Analyse Your WiFi Environment Objectively

When you setup a network of computers, in your home or small office, a mass of Ethernet cables running everywhere can be a problem. WiFi, or Wireless networking, can provide relief from the mass of cables. But WiFi is not an effortless replacement for Ethernet. Installing a WiFi network takes careful preparation.

There are many reasons why you won't get the expected bandwidth from any WiFi network. Some of them you can correct, others you can't. And sometimes, even without you making any changes, you'll have problems. All the planning you do is useless when your neighbours install a WiFi LAN next door.

With all of that in mind, you need to evaluate your WiFi environment objectively, both before setting up a WiFi LAN, and after. When "it stops working", find out why. When your Ethernet network stops working, you can start with a simple IP scan of the subnet. With a WiFi network, you have to go a level deeper than Internet Protocol (sometimes, IP may not even be relevant).

There are many tools to objectively analyse your WiFi network; some are free, others cost good money. Here are but two.

Netstumbler makes a free, lightweight WiFi spectrum analyser from your computer and WiFi adapter of your choice. Netstumbler continuously scans the WiFi spectrum covered by your WiFi adapter, identifying each WiFi network device (whether access point / router, or client), and recording a dozen or so metrics about each network device found.

NetStumbler has two displays, both very useful. The display that you see immediately is the AP inventory, which enumerates each AP observed, and includes over a dozen very useful details about each. But you can discover more.

If you identify an interesting AP from the main list, you can find the MAC address for that AP. From a tree entry in the left column, you select a specific MAC address, and you can observe a running signal to noise graph for that network device.

Netstumbler, though free, and easy to use, has disadvantages.

• It does not work with every known WiFi adapter.
• It does not analyse non WiFi signals. If you have a cordless phone, microwave oven, or nearby ham radio operator, NetStumbler will show those merely as "noise", as part of the signal to noise ratio for any WiFi network device.
• NetStumbler binds to the WiFi adapter just like any other WiFi client. If you run NetStumbler while you're attached normally to your network, using WiFi, you'll experience the same instabilities as when when you run multiple WiFi client managers.
• It's not compatible with Windows Vista.

The Wi-Spy Spectrum Analyzer overcomes some of the disadvantages of Netstumbler. The Wi-Spy is a USB dongle / WiFi receiver, that will receive and analyse signals in the WiFi spectrum.

• It does not require an add-on WiFi adapter, and has no compatibility problems like NetStumbler.
• It provides the same sort of analyses about all detectable WiFi network devices, as NetStumbler. Also, it analyses the noise (signals from non-WiFi devices) in the spectrum, and attempts to identify the device producing the noise, from a database of known interference sources.
• It works with Linux, Mac, and Windows (Windows 2000 or XP, and yes, Vista).
• It is not inexpensive, but it is worth the price.

Note that NetStumbler has its shortcomings, in lack of support for new technology. Fortunately, alternative products are available.

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