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WLAN Design: Page 4 of 6

Can You Hear Me Now?

After setting up the access point, slowly walk the floor of your facility with laptop or PDA in hand. If you move too fast, you can get inaccurate readings. Take note of three key numbers that the tool registers: signal strength, SNR (signal-to-noise ratio) and connection speed. You may need to repeat this test regularly if your facility experiences fluctuations in inventory or personnel, or if you have modular walls or other large RF obstacles, to ensure consistent wireless coverage.

Signal strength is represented in many ways, but the most common is a percentage--signal levels as low as 20 percent, for instance, typically suffice for passing data. But try to design your WLAN to support a minimum signal of 30 percent throughout so your cards don't have trouble passing data. This percentage can vary slightly from WLAN card to card, and cards will vary in sensitivity. So try to survey with a card that will be the most common one in your WLAN. If your WLAN will consist of a mix of WLAN cards, use your lowest-end card in the survey to ensure that everyone gets adequate coverage.

Once your WLAN is installed and online, conduct regular site surveys--and do one whenever you add new wireless hardware. Perform surveys every six months or so, depending on the frequency and likelihood of RF changes in your WLAN. Ekahau, a Wi-Fi positioning and survey software company, has a new site-survey utility that can ease the verification process. The Ekahau Site Survey tool graphically represents your 802.11b coverage, inferring throughput based on signal strength. It also recommends locations for new access points.

As long as you provision your WLAN for high-user density and the proper throughput, your wireless network will be set to keep up with additional wireless-enabled devices and usage as your business gets more mobile. But if you don't properly provision your WLAN, it will fall flat and cost you more in the end.