Backup Routing Method Considering Multiple Communication Link Failures in Optical Communication Satellite Networks

The demand for space communication has been escalating due to several factors such as the expanded use of Earth observation satellites, the need for alternative communication pathways during terrestrial communication disruptions caused by natural disasters, and the necessity for robust internet connectivity in maritime and aerial environments. To meet these demands, there is a growing focus on the development of non-terrestrial networks that integrate optical communication, which offers significantly higher data rates than traditional radio frequency communication, with low Earth orbit (LEO) satellite constellations that ensure broad coverage with low latency. However, LEO optical communication constellation networks face unique challenges. These include the dynamic nature of communication links due to the orbital movement of satellites, interruptions caused by cloud cover, and the increased risk of equipment failures or malfunctions in the harsh space environment. Traditional routing methods used in terrestrial networks, when applied directly to LEO optical communication constellations, lead to frequent link switches and unexpected link failures, resulting in data loss and increased latency. This paper proposes a novel routing method to mitigate the impact of unpredictable link failures across multiple communication links, thereby minimizing packet loss and delay. For each satellite, the proposed method selects multiple communication links in the network and pre-calculates backup routing tables to be robust against the failures of the selected links. Each satellite can autonomously decide which backup table to use based on the current network status, ensuring a swift and efficient response to sudden link failures. The selection process for multiple communication links to anticipate potential failures is based on the hop count from each satellite to the link and the overall placement of ground stations within the network. This proactive strategy improves both the reliability and efficiency of LEO optical communication satellite constellations. To evaluate the effectiveness of the proposed routing method, we model the structure and data flow of a LEO optical communication satellite constellation network. This modeling facilitates precise simulation of network operations under various conditions. Numerical simulations are conducted with scenarios where sudden link failures can occur. We assess the communication performance from the simulation results and demonstrate the proposed method's capability to enhance the robustness and efficiency of LEO optical communication satellite constellation networks.