2026· IEEE Transactions on Wireless Communications· Vol 25, pp. 21166-21182· 0 citations· 62 references
Computer Science
Abstract
Due to their resilience and global coverage, satellite networks are poised to become a key component for non-terrestrial networks in the future. However, given the scarcity of spectrum resources, the dense deployment of low Earth orbit (LEO) satellites introduces significant interference challenges. Meanwhile, the limited computing power and backhaul capacity of satellites have become bottlenecks hindering the development of advanced interference mitigation techniques. This paper studies beamforming in GEO-LEO heterogeneous multi-satellite systems. For the GEO system, we develop a multicast beamforming approach based on a nonlinear eigenvalue problem (NEPv) for beam direction design and Lagrange dual decomposition (LDD) for power allocation. For the LEO system, we propose a general distributed beamforming framework and two distributed beamforming methods. Specifically, we first leverage equivalent multi-dimensional fractional programming (FP) to decompose the objective function. The resulting subproblems are then optimized in a distributed manner across multiple satellites via the parallel block coordinate descent (PBCD) method. For the distributed optimization subproblems, we derive semi-closed-form solutions using Lagrangian dual ascent (LDA) and alternating direction method of multipliers (ADMM) for scenarios without and with GEO-LEO interference avoidance, respectively. Simulation results show that the proposed NEPv-LDD method strictly satisfies the QoS constraints of users and achieves near-optimal performance with low complexity. For the LEO beamforming, the developed distributed FP (DiFP) framework exhibits strong scalability in large-scale constellations. Built upon the DiFP framework, the proposed DiFP-NoSIA incurs almost no performance loss, while DiFP-ADMM shows only an 8.58% performance degradation compared to the centralized benchmark.
Comparative analyses against ablation experiment frameworks and multiple access benchmark frameworks demonstrate that the proposed joint resource allocation distributed rate-splitting multiple access framework can improve the performance of low Earth orbit satellite communication systems while satisfying multiple constraint conditions.
Xianpeng Wang, Xi Han, Mingqi Gao et al.· IEEE Access· 0 citations
Numerical results indicate that the proposed framework outperforms benchmark schemes while accounting for traffic demands and EE, resulting in a mixed-integer nonlinear program (MINLP) for which finding a globally optimal solution is generally intractable.
Wooseok Cha, Kyeongsoo Kim, Seonghoon Kim et al.· IEEE Transactions on Wireles...· 0 citations
LEO satellites play a critical role in non-terrestrial networks (NTNs), where beam hopping (BH), enabled by phased-array antennas and flexible time-frequency division multiplexing (TFDM), enhances payload utilization. However, existing BH studies for spectrum-sharing LEO–GEO systems often neglect the co-frequency interference (CFI) imposed by LEO downlink beams on GEO user terminals, and lack a coordinated optimization of the strongly coupled BH pattern and spectrum resource allocation. These limitations hinder effective interference mitigation and restrict system capacity. Therefore, this paper proposes a downlink BH method with CFI avoidance for LEO satellites in spectrum sharing with GEO systems. Specifically, a dynamic multi-objective optimization mechanism is designed to jointly optimize system throughput and delay fairness while reducing the CFI on GEO user terminals through coordinating beam pointing and frequency assignment. Furthermore, a dual-agent soft actor-critic (SAC) framework is proposed to collaboratively optimize BH pattern and resource allocation. It balances exploration and exploitation through entropy maximization, enhances training stability via soft target network updates, and mitigates estimation errors using the actor-critic architecture. Simulation results demonstrate that the proposed method reduces CFI on GEO user terminals by 31%, while ensuring that 83% of LEO cells achieve over 90% traffic satisfaction rate, thereby significantly improving system performance and resource utilization efficiency.
Ning Chen, Ailing Xiao, Sheng Wu et al.· IEEE Transactions on Wireles...· 0 citations
High-capacity satellite network is the cornerstone of future space-air-ground integrated networks. However, the satellite uplink transmissions still face critical challenges, including severe path loss, complex multi-user interference, and payload constraints. Recently, Reconfigurable Intelligent Surfaces (RIS) and Fluid Antenna Systems (FAS) have shown promise for satellite communications through their dynamic signal reconfiguration. This paper proposes a multi-RIS-assisted satellite Compact Ultra-Massive Antenna Array (CUMA) architecture for multi-user satellite uplink transmission. Specifically, we deploy multiple RISs on the terrestrial side to separate interfering Line-of-Sight (LoS) channels via optimized phase shifts, and adopt a CUMA receiver on the satellite to further mitigate interference through FAS port selection. To solve a sum-rate maximization problem, we alternately optimize FAS port selection using a Forward-Backward Greedy Selection (FBGS) algorithm and RIS phase shifts based on Fractional Programming (FP). To the best of our knowledge, this is the first work to jointly optimize multi-RIS and CUMA in a satellite uplink context, where strong LoS and extreme path loss fundamentally distinguish the design from terrestrial counterparts. Simulation results confirm the effectiveness of the proposed architecture across frequency bands. At 6 GHz, our scheme achieves 181% and 32% rate gains over fixed antennas and traditional CUMA schemes, respectively, while the gains also reach 138% and 27% at 26 GHz, illustrating superiority in both interference-limited and noise-limited regimes.
Kai Feng, Runke Fan, Tianheng Xu et al.· IEEE Open Journal of the Com...· 0 citations
Low Earth orbit (LEO) satellite communications face critical challenges in serving blocked users due to severe penetration loss and signal blockage. Conventional active relay solutions incur high energy consumption and hardware costs. This letter introduces a pinching-antenna relay system (PARS) for energy-efficient LEO satellite communication in blockage environments. By using dielectric waveguides with dynamically reconfigurable PAs, PARS provides flexible spatial diversity and beamforming gains with the circuit control and PA actuation power. We formulate an energy-efficiency (EE) maximization problem by jointly optimizing the satellite precoding and PA positions. A Dinkelbach-based block coordinate descent (BCD) algorithm is proposed to solve the non-convex fractional program via iterative weighted minimum mean square error (WMMSE) transformation and projected gradient descent (PGD) updates. Simulations show that the proposed PARS achieves superior EE over direct transmission, fixed-PA, decode-and-forward (DF) and zero-forcing (ZF) baselines. The resulting performance crossover further identifies the PARS-dominant region, providing practical deployment guidance for blockage-affected scenarios.
Ruihong Jiang, Jincong Mo, Hui-Min Hu et al.· IEEE Wireless Communications...· 0 citations
An unmanned aerial vehicle (UAV)-enabled ISAC system employing rate-splitting multiple access (RSMA) and a joint beamforming and trajectory optimization framework is investigated and results demonstrate that the proposed algorithm significantly improves the achievable system downlink rate.
Shunxuan Wang, Qi Zhu· Italian National Conference...· 0 citations
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