Asymmetric Stream Allocation and Linear Decodability in MIMO Coded Caching

TL;DR

This paper develops a criterion for linear decodability in MIMO coded caching systems and proposes an asymmetric stream allocation framework to improve achievable degrees of freedom across all SNR regimes.

Contribution

It introduces a simple criterion for linear decodability based on per-user stream allocation and proposes a heuristic scheduling framework for asymmetric stream allocation in MIMO-CC.

Findings

The criterion guarantees linear decodability for symmetric and non-symmetric schemes.

Asymmetric stream allocation expands the feasible DoF region.

The proposed framework improves system performance across SNR regimes.

Abstract

Coded caching (CC) can transform cache memory at network devices into an active communication resource. Prior studies have shown that CC can significantly enhance the achievable Degrees of Freedom (DoF) in multi-input multi-output (MIMO) systems. To fully exploit MIMO-CC gains across all SNR regimes and enable practical linear receivers, flexible scheduling is required. Existing DoF analysis, scheduling, and linear receiver design, however, largely assume symmetric stream allocations across users. This paper extends the authors' recent work on DoF and linear decodability analysis for MIMO-CC systems by deriving a simple criterion, based on per-user stream allocation, that guarantees linear decodability for both symmetric and non-symmetric bit-level CC schemes. Building on this, we propose a heuristic MIMO-CC delivery and scheduling framework that enables asymmetric stream allocation while adhering to linear decodability, thereby expanding the feasibility region of achievable DoF compared to symmetric-constrained designs.