Simultaneous Information Relaying and Jamming via IRS to Secure NOMA Networks

This paper proposes a new simultaneous information relaying and jamming (SIRJ) scheme based on a multi-functional intelligent reflecting surface (IRS) to improve physical layer security of non-orthogonal multiple access networks. Specifically, the elements of IRS are split into two groups, where one group reflects the signal to improve the legitimate reception quality while the other group generates jamming signal to interfere with the eavesdropper. We aim to maximize the minimum secrecy rate (MSR) by jointly optimizing the transmit beamforming of the base station and the reflect beamforming of the IRS to enhance the secrecy performance. To tackle this intractable non-convex problem, a penalty based alternating algorithm is developed. Simulation results demonstrate the secrecy enhancement of the proposed SIRJ scheme over existing baseline schemes in terms of achieving a higher MSR.