Propagation modelling-past, present and future

Propagation models are used to represent the wealth of information available about a propagation phenomena. Models are developed from physical analyses and statistical analyses of experimental observations. The modeling process is iterative. As one´s understanding of a particular phenomenon improves, so do the models used to describe that phenomenon. Several models that describe propagation through the troposphere at frequencies above 1 GHz are considered. The current state of model development for attenuation by rain and for transhorizon scatter propagation is presented. A cursory historical review is given, the currently available models are described, and probable new model developments are forecast