Fundamental Limits of Cloud and Cache-Aided Interference Management with Multi-Antenna Base Stations

In cellular systems, content delivery latency can be minimized by jointly optimizing edge caching, fronthaul transmission from a cloud processor (CP) with access to the content library, and wireless transmission. In this paper, this problem is studied from an information-theoretic viewpoint by making the following practically relevant assumptions: 1) the ENs have multiple antennas; 2) only uncoded fractional caching is allowed; 3) the fronthau llinks are used to send fractions of contents; and 4) the ENs are constrained to use one-shot linear precoding on the wireless channel. Assuming offline caching and focusing on a high signal-to-noise ratio (SNR) latency performance metric, the proposed caching and delivery policy is shown to be either exactly optimal or optimal within a multiplicative factor of 3/2. The results bring insights into the optimal interplay between edge and cloud processing in fog-aided wireless networks as a function of system resources, including the number of antennas at the ENs, the ENs' cache capacity and the fronthaul capacity.