Future wireless networks, in particular, 5G and beyond, are anticipated to deploy dense Low Earth Orbit (LEO) satellites to provide global coverage and broadband connectivity. However, the limited frequency band and the coexistence of multiple constellations bring new challenges for interference management. In this paper, we propose a robust multilayer interference management scheme for spectrum sharing in heterogeneous satellite networks with statistical channel state information (CSI) at the transmitter (CSIT) and receivers (CSIR). In the proposed scheme, Rate-Splitting Multiple Access (RSMA), as a general and powerful framework for interference management and multiple access strategies, is implemented distributedly at GEO and LEO satellites, coined Distributed-RSMA (D-RSMA). By doing so, D-RSMA aims to mitigate the interference and boost the user fairness of the overall multilayer satellite system. Specifically, we study the problem of jointly optimizing the GEO/LEO precoders and message splits to maximize the minimum rate among User Terminals (UTs) subject to a transmit power constraint at all satellites. A robust algorithm is proposed to solve the original non-convex optimization problem. Numerical results demonstrate the effectiveness and robustness towards network load and CSI uncertainty of our proposed D-RSMA scheme. Benefiting from the interference management capability, D-RSMA provides significant max-min fairness performance gains compared to several benchmark schemes.

翻译：未来无线网络，特别是5G及以后，预计将部署密集的低地球轨道（LEO）卫星，以提供全球覆盖和宽带连接。然而，有限的频带和多个星座的共存给干扰管理带来了新的挑战。本文提出了一种稳健的多层干扰管理方案，用于在具有发射端（CSIT）和接收端（CSIR）统计信道状态信息（CSI）的异构卫星网络中进行频谱共享。在所提出的方案中，速率分裂多址接入（RSMA）作为一种通用且强大的干扰管理和多址接入策略框架，被分布式地部署在地球同步轨道（GEO）和低地球轨道（LEO）卫星上，称为分布式RSMA（D-RSMA）。通过这种方式，D-RSMA旨在减轻干扰并提升整个多层卫星系统的用户公平性。具体而言，我们研究了联合优化GEO/LEO预编码器和消息分裂的问题，以在所有卫星的发射功率约束下最大化用户终端（UT）中的最小速率。提出了一种稳健算法来解决原始非凸优化问题。数值结果表明，我们提出的D-RSMA方案在网络负载和CSI不确定性方面具有有效性和稳健性。得益于其干扰管理能力，D-RSMA在最大最小公平性性能方面相比几种基准方案带来了显著增益。