Caching in combination networks: Novel multicast message generation and delivery by leveraging the network topology
Kai Wan, Mingyue Ji, Pablo Piantanida, Daniela Tuninetti · HAL (Le Centre pour la Communication Scientifique Directe) · 2018
Maddah-Ali and Niesen's original coded caching scheme for shared-link broadcast networks is now known to be optimal to within a factor two, and has been applied to other types of networks. For practical reasons, this paper considers that a server communicates to cache-aided users through H intermediate relays. In particular, it focuses on combination networks where each of the K = ( r H ) users is connected to a r distinct r-subsets of relays. By leveraging the symmetric topology of the network, this paper proposes a novel method to generate multicast messages such that each multicast message sent to each relay is useful for the largest possible subset of users connected to this relay. By numerical evaluations, the proposed scheme is shown to reduce the download time compared to the schemes available in the literature. The idea is then extended to decentralized combination networks, more general relay networks, and combination networks with cache-aided relays and users. Also in these cases the proposed scheme outperforms known ones.