Secure Transmission in Segmented RIS-Assisted NOMA Networks with Imperfect SIC

In recent years, the use of reconfigurable intelligent surfaces (RIS) to enhance physical layer secure transmissions has been widely researched. To further enhance the secrecy rate and effectively reduce system complexity, this paper innovatively proposes a secure non-orthogonal multiple access (NOMA) communication scheme based on the assistance of a segmented RIS. In order to maximize the minimum secrecy rate, an optimization problem is established to joint optimize base station (BS) beamforming, RIS phase shifts and RIS segmentation matrix. An alternating optimization algorithm is proposed to solve the non-convex problem by combing successive convex approximation (SCA), semi-definite programming (SDP) and greedy algorithm. The simulation results show the superiority of the proposed scheme in enhancing the secrecy rate compared with traditional OMA, non-RIS-assisted, and fixed-segmentation RIS-assisted schemes.