# GPU-Accelerated Eclipse-Aware Routing for SpaceWire-Based OBC in Low-Earth-Orbit Satellite Networks
## 1 Introduction  
As the global demand for fast and stable communication networks continues to rise, satellite-based networks are gaining attention as a complementary solution to traditional communication infrastructure. In particular, LEO satellite networks, which can effectively cover the entire globe while providing low latency, are emerging as a key technology for next-generation satellite communications [1, 2]. LEO satellite networks enable high-speed internet services even in regions with underdeveloped terrestrial infrastructure. Additionally, large-scale satellite deployments, such as mega-constellations, can connect the world into a single network, while advancements in laser communication technology facilitate high-speed data transmission. Due to these advantages, LEO satellites are being utilized across various fields, including disaster relief, logistics tracking, and maritime and aviation communications [3]. Routing algorithms are as essential in LEO satellite networks as they are in terrestrial networks. However, the unique characteristics of LEO satellites make it challenging to directly apply conventional routing algorithms. Compared to Medium-Earth-Orbit (MEO) and Geostationary-Earth-Orbit (GEO) satellites, LEO satellites are positioned closer to the Earth's surface, resulting in reduced latency and lower path loss [4, 5]. While these attributes offer advantages, they also introduce significant challenges. To achieve globalcoverage, LEO satellite networks require the deployment of hundreds or even thousands of satellites. Furthermore, the high mobility of LEO satellites leads to a highly dynamic network topology, posing a critical challenge in satellite routing research. Due to their continuous movement relative to the Earth, inter-satellite links frequently change, creating a dynamic topology that must be efficiently managed [6; 7; 8]. As a result, extensive research is being conducted to develop routing strategies that account for the specific characteristics of LEO satellite networks. Energy constraints are also a critical factor in LEO satellite networks. When a satellite is exposed to sunlight, it generates energy through solar panels, which is used for data processing and communication while simultaneously charging its onboard battery. However, when the satellite enters the Earth's shadow region, known as an eclipse, it can no longer receive solar energy and must rely solely on stored battery power to maintain its operations. During this period, the number of charge and discharge cycles of the battery is limited, a phenomenon referred to as the Depth of Discharge (DoD) cycle. As DoD increases, the maximum number of charge-discharge cycles decreases, leading to a reduction in the battery's overall lifespan. Therefore, to maintain a low DoD level and prolong battery life, excessive energy consumption must be avoided during eclipse periods [9; 10; 11]. This paper proposes an Eclipse-Aware Routing (EAR) approach based on the K-Shortest Path (KSP) algorithm, which incorporates satellite battery status and eclipse conditions into the routing decision process. Unlike conventional shortest path algorithms that determine only a single optimal route, the KSP algorithm identifies a set of K shortest path candidates. This feature is particularly beneficial in LEO satellite networks, where frequent disruptions in inter-satellite links are likely due to high mobility. The primary goal of this work is to enhance the robustness and energy efficiency of routing under realistic LEO conditions, where dynamic topology changes and energy constraints coexist. The KSP algorithm was selected to support this goal by enabling proactive route planning with multiple alternatives, allowing the system to adapt quickly to link failures and reduce the need for repeated full-route recalculations. By preemptively securing multiple alternative routes, network disconnections can be effectively mitigated [12].