Coded Caching in Satellite Networks

Coded caching is an effective technique to reduce the downlink traffic on the network. While coded caching has been extended to many scenarios, coded caching in satellite networks has not been well investigated in the literature. In this paper, we introduce a novel model of coded caching in satellite networks, which consists of P satellites periodically moving in a given orbit and K users on the earth. In this model, at each timeslot, every satellite (regarded as a server) serves Q consecutive users in a regime, while each user can access one satellite. Due to the cyclic mobility of satellites, the connections between satellites and users could be predictable but also dynamically change in a cyclic shift pattern. Thus, the connections between different satellites and different users at different timeslots could be highly coupled. Taking advantage of the predictable connections, we propose a centralized achievable scheme such that different satellites can serve the users jointly. For the converse bound, we introduce a novel method to construct request patterns such that the connections between users and satellites involved could be decoupled. The gap between the achievable rate and the converse bound is shown to be at most a constant. Numerical results for the performance of our scheme are also demonstrated.