In this paper, we consider a cooperative communication network where multiple low-Earth-orbit satellites provide services for ground users (GUs) (at the same time and on the same frequency). The multi-satellite cooperative network has great potential for satellite communications due to its dense configuration, extensive coverage, and large spectral efficiency. However, the communication and computational resources on satellites are usually restricted. Therefore, considering the limitation of the on-board radio-frequency chains of satellites, we first propose a hybrid beamforming method consisting of analog beamforming for beam alignment and digital beamforming for interference mitigation. Then, to establish appropriate connections between the satellites and GUs, we propose a low-complexity heuristic user scheduling algorithm which determines the connections according to the total spectral efficiency increment of the multi-satellite cooperative network. Next, considering the intrinsic connection between beamforming and user scheduling, a joint hybrid beamforming and user scheduling (JHU) scheme is proposed to dramatically improve the performance of the multi-satellite cooperative network. In addition to the single-connection scenario, we also consider the multi-connection case using the JHU scheme. Moreover, simulations are conducted to compare the proposed schemes with representative baselines and to analyze the key factors influencing the performance of the multi-satellite cooperative network.

翻译：本文研究了一种多颗低轨卫星同时在相同频率上为地面用户提供服务的协作通信网络。多卫星协作网络因其密集的配置、广泛的覆盖范围和大频谱效率而在卫星通信领域具有巨大潜力。然而，卫星上的通信与计算资源通常受限。因此，考虑到卫星星载射频链路的限制，我们首先提出了一种混合波束赋形方法，该方法包含用于波束对准的模拟波束赋形和用于干扰抑制的数字波束赋形。随后，为建立卫星与地面用户之间的适当连接，我们提出了一种低复杂度启发式用户调度算法，该算法根据多卫星协作网络的总频谱效率增量来确定连接关系。进而，考虑到波束赋形与用户调度之间的内在联系，我们提出了一种联合混合波束赋形与用户调度（JHU）方案，以显著提升多卫星协作网络的性能。除单连接场景外，我们还考虑了采用JHU方案的多连接情况。此外，通过仿真将所提方案与代表性基线方法进行了对比，并分析了影响多卫星协作网络性能的关键因素。