Unbalanced site diversity and propagation data required for its performance evaluation

Regarding the site diversity scheme, studies to date have mostly been concerned with balanced diversity, that is, the diversity using two earth stations with equal performance. In addition to the diversity of this type, however, "unbalanced" diversity (that is, the diversity using two unequal earth stations) should also be worthy of note, because such situations are liable to occur as the main station is operated together with other lower frequency bands, or the substation has to be much simplified from some technical and operational reasons. In designing the unbalanced diversity system, propagation data should be provided in the form of the conditional probability statistics, rather than the conventional joint-exceedance statistis, but data of this kind have not been presented to date. From this point of view, the properties of the conditional probability statistics on rain rates based on the multisite measurement in Japan are discussed.