6G networks are expected to integrate low Earth orbit satellites to ensure global connectivity by extending coverage to underserved and remote regions. However, the deployment of dense mega-constellations introduces severe interference among satellites operating over shared frequency bands. This is, in part, due to the limited flexibility of conventional frequency division duplex (FDD) systems, where fixed bands for downlink (DL) and uplink (UL) transmissions are employed. In this work, we propose dynamic re-assignment of FDD bands for improved interference management in dense deployments and evaluate the performance gain of this approach. To this end, we formulate a joint optimization problem that incorporates dynamic band assignment, user scheduling, and power allocation in both directions. This non-convex mixed integer problem is solved using a combination of equivalence transforms, alternating optimization, and state-of-the-art industrial-grade mixed integer solvers. Numerical results demonstrate that the proposed approach of dynamic FDD band assignment significantly enhances system performance over conventional FDD, achieving up to 94\% improvement in throughput in dense deployments.

翻译：6G网络预计将集成低地球轨道卫星，通过将覆盖范围扩展至服务不足和偏远地区来确保全球连接。然而，密集巨型星座的部署在共享频段上运行的卫星之间引入了严重干扰。这部分是由于传统频分双工（FDD）系统的灵活性有限，其采用固定的下行链路（DL）和上行链路（UL）传输频段。在本研究中，我们提出动态重新分配FDD频段以改善密集部署中的干扰管理，并评估该方法的性能增益。为此，我们构建了一个联合优化问题，该问题结合了双向的动态频段分配、用户调度和功率分配。这一非凸混合整数问题通过等价变换、交替优化和最先进的工业级混合整数求解器的组合得以解决。数值结果表明，所提出的动态FDD频段分配方法在密集部署中显著提升了系统性能，相比传统FDD实现了高达94%的吞吐量改进。