Joint Secure Primary and Secondary Transmission Enhancement via Active STAR-RIS in Spectrum Sharing Cognitive Radio Networks

Abstract

In this letter, we consider an active simultaneous transmission and reflecting reconfigurable intelligent surface (STAR-RIS) aided spectrum sharing cognitive radio networks, and aims at jointly enhancing the secure transmission performance of primary users (PUs) and secondary users (SUs). Based on the imperfect channel state information of eavesdropper’s channels, a non-convex worst-case transmission rate optimization problem subject to maximum eavesdropping rate constraint (ERC) is formulated. To optimize this problem, the ERC is firstly tightened, and an efficient successive convex approximation and alternating optimization combined algorithm is proposed to obtain a suboptimal solution, in which the vector variables are directly optimized without using conventional semi-definite relaxation. Simulations have verified the superiority of the performance by the proposed algorithm over benchmark schemes.