Cooperative regional caching and distribution in space-terrestrial integrated networks

Satellites can offer wide coverage for almost all geographical environment together with terrestrial networks, providing mobile users better services. However, the delay of satellite-to-terrestrial backhaul link is large, and satellite network topology changes dynamically. Therefore, caching content on satellites can quickly and efficiently transmit data to users. Due to the limited resources on the satellite, the cache strategy needs to achieve efficient content transmission with small cache redundancy. This paper proposes a caching and distribution strategy with regional cooperation. We divide the network topology into multiple regions, and find the collection of similar regions based on the regional cache similarity defined by the similarity of the requested content and the geographic distance among regions. Then, using the similar regions, we remove redundant content, and when the request does not hit in the regional cache, it will search for content among similar regions. Simulation shows that this solution can reduce cache redundancy, improve cache hit rate and network throughput. In addition, we optimized the scheme of content transmission between cached satellites when the snapshot is switched, avoiding repeated requests for content from the terrestrial server, and reducing the waste of inter-satellite link resources caused by transmission back and forth between orbits. Simulation results given in the paper show the effectiveness of the proposed scheme.