Six steps to a wireless site survey

Computerworld - To get the best performance out of your wireless network, you must both ensure that your access points (AP) are in the most optimal locations and that other radio emitters, which can cause interference, are kept to a minimum. This requires you to periodically perform site surveys of your wireless spectrum.

Depending on the scale of your installation, there are a number of tools available for the task, such as software that walks you through the site survey process. But no matter what size network you will have, you'll need to follow these basic steps:

1. Have a blueprint or floor plan(s) of the areas you want the wireless network to cover. Some software products can work off these floor plans directly. Look at your plans and identify major building obstacles such as walls, halls, elevators and floors that will block radio signals. Also note where your users will be located -- and where they won't -- to determine coverage areas.
2. Determine where you can locate APs based on power and cabling that you can run to connect the AP to the rest of the network. Remember that you shouldn't place APs close to metal or concrete walls and you should put them as close to the ceiling as possible.
3. Estimate the total number of APs needed for your overall coverage. A good rule of thumb is one AP can cover a circle with a 100-foot radius. This will give you preliminary AP locations that you can use at the beginning of your survey. If you already have some APs, note their locations on your floor plans.
4. Run the survey tool. Make sure to use the same AP model for the survey that is used in your actual infrastructure. See below for recommendations about which tool to use.
5. Relocate APs and retest, depending on the results of your survey.
6. Document your findings. Record the locations and log your signal readings and data rates observed for future reference.

So, how do you pick the right tool for your surveying needs? There are three basic types:

First, there are simple Windows-based software tools that you can use on a single laptop used for recording measurements such as signal strength as you walk around your building. You just need to buy a single AP and move it around to the potential locations that you came up with in Step 3. These tools are good for smaller installations of, say, one to three APs.

They are also good for situations in which you don't have a simple open-office plan but rather have various corridors and potential radio dead spots scattered around multiple floors. There are free tools, such as NetStumbler, and more capable ones, such as AirMagnet Survey, Visiwave, Fluke Networks InterpretAir and Ekahau Site Survey, which cost several thousand dollars.