Secure Energy Efficiency for RIS-Aided Cognitive Radio Networks With Hardware Impairments

In practical applications, transceiver hardware impairments (HWIs) and phase errors (PEs) in reconfigurable intelligent surfaces (RIS) can distort signals in cognitive radio (CR) networks, reducing the system’s anti-interference and security performance. This letter investigates secure communication design for RIS-assisted CR systems affected by HWIs and RIS PEs. To maximize the security energy efficiency (SEE) of cognitive users (CUs), a joint optimization method for base station (BS) beamforming, artificial noise (AN), and RIS reflection phase is proposed. An alternating iterative approach addresses this optimization problem by first optimizing beamforming and AN through variable substitution and successive convex approximation (SCA), then optimizing the passive beamforming using Semidefinite Relaxation (SDR) and singular value decomposition (SVD), assuming PEs follow a uniform or von mises distribution. Numerical results show the proposed method surpasses benchmark schemes in security and robustness.