Fundamental Limits on Latency in Small-Cell Caching Systems: An Information-Theoretic Analysis

Caching of popular multimedia content at small-cell base stations (BSs) is a promising solution to reduce the traffic load of macro-BSs without relying on a high-speed backhaul architecture. While most prior work analyzed the effect of smallcell caching, or femto-caching, under the assumption of negligible interference between macro-BS and small-cell BS, this paper contributes to a more recent line of work in which the benefits of caching are reconsidered in the presence of interference on the downlink channel. In particular, a binary fading one-sided interference channel is considered in which the small-cell BS, whose transmission is interfered by the macro-BS, has a limitedcapacity cache. An information-theoretic metric that captures the delivery latency is defined and fully characterized through information-theoretic achievability and converse arguments as a function of the cache capacity, as well as of the capacity of the backhaul link connecting cloud and small-cell BS.