Coded Caching in Satellite Networks with Non-uniform User Distribution

Satellite networks are emerging rapidly to serve mobile users and vehicles on the ground. To alleviate the downlink transmissions between moving satellites and ground users, [12] proposes to adopt coded caching in satellite networks. One key assumption in [12] is that, the users are assumed to be uniformly distributed on earth, which could be different from the reality. In this paper, we investigate coded caching in satellite networks with non-uniform user distribution. For arbitrary user distribution, we propose a decentralized coded caching scheme such that satellites can cooperatively serve the users. For the converse bound, basing on the concept of decoupling, we employ cut-set technique to characterize a novel lower bound. This converse bound is based on a novel request pattern construction in a cyclic wrap-around fashion which makes the users in a densely distributed region request more files. With the derived lower bound, we also prove that the upper bound of achievable rate is at most a constant gap from it. Numerical results demonstrates superior performance of our proposed algorithm in satellite networks.