Non-Orthogonal Multiple Access for Degraded Broadcast Channels: RA-CEMA

TL;DR

RA-CEMA introduces a non-orthogonal multiple access scheme that multiplexes users with different SNRs using a multiplexing matrix and interference cancellation, achieving higher spectral efficiency than traditional methods.

Contribution

It presents RA-CEMA, a novel non-orthogonal multiple access scheme that improves spectral efficiency and compatibility with existing systems for degraded broadcast channels.

Findings

Higher spectral efficiency than orthogonal multiplexing

Compatible with current coding and modulation schemes

Effective interference cancellation algorithm

Abstract

A new non-orthogonal multiple access scheme performing simultaneous transmission to multiple users characterized by different signal-to-noise ratios is proposed. Different users are multiplexed by storing their codewords into a multiplexing matrix according to properly designed patterns and then mapping the columns of the matrix onto the symbols of a higher-order constellation. At the receiver, an interference cancellation algorithm is employed in order to achieve a higher spectral efficiency than orthogonal user multiplexing. Rate-Adaptive Constellation Expansion Multiple Access (RA-CEMA) is an alternative to conventional superposition coding as a solution for transmission on the degraded broadcast channel. It combines the benefits of an increased spectral efficiency with the advantages of reusing the coding and modulation schemes already used in contemporary communication systems, thereby facilitating its adoption in standards.