Achievable DoF Bounds for Cache-Aided Asymmetric MIMO Communications

TL;DR

This paper introduces three innovative cache-aware MIMO strategies that optimize degrees of freedom in asymmetric wireless networks, significantly improving performance by considering user antenna configurations and dynamic resource allocation.

Contribution

It proposes three novel content-aware MIMO-CC schemes—min-G, Grouping, and Phantom—that adaptively optimize DoF in asymmetric MIMO systems with caching.

Findings

Significant DoF improvements demonstrated across various configurations.

The Phantom scheme bridges performance between min-G and Grouping strategies.

Analytical and numerical results validate the effectiveness of the proposed schemes.

Abstract

Integrating coded caching (CC) into multiple-input multiple-output (MIMO) communications can significantly enhance the achievable degrees of freedom (DoF) in wireless networks. This paper investigates a practical cache-aided asymmetric MIMO configuration with cache ratio $\gamma$, where a server equipped with $L$ transmit antennas communicates with $K$ users, each having $G_k$ receive antennas. We propose three content-aware MIMO-CC strategies: the \emph{min-G} scheme, which treats the system as symmetric by assuming all users have the same number of antennas, equal to the smallest among them; the \emph{Grouping} scheme, which maximizes spatial multiplexing gain separately within each user subset at the cost of some global caching gain; and the \emph{Phantom} scheme, which dynamically redistributes spatial resources using virtual or ``phantom'' antennas at the users, bridging the performance gains of the min-$G$ and Grouping schemes. These strategies jointly optimize the number of users, $\Omega$, and the parallel streams decoded by each user, $\beta_k$, ensuring linear decodability for all target users. Analytical and numerical results confirm that the proposed schemes achieve significant DoF improvements across various system configurations.