The Doppler spread in a highly dynamic environment leads to a large-scale channel variation over time for unmanned aerial vehicles (UAVs). In this letter, we adopt the high spatial resolution of massive multi-input multi-output (MIMO) technology to reduce the influence of Doppler spread. An algorithm is proposed for the asymptotically-optimal steering angle to achieve the longest virtual coherence time for large antenna arrays. We first design a matrix to detect array steering vectors of separated propagation paths. A closed-form expression of virtual coherence time over virtual channel for large antenna arrays is therefore derived for the optimal steering angle. Simulation results show that our proposed algorithm can improve the average virtual coherence time by about 13.65 to 27.35 times as compared to benchmarks.

中文翻译：

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用于随时间变化的无人机通信信道的高空间分辨率的最佳阵列转向

高度动态环境中的多普勒扩展会导致无人机 (UAV) 随时间发生大规模信道变化。在这封信中，我们采用了大规模多输入多输出（MIMO）技术的高空间分辨率来减少多普勒扩展的影响。提出了一种渐近最优转向角算法，以实现大型天线阵列的最长虚拟相干时间。我们首先设计一个矩阵来检测分离传播路径的阵列导向向量。因此，对于最佳转向角，导出了大型天线阵列虚拟信道上虚拟相干时间的封闭形式表达式。仿真结果表明，与基准相比，我们提出的算法可以将平均虚拟相干时间提高约 13.65 到 27.35 倍。