This visualization shows the
signal-to-noise ratio (SNR) measured in dB. SNR is a measure to
quantify by how much the signal level exceeds the noise level.
Noise is generated by non-802.11 sources of radio waves (this
includes 802.11 frames damaged during propagation). In low SNR
zones, client devices may not be able to communicate with APs. SNR
is shown for the AP that has the strongest signal in the given map
area among the APs selected for analysis. You can deselect one or
several of the selected APs to see SNR values for less strong
In a typical environment, the
noise level is about -90 dBm. The signal level measured within a
few meters from the AP would be about -50 dBm. This gives an SNR
value of 40 dB, which is considered excellent. Marginal
connectivity is possible when the AP signal level is -85 dBm, so an
SNR value of 5 dB is considered poor. A higher noise level and,
correspondingly, a lower SNR are usually caused by Bluetooth
devices, cordless phones, and microwave ovens.
Double-clicking on the SNR
legend on the status bar allows you to configure the color scheme
and change its value range.
When low SNR areas are
discovered, two possible strategies should be considered:
increasing the signal level or decreasing the noise level. The
first strategy is discussed in the previous chapter; to decrease
the noise level, the following solutions are suggested:
the environment for potential sources of noise and turn them off,
if possible, to see how that affects SNR.
experience low SNR values in the 2.4 GHz band, consider switching
your APs to the 5 GHz band, where noise level is typically
switching to the 5 GHz band is not an option, try to select a
different channel in the 2.4 GHz band.
Note that identifying and
removing the source of noise might not be an easy task. In
practice, the easiest solution is usually increasing the signal
level rather than decreasing the noise level.