fading

Fading is slow field strength fluctuations in radio transmission caused by ground topology, humidity or interference.

At low frequencies, i.e. longer wavelengths, interference can form between room and ground waves; at higher frequencies, the shorter wavelengths are reflected by buildings or ground elevations, resulting in interference between the direct radiation and the reflected waves.

Signals that are loaded with fading are subject to strong level fluctuations. This is due to the fact that the levels of the various radio reflections at the receiving location overlap or partially compensate each other. This phenomenon is very pronounced in shortwave, where the reflected space waves can overlap at the receiving site.

In mobile communications, fading can lead to a reduction in data rate andvoice quality. For this reason, different transmission values are specified for a line-of-sight( LOS) and anon-line-of-sight ( NLOS) connection for different radio standards.