  This paper aims at designing an on-board beam generation process for
multibeam satellite systems with the goal of reducing the traffic at the feeder
link. Full frequency reuse among beams is considered and the beamforming at the
satellite is designed for supporting interference mitigation techniques. In
addition, in order to reduce the payload cost and complexity, this on-board
processing is assumed to be constant and the same for forward and return link
transmissions. To meet all these requirements a novel robust minimum mean
square error (MMSE) optimization is conceived. The benefits of the considered
scheme are evaluated with respect to the current approaches both analytically
and numerically. Indeed, we show that with the DVB-RCS and DVB-S2 standards,
our proposal allows to increase the total throughput within a range between 6\%
and 15\% with respect to other on-board processing techniques in the return and
forward link, respectively. Furthermore, the proposed solution presents an
implicit feeder link bandwidth reduction with respect to the on-ground beam
generation process.
