Resource Management in RIS-Assisted Rate Splitting Multiple Access for Next Generation (xG) Wireless Communications: Models, State-of-the-Art, and Future Directions

Next generation wireless networks require more stringent performance levels. New technologies such as Reconfigurable intelligent surfaces (RISs) and rate-splitting multiple access (RSMA) are candidates for meeting some of the performance requirements, including higher user rates at reduced costs. RSMA provides a new way of mixing the messages of multiple users, and the RIS provides a controllable wireless environment. This paper provides a comprehensive survey on the various aspects of the synergy between reconfigurable intelligent surfaces (RISs) and rate splitting multiple access (RSMA) for next-generation (xG) wireless communications systems. In particular, the paper studies more than 60 articles considering over 20 different system models where the RIS-aided RSMA system shows performance advantage (in terms of sum-rate or outage probability) over traditional RSMA models. These models include reflective RIS, simultaneously transmitting and reflecting surfaces (STAR-RIS), as well as transmissive surfaces. The state-of-the-art resource management methods for RIS-assisted RSMA communications employ traditional optimization techniques and/or machine learning techniques. We outline major research challenges and multiple future research directions.