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In this paper, we consider the $K$-user cache-aided wireless MISO broadcastchannel (BC) with random fading and delayed CSIT, and identify the optimalcache-aided degrees-of-freedom (DoF) performance within a factor of 4. Theachieved performance is due to a scheme that combines basic coded-caching withMAT-type schemes, and which efficiently exploits the prospective-hindsightsimilarities between these two methods. This delivers a powerful synergybetween coded caching and delayed feedback, in the sense that the totalsynergistic DoF-gain can be much larger than the sum of the individual gainsfrom delayed CSIT and from coded caching.  The derived performance interestingly reveals --- for the first time ---substantial DoF gains from coded caching, even when the (normalized) cache size$\gamma$ (fraction of the library stored at each receiving device) is verysmall. Specifically, a microscopic $\gamma \approx e^{-G}$ can come within afactor of $G$ from the interference-free optimal. For example, storing at eachdevice only a \emph{thousandth} of what is deemed as `popular' content($\gamma\approx 10^{-3}$), we approach the interference-free optimal within afactor of $ln(10^3) \approx 7$ (per user DoF of $1/7$), for any number ofusers. This result carries an additional practical ramification as it revealshow to use coded caching to essentially buffer CSI, thus partially amelioratingthe burden of having to acquire real-time CSIT.

The Synergistic Gains of Coded Caching and Delayed Feedback