Alpha Fair Coded Caching

Abstract

The performance of existing \emph{coded caching} schemes is sensitive to worst channel quality, a problem which is exacerbated when communicating over fading channels. In this paper we address this limitation in the following manner: \emph{in short-term}, we allow transmissions to subsets of users with good channel quality, avoiding users with fades, while \emph{in long-term} we ensure fairness across the different users.Our online scheme combines (i) joint scheduling and power control for the broadcast channel with fading, and (ii) congestion control for ensuring the optimal long-term average performance. We restrict the caching operations to the decentralized scheme of \cite{maddah2013decentralized}, and subject to this restriction we prove that our scheme has near-optimal overall performance with respect to the convex alpha-fairness coded caching optimization. By tuning the coefficient alpha, the operator can differentiate user performance with respect to video delivery rates achievable by coded caching. We demonstrate via simulations our scheme's superiority over legacy coded caching and unicast opportunistic scheduling, which are identified as special cases of our general framework.