2025

Majamaa, Mikko

5G introduces a paradigm shift to mobile communications with stringent performance and the introduction of satellite communications into the ecosystem. In the past, mobile and satellite communications have been separate markets, but recent technological advancements and standardization activities have enabled the deployment of 5G and beyond via satellites. These advancements include improved reusable launch vehicles and mass satellite manufacturing. Standardization activities can be attributed to the efforts of mobile communications standards organizations, such as the 3rd Generation Partnership Project (3GPP). In 2022, 3GPP included satellite and airborne communications, also known as 3GPP Non-Terrestrial Networks (NTNs), in its Release 17 standards. The focus of this thesis is satellite communications. In 5G, the integration of NTNs into the existing mobile communications ecosystem is accomplished by adapting NTNs to Terrestrial Networks (TNs). In 6G, however, NTNs and TNs will make up a unified network, meaning that the standards will consider the unique characteristics of each system from the outset. The vision of satellite communications in 5G and beyond has been laid out by industry and academia. However, there are still open issues to be addressed before this vision can be realized. This thesis aims to address some of these issues by advancing the integration of satellite communications into 5G and beyond. In particular, the performance of NTNs is studied, as is satellite integration into 5G through dynamic spectrum sharing and Multi-Connectivity (MC). In relation to the prior state of the art, this thesis provides novel perspectives on NTN performance and new algorithms for spectrum sharing and MC in NTNs. Furthermore, MC in NTNs has been an overlooked topic thus far. This thesis aims to fill this research gap in part. System-level simulations are used to back up the analysis and algorithms, which are readily available for industry and academia, providing real practical value in enhancing connectivity and, thus, increasing the quality of life for all.