ITU-R P.620-6

Abstract

<strong>Introduction</strong> <br>This Annex provides propagation data for use in the calculation of a coordination area and sets out a straightforward method for the assessment of the propagation factors concerned in the determination of coordination distances. <br>The coordination area represents the area outside of which interference between an earth station and terrestrial stations (or between bidirectionally operating earth stations), operating within the conservative assumptions given elsewhere, may be considered negligible. In the remainder of this Recommendation the words terrestrial stations may also represent bidirectionally operating earth stations. The determination of coordination distance therefore necessitates the comparison of the required transmission loss (minimum permissible basic transmission loss, <em>L_b</em>( <em>p</em>) (dB), not exceeded for a given annual percentage time <em>p</em>), based on system and interference model considerations, with the transmission loss contributed by the propagation medium. The required coordination distance is that at which these two losses become equal. <br>Various propagation models are provided to cover different frequency ranges and to take account of different propagation mechanisms. These models predict propagation loss as a function of distance. Coordination distances are determined by calculating propagation loss iteratively with distance until either the required transmission loss is achieved or a limiting distance is reached. <br>It is important to note that the coordination area does not represent a zone within which the sharing of frequencies between the earth station and the terrestrial station is excluded. Such sharing is often possible, and the coordination area serves to assist this arrangement by indicating where the potential for interference between the earth station and any terrestrial stations needs to be evaluated using a more detailed analysis based on the relevant ITU-R Recommendations. <br>In addition to providing the method of calculation for the coordination contour, this Recommendation also provides information that enables the preparation of auxiliary contours to assist in the rapid elimination of the majority of potential interference cases during the subsequent coordination analysis for terrestrial stations falling within the coordination contour.