A sum-rate maximization method is proposed for two Simultaneously Transmitting And Reflecting Reconfigurable Intelligent Surface(STAR-RIS)assisted downlink Non-Orthogonal Multiple Access(NOMA)systems.Firstly,the optimization problem for maximizing sum rate is constructed,with STAR-RIS phase shifts,power allocation and time allocation as optimization parameters.Then the Semi-Definite Programming method(SDP)is used to optimize the phase shifts of these two STAR-RISs.Finally,the power allocation and time allocation are optimized alternately by iterative method.In each iteration,Lagrange dual decomposition method is used to optimize power allocation and function extremum method is used to optimize time allocation.Simulation results show that the sum rate of the dual STAR-RIS-assisted NOMA system is higher than that of the single STAR-RIS-assisted NOMA system.
维普
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