For unforeseen emergencies, such as natural disasters and pandemic events, it is highly demanded to cope with the explosive growth of mobile data traffic in extremely critical environments. An Unmanned aerial vehicle (UAV) fleet is an effective way to facilitate the Emergency wireless COmmunication NETwork (EcoNet). In this article, a MUlti-tier Heterogeneous UAV Network (MuHun), which is with different UAV fleets in different altitudes, is proposed to flexibly serve various emergencies. We refresh the key performance indicators of full coverage, network capacity, low latency, and energy efficiency in harsh environments. Then, we present the special challenges regarding shadowing-dominated complex channel model, energy supply limited short-endurance, various communication mechanisms coexistence, and communication island for underground users in UAV-based EcoNet, followed by the MuHun-based EcoNet architecture and its advantages. Furthermore, some potential solutions such as the new hybrid-channel adapted resource allocation, reconfigurable intelligent surface assisted UAV communications, competitive heterogenous-networks, and magnetic induction based air-to-ground/underground communications are discussed to effectively achieve full coverage, high capacity, high energy efficiency, and diverse qualities of services for EcoNets in harsh environments.

翻译：针对自然灾害和疫情事件等突发紧急情况，亟需在极端关键环境中应对移动数据流量的爆炸式增长。无人机编队是构建应急无线通信网络的有效途径。本文提出一种多层级异构无人机网络，通过在不同高度部署差异化无人机编队，灵活应对各类突发事件。我们重新审视了恶劣环境下全覆盖、网络容量、低时延与能效等关键性能指标。随后，分析了无人机应急通信网络面临的特殊挑战：阴影主导的复杂信道模型、能源受限的短续航问题、多通信机制共存困境以及地下用户通信孤岛现象，继而阐述了基于多层级异构网络的应急通信体系架构及其优势。此外，探讨了若干潜在解决方案：新型混合信道自适应资源分配、可重构智能表面辅助无人机通信、竞争式异构网络以及基于磁感应的空-地/地下通信技术，以实现在恶劣环境下为应急通信网络提供全覆盖、高容量、高能效及多样化服务质量保障。