AI 中文总结
研究多用户无人机辅助下行链路通信中联合无人机放置与波束成形问题，提出相关性感知几何框架，先依长期信道统计优化位置，再据瞬时 CSI 优化波束成形，可提升最小用户频谱效率。
AI 中文摘要
在多用户无人机辅助下行链路通信中，无人机放置和发射波束成形通过传播几何内在耦合。基于瞬时信道状态信息的完全联合设计不切实际，现有方法未针对用户间导向相关性引起的几何相关多用户干扰优化无人机位置。为此提出相关性感知几何框架，先基于长期信道统计优化无人机位置，利用保守高斯替代纳入导向向量相关性，再用连续凸近似等技术处理非凸定位问题，最后根据瞬时 CSI 优化发射波束成形。仿真结果表明该框架显著提高了最小用户频谱效率。
英文摘要
In multiuser unmanned aerial vehicle (UAV)-assisted downlink communications, UAV placement and transmit beamforming are inherently coupled through the propagation geometry. However, fully joint design based on instantaneous channel state information (CSI) is impractical, because the small-scale fading depends on the UAV location to be optimized and thus is unavailable a priori. Moreover, existing joint placement and beamforming methods do not explicitly optimize the UAV position with respect to the geometry-dependent multiuser interference induced by inter-user steering correlation. To address this issue, we propose a correlation-aware geometric framework for joint UAV placement and beamforming. Specifically, the UAV position is first optimized based on long-term channel statistics, where the steering-vector correlation is incorporated into the placement design through a conservative Gaussian surrogate that avoids interference underestimation. The resulting nonconvex positioning problem is then handled using successive convex approximation, auxiliary-variable decoupling, and quadratic transform techniques. For the obtained UAV location, the transmit beamformer is then optimized using instantaneous CSI. Simulation results show that the proposed framework significantly improves the minimum user spectral efficiency by enhancing angular separability among users and reducing inter-user interference. These results demonstrate that UAV placement should be designed not only for desired-link enhancement but also for interference mitigation through geometry-aware user separation.
Comments13 pages, 12 figures
