Satellite-terrestrial integrated networks (STINs) are promising architecture for providing global coverage. In STINs, full frequency reuse between a satellite and a terrestrial base station (BS) is encouraged for aggressive spectrum reuse, which induces non-negligible amount of interference. To address the interference management problem in STINs, this paper proposes a novel distributed precoding method. Key features of our method are: i) a rate-splitting (RS) strategy is incorporated for efficient interference management and ii) the precoders are designed in a distributed way without sharing channel state information between a satellite and a terrestrial BS. Specifically, to design the precoders in a distributed fashion, we put forth a spectral efficiency decoupling technique, that disentangles the total spectral efficiency function into two distinct terms, each of which is dependent solely on the satellite's precoder and the terrestrial BS's precoder, respectively. Then, to resolve the non-smoothness raised by the RS strategy, we approximate the spectral efficiency expression as a smooth function by using the LogSumExp technique; thereafter we develop a generalized power iteration inspired optimization algorithm built based on the first-order optimality condition. Simulation results demonstrate that the proposed method offers considerable spectral efficiency gains compared to the existing methods.

翻译：星地一体化网络（STINs）是为实现全球覆盖而提出的有前景架构。在STINs中，鼓励卫星与地面基站（BS）之间采用全频率复用以实现激进的频谱复用，但这会引入不可忽略的干扰。为解决STINs中的干扰管理问题，本文提出了一种新颖的分布式预编码方法。该方法的核心特征包括：i）引入速率分裂（RS）策略以实现高效干扰管理；ii）在卫星与地面基站之间不共享信道状态信息的情况下，以分布式方式设计预编码器。具体而言，为实现分布式预编码设计，我们提出了一种频谱效率解耦技术，将总频谱效率函数分解为两个独立项，分别仅依赖于卫星预编码器和地面基站预编码器。随后，为解决RS策略带来的非平滑性，我们利用LogSumExp技术将频谱效率表达式近似为平滑函数；进而基于一阶最优性条件开发了一种基于广义幂迭代的优化算法。仿真结果表明，与现有方法相比，所提方法可带来显著的频谱效率增益。