Space-Air-Ground integrated 6G wireless communication networks: a review of antenna technologies and application scenarios

A review of technological solutions and advances in the framework of a Vertical Hetero-15 geneous Network (VHetNet) integrating satellite, airborne and terrestrial networks is presented. 16 The disruptive features and challenges offered by a fruitful cooperation among these segments 17 within a ubiquitous and seamless wireless connectivity are described. The available technologies 18 and the key research directions for achieving a global wireless coverage by considering all these 19 layers are thoroughly discussed. Emphasis is put on the available antenna systems in satellite, air-20 borne and ground layers by highlighting strengths and weakness as well as by providing some 21 interesting trends in research. A summary of the most suitable applicative scenarios for future 6G 22 wireless communications are finally illustrated.