Rate-Splitting Multiple Access: Fundamentals, Survey, and Future Research Trends

TL;DR

RSMA is a promising framework for wireless communication that enhances spectral efficiency, robustness, and user fairness, with potential to revolutionize future networks, but faces challenges in standardization.

Contribution

This paper provides the first comprehensive survey of RSMA, detailing its architecture, applications, and comparing it with existing multiple access schemes, while discussing future research challenges.

Findings

RSMA achieves optimal Degrees-of-Freedom in various scenarios.

RSMA improves spectral efficiency, energy efficiency, and user fairness.

RSMA offers higher robustness against imperfect channel information.

Abstract

Rate-splitting multiple access (RSMA) has emerged as a novel, general, and powerful framework for the design and optimization of non-orthogonal transmission, multiple access (MA), and interference management strategies for future wireless networks. Through information and communication theoretic analysis, RSMA has been shown to be optimal (from a Degrees-of-Freedom region perspective) in several transmission scenarios. Compared to the conventional MA strategies used in 5G, RSMA enables spectral efficiency (SE), energy efficiency (EE), coverage, user fairness, reliability, and quality of service (QoS) enhancements for a wide range of network loads (including both underloaded and overloaded regimes) and user channel conditions. Furthermore, it enjoys a higher robustness against imperfect channel state information at the transmitter (CSIT) and entails lower feedback overhead and complexity. Despite its great potential to fundamentally change the physical (PHY) layer and media access control (MAC) layer of wireless communication networks, RSMA is still confronted with many challenges on the road towards standardization. In this paper, we present the first comprehensive overview on RSMA by providing a survey of the pertinent state-of-the-art research, detailing its architecture, taxonomy, and various appealing applications, as well as comparing with existing MA schemes in terms of their overall frameworks, performance, and complexities. An in-depth discussion of future RSMA research challenges is also provided to inspire future research on RSMA-aided wireless communication for beyond 5G systems.