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Joint Beamforming and Illumination Pattern Design for Beam-Hopping LEO Satellite Communications

Jing Wang, Chenhao Qi, Shui Yu, Shiwen Mao

Abstract

Since 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 design subject to the HBF constraints and sum-rate requirements. To address the non-convexity of the HBF constraints, we temporarily replace the HBF constraints with the FDBF constraints. Then we propose an FDBF and illumination pattern random search (FDBF-IPRS) scheme to optimize illumination patterns and fully-digital beamformers using constrained random search and fractional programming methods. To further reduce the computational complexity, we propose an FDBF and illumination pattern alternating optimization (FDBF-IPAO) scheme, where we relax the integer illumination pattern to continuous variables and after finishing all the iterations we quantize the continuous variables into integer ones. Based on the fully-digital beamformers designed by the FDBF-IPRS or FDBF-IPAO scheme, we propose an HBF alternating minimization algorithm to design the hybrid beamformers. Simulation results show that the proposed schemes can achieve satisfactory sum-rate performance for BH LEO SatComs.

Joint Beamforming and Illumination Pattern Design for Beam-Hopping LEO Satellite Communications

Abstract

Since 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 design subject to the HBF constraints and sum-rate requirements. To address the non-convexity of the HBF constraints, we temporarily replace the HBF constraints with the FDBF constraints. Then we propose an FDBF and illumination pattern random search (FDBF-IPRS) scheme to optimize illumination patterns and fully-digital beamformers using constrained random search and fractional programming methods. To further reduce the computational complexity, we propose an FDBF and illumination pattern alternating optimization (FDBF-IPAO) scheme, where we relax the integer illumination pattern to continuous variables and after finishing all the iterations we quantize the continuous variables into integer ones. Based on the fully-digital beamformers designed by the FDBF-IPRS or FDBF-IPAO scheme, we propose an HBF alternating minimization algorithm to design the hybrid beamformers. Simulation results show that the proposed schemes can achieve satisfactory sum-rate performance for BH LEO SatComs.
Paper Structure (8 sections, 49 equations, 7 figures, 1 table, 3 algorithms)

This paper contains 8 sections, 49 equations, 7 figures, 1 table, 3 algorithms.

Table of Contents

  1. Introduction
  2. System Model
  3. Joint Beamforming and Illumination Pattern Design
  4. FDBF-IPRS Scheme
  5. FDBF-IPAO Scheme
  6. HBF-AM algorithm
  7. Simulation Results
  8. Conclusion

Figures (7)

  • Figure 1: Illustration of system model.
  • Figure 2: Comparisons of sum-rate of total $N_{\rm s}$ beam positions under different $\gamma_n$ for FDBF design and HBF design with different $P_{\rm tot}$.
  • Figure 3: Comparisons of sum-rate of total $N_{\rm s}$ beam positions under different $N_{\rm BS}$ for FDBF design and HBF design with different $\gamma_n$.
  • Figure 4: Convergence of the sum-rate of FDBF-IPAO scheme with different $P_{\rm tot}$.
  • Figure 5: Comparisons of sum-rate of FDBF-IPRS and FDBF-IPAO schemes under different $P_{\rm tot}$.
  • ...and 2 more figures