The upcoming sixth generation (6G) wireless communication network is envisioned to cover space, air, and maritime areas, in addition to urban-centered terrestrial coverage by the fifth generation (5G) network, to support intelligent Internet of Things (IoT). Towards this end, we investigate structured integration of satellites, unmanned aerial vehicles (UAVs), and terrestrial networks, aiming to serve future universal IoT possibly with a massive number of devices in the coverage holes of current 5G. The hybrid satellite-UAV-terrestrial network usually leads to high system complexity, due to the heterogeneity and dynamics of space/air/ground links. With a systematic thinking, we propose to create and exploit hierarchies for the integrated network. Four basic structures are discussed by learning from the synergies in our human body. To orchestrate multiple heterogeneous basic structures, we further propose a process-oriented on-demand coverage method, which characterizes the system behavior as a series of events over time and is able to tackle the system complexity elaborately. We also outline open issues for promoting the agility and intelligence of structured satellite-UAV-terrestrial networks in the making.

翻译：即将到来的第六代（6G）无线通信网络被设想为在第五代（5G）网络以城市为中心的地面覆盖基础上，进一步覆盖太空、空中及海洋区域，以支持智能物联网（IoT）。为此，我们研究了卫星、无人机（UAV）与地面网络的结构化集成，旨在服务于未来可能拥有海量设备的通用物联网，尤其是填补当前5G覆盖盲区。由于空间/空中/地面链路的异构性与动态性，混合卫星-无人机-地面网络通常导致系统复杂度较高。基于系统思维，我们提出为集成网络创建并利用层次结构。通过借鉴人体协同机制，讨论了四种基本结构。为协调多个异构基本结构，我们进一步提出一种面向过程的按需覆盖方法，该方法将系统行为表征为随时间推移的一系列事件，能够精细应对系统复杂性。我们还概述了推动构建中的结构化卫星-无人机-地面网络具备敏捷性与智能性的开放性问题。