Resource allocation for practical phase shift STAR-RIS enabled MISO-NOMA wireless network with non ideal hardware

Abstract

This study investigates the sum secrecy rate $\left(S{R}_{sum}\right)$ of a simultaneous transmission and reflection reconfigurable intelligent surface (STAR-RIS)-enabled multiple input single-output (MISO) non-orthogonal multiple access (NOMA) downlink network with non-ideal hardware defects (HWDs) at the transceivers. Earlier STAR-RIS studies assumed an ideal phase shift model, with each element reflect and transmit the signal without regard to its phase shift. The proposed practical phase shift model accounts for the phase-dependent amplitude variation in the reflection and transmission (RAT) coefficients. The goal is to maximize the $S{R}_{sum}$ through an alternating optimization (AO) iterative algorithm, leverages a classical semidefinite relaxation (SDR) for beamformer vector design (BVD), and employs an interior point method (IPM) to calculate NOMA power allocation factors $\left({\alpha }_t,{\alpha }_r\right)$. The analysis focuses on the evaluation of the $S{R}_{sum}$ in scenarios with eavesdroppers, under the consideration of both ideal and practical phase shift cases. The study examines the impact of different non-ideal HWDs on the $S{R}_{sum}$ of the system and provides insights into vulnerabilities and limitations arising from these effects.