Radio Propagation

The electromagnetic field radiated by an antenna propagates through the radio channels between transmitter Tx and receiver Rx. The mechanism of radio propagation can generally be described as reflection, diffraction and scattering. Propagation models are traditionally focused on prediction of the average received signal strength used to define the coverage area in a mobile cellular environment. Multipath propagation gives rise to a fine structure of signal fluctuations, which results in corresponding variations (fast fading) in the input signal to the mobile unit. Averaging with respect to the fast fading structure gives the local mean of the propagation path loss or received signal strength. In a typical propagation situation there are considerable shadow effects. The propagation loss with respect to the local mean is generally much greater than when there is free-space propagation, owing to the strong influence of the terrain.