Rate-Splitting Multiple Access for Downlink MIMO: A Generalized Power Iteration Approach

Rate-splitting multiple access (RSMA) is a general scheme for downlink multi-antenna systems embracing both classical spatial division and more recent non-orthogonal access. Finding linear precoding strategy that maximizes the sum spectral efficiency of RSMA challenging yet significant problem. In this paper, we put forth novel precoder design framework jointly finds precoders common private messages RSMA. Our approach first to approximate non-smooth minimum function part in using LogSumExp technique. Then, reformulate maximization problem as form log-sum Rayleigh quotients convert it into tractable form. By interpreting first-order optimality condition reformulated an eigenvector-dependent nonlinear eigenvalue problem, reveal leading eigenvector derived local optimal solution. To find eigenvector, propose algorithm inspired by power iteration. Simulation results show proposed transmission provides improvement compared state-of-the-art methods.