Fade Mechanisms

Microwave fades fall into the following categories:

• Multipath fading
• Obstruction fading
• Fading due to a specular reflection
• Ducting and propagation anomalies
• Rain fading (above ~ 8 GHz)

With the exception of rain fading, microwave fading only depends on the change of the refractive index with height along the path

Availability	Seconds	Minutes	Hours
99%	315360	5256	87.6
99.9%	31536	525	8.76
99.99%	3153	52.5	0.876
99.999%	315	5.3	0.088

Link Performance Definition The definition of link performance only considers multipath and rain fades. This implies the following assumptions:

• the path has sufficient clearance / fade margin to obviate the possibility of an obstruction fade.
• signal nulls due to a specular reflection are small com-pared to the fade margin or a space diversity configura-tion has been implemented.
• the probability of ducting is unknown.