A Survey on Constellation Routing Methods in 6G Non-Terrestrial Networks

In the era of 6G, Non-Terrestrial Networks (NTNs) are gaining attention due to their potential to provide global coverage and enhanced connectivity. This survey explores the diverse routing methods employed in NTN constellations, focusing on centralized, distributed, and hybrid approaches. Centralized routing, incorporating AI control layers and reinforcement learning, offers global optimization, reducing latency and packet loss. Distributed routing methods like LCO-RIP and ADR address link congestion and enhance flexibility and responsiveness in dynamic environments. Hybrid routing strategies, exemplified by MaCRo and SDMCN architectures, integrate the advantages of centralized and distributed methods, optimizing data transmission and reliability. Evaluations based on parameters like end-to-end delay, packet loss rate, and throughput highlight the effectiveness of these routing strategies. The survey underscores the significant achievements in improving network performance and reliability, providing a comprehensive foundation for the efficient operation of NTN constellation systems in 6G networks.