On RIS-Aided Multicarrier NOMA System With Frequency-Selective Phase Shift Errors

The integration of reconfigurable intelligent surface (RIS) and non-orthogonal multiple access (NOMA) is treated as an effective way to boost system performance for next-generation wireless networks. In this letter, a power minimization problem is investigated for RIS-aided multicarrier NOMA systems, in which both the phase shift errors and the reflections between RISs are considered. According to the relation between the phase shifts and the required transmit power, the formulated problem is converted into the one about phase shift optimization, which is still quite complicated due to the non-convex objective function and constraints. To render the transformed problem tractable, an alternating optimization method is invoked to decompose it into two subproblems. To proceed, a sequential angle rotation method is developed to address the subproblems with regard to phase shifts. Simulation results show that the proposed scheme outperforms several baselines in terms of power consumption by considering frequency-selective phase shift errors in the design.