Security Enhancement for Coupled Phase-Shift STAR-RIS Networks

The secure transmission of the simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) aided communication system is investigated. Considering the coupled phase shifts of STAR-RISs and the fair secrecy requirement of users, a new secure beamforming design is proposed for addressing the unique full-space mutual eavesdropping in STAR-RIS aided communications. In particular, a penalty-based secrecy beamforming algorithm is proposed to solve the resulting non-convex optimization problem, where closed-form solutions of the coupled phase-shift coefficients are obtained in each iteration. Numerical results demonstrate that 1) the proposed scheme achieves higher secrecy capacity than conventional RIS; 2) 4-bit discrete phase shifters are sufficient for secrecy guarantee.

Automated summary

This study investigates the secure transmission of the simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) aided communication system. A new secure beamforming design is proposed to address the unique full-space mutual eavesdropping in STAR-RIS aided communications, considering the coupled phase shifts of STAR-RISs and the fair secrecy requirement of users. Numerical results show that the proposed scheme achieves higher secrecy capacity than conventional RIS and 4-bit discrete phase shifters are sufficient for secrecy guarantee.