On the Benefits of Asymmetric Coded Cache Placement in Combination Networks with End-User Caches

Wan Kai (1) , Mingyue Ji (2) , Pablo Piantanida (1) , Daniela Tuninetti (3)

1 L2S - Laboratoire des signaux et systèmes
2 University of Utah
3 Department of Electrical and Computer Engineering [Chicago]

This paper investigates the fundamental tradeoff between cache size and download time in the (H, r, M, N) combination network, where a server with N files is connected to H relays (without caches) and each of the K: = Hr users (with caches of size M files) is connected to a different subset of r relays. Existing schemes fall within two categories: either use the uncoded symmetric cache placement originally proposed for the shared-link model and design delivery phase dependent on the network topology, or effectively divide the combination network into H uncoordinated shared-link networks each serving K ' := H-1r-1 users; in either case, the placement phase leverages effectively the connectivity of relay s/users. In this paper, a novel strategy is proposed where the coded cache placement is dependent on network topology. The proposed scheme is shown to be information theoretically optimal for large cache size. In addition, when not exactly optimal, the proposed scheme can also outperform existing schemes.

Domains: Information Theory [cs.IT]; Networking and Internet Architecture [cs.NI]; Information Theory [math.IT]; Statistics [math.ST]

Wan Kai, Mingyue Ji, Pablo Piantanida, Daniela Tuninetti. On the Benefits of Asymmetric Coded Cache Placement in Combination Networks with End-User Caches. IEEE International Symposium on Information Theory (ISIT 2018), Jun 2018, Vail, U.S. Outlying Islands. ⟨10.1109/isit.2018.8437462⟩. ⟨hal-01756016⟩