Utility Optimal Scheduling for Coded Caching in General Topologies

TL;DR

This paper develops a simple, threshold-based scheduling policy for coded caching over fading broadcast channels that maximizes utility and fairness, achieving near-optimal performance with minimal feedback and statistical channel information.

Contribution

It introduces a low-complexity, threshold-based opportunistic scheduling scheme that attains optimal utility in large user regimes using only statistical information and minimal feedback.

Findings

The proposed scheme achieves near-optimal utility compared to full channel state information.

It requires only one-bit feedback per user based on SNR thresholds.

Performance remains robust across different fading statistics and user numbers.

Abstract

We consider coded caching over the fading broadcast channel, where the users, equipped with a memory of finite size, experience asymmetric fading statistics. It is known that a naive application of coded caching over the channel at hand performs poorly especially in the regime of a large number of users due to a vanishing multicast rate. We overcome this detrimental effect by a careful design of opportunistic scheduling policies such that some utility function of the long-term average rates should be maximized while balancing fairness among users. In particular, we propose a threshold-based scheduling that requires only statistical channel state information and one-bit feedback from each user. More specifically, each user indicates via feedback whenever its SNR is above a threshold determined solely by the fading statistics and the fairness requirement. Surprisingly, we prove that this simple scheme achieves the optimal utility in the regime of a large number of users. Numerical examples show that our proposed scheme performs closely to the scheduling with full channel state information, but at a significantly reduced complexity.