SpaceCache+: Towards Pervasive Content Delivery via Low-Earth Orbit Mega-Constellations

Emerging Low-Earth Orbit (LEO) mega-constellations face challenges such as limited bandwidth and highly variable user demand, which can degrade network performance and lead to inefficient satellite resource utilization. One promising solution is to enable Content Delivery Networks (CDNs) within LEO satellites by deploying cache-equipped satellites. However, many existing approaches rely on inter-satellite links, which are not widely used in practice and are typically activated only when terrestrial ground station coverage is insufficient. Furthermore, the dynamic coverage patterns of satellites and diverse regional content preferences add to the complexity of efficient CDN deployment in space. To address these challenges, we propose SpaceCache+, a satellite-based CDN framework. We introduce a new metric, user benefit, that jointly captures user coverage and latency reduction to assess the effectiveness of cache satellite deployment. Recognizing that deployment typically occurs incrementally, we formulate the User Benefit-centric Cache Satellite Deployment problem and design an efficient heuristic solution. To enhance content placement, we also propose a cache replacement policy based on zero-shot meta-learning, which adapts to both regional content popularity and satellite mobility. We evaluate the performance of SpaceCache+ using real-world constellation settings with CDN traces. Compared with benchmark strategies, SpaceCache+ improves user benefit and cache hit ratio by up to 66.29% and 77.12%, respectively.