the lack of political will means there is little chance that those pushing for deregulation of broad swathes of the spectrum will have any success. We will have to live with flakey wifi for a while yet.

By Bill Thompson, Journalist, Commentator and Technology Critic
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Share your comments

We can use short-range wireless networks or wired networks Chano Gomez  –  May 13, 2009 3:27 PM PST

There are two ways to alleviate the problem. One is to use wireless networks that operate in frequencies that keep signals in short range. One example is the recently announced WiGig initiative (which is trying to create a WiFi-like specification that operates in the 60 GHz band). 60 GHz has been chosen by it's the frequency where electromagnetic absorption by Oxygen is the highest, which means that 60GHz signals don't travel too long, and they remain contained inside a single room. (Also, 60-GHz is free from "baby monitors"...)

Another option, specially if you need a network that can operate across multiple walls, is to used a wired networking standard such as G.hn. G.hn is a standard developed by ITU, which can provide data rates up to 1 Gbit/s, and which can work over any type of home wiring (coaxial cables, power lines or phone lines). [Disclaimer: I'm involved in the development of G.hn]

I think future home networks will be based on a combination of multiple technologies: 60-GHz wireless networks for short-range and QoS-sensitive applications, G.hn wired networks for long-range and QoS-sensitive applications, and 2.4/5-GHz Wi-Fi for long-range apps that need mobility and don't have QoS requirements.

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