Home improvement

There's no doubt about it: Wi-Fi in the home rivals sliced bread as the best thing ever. It makes the associated hassle, cost and mess of cabling up your house a thing of the past and, if you have a notebook, you're even better off because you can even access the network outside the house if you want. Add in broadband Internet access and you're not far off networking nirvana, all thanks to good old Wi-Fi.

There's a but, though. I'm very happy with the setup I have at home, but even though my house is of the standard terraced variety I do get reception problems now and again. I've got my Wi-Fi router (a Netgear DG834G) in the first floor back room and when I try to use my notebook in the ground floor front room - which is no more than 30ft away - it works well most of the time, its signal-strength monitor reporting excellent reception.

But every now and again, reception will drop to "low". And, as all Wi-Fi fiends will know, when this happens the speed of your connection is affected too - maybe slowing to as little as 1Mbps before it gives up the ghost entirely.

Luckily, there are plenty of things you can do to optimise the performance of your Wi-Fi network - some of which won't cost you a cent.

Location, location...

The most obvious way to improve the performance of your network is to locate your router as close as possible to the area where you need the best reception. This can be tricky, as the Wi-Fi router often needs to be located close to a phone socket in order to get ADSL broadband in the first place. You can always install a phone extension socket if your main one is poorly sited.

Given a choice, you should place the Wi-Fi router higher rather than lower: on top of a cabinet or shelf is better than inside it. Try to keep it away from large metal objects, such as radiators or pipework. Aquariums and foil-backed insulation are bad news for radio waves, too. And try to keep it away from sources of interference, such as microwaves, cordless phones and other computers.

You should also site your Wi-Fi router somewhere near the centre of your house. This is because the signal radiates in a doughnut/sphere-like shape, thanks to the omni-directional antennas most routers have.

A good antenna

Antennas are pretty important to the successful operation of Wi-Fi. Did you know that most Wi-Fi cards have a power output of just 32mW, which is roughly the same amount of juice required to light a strong LED? Try spotting an LED when you're 30m away from it. The power output can't be increased because it uses the same frequencies as microwave ovens, and we all know that tanning is bad for us.

So you need a good antenna. Typically Wi-Fi offers better coverage horizontally, but it's important to make sure the antenna is vertical (perpendicular to the signal) for best reception. This advice is particularly relevant to laptop users with PC Card Wi-Fi adapters angled horizontally - it's much better to have a USB adapter with a hinged antenna or have one built into the lid of the machine.

However, the above only applies to single-floor buildings. For buildings of more than one story, you might find placing antennas at 45 degrees (diagonally) or 0 degrees (parallel to the floor) is more effective. Many retailors offer more powerful antennas for their Wi-Fi kits, but check to make sure the antenna will fit your router (see here).

Boosting signal power

The measure of an antenna is its gain, which represents how well it increases effective signal power, with decibels (dB) as the unit of measure. Or to be exact, dBi, which is the gain relative to an imaginary isotropic source. Most Wi-Fi access points/routers and NICs (network interface cards) come with a feeble 2dB antenna. Sadly, many are fixed and can't be changed for something better.

But some, such as those from Netcomm, Linksys or the more expensive Netgear models, have screw-on antennas which can be changed. Most wireless desktop network cards also have detachable antennas. So, it's easy to fit a larger antenna, one that has, say, a 5dB gain, which doubles the power and increases the throughput and range by up to 50 per cent.

Replacement antennas cost around $30 each and simply screw in to the back of your Wi-Fi router. One thing to consider though - there is no standard for antenna connectors, so make sure your new one will fit the socket of your hardware.

Some are just a straight replacement, but the better ones have a little desk stand and come with a thin extension lead. This lets you place the antenna in the perfect position to deliver the best reception/transmission. Most Wi-Fi software has a built signal-strength meter that can be used to optimise the antenna siting, too.

Neighbouring networks

If your neighbour also has Wi-Fi, both of you might end up suffer­ing unless you consider this: for 802.11b and g, there are 13 channels available for broadcast. When there is interference from wireless networks that overlap with one another, each should use one of the "non-overlapping" channels: 1, 7, 13.

That way, three networks can use the same space with mini­­mum interference. Note that SuperG technology (proprietary implementations, offering faster speeds) uses two non-configurable channels and therefore it may not be possible to pick other channels that avoid its interference.

With SSID Broadcasting (Ser­vice Set IDentifier) switched on, equipment easily finds the strongest signal. But when your SSID is broad­cast, your neighbour's Wi-Fi equipment may lock on to it and automatically try to connect several times a second - this can lead to significant performance reduction. So where there are close networks, turn off SSID Broadcast and change the default SSID.

Turning off WEP (Wired Equivalent Privacy) and WPA (Wi-Fi Protected Access) may increase network throughput, but it also exposes your network to hackers. Instead, you can limit access to your Wi-Fi network by only allowing PCs with permitted MAC (Media Access Control) addresses to connect (screen shot).

Other interference

As with all radio systems, interference is always an issue. Wi-Fi systems suffer in the same way as, say, an AM radio channel does when you hear static. However, they don't have problems to such a large degree.

Things that cause interference with Wi-Fi systems are microwave ovens, fax machines, photocopiers, certain lighting systems, other 802.11 access points or systems, and microwave transmitters. Not to mention your next door neighbour's electric lawnmower. Even high-speed computer processors can cause interference for 802.11 systems. All these factors must be isolated before you can expect any significant range out of your system.

BUILDING LINKS

Sometimes you want to link networks in two separate buildings. It would be costly to do with cable but is very cheap with wireless - providing, of course, there's a direct line of sight between the two networks in question.

The good news is that such point-to-point connections are possible, but you'll need to change your antennas. Omni-directional antennas broadcast equally in all directions, so their maximum range is limited. What you need are ones that are tightly focused, which dramatically increases their reach.

Obviously, such antennas need to be accurately pointed at each other. You can use Yagi arrays (often called Yagi-Uda antennas after their creators, Hidetsugu Yagi and Shintaro Uda), which were originally designed for radio systems but are now also used for 802.11 (you can see one here). Given a good following wind, these guys can communicate over several miles. An even more powerful, and expensive, solution is the parabolic reflector. It's a bit like the common or garden satellite dish.

If you're feeling adventurous, you might also try out an old Wi-Fi craze. The cantenna is a home-brewed tubular antenna made of old tin cans. There are several Web sites that show you how to make one (see www.oreillynet.com/pub/wlg/448) or you can buy a pre-made cantenna (and save yourself a weekend of soldering and calculations) from www.coolpc.com.au (see this screen shot).

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