On the Efficient Design of RIS-Assisted Secure MISO Transmission

For the sake of improving the physical-layer security, reconfigurable intelligent surface (RIS) has been suggested to assist artificial noise (AN) to bridge both their advantages in multiple-input single-output (MISO) systems. Specifically, for achieving the trade-off between the reliability and security of transmission, the phase shifts (PSs) and beamforming are jointly designed based on the oblique manifold (OM) algorithm (Wang et al. , 2020) without eavesdropper's channel state information (CSI). In order to alleviate the computational complexity, a novel alternating direction (AD) algorithm is proposed in this contribution. Specifically, the initial problem is transformed into several subproblems, each of which determines a specific RIS unit via a closed-form solution when the other configurations are fixed. Furthermore, the AD algorithm is investigated to exhibit the low-complexity advantage in contrast to OM. Simulation results illustrate that AD can converge faster and more stably compared to OM with the same performance.