  Rate-splitting multiple access (RSMA) has been recognized as a promising and
powerful multiple access (MA) scheme, non-orthogonal transmission framework and
interference management strategy for 6G. Inspired by the appealing spectral
efficiency gain achieved by RSMA over conventional MA schemes in multi-user
multi-antenna transmission, in this paper we introduce RSMA to reconfigurable
intelligent surface (RIS)-aided multiple-input single-out (MISO) broadcast
channel (BC). To further enhance the spectral efficiency, a more generalized
RIS architecture called fully connected RIS is considered. By jointly
optimizing the scattering matrix of the fully connected RIS and the transmit
beamformers to maximize the sum-rate, we show that the proposed fully connected
RIS aided RSMA transmission scheme significantly improves the spectral
efficiency compared with the conventional single connected RIS schemes and the
schemes without RIS. It acts as a new benchmark for linearly precoded
multi-user multi-antenna networks.
