What is Fade Margin?

Fade margin is the difference, in dB, between the received signal at the receiver input and the minimum level of signal determined for reliable operation. Higher the fade margin, the more reliable the link will be. The exact amount of fade margin required depends on the desired reliability of the link.

How much fade margin we need?

In order for the link to work the receiver must receive fade margin above 0 which means that the received signal is equal or bigger than the threshold.
To make the link reliable, a good rule of thumb is to get 20 to 30 dB of fade margin.

Calculation

Fade Margin (dB) = Received Signal(dB) - Receiver Threshold(dB)

Simulation

In the fade margin Simulation the Receiver Threshold is a fixed value (-72dB). We are able to control the link budget between the transmitter and the receiver therefore changing the ratio between the receiver threshold and the recieved signal.