Towards Coverage-Aware Cooperative Video Caching in LEO Satellite Networks

Video services such as short video sharing have exploded due to the rapid development of Internet social media platforms. Caching video segments on satellites effectively shortens service delay and speeds up video sharing, especially for users without terrestrial Internet access. However, where to place what video and how to replace it in time is by no means an easy task, requiring careful consideration of many factors, e.g., satellite coverage, video popularity, and limited caching resource. In this paper, we propose a coverage-aware cooperative video caching algorithm (CACVC) that considers the prevalence of video in the coverage area and the collaboration between adjacent satellites. In CACVC, we model the cache placement problem of video as a Partially Observable Markov Decision Process (POMDP) to optimize the service delay of video provided by access satellites, neighboring satellites, or ground stations. We derive the optimal cache strategy by utilizing Multi-Agent Deep Deterministic Policy Gradient (MADDPG) algorithm with a centralized training and distributed execution paradigm. Simulation results show that the cache hit ratio can be improved by 4%~18%, and the average service delay can be reduced by 1%~14%.