  High throughput satellites employing multibeam antennas and full frequency
reuse for broadband satellite services are considered in this paper. Such
architectures offer, for example, a cost-effective solution to optimize data
delivery and extend the coverage areas in future 5G networks. We propose the
application of the multiple-input-multiple-output (MIMO) technology in both the
feeder link and the multiuser downlink. Spatial multiplexing of different data
streams is performed in a common feeder beam. In the user links, MIMO with
multiple beams is exploited to simultaneously serve different users in the same
frequency channel. Under particular design constraints, effective spatial
separation of the multiple user signals is possible. To mitigate the
interstream interference in the MIMO feeder link as well as the multiuser
downlink, precoding of the transmit signals is applied. Simulation results
illustrate the performance gains in terms of sum throughput.
