Joint redundant MDS codes and cluster cooperation based coded caching in fog radio access networks

In this paper, we investigate maximum-distance separable (MDS) codes and cluster based coded caching in fog radio access networks (F-RANs). In order to minimize the fronthaul rate, multicast opportunities need to be constructed at the cloud server. Firstly, a redundant MDS codes based coded placement scheme is proposed to provide redundant coded packets and symmetrical cache contents. The redundant coded packets can be used to construct multicast opportunities for requests on the same file. Furthermore, based on the symmetrical cache contents, we propose a cluster cooperation based coded delivery scheme, which can induce considerable multicast opportunities between any two clusters regardless of whether the requests are on the same file or not. Finally, by utilizing the redundant coded packets and the symmetry of cache contents, a joint redundant MDS codes and cluster cooperation based coded caching policy is proposed to minimize the fronthaul rate. Simulation results show that our proposed policy can provide 30% savings of the fronthaul rate compared to the MDS-based uncoded delivery policy.