Fixing Wi-Fi problems

Posted on 27 May 2011 at 15:12

We reveal how to find what's interfering with your Wi-Fi and then what to do about it

Before you can even think about fixing a problem with Wi-Fi congestion or interference, you need to know what’s causing your network to misbehave.

Fortunately, there are a number of free applications that will help uncover the root of your problem, and more sophisticated RF devices for keen interference hunters.

Free diagnostics

A brilliant free tool for discovering precisely how many other Wi-Fi networks you’re competing with in your home or office is inSSIDer 2.

This lists every access point within range of your PC and is far smarter than the list provided by Windows’ Wireless Network Connection Manager for a number of reasons.

First, it lists a barrage of useful information about each access point within range, including channel number, the strength of the signal, and the make of the router itself.

Better still, if you leave inSSIDer running for a few hours, it will remember all of the access points that have been switched on/off during that period, not merely list the ones currently running as Windows does. So if your neighbours only switch on their (potentially interfering) routers during the evening, you’ll know about it.

The list of available networks can be sorted by channel number, so you can easily see how many neighbouring networks are sharing your channel. The amplitude and channel number of each access point are also plotted on a graph, allowing you to see who your noisiest neighbours are – in Wi-Fi terms, at least.

Using the graph shown below, for instance, it would make perfect sense to assign your router to channel 11, where none of the neighbouring access points would overlap, while channel 6 should clearly be avoided.

For those using dual-band routers, there are separate graphs for both the 2.4GHz and 5GHz bands, allowing you to find a suitable gap.
Another exceptionally useful free tool for large homes or offices is ekahau HeatMapper.

With HeatMapper, you can either upload a plan of your home/office/site, or effectively create one from scratch using the software. You can then wander around your office with your laptop, left-clicking the mouse as you walk from room to room or desk to desk.

The end result is a Wi-Fi heatmap of your premises, allowing you to see which parts suffer most from Wi-Fi congestion and make an informed decision about where to locate your router or clients.

If, for example, the desks next to the windows in your office are drenched in red, you might want to move the hot-desks for your laptop-toting staff into a more central position.

If, however, the heatmap reveals your neighbour has their router next to a party wall, it might make sense for you to avoid plugging in your router there, or at least make sure you’re using non-overlapping channels.

However, both inSSIDer and HeatMapper have one unavoidable weakness: they rely on your PC’s wireless card and are thus incapable of detecting any non-Wi-Fi interference. Other Wi-Fi traffic may actually be the least of your problems.

To detect and eliminate other sources of RF interference, you’ll need a dedicated piece of kit. MetaGeek’s Wi-Spy spectrum analysers, along with the company’s Chanalyzer software, come recommended by our Real World Computing experts Paul Ockenden and Jon Honeyball. In fact, Jon recently wrote that “trying to debug Wi-Fi without them is just voodoo”.

Trying to debug Wi-Fi without a spectrum analyser is just voodoo

These USB dongles not only detect neighbouring Wi-Fi networks, they also map and measure other RF interference, allowing you to make an informed decision on the placement of your router and which channel to use.

The Wi-Spy devices come at a variety of prices, ranging from $99 for the 2.4GHz-only Wi-Spy 2.4i, which comes with the Lite version of the Chanalyzer software, right up to the $999 Wi-Spy DBx Pro, which scans both the 2.4GHz and 5GHz bands and comes with advanced software features such as device tracking and detailed reporting.

The latter will clearly only appeal to IT professionals who regularly install wireless access points, while the $99 Wi-Spy 2.4i should suffice for detecting domestic interference from a leaky microwave oven, for example.

Router placement

Although software such as HeatMapper and Chanalyzer will help you find the least interference-prone areas to park your router, there are some more general dos and don’ts to maximise performance.

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