In this paper, a lightweight LEO satellite-assisted flexible faster-than-Nyquist (FTN)-orthogonal time frequency space (OTFS) (LEO-FFTN-OTFS) scheme is proposed to address the stringent constraints on onboard power consumption and the severe impact of fast time-varying channels in non-terrestrial networks. A rigorous system framework incorporating realistic 3GPP Tapped Delay Line (TDL) channel models is established to accurately capture high-mobility propagation characteristics. To counteract channel aging effects while maintaining low computational complexity, an SNR-aware flexible FTN strategy is introduced, wherein a low-complexity Look-Up Table (LUT) is utilized to adaptively optimize the time-domain compression factor based on instantaneous channel responses. Through this mechanism, the trade-off between rate acceleration and interference penalty is effectively resolved, ensuring that spectral efficiency is maximized while strict reliability constraints are satisfied with minimal processing overhead. Moreover, a comprehensive theoretical analysis is provided, in which analytical expressions for effective throughput, energy efficiency, and bit error rate are derived. Finally, it is demonstrated by extensive simulations that the proposed scheme significantly outperforms static FTN benchmarks, offering a superior balance of high throughput and robustness for next-generation LEO communications.

翻译：本文提出了一种轻量化的低地球轨道卫星辅助灵活超奈奎斯特正交时频空方案，以应对非地面网络中星载功耗的严格限制与快速时变信道的严重影响。通过引入符合实际3GPP抽头延迟线信道模型的严谨系统框架，该方案能够精确刻画高动态传播特性。为在保持低计算复杂度的同时抑制信道老化效应，本文提出了一种信噪比感知的灵活FTN策略，利用低复杂度的查找表，根据瞬时信道响应自适应地优化时域压缩因子。通过该机制，系统有效解决了速率提升与干扰代价之间的权衡问题，在满足严格可靠性约束且处理开销最小的前提下，实现了频谱效率的最大化。此外，本文提供了完整的理论分析，推导了有效吞吐量、能量效率与误码率的解析表达式。最终，大量仿真结果表明，所提方案显著优于静态FTN基准方案，为下一代LEO通信系统提供了高吞吐量与强鲁棒性的更优平衡。