Providing seamless connectivity to unmanned aerial vehicle user equipment (UAV-UE) is very challenging due to the encountered line-of-sight interference and reduced gains of down-tilted base station (BS) antennas. For instance, as the altitude of UAV-UEs increases, their cell association and handover procedure become driven by the side-lobes of the BS antennas. In this paper, the performance of cellular-connected UAV-UEs is studied under 3D practical antenna configurations. Two scenarios are studied: scenarios with static, hovering UAV-UEs and scenarios with mobile UAV-UEs. For both scenarios, the UAV-UE coverage probability is characterized as a function of the system parameters. The effects of the number of antenna elements on the UAV-UE coverage probability and handover rate are then investigated. Moreover, a lower bound on the handover probability is derived as a function of the number of antenna elements and the UAV-UE mobility speed. Results reveal that the UAV-UE coverage probability under a practical antenna pattern is lower than that under a simple antenna model. Moreover, vertically-mobile UAV-UEs are susceptible to altitude handover due to consecutive crossings of the nulls and peaks of the antenna side-lobes. The effect of altitude handover is also shown to be effectively mitigated by serving UAV-UEs cooperatively from multiple ground BSs.

中文翻译：

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实际天线配置下移动蜂窝连接无人机的性能

由于遇到视距干扰和下倾基站 (BS) 天线的增益降低，​​为无人机用户设备 (UAV-UE) 提供无缝连接非常具有挑战性。例如，随着 UAV-UE 的高度增加，它们的小区关联和切换过程由 BS 天线的旁瓣驱动。在本文中，研究了蜂窝连接 UAV-UE 在 3D 实际天线配置下的性能。研究了两种场景：静态、悬停 UAV-UE 的场景和移动 UAV-UE 的场景。对于这两种情况，UAV-UE 覆盖概率被表征为系统参数的函数。然后研究了天线单元数量对 UAV-UE 覆盖概率和切换率的影响。而且，切换概率的下限是作为天线单元数量和 UAV-UE 移动速度的函数得出的。结果表明，实际天线方向图下的无人机-UE覆盖概率低于简单天线模型下的覆盖概率。此外，垂直移动的 UAV-UE 容易受到由于天线旁瓣的零点和峰值的连续交叉而导致的高度切换。通过从多个地面 BS 协作服务 UAV-UE 也可以有效地减轻高度切换的影响。