Physical Layer Secure Communication for Active Dual-RIS Assisted MISO System

This paper investigates physical layer security issues in a multiple-input single-output (MISO) network assisted by dual reconfigurable intelligent surfaces (RIS). Addressing the mutual cascading effects between the two RISs and the double fading phenomenon occurring in the communication reflection channel links, we propose an active dual-RIS MISO system model. To further enhance the system’s secrecy, we introduce artificial noise (AN) technology at the base station (BS) and derive the signal-to-interference-plus-noise ratio expressions for both the user (User) and the eavesdropper (Eve). To tackle the non-convex optimization problem of maximizing the secrecy transmission rate in the dual-RIS assisted MISO scenario, we employ an efficient alternating optimization algorithm combined with the Charnes-Cooper transformation. The simulation results demonstrate that the dual-RIS setup outperforms the single RIS configuration in terms of secrecy performance. Moreover, the integration of active RISs effectively mitigates the double fading phenomenon, and the introduced AN yields superior secrecy performance. Additionally, we analyze the impact of key parameters, including the BS’s transmit power, antenna configuration, the number of reflecting elements on the RISs, the amplification factor, and the distances between the RISs and both the User and Eve, on the secrecy rate. Our findings indicate that, compared to other schemes, the proposed system model achieves significant performance improvements.