Core Concepts
RIS and RSMA can be synergistically combined to achieve higher user rates, improved energy/spectral efficiency, and reduced complexity compared to traditional multiple access techniques like NOMA and SDMA.
Abstract
This comprehensive survey examines over 60 articles that explore the synergistic use of reconfigurable intelligent surfaces (RIS) and rate splitting multiple access (RSMA) for next-generation wireless communications. The key insights are:
RIS can provide controllable wireless environments to assist RSMA, which is a flexible non-orthogonal multiple access technique. This combination can outperform traditional NOMA and SDMA in terms of sum-rate, outage probability, energy efficiency, and complexity.
Various RIS models are considered, including reflective, transmissive, and simultaneously transmitting and reflecting (STAR) surfaces. Resource management methods employ traditional optimization techniques and/or machine learning.
RIS-assisted RSMA shows performance advantages over RIS-assisted NOMA and RIS-assisted SDMA in both downlink and uplink scenarios. Benefits include higher user rates, improved energy/spectral efficiency, and reduced complexity.
Key research challenges include channel estimation, joint optimization of RIS and RSMA parameters, and extension to MIMO scenarios. Future research directions include covert communications, integrated sensing and communication, and application of advanced machine learning techniques.
Stats
RIS can provide up to 16.5% increase in performance compared to RSMA without RIS. [7]
RIS-assisted RSMA can achieve nearly 95% gain in energy efficiency compared to RSMA alone. [14]
RIS-assisted RSMA Short Packet Communication can be more energy efficient than RIS-assisted Long Packet Communication with NOMA or SDMA for some packet sizes. [23]
Quotes
"RSMA can match or surpass the performance of NOMA with a single SIC decoding step at each receiver, which is the case of 1L-RS."
"RSMA can achieve more than 90% of the performance of NOMA with a single SIC layer."
"In the non-degraded SISO-BC channel, RSMA always outperforms NOMA in terms of rate region."