Implementation, Design and Performance Evaluation of Scheduling Protocols for Non-Terrestrial Networks (NTN)

The consolidation of fifth generation cellular system (5G) and the imminent arrival of the sixth generation mobile systems (6G) have improved internet coverage, especially in the urban areas. These advancements promise to revolutionize various sectors, including healthcare, transportation, and entertainment, by enabling faster data transmission and more reliable connections. On the other hand, this will lead to new challenges to be faced, like extending coverage to remote areas and enhancing disaster response and recovery. In addressing this, the research community is focusing on Non-Terrestrial Networks (NTN), which utilize Unmanned Aerial Vehicles (UAVs), High Altitude Platforms (HAPs), and satellites as aerial or space gateways. These platforms are positioned to play a crucial role in achieving the ambitious goals of 5G and beyond, especially in areas where terrestrial infrastructure is lacking or impractical. Despite their potential benefits, NTN present unique engineering challenges: factors such as the high mobility and long propagation delays inherent to satellite communications, and the unpredictability of intermittent connectivity necessitate innovative solutions in network design and management. Efficient scheduling protocols are particularly critical in these networks, as they directly impact the quality of service and overall network performance. Acknowledging these challenges, this thesis adopts a comprehensive approach into the design and optimization of NTN. Notably, we explore the performance of 3rd Generation Partnership Project (3GPP)-like terrestrial scheduling, and propose new solutions specifically tailored to the NTN satellite scenario. To evaluate the performance of our models, we use the ns-3 full-stack end-to-end network simulator, which guarantees that numerical results are realistic. Specifically, we extend the ns3-ntn module, that currently implements the NTN channel model and physical layer, to simulate scheduling. First, the work focuses on the weaknesses of User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) in scenarios with large propagation delay. Then, disadvantages of Grant Based Scheduler (GBS) approach will be highlighted and discussed. For this reason, a dedicated Semi Persistent Scheduling (SPS) approach will be implemented and tested in periodic and aperiodic traffic scenarios.