Novel inner bounds with uncoded cache placement for combination networks with end-user-caches

International audienceThis paper considers combination networks with end-user-caches, where a server with N files communicates through H relays (without caches) to K = (H r) users equipped with caches of size M files. In this setting, each user is connected to a different subset of r relays. The tradeoff between the cache size and the worst-case download time is studied. Several novel caching schemes are proposed, which leverage the symmetries of combination networks and interference elimination at the end-users. The proposed schemes are proved: (i) to be optimal for some choices of the parameters (N, M, H, r) under the constraint of uncoded cache placement, and (ii) to outperform the state-of-the-art schemes in numerical evaluations