Energy Efficiency Optimization for RIS Assisted RSMA System over Estimated Channel

In this paper, we consider a reconfigurable intelligent surface (RIS) assisted rate splitting multiple access (RSMA) transmission system with estimated channel state information (CSI). The RIS is used to artificially construct the transmission environment to achieve more energy efficient transmission. An energy efficiency maximization problem is formulated by satisfying the constraint of power budget, the design principles of RSMA and RIS. To solve this problem, fractional programming is first used to decouple the single ratio objective function. Then the optimal power allocation coefficients and the phase shift matrix of RIS are obtained by the proposed alternative optimization method, respectively. Numerical results demonstrate that the energy efficiency performance of the RIS assisted RSMA system can be significantly improved by the proposed alternative joint optimization.