IRS-Assisted Rate-Splitting Multiple Access for Overloaded Multiuser MISO Transmission

An intelligent reflecting surface (IRS)-assisted rate-splitting multiple access (RSMA) system is proposed in this paper for overloaded multiuser multiple-input single-output (MISO) transmission with imperfect channel state information at the transmitter (CSIT). In this proposed system, the weighted minimum mean square error (WMMSE)-based approach and alternative optimization (AO) framework are adopted in order to solve the weighted sum-rate (WSR) problem in RSMA transmission with partial CSIT. In this work, both phase-shifting and beam-forming matrices are iteratively optimized until convergence. The performance of time partitioning RSMA (TP-RSMA) and power partitioning RSMA (PP-RSMA) in terms of the sum-rate is also examined for the purpose of fair comparison. Simulation results showed that the proposed IRS-assisted RSMA systems provide a significant performance gain over the conventional non-IRS-assisted systems. This gain increases with increasing the number of antennas, users and IRS reflecting elements.