3.1 Predicting Path Loss by the Model-Analysis Method

In the analysis of radio-wave propagation for mobile communication, one of the major parameters of interest is propagation-path loss. A measure of propagation-path loss is the difference between the effective power transmitted and the average field strength of the received signal. The field strength of the received signal is an indication of the relative signal amplitude at the transmitted carrier frequency. As previously discussed in Chap. 1, the field strength recorded at the location of a moving mobile receiver fluctuates as a result of the effects of various multipath phenomena.

The average field strength can be calculated by averaging the random trial samples of instantaneous field-strength measurements recorded over a certain path length or distance. The variations in the average field strength are referred to as "long-term" fading; the short-term fading effects of multipath phenomena, which may be readily observed in the trial samples, are practically unnoticeable in the average-field-strength calculations.

General features and roughness of the terrain contour and the occasional scatterers along the distant portions of the propagation path tend to defocus the energy reaching the mobile receiver, and this also contributes to the overall path loss. The more substantial differences in terrain and the unique properties of individual scatterers can cause the path losses to be somewhat different in each of the respective areas studied.

The following factors should always be considered in attempting to predict the propagation-path loss for a particular mobile-radio environment.