Stacked Intelligent Metasurfaces-Aided Rate Splitting Multiple Access System

Stacked intelligent metasurfaces (SIM) is a promising emerging technology that can effectively suppress multi-user interference and reduce latency by implementing precoding in the wave domain. This letter proposes a novel system design for downlink rate splitting multiple access (RSMA) using SIM technology. Specifically, installing the SIM at the base station and directly implementing multi-user beamforming in the wave domain, compared to traditional digital beamforming, can simplify the transmitter structure and reduce computational load. To fully utilize the advantages of SIM and maximize user sum rate under the constraints of base station transmit power and QoS rate requirements, this letter customizes an alternating optimization (AO) algorithm based on the coati optimization algorithm and iterative projection gradient ascent algorithm to achieve optimization results by jointly optimizing the common rate, transmit power, and phase shift in the wave domain. Our simulation results demonstrate the effectiveness of the proposed SIM-aided RSMA system and the improvement of user sum rate by the AO algorithm.