Reconfigurable Intelligent Surface (RIS) draws great attentions in academic and industry due to its passive and low power consumption nature, and has currently been used in physical layer security to enhance the secure transmission. However, due to the existence of double fading effect on the reflecting channel link between transmitter and user, RIS helps achieve limited secrecy performance gain compared with the case without RIS. In this correspondence, we propose a novel active RIS design to enhance the secure wireless transmission, where the reflecting elements in RIS not only adjust the phase shift but also amplify the amplitude of signals. To solve the non convex secrecy rate optimization based on this design, an efficient alternating optimization algorithm is proposed to jointly optimize the beamformer at transmitter and reflecting coefficient matrix at RIS. Simulation results show that with the aid of active RIS design, the impact of double fading effect can be effectively relieved, resulting in a significantly higher secrecy performance gain compared with existing solutions with passive RIS and without RIS design.
翻译:重新配置的智能表面(RIS)因其被动和低电耗性质而引起学术界和产业界的极大关注,目前被用于物理层安全,以加强安全传输;然而,由于发射机和用户之间反射频道连接存在双重淡化效应,RIS帮助实现了与无RIS相比有限的保密性能收益。在本函文中,我们提议了一种新的主动的RIS设计,以加强安全无线传输,使IRS中的反映要素不仅调整了阶段转移,而且还扩大了信号的振幅。为了解决基于这一设计的非电离保密率优化,建议采用高效的交替优化算法,共同优化发射机的光谱并反映RIS的系数矩阵。模拟结果表明,在主动的RIS设计的帮助下,双重减速效应的影响可以有效地减轻,从而大大提高与被动的RIS和不设计的现有解决方案相比的保密性能收益。