Cache-Aided Non-Orthogonal Multiple Access: The Two-User Case

TL;DR

This paper introduces a cache-aided NOMA scheme that leverages user cache data for interference cancellation, enhancing spectral efficiency and reducing file delivery times in downlink transmission.

Contribution

It proposes a novel cache-aided NOMA scheme that exploits cached data for interference cancellation and optimizes decoding order, power, and rate allocation for improved performance.

Findings

Expanded achievable rate region compared to baseline schemes

Increased sum rate in downlink transmission

Significantly reduced file delivery times

Abstract

In this paper, we propose a cache-aided non-orthogonal multiple access (NOMA) scheme for spectrally efficient downlink transmission. The proposed scheme not only reaps the benefits associated with NOMA and caching, but also exploits the data cached at the users for interference cancellation. As a consequence, caching can help to reduce the residual interference power, making multiple decoding orders at the users feasible. The resulting flexibility in decoding can be exploited for improved NOMA detection. We characterize the achievable rate region of cache-aided NOMA and derive the Pareto optimal rate tuples forming the boundary of the rate region. Moreover, we optimize cache-aided NOMA for minimization of the time required for completing file delivery. The optimal decoding order and the optimal transmit power and rate allocation are derived as functions of the cache status, the file sizes, and the channel conditions. Simulation results confirm that, compared to several baseline schemes, the proposed cache-aided NOMA scheme significantly expands the achievable rate region and increases the sum rate for downlink transmission, which translates into substantially reduced file delivery times.