Q.What is fading? Explain.

Fading is the fluctuation in the strength of a received radio signal. Instead of arriving steady, the signal at the receiver rises and falls in strength over time. This happens during propagation, as the wave interacts with the atmosphere on its way to the receiver.

Several effects cause fading. As the wave travels it may be partly absorbed in the atmospheric layers, lost during refraction in the ionosphere, or scattered by irregularities along the path. Any of these can change how much energy actually reaches the receiver from moment to moment, so the received strength wanders up and down rather than staying constant.

Fading is not a single phenomenon but comes in several named types, including interference fading, polarization fading, absorption fading and skip fading, along with statistical descriptions such as Rayleigh, Ricean, Nakagami and Weibull fading. Each describes a particular mechanism or pattern by which the signal strength varies. …