Abstract :
The purpose of the paper is to deduce the overall statistical distribution of signal/noise ratio over a 2-hop line-of-sight radio link when the fading statistics for the individual hops are assumed to be known. A theoretical model is proposed that reproduces the essential features of the situation. The results deduced from the model are intended to have particular reference to double over-water hops. The model is also adapted to allow ideal diversity reception to be assumed on both sections of the link. The general results are applied to the Rayleigh fading distribution, and in this case the overall distributions are obtained in closed form together with much simpler asymptotic forms which are adequate for most system planning applications. It is seen that, if the asymptotic expression is used instead of the full expression to determine the median signal/noise ratio for the 2-hop link (without diversity), a maximum error of 1. 5 dB can occur. A parameter k appears in the distributions that can be adjusted to allow for inequalities in path loss, feeder losses, aerial gains and receiver temperatures.
