Benefits of Edge Caching With Coded Placement for Asymmetric Networks and Shared Caches

Abstract

This paper considers a cache-aided network where the users have access to helper-caches with heterogeneous sizes. First, coded placement schemes are proposed that exploit the heterogeneity in cache sizes when one user is connected to each cache. In the proposed scheme, the unicast/multicast signals intended to serve users connected to small memories are utilized in decoding the contents of the larger memories. A reduction in delivery load with coded placement is shown compared to uncoded placement for three-user systems with arbitrary cache sizes and larger systems in the small total memory regime. Next, systems with equal-size caches where multiple users are associated with each cache are considered. It is shown that coded placement outperforms the best uncoded placement scheme. In the proposed scheme, the unicast/multicast signals sent to the overloaded helper-caches facilitate the decoding of the coded subfiles stored at the underloaded helper-caches. The gain from coded placement is explicitly characterized for two-cache systems. For larger systems, the parameters of the coded placement scheme are obtained by optimization. It is observed that the gain from coded placement becomes more evident with increasing asymmetry in users’ connectivity. Finally, a unified coded placement scheme for two-cache systems that exploits the asymmetry in both the cache sizes and the connectivity pattern is presented.