Bill Pechey

Over the past few weeks, I have helped five local people to install wireless systems so that they can share their broadband connections. Until a year ago, my home wireless network was the only one I knew of in my locality.

The new systems follow the trend for a huge increase in WLANs worldwide. This growth is going to cause a few problems, not least of which will be interference among wireless networks. As some readers may remember, I help to run a wireless broadband network in our rural community and we have noticed interference from other 802.11b/g networks.

The density of WLANs in rural areas is not yet high, in contrast to the situation in cities where large numbers of WLANs are within range of each other. The effect of interference between WLANs is to reduce the range, data throughput and availability - and in severe cases these wireless networks may not function at all. Add to this the possibility of simple denial-of-service attacks, and it is clear that businesses need to plan now to keep ahead of the game.

So what can be done about it? Well, a lot can be learnt from cellular mobile networks, since they increase network capacity and control interference by reducing cell size and keeping the power levels as low as necessary. Careful radio-frequency planning is also a good idea. A radio survey is one of the first things to do when installing a WLAN, just to see what other networks are nearby and on what channels.

Choose an unused channel, if available, and make sure your network has just enough range for its users by adjusting power levels and siting access points carefully.

Don't forget that 802.11a systems use the 5GHz band, rather than 2.4GHz, so choosing 802.11a reduces the likelihood of interference - and since there is also more spectrum available at 5GHz, this further reduces the chances of interference.

Standards bodies such as Ofcom are aware of the problems and are considering what can be done to improve matters. Guidelines already exist to help standards-makers minimise the interference between Bluetooth and WLANs. And UK company Supergold has developed technology that can improve WLANs' resistance to interference, though this technology would have to be built into devices.

Hopefully the current problems won't discourage people from using WLANs, since the benefits are just too great to be ignored. However, a little care taken in the design and implementation of your WLAN means your system will operate at peak performance, for a little while at least.

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