![]() This can result in either constructive or destructive interference, amplifying or attenuating the signal power seen at the receiver. ![]() ![]() Each signal copy will experience differences in attenuation, delay and phase shift while traveling from the source to the receiver. As a result, the receiver sees the superposition of multiple copies of the transmitted signal, each traversing a different path. The presence of reflectors in the environment surrounding a transmitter and receiver create multiple paths that a transmitted signal can traverse. In wireless systems, fading may either be due to multipath propagation, referred to as multipath-induced fading, weather (particularly rain), or shadowing from obstacles affecting the wave propagation, sometimes referred to as shadow fading. A fading channel is a communication channel that experiences fading. Fading is often modeled as a random process. These variables include time, geographical position, and radio frequency. ![]() In wireless communications, fading is variation of the attenuation of a signal with the various variables. Time is shown on the horizontal axis, frequency on the vertical axis and signal strength as grey-scale intensity. Term in wireless communications Frequency-selective time-varying fading causes a cloudy pattern to appear on a spectrogram. ![]()
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