the difference between the receive signal level on a good day and what the radio will fail at. Must be large enough to overcome losses induced by rain and other natural occurrences. Is expressed in Db.
The loss in signal along a signal path, measured in dBi , caused by environmental factors such as terrain, atmospheric conditions, etc.
A design allowance that provides for sufficient system gain or sensitivity to accommodate expected fading, for the purpose of ensuring that the required quality of service is maintained. Also, the amount by which a received signal level may be reduced without causing system performance to fall below a specified threshold value.
The ratio, general expressed in dB, of a received signal to the threshold of successful demodulation in a particular receiver
Normally an extra 10dB is allowed for above the amount required for the link to work. This is to allow for unforeseen effects. The additional fade can be due to changes in ground reflectivity due to changes in atmospheric conditions or non constant multipath interference.
Fade margin is the difference, in dB, between the magnitude of 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, but a good rule-of-thumb is 20 to 30 dB. Fade margin is often referred to as "thermal" or "system operating margin".
The greatest tolerable reduction in average received signal strength that will be anticipated under most conditions. Provides an allowance for reduced signal strength due to multipath, slight antenna movement or changing atmospheric losses. A fade margin of 20 to 30 dB is normally sufficient in most systems.
