2026· IEEE Open Journal of the Communications Society· Vol 7, pp. 9945-9959· 0 citations· 51 references
Abstract
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.
In rapidly expanding low Earth orbit (LEO) satellite networks, the transmission capacity of satellite-to-ground downlinks has become a critical bottleneck for massive data backhaul. In practical systems, the severe supply-demand imbalance between limited gateway antennas and numerous passing satellites makes it impossible to establish links simultaneously, severely limiting the transmission capacity of the downlinks. To address this challenge, we propose a multi-antenna cooperative dynamic scheduling method. First, the antenna-satellite matching strategy is formulated as a mixed-integer nonlinear programming (MINLP) problem aimed at maximizing total system throughput. Second, given the NP-hard nature of this problem, it is further transformed into a Markov decision process (MDP), and a Cooperative Antenna Scheduling Reinforcement Learning (CAS-RL) algorithm is proposed. Finally, simulation results demonstrate that the proposed algorithm increases the average system throughput by more than $\mathbf{1 6}$% compared to benchmarks.
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, Jin-Cong Mo, Hui-Min Hu et al.· IEEE Wireless Communications...· 1 citation
Simulation results show that the proposed method can significantly improve the sum rate of users as compared to benchmark with FPA + Optimized STAR-RIS, 6DMA + Random STAR-RIS, and FPA + Random STAR-RIS.
Yuewei Wu, Ming-Hao Chen, Jingjing Yang et al.· IEEE Open Journal of the Com...· 0 citations
This paper considers a satellite-to-ground communication system in which a ground station (GS) equipped with independently rotatable antenna (RA) elements jointly decodes independent streams from multiple low-Earth-orbit (LEO) satellites over a shared time--frequency resource. Specifically, we formulate a two-timescale throughput maximization problem under exogenous cochannel interference, capturing serving-set composition, RA-enabled channel shaping, time-varying satellite geometry, and mechanically constrained inter-epoch reconfiguration. We first characterize the joint effects of interference-whitened channel strength and spatial separability on multi-satellite reception, motivating the joint design of satellite selection and RA control. With the RA trajectory fixed, we establish the monotone submodularity of the epoch-level selection objective and construct an incumbent-tight modular lower-bound surrogate, leading to an efficient discrete Minorization-Maximization (MM) selection algorithm. For fixed serving sets, we develop slew-feasible RA updates based on Riemannian gradients and organize them into a two-color parallel update scheme. The two blocks are integrated into a monotone alternating algorithm with guaranteed objective convergence. Simulations demonstrate consistent gains over benchmark schemes and reveal an optimal balance between channel strength and spatial separability. The results further show that satellite selection is particularly important in underloaded and actuator-limited regimes, whereas RA shaping becomes more influential near full spatial loading.
Xingxiang Peng, Qingqing Wu, Hai-Ying Hu et al.· 0 citations
This article studies transmissive reconfigurable intelligent surface (RIS)-assisted architectures. It compares them with electronically steered phased arrays for the deployment of vehicular direct-to-satellite (D2S) communications in future satellite networks. Rather than treating RIS as a direct replacement for phased arrays, we clarify the operating regimes in which RIS can serve as a low-power wavefront-shaping aperture and those in which phased arrays remain preferable because of their high gain and mature beam-tracking capability. Moreover, phased arrays can support multi-beam operation, which is particularly beneficial for dual connectivity and seamless handover. We distinguish analog, digital, and hybrid phased arrays, discuss the relationship between transmissive RIS and reconfigurable transmitarrays, and highlight practical profile, tracking, and link-budget constraints for mobile terminals. The comparison shows that passive RIS offers attractive power efficiency and aperture scalability, active RIS can partially improve the link budget, and phased arrays remain preferable for high-throughput.
W. Khan, Abdullah Abdullah, Juan Andres Vazquez-Peralvo et al.· 0 citations
To address the interference issues caused by channel aging in high-speed railway (HSR) communications and further reduce the signal processing latency to meet the ultra-low latency requirements of accelerating HSR speed, considering the native electromagnetic signal processing of stacked intelligent metasurfaces (SIMs) and the interference cancellation capability of rate-splitting multiple access (RSMA), we propose a novel RSMA-aided SIM-enhanced cell-free massive MIMO architecture for HSR train-ground wireless communications. Based on the minimum mean square error channel estimates, closed-form expressions for the spectral efficiency (SE) are derived for both perfectly known and unavailable initial line-of-sight (LoS) phase conditions to delineate the performance bounds of the system. Additionally, to address the challenge of communication quality degradation caused by high-speed movement, a heuristic algorithm is developed to jointly optimize the SIM beamforming matrix and the rate-splitting factor, thereby maximizing the sum SE. Moreover, an access points (APs) selection based scheme on normalized channel estimation is proposed to improve the scalability of HSR communication system. The simulation results demonstrate the effectiveness of the proposed joint optimization algorithm. It is also shown that RSMA effectively mitigates channel aging-induced interference, especially under a perfectly known LoS initial phase, and that the proposed SIM-enhanced cell-free massive MIMO system, enabled by the beamforming algorithm, outperforms the conventional system when the initial phase of LoS path is available at APs.
Qing-Feng Ding, Hui-Fan Peng, Ke Guan· IEEE Transactions on Wireles...· 0 citations
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