这篇研究论文提出了一种双基地低地球轨道（LEO）卫星综合感知与通信（ISAC）框架，旨在克服传统LEO卫星ISAC系统中的挑战，例如严重的雷达回波路径损耗、难以获取瞬时通信信道状态信息（CSI）以及函数间/函数内干扰管理。该框架通过将地面雷达接收器与LEO卫星分离来显著降低回波路径损耗，并利用速率分裂多址（RSMA）技术来有效管理通信用户和雷达功能之间的干扰，即使存在几何信道信息不确定性也能保持鲁棒性能。作者还开发了一种两层迭代优化算法来设计双功能预编码器，以在满足雷达性能要求（通过Cramér-Rao下界约束）的同时最大化最小用户速率。数值结果验证了所提出框架在减少路径损耗、增强抗干扰能力和对信道信息误差的鲁棒性方面的优势，并强调了公共流在雷达波束形成和多功能干扰管理中的关键作用。

A Bistatic ISAC Framework for LEO Satellite Systems: A Rate-Splitting Approach

Abstract:

Achieving ubiquitous connectivity and radar sensing on the same platform with improved spectral/energy efficiency is a critical challenge for low Earth orbit (LEO) satellite systems. To mitigate severe radar echo loss at high altitudes, we put forth a bistatic integrated sensing and communication (ISAC) framework, where a ground-based radar receiver operates separately from the satellite. For robust and effective interference management, we employ rate-splitting multiple access (RSMA), which splits and encodes users' messages into private and common streams. Instead of relying on instantaneous communication channel state information (CSI), we exploit the geometric and statistical characteristics of the satellite channel while accounting for uncertainty in the geometric information. Based on this practical modeling, we optimize the robust dual-functional precoders to maximize the minimum user rate while satisfying Cramér-Rao bound (CRB) constraints. To achieve this, we develop an efficient optimization algorithm using multiple mathematical relaxation techniques for joint precoder design. Numerical results show that the proposed framework efficiently performs both communication and radar sensing, exhibiting strong interference mitigation even under geometric channel uncertainty. Furthermore, it is validated that the common stream plays three vital roles: i) beamforming towards the radar target, ii) interference management between communications and radar, and iii) interference management among communication users. By leveraging the multi-functionality of the common stream, efficient and robust joint operation of radar sensing and communication is achieved even without requiring a dedicated radar sequence.

Published in: IEEE Transactions on Aerospace and Electronic Systems ( Early Access )

Page(s): 1 - 19

Date of Publication: 28 August 2025

ISSN Information:

Print ISSN: 0018-9251

Electronic ISSN: 1557-9603

CD: 2371-9877

DOI: 10.1109/TAES.2025.3603500

Publisher: IEEE