Analysis of Laser Inter-Satellite Links and Topology Design for Mega-Constellation Networks

Mega-Constellation Networks (MCNs), comprising an expansive array of orbits and satellites, will be a pivotal component of the prospective Non-Terrestrial Network (NTN). Laser inter-satellite links (LISLs) represent a promising technology for the establishment of satellite networks, offering high capacity and highly reliable communication links. Nevertheless, LISL still has some technical challenges, such as link establishment instability, satellite payload capacity and topology design. For a considerable number of satellites and laser communication constraints, LISLs have elevated the complexity and difficulty of routing and topology construction. In this paper, we focus on the LISL connecting stability and propose a novel method to evaluate the inter-satellite link selection based on the acquisition probability of the laser terminal system. Subsequently, a non-linear optimization model is formulated for the laser link selection problem, where the terminal acquisition probability is maximized. Finally, an MCN topology design algorithm (MTDA) is proposed to establish greater stability and higher channel gain within the different access distances of the laser terminal. Using the satellite constellation for Phase 1 of Starlink, three different laser MCN topologies were constructed by MTDA, adapting to the maximum access distance of the laser terminal within 5,000 kilometers. The impact of these differing topologies on network latency and hop count was then analyzed in a full satellite period. Compared with the baseline, MTDA has a 15.7% latency advantage and 14.0% hop advantage under the same access distance of laser terminal. The numerical results show that the proposed algorithm has a positive impact on the average network latency, hop count and their respective variances.