RIS-Assisted Secure Communications: Low-Complexity Beamforming Design
Zhenqiao Cheng, Nanxi Li, Jianchi Zhu, Xiaoming She, Chongjun Ouyang, Peng Chen
Abstract
Joint active and passive beamforming optimization is investigated to enhance the physical layer security of a reconfigurable intelligent surface (RIS)-assisted multiple-antenna communication system. The problems are formulated under two criteria: secrecy rate maximization and power consumption minimization. For each design problem, a novel collaborative design algorithm is proposed by capitalizing on the mathematical structure of the optimal active beamforming vector, which requires no iterative updating between the transmit beamformer and the RIS-reflecting beamformer. Numerical results demonstrate that the proposed algorithms enjoy much lower computational complexity than the state-of-the-art alternating optimization-based methods while achieving almost identical secrecy performance.