On antenna design and capacity analysis for the forward link of a multibeam power controlled satellite CDMA network

Abstract

This paper deals with the problem of rigorously analyzing the forward link behavior of a power controlled CDMA-based satellite multibeam communication system. For the first time, the complete system links equations are expressed in a compact matrix form so that they can be solved simultaneously, thus leading to an exact problem solution. In particular the effect of actual antenna beam patterns, overlapping satellites interference, users location, conventional and linear blind minimum output energy (MOE) CDMA detectors are accounted for by comprehensive system analysis. Under simplified yet realistic system assumptions, the proposed technique allows us to derive the key satellite antenna parameters. It is shown that for power controlled CDMA satellite networks, the key antenna figure of merit is the average gain and the so-called antenna inverse average interference-to-carrier ratio rather than the more intuitive average carrier-to-interference ratio. It is shown that under simplified system assumptions, these parameters can be used to compute simple yet accurate one-dimensional system link budget. Also, by means of a simplified system analysis, the antenna beam overlapping point capacity impact is determined. Furthermore, results about system capacity and outage probability for a practical personal communication satellite network are presented with and without adopting an advanced CDMA MOE single-user detector. The MOE advantages in terms of capacity increase for a given outage probability are shown to be substantial when the system loading is appreciable, even assuming perfect power control.