SmallNetBuilder

Introduction

Updated 6/25/2009: Added MetaGeek Wi-Spy 2.4i

In Part 1 of this series, I provided an explanation of WLAN basics and described common wireless problem symptoms and their probable causes. In this installment, I'll show you how to use equipment that you probably already have to perform some simple tests that can help point you to the correct problem(s) to solve.

To uncover potential issues or causes of problems when troubleshooting Wireless LANs and for an overall better Wi-Fi networking experience, you should scan the airwaves, i.e. perform a site survey.

For small residential or small-office wireless networks, a site survey can serve three purposes:

• To check for nearby wireless networks
• To verify desired wireless coverage
• Look for non-WiFi RF (Radio Frequency) sources

Site surveys for Enterprises can be quite involved and often include RF spectrum scans, which can detect non Wi-Fi RF interference. RF spectrum analyzers such those from Cognio and Airmagnet [reviewed] can cost up to $4,000. But there are lower-cost alternatives, such as the Wi-Spy [reviewed] and AirSleuth, for personal use.

But since we're the targeting home and small-office users, I'll be discussing slimmed-down site surveys that can be done quickly and easily.

Surveying Tools

If you already have a notebook with either a built-in or add-on wireless card, you might already have what you need to do a simple site survey. The software utilities included with many wireless adapters have a survey or scan function, such as shown in Figure 1. Note that what are listed are Access Points (APs), or wireless routers. (When I use "AP", please think access point or wireless router.) The information we're interested are the SSID or network name, signal strength and channel number.

Figure 1: Example of a wireless adapter utility.

Your wireless adapter's utility might be found on your Windows Start > Programs menu, or there might be an icon in the system tray that can be clicked to bring it up.

If it's not already installed, you might be able to download the utility from the manufacturer's website. Note that the utility might be bundled with the adapter's driver download. But keep in mind not all manufacturers release utilities for all their adapters.