To meet the target requirements of 5G and 6G systems in terms of throughput and global connectivity, the upcoming Low Earth Orbit (LEO) mega-constellations are set to seamlessly integrate into terrestrial communication networks. Although extensively utilized in terrestrial systems, multi-user multiple-input multiple-output (MU-MIMO) transmission has not yet been implemented in LEO mega-constellation communication systems. In this work, we compare the throughput performance of a MU-MIMO downlink transmission and full frequency reuse (FFR) with the throughput of a multibeam LEO system with conventional four-color frequency reuse (FR4). We employ a deterministic modeling approach of the spacecraft motion, the satellite channel and the pre-generation of the downlink channel state information (CSI). To mitigate co-channel interference in the MIMO case, zero-forcing precoding is applied. We study the effects of an outdated CSI on the MIMO downlink performance. Simulation results confirm that even under the effects of an outdated CSI at the precoder, the MIMO LEO satellite system with FFR substantially outperforms the multibeam scenario with the FR4.    «

To meet the target requirements of 5G and 6G systems in terms of throughput and global connectivity, the upcoming Low Earth Orbit (LEO) mega-constellations are set to seamlessly integrate into terrestrial communication networks. Although extensively utilized in terrestrial systems, multi-user multiple-input multiple-output (MU-MIMO) transmission has not yet been implemented in LEO mega-constellation communication systems. In this work, we compare the throughput performance of a MU-MIMO downlink...    »