用智能表面与无人机协同波束成形,提升低空通信信号质量。
STAR-RIS-assisted Collaborative Beamforming for Low-altitude Wireless Networks
- 联合优化无人机与智能表面的波束成形策略
- 系统速率随无人机和智能表面元素数量增加而提升
- 适合研究低空网络、智能反射面应用的工程师
基于无人飞行器的低空无线网络(LAWNs)虽具高移动性与广覆盖优势,但在密集城市环境中易受遮挡导致信号衰减严重。为此,本文引入无人机协同波束成形(CB)与同时收发型可重构智能表面(STAR-RIS)的全向波束成形(ORB),以增强信号质量与方向性。在此基础上,提出联合速率与能耗优化问题(JREOP),旨在最大化系统传输速率并最小化无人机集群能耗。由于该问题非凸且为NP难,本文设计异构多智能体协作动态(HMCD)优化框架,包含基于模拟退火的STAR-RIS控制方法(动态优化反射/透射系数)与改进的多智能体深度强化学习方法(融合自注意力机制捕捉无人机间交互,采用自适应速度转移机制提升训练稳定性)。仿真表明,HMCD在收敛速度、平均传输速率与能耗方面均优于多个基线。进一步分析显示,系统平均传输速率随无人机数量与STAR-RIS元件数增加而正向增长。
原文摘要 · Abstract (English)
While low-altitude wireless networks (LAWNs) based on uncrewed aerial vehicles (UAVs) offer high mobility, flexibility, and coverage for urban communications, they face severe signal attenuation in dense environments due to obstructions. To address this critical issue, we consider introducing collaborative beamforming (CB) of UAVs and omnidirectional reconfigurable beamforming (ORB) of simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS) to enhance the signal quality and directionality. On this basis, we formulate a joint rate and energy optimization problem (JREOP) to maximize the transmission rate of the overall system, while minimizing the energy consumption of the UAV swarm. Due to the non-convex and NP-hard nature of JREOP, we propose a heterogeneous multi-agent collaborative dynamic (HMCD) optimization framework, which has two core components. The first component is a simulated annealing (SA)-based STAR-RIS control method, which dynamically optimizes reflection and transmission coefficients to enhance signal propagation. The second component is an improved multi-agent deep reinforcement learning (MADRL) control method, which incorporates a self-attention evaluation mechanism to capture interactions between UAVs and an adaptive velocity transition mechanism to enhance training stability. Simulation results demonstrate that HMCD outperforms various baselines in terms of convergence speed, average transmission rate, and energy consumption. Further analysis reveals that the average transmission rate of the overall system scales positively with both UAV count and STAR-RIS element numbers.
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