User's Manual

Chapter 1 Preparing for a WLAN Deployment
20 Aerohive
Figure 3 Path Loss in an Open Space
When clients send a packet, the ratio of the signal-to-noise (SNR) level defines the quality of the link, which is
directly related to the performance of the network. Based on the SNR, the client and AP negotiate a data rate in
which to send the packet, so the higher the SNR the better. For good performance, the SNR should be greater than
20 dB, and for optimal performance it should be at least 25 dB.
Signal strength not only diminishes over distance but it can also be affected by objects in the way (see Figure 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. While this appears to be a bad thing, clever Wi-Fi installers use it
to their advantage. It allows 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.
Figure 4 Path Loss through a Wall
Signal-to-Noise
Ratio
Distance
Noise
Received Signal
Signal-to-Noise
Ratio
Distance
Noise
Received Signal
Wall