We consider a cellular network deployment where UAV-to-UAV (U2U) transmit-receive pairs share the same spectrum with the uplink (UL) of cellular ground users (GUEs). For this setup, we focus on analyzing and comparing the performance of two spectrum sharing mechanisms: (i) underlay, where the same time-frequency resources may be accessed by both UAVs and GUEs, resulting in mutual interference, and (ii) overlay, where the available resources are divided into orthogonal portions for U2U and GUE communications. We evaluate the coverage probability and rate of both link types and their interplay to identify the best spectrum sharing strategy. We do so through an analytical framework that embraces realistic height-dependent channel models, antenna patterns, and practical power control mechanisms. For the underlay, we find that although the presence of U2U direct communications may worsen the uplink performance of GUEs, such effect is limited as base stations receive the power-constrained UAV signals through their antenna sidelobes. In spite of this, our results lead us to conclude that in urban scenarios with a large number of UAV pairs, adopting an overlay spectrum sharing seems the most suitable approach for maintaining a minimum guaranteed rate for UAVs and a high GUE UL performance.

中文翻译：

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蜂窝网络中的无人机到无人机通信

我们考虑蜂窝网络部署，其中 UAV 到 UAV (U2U) 发射-接收对与蜂窝地面用户 (GUE) 的上行链路 (UL) 共享相同的频谱。对于这种设置，我们重点分析和比较两种频谱共享机制的性能：（i）underlay，其中 UAV 和 GUE 可以访问相同的时频资源，导致相互干扰，以及（ii）overlay，其中可用资源被划分为正交部分，用于 U2U 和 GUE 通信。我们评估两种链路类型的覆盖概率和速率及其相互作用，以确定最佳频谱共享策略。我们通过一个包含实际高度相关信道模型、天线模式和实用功率控制机制的分析框架来实现这一点。对于底层，我们发现，虽然 U2U 直接通信的存在可能会恶化 GUE 的上行链路性能，但这种影响是有限的，因为基站通过其天线旁瓣接收功率受限的无人机信号。尽管如此，我们的结果使我们得出结论，在拥有大量无人机对的城市场景中，采用重叠频谱共享似乎是保持无人机最低保证速率和高 GUE UL 性能的最合适方法。