High-Altitude Platform Stations as IMT Base Stations: Connectivity from the Stratosphere.

High-altitude platform station (HAPS) as International Mobile Telecommunications (IMT) base station (HIBS) has been attracting the attention of aerospace and telecommunication companies from many countries in recent years. The HIBS' remarkable differential feature is the possibility of using HAPS to complement the IMT terrestrial coverage, benefiting from the platforms being located in the stratosphere, enabling much wider coverage when compared to conventional terrestrial solutions. In addition, the COVID-19 pandemic has highlighted the technological and social differences among countries, mainly due to the poor quality, or even absence, of Internet connectivity. HIBSs might efficiently support reducing the digital divide, since they provide connectivity to the same mobile devices as the terrestrial networks, which allows this non-terrestrial connectivity solution to increase global coverage and expand mobile connectivity for everyone. This article describes the fundamentals of the HIBS, as well as its deployment scenarios and regulatory aspects. Furthermore, it is reported, for the first time in the literature, a coexistence analysis between HIBS and fixed services point-to-point (FS-PP), as an International Telecommunication Union - Radio-communication Sector preparatory study for the support of decisions to be made at the 2023 World Radiocommunication Conference. The simulations demonstrate the feasibility of coexistence between HIBS and FS-PP active links, sharing the HIBS Band 2 around 2 GHz. [ABSTRACT FROM AUTHOR]