We consider a cell-free massive multiple-input multiple-output (mMIMO) network, where unmanned aerial vehicles (UAVs) equipped with multiple antennas serve as distributed UAV-access points (UAV-APs). These UAV-APs provide seamless coverage by jointly serving user equipments (UEs) with out predefined cell boundaries. However, high-capacity wireless networks face significant challenges due to fronthaul limitations in UAV-assisted architectures. This letter proposes a novel UAV-based cell-free mMIMO framework that leverages distributed UAV-APs to serve UEs while addressing the capacity constraints of wireless fronthaul links. We evaluate functional split Options 7.2 and 8 for the fronthaul links, aiming to maximize the minimum signal-to-interference-plus-noise ratio (SINR) among the UEs and minimize the power consumption by optimizing the transmit powers of UAV-APs and selectively activating them. Our analysis compares sub-6 GHz and millimeter wave (mmWave) bands for the fronthaul, showing that mmWave achieves superior SINR with lower power consumption, particularly under Option 8. Additionally, we determine the minimum fronthaul bandwidth required to activate a single UAV-AP under different split options.

翻译：本文研究一种无蜂窝大规模多输入多输出网络，其中配备多天线的无人机作为分布式无人机接入点。这些无人机接入点通过联合服务用户设备提供无缝覆盖，无需预定义小区边界。然而，在无人机辅助架构中，前传限制给高容量无线网络带来了重大挑战。本通信提出一种基于无人机的创新无蜂窝大规模MIMO框架，该框架利用分布式无人机接入点服务用户设备，同时解决无线前传链路的容量约束问题。我们评估前传链路的功能切分选项7.2和8，通过优化无人机接入点的发射功率并选择性激活它们，旨在最大化用户设备间的最小信干噪比并降低功耗。我们的分析比较了前传链路的亚6GHz与毫米波频段，结果表明毫米波在选项8下能以更低功耗实现更优的信干噪比。此外，我们确定了在不同切分选项下激活单个无人机接入点所需的最小前传带宽。