  Satellite communication systems are a fundamental component in support of
Europe's ambition to deploy smart and sustainable networks and services for the
success of its digital economy. To cope with the 5G and beyond ever increasing
demand for larger throughput, aggressive frequency reuse schemes (i.e., full
frequency reuse), with the implementation of precoding/beamforming to cope with
the massive co-channel interference, are recognised as one of the key
technologies. While the best performance can be obtained with the knowledge of
the Channel State Information (CSI) at the transmitter, this also poses some
technical challenges related to signalling and synchronisation. In this paper,
we focus on precoding solutions that only needs the knowledge of the users'
positions at the transmitter side, namely the recently introduced Switchable
Multi-Beam (MB) and Spatially Sampled MMSE (SS-MMSE) precoding. Compared to the
vast majority of the studies in the literature, we take into account both the
users' and the satellite movement in a Low Earth Orbit (LEO)
mega-constellation, also proposing two system architectures. The extensive
numerical assessment provides a valuable insight on the performance of these
two precoding schemes compared to the optimal MMSE solution.
