Rate Splitting Multiple Access in C-RAN

Rate-splitting multiple access (RSMA), recognized as a promising technique for future communication systems to generalize and outperform existing multiple access techniques, has been shown to enhance the spectral and energy efficiencies of multi-user multi-antenna broadcast channels (BCs). In this work, motivated by the benefits of RSMA discovered in multi-antenna BCs, we investigate the performance of RSMA in cloud radio access networks (C-RANs). Specifically, the beamforming vectors, message splits, and stream-to-base stations (BSs) allocation are jointly designed with the aim to maximize the sum rate subject to per-BS power constraints and fronthaul capacity constraints. Numerical results demonstrate that RSMA boosts the sum rate in C-RAN especially in strong interference regimes. Therefore, RSMA is a more promising transmission technique for C-RAN than other conventional transmission schemes such as treating interference as noise (TIN) or orthogonal multiple access schemes.