Constrained Capacities in Log-Normal Channels with Site Diversity at Ka Band

Abstract

This paper considers the use of site diversity to mitigate rain effects. It uses information theoretic tools to compute the constrained capacity of log-normally distributed rain-fading channels in the Ka band (20-30 GHz) in which practical constellations, such as those found in the DVB-S2 standard are used, as opposed to the Gaussian distribution assumed for the input signal in Shannon capacity calculations. To the authors' knowledge, this has not been done before. Two types of rain environments are considered: a tropical environment and a fairly dry European environment. The results of such an approach can help the satellite planner determine the utility of site diversity and determine realistic upper limits for the throughput of a satellite link given the statistics of rain fades experienced by the link. This paper describes this information theoretic approach to determining the benefits of diversity and gives the gains in outage capacity due to diversity for a tropical rain region and a fairly dry rain region under the constraint that practical constellations are transmitted.