查看文章

This correspondence investigates a reconfigurable intelligent surface (RIS)-assisted wireless communication system with security threats. The RIS is deployed to enhance the secrecy outage probability (SOP) of the data sent to a legitimate user. By deriving the distributions of the received signal-to-noise-ratios (SNRs) at the legitimate user and the eavesdropper, we formulate, in a closed-form expression, a tight bound for the SOP under the constraint of discrete phase control at the RIS. The SOP is characterized as a function of the number of antenna elements, , and the number of discrete phase choices, . It is revealed that the performance loss in terms of SOP due to the discrete phase control is ignorable for large when . In addition, we explicitly quantify the SOP loss when binary phase shifts, i.e., , are utilized. It is found that increasing the number of RIS elements by 1.6 times provides the …