Secrecy Energy Efficiency Maximization for ARIS-Assisted Multiuser MISO Systems

In this letter, we investigate secure secrecy maximization with the aid of active reconfigurable intelligent surface (ARIS). In particular, we consider the multiuser multiple-input and single-output (MISO) system under the presence of a multi-antenna eavesdropper, where full-duplex (FD) legitimate users proactively emit artificial noise (AN) to disrupt the eavesdropper’s reception. Towards this end, we formulate the secrecy energy efficiency (SEE) maximization problem and propose an alternating optimization-based two-level algorithm to solve it, where the semi-definite programming (SDP) combined with successive convex approximation (SCA) is adopted. Simulation results reveal that the proposed scheme has an 84.9% SEE gain over the passive RIS scheme for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=150$ </tex-math></inline-formula> and gradually decreases when N increases. Moreover, a maximum 13.6% SEE gain for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=250$ </tex-math></inline-formula> can be further obtained compared to the ARIS scheme without AN.