This letter models the high-altitude air-to-ground (A2G) channel for aerial base stations (BSs), which are carried by fixed-wing unmanned aerial vehicles (UAVs). Different from ground BS, fixed-wing UAVs have to periodically hover to provide coverage to ground users (GUs), which may result in the instability of A2G wireless links. On the one hand, pathloss is modeled as a function of distance from UAV to GUs, which includes hover radius and flight altitude, and the elevation angle of GUs. On the other hand, the model of multipath and shadow (MS) fading is dependent on the elevation angle as well. Specifically, we show that generalized Gamma distribution is suitable to model MS fading under large elevation angle, while log-normal fading is suitable otherwise. Moreover, we further investigate the spatial-temporal correlation of the A2G channel, which is shown to depend on the movement distance/direction of GU and the distance from GU to the hover center.

中文翻译：

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固定翼无人机安装的空中基站的高空空地通道建模

这封信模拟了由固定翼无人驾驶飞机（UAV）承载的空中基站（BS）的高空空对地（A2G）通道。与地面BS不同，固定翼UAV必须定期悬停以向地面用户（GU）提供覆盖，这可能会导致A2G无线链路的不稳定。一方面，路径损耗被建模为从无人机到GUs的距离的函数，包括悬停半径和飞行高度以及GUs的仰角。另一方面，多径和阴影（MS）衰落模型也取决于仰角。具体来说，我们表明广义Gamma分布适合于在大仰角下模拟MS衰落，而对数正态衰落则适合于其他情况。此外，我们进一步研究了A2G频道的时空相关性，