Hardware Impairment Aware Transmit Power Minimization for Secure RIS-Aided Full-Duplex NOMA Communications

To enhance system performance, future wireless networks are expected to integrate various unconventional physical layer schemes. This work investigates a reconfigurable intelligent surface (RIS)-aided secure full-duplex (FD) non-orthogonal multiple access (NOMA) system, considering transceiver hardware impairments (HWI). Our primary objective is to minimize the total transmit power of the base station (BS) and uplink (UL) users by designing an optimal power allocation scheme and passive beamforming at the RIS with HWIs. This design ensures compliance with minimum rate requirements despite significant cross-interference and unit-modulus constraints for passive beamforming at the RIS. We propose an iterative algorithm that optimizes the transmit power at the BS and UL users and the passive beamforming at the RIS. Given the non-convex nature of the problem, we employ generalized convex approximations to achieve a near-optimal solution. Simulation results demonstrate the superiority of the proposed secure RIS-aided FD-NOMA system over conventional half-duplex (HD), orthogonal multiple access (OMA), and space division multiple access (SDMA) systems in terms of average total transmit power. Additionally, we analyze the impact of various key system parameters, such as the number of UL and downlink users, the number of RIS elements, noise power, and residual self-interference on system performance.