Optimal linear precoding scheme for multibeam satellite systems based on partial channel information

Existing work on the precoding scheme for multibeam satellite systems assumes the availability of perfect channel state information (CSI) at the satellite transmitter. Unfortunately, this assumption is not applicable to mobile satellite systems because of long propagation delays, and this is especially true for the geostationary earth orbit (GEO) satellite systems. In this paper, we present a linear precoding scheme for the downlink of a multibeam mobile satellite system assuming availability of only partial CSI. Employing the Shadowed-Rice fading channel model, an approximate analytical expression is first derived for the outage capacity. The optimal linear precoding problem is then considered based on the max-min criterion. It is shown that the optimal solutions to the problem can be obtained by using standard convex optimization tools. Simulation results show substantial performance gains compared with the conventional single-beam based processing scheme.