Physical-Layer Schemes for Wireless Coded Caching

TL;DR

This paper explores physical-layer schemes for wireless coded caching, proposing novel methods that improve finite SNR performance while maintaining high DoF, and extends these schemes to interference channels with ergodic rate analysis.

Contribution

It introduces a new finite field-based linear combination scheme for wireless coded caching that enhances finite SNR performance and extends to interference channels.

Findings

Near-optimal DoF achieved by the proposed schemes.

Significant finite SNR performance improvements over baseline.

Extension of schemes to interference channels with ergodic rate analysis.

Abstract

We investigate the potentials of applying the coded caching paradigm in wireless networks. In order to do this, we investigate physical layer schemes for downlink transmission from a multiantenna transmitter to several cache-enabled users. As the baseline scheme we consider employing coded caching on top of max-min fair multicasting, which is shown to be far from optimal at high SNR values. Our first proposed scheme, which is near-optimal in terms of DoF, is the natural extension of multiserver coded caching to Gaussian channels. As we demonstrate, its finite SNR performance is not satisfactory, and thus we propose a new scheme in which the linear combination of messages is implemented in the finite field domain, and the one-shot precoding for the MISO downlink is implemented in the complex field. While this modification results in the same near-optimal DoF performance, we show that this leads to significant performance improvement at finite SNR. Finally, we extend our scheme to the previously considered cache-enabled interference channels, and moreover, we provide an Ergodic rate analysis of our scheme. Our results convey the important message that although directly translating schemes from the network coding ideas to wireless networks may work well at high SNR values, careful modifications need to be considered for acceptable finite SNR performance.