Fundamental Limits of Cache-Aided Cache Aided Wireless BC: Interplay of Coded-Caching Coded and CSIT Feedback
Abstract: Building on the recent coded coded-caching caching breakthrough by Maddah Maddah-Ali and Niesen, the work here considers the K -user cache-aided aided wireless multi-antenna multi symmetric broadcast channel with random fading and imperfect feedback, and analyzes the throughput performance as a function of feedback statistics and cache size. In this setting, this paper identifies the optimal cache cache-aided degreesof-freedom (DoF) within in a factor of 4, by identifying near near-optimal optimal schemes that exploit a new synergy between coded caching and delayed CSIT, as well as by exploiting the unexplored interplay between caching and feedback-quality. feedback The DoF expressions reveal an initial gain due to current CSIT, and an additional gain due to coded caching, which is exponential in the sense that any linear decrease in the required DoF performance, allows for an exponential reduction in the required cache size. In the end, this paper reveals three new new aspects of caching: a synergy between memory and delayed feedback, a tradeoff between memory and current CSIT, and a powerful ability to provide cache-aided cache aided feedback savings.