The miniaturization of satellite payloads and the reduction in launch costs have driven the rapid development of Low Earth Orbit (LEO) satellites in the fields of communication, navigation, and remote sensing (CNS), reshaping the industry and global information infrastructure. However, there remain significant challenges and obstacles in the application of LEO satellites within these domains. This paper aims to provide a comprehensive analysis of LEO satellites, with particular emphasis on the development and challenges of communication payloads, to promote further research and applications in these areas. First, the paper examines the evolution of LEO systems and communication payload capabilities from different historical perspectives and user demands. It then explores the opportunities for LEO satellites in the context of global communication infrastructure, particularly in enhancing global connectivity, supporting intelligent transportation through high-precision positioning, navigation, and timing (PNT), and advancing environmental monitoring via passive radar in remote sensing applications. By systematically reviewing the literature on network architectures, medium access control, physical layer technologies, constellation designs, interference management, the application of artificial intelligence, and cost control strategies, this study identifies the major challenges these technologies face in CNS applications. Additionally, the paper discusses future research directions, including large-scale constellations, multi-functional platform integration, advances in intelligence and automation, network convergence and interoperability, interference mitigation, and sustainability. These areas are explored to provide pathways for further technological advancements.

Enhancing user access capacity in satellite beam-hopping systems remains challenging due to dynamic traffic and limited beam dwell times. Conventional Multi-Frequency Time-Division Multiple Access (MF-TDMA) proves highly inefficient under such constraints. To overcome this, we propose a novel scheme that integrates power-domain Non-Orthogonal Multiple Access (NOMA) with MF-TDMA, employing Successive Interference Cancelation (SIC) for multi-user signal separation. A bi-directional adaptive carrier synchronization method and optimized burst structure are introduced, which collectively reduce synchronization overhead by over 40% compared to MF-TDMA. Simulations demonstrate a dramatically improved frame error rate of 0.0005% at 4 dB SNR—30 times lower than the 0.016% achieved by MF-TDMA—and a transmission efficiency of 92–97%, significantly outperforming conventional MF-TDMA. These results validate the proposed method’s substantial gains in capacity and efficiency for next-generation satellite systems.

Satellite array receivers must suppress interference whose spatial, spectral, and temporal characteristics vary across operating conditions, often with limited known symbols for adaptation. This paper studies when learned subspace augmentation is useful under finite pilot support. The receiver retains the instantaneous complex-linear receive subspace and adds a low-dimensional orthogonal complement generated from temporal and spectral features, with all basis coefficients estimated jointly from known symbols. A finite-sample analysis separates oracle representation gain from the additional pilot-to-payload estimation error caused by basis enlargement. Across 720 seen-family conditions, the proposed receiver achieves mean uncoded bit error rate (BER) 0.06521, versus 0.06572 for the receive-span ablation and 0.06719 for minimum-variance distortionless response; the 0.78% reduction relative to receive-span is modest and concentrated in spatially loaded narrowband regimes. A same-frame trained-versus-untrained comparison shows an average benefit from parameter optimization in the reference realization. Independent retraining from three initializations yields closely clustered held-out performance, while the selected model order varies between $L=1$ and $L=2$. For three unseen interference families, mean net augmentation gain is negative and aggregate MSE does not improve over receive-span. The results therefore identify a condition-dependent regime in which subspace augmentation is useful when representation gain exceeds finite-pilot estimation cost, rather than a broadly transferable advantage across interference types.