Hybrid Beamforming Design for Beam-Hopping LEO Satellite Communications

Since the hybrid beamforming (HBF) can approach the performance of fully-digital beamforming (FDBF) with much lower hardware complexity, we investigate the HBF design for beam-hopping (BH) low earth orbit (LEO) satellite communications (SatComs). Aiming at maximizing the sum-rate of totally illuminated beam positions during the whole BH period, we consider joint beamforming and illumination pattern (BIP) design subject to the HBF constraints and sum-rate requirements. To address the nonconvexity of the HBF constraints, we temporarily replace the HBF constraints with the FDBF constraints. Then a joint FDBF and illumination pattern design scheme is proposed using random search and fractional programming (FP) methods. Based on the designed illumination patterns, we optimize the digital beamformers with the constrained analog beamformers by utilizing the FP methods, where a sum-rate maximization HBF scheme is proposed. Simulation results show that the proposed schemes can achieve satisfactory sum-rate performance for BH LEO SatComs.