AI 中文总结
针对基于CP-OTFS的低轨卫星系统中多普勒斜视效应破坏信道稀疏性的问题，提出优化帧结构与先验辅助迭代信道重构算法，推导克拉美罗下界提供性能基准。
AI 中文摘要
正交时频空间（OTFS）调制已成为缓解低轨（LEO）卫星通信中严重多普勒频移的有前景方案。然而，LEO卫星高移动性导致的频率相关多普勒频移会引发多普勒斜视效应（DSE），该效应会破坏延迟-多普勒（DD）域的信道稀疏性，使现有信道估计方法失效。为克服这一挑战，本文针对基于循环前缀OTFS（CP-OTFS）的LEO卫星系统提出了一种抗DSE的传输方案。具体而言，我们分析了基于CP-OTFS的LEO卫星通信系统的输入输出关系，并推导了DD域中星地信道的DSE感知表示。为高效捕获DSE感知信道特性，我们提出了一种新型OTFS帧结构，该结构允许接收信号的能量分布作为信道估计的先验信息；同时，该帧结构合理分配导频符号以实现均匀能量分布并降低峰均功率比（PAPR），还施加了时域波形连续性约束以抑制矩形脉冲引发的带外辐射（OOBE）。基于该帧结构，我们提出了先验辅助迭代信道重构（PAICR）算法以缓解DSE引发的严重功率泄漏；该算法利用多普勒域接收信号能量观测值迭代提取并去除主导信道分量，带有确保可靠终止的收敛准则。此外，本文推导了克拉美罗下界，为评估算法性能提供理论基准。
英文摘要
Orthogonal time frequency space (OTFS) modulation has emerged as a promising solution to mitigate the severe Doppler shift in low Earth orbit (LEO) satellite communications. However, the frequency-dependent Doppler shift induced by the high mobility of LEO satellites leads to the Doppler squint effect (DSE). This effect compromises the channel sparsity in the delay-Doppler (DD) domain, rendering existing channel estimation methods ineffective. To overcome this challenge, this paper proposes a DSE-resilient transmission scheme for cyclic prefix OTFS (CP-OTFS)-based LEO satellite systems. Specifically, we analyze the input-output relationship of the CPOTFS- based LEO satellite communication system and derive a DSE-aware representation of the satellite-terrestrial channel in the DD domain. To efficiently capture DSE-aware channel characteristics, we propose a novel OTFS frame structure that allows the energy distribution of the received signal to serve as prior information for channel estimation. Meanwhile, this frame structure strategically allocates pilot symbols to achieve uniform energy distribution and reduce the peak-to-average power ratio (PAPR), while imposing a time-domain waveform continuity constraint to suppress out-of-band emission (OOBE) caused by rectangular pulses. Based on the frame structure, we propose a prior-aided iterative channel reconstruction (PAICR) algorithm to mitigate the severe power leakage induced by DSE. The proposed algorithm iteratively extracts and removes dominant channel components using Doppler-domain received signal energy observations, with a convergence criterion ensuring reliable termination. Furthermore, a Cramer-Rao lower bound is derived to provide a theoretical benchmark for evaluating the algorithm's performance.
Comments16 pages, 10 figures, Accepted by IEEE Transactions on Wireless Communications
