Black Box LWN602A User Manual page 23

Chapter 2: Preparing for a WAN Deployment
Signal strength not only diminishes over distance, but it can also be affected by objects in the way (see Figure 2-4). This can be a
wall, a tree, or even a person. There is a fairly predictable dB drop through most objects that also decreases the SNR, thus
decreasing the data rate. Although this appears to be a bad thing, clever Wi-Fi installers use it to their advantage. It enables them
to place more access points in a tighter spot by using pre-existing walls and other impediments to Wi-Fi propagation to keep
them from interfering with each other.
Received Signal
Wall
Signal-to-Noise
Ratio
Noise
Distance
Figure 2-4. Path loss through a wall.
Microwave ovens, wireless video cameras, Bluetooth headsets, and cordless phones can all interfere with Wi-Fi signals (see Figure
2-5). Excess noise in an environment is often difficult to diagnose and can have a major negative impact on network performance.
To discover noise sources, a spectrum analysis system is needed. AirMagnet provides an affordable spectrum analysis tool that
operates in the 2.4-GHz and 5-GHz spectra.
Received Signal
Signal-to-Noise
Ratio
Noise
Distance
Figure 2-5. Path loss with noise (from a microwave).
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