In this paper, we present the vision of our project 6G for Connected Sky (6G-SKY) to integrate terrestrial networks (TNs) and non-terrestrial networks (NTNs) and outline the current research activities in 6G research projects in comparison with our project. From the perspectives of industry and academia, we identify key use case segments connecting both aerial and ground users with our 6G-SKY multi-layer network architecture. We explain functional views of our holistic 6G-SKY architecture addressing the heterogeneity of aerial and space platforms. Architecture elements and communication links are identified. We discuss 6G-SKY network design and management functionalities by considering a set of inherent challenges posed by the multi-layer 3-dimensional networks, which we termed as combined airspace and NTN (combined ASN). Finally, we investigate additional research challenges for 6G-SKY project targets.

翻译：本文阐述了我们的“6G面向连接天空”（6G-SKY）项目融合地面网络（TNs）与非地面网络（NTNs）的愿景，并概述了当前6G研究项目中的研究活动及其与我们的项目比较。从工业界和学术界视角，我们识别了连接空中与地面用户的关键用例细分领域，并基于6G-SKY多层网络架构进行了阐述。我们解析了面向空中与空间平台异构性的整体6G-SKY架构功能视图，明确了架构要素与通信链路。通过考虑多层三维网络（我们称之为组合空域与非地面网络，即组合ASN）所固有的挑战，我们探讨了6G-SKY网络设计与管理功能。最后，我们进一步研究了6G-SKY项目目标所面临的额外研究挑战。