The hybrid relay-reflecting intelligent surface (HR-RIS) has been recently introduced as an efficient solution to overcome the double path loss and limited beamforming diversity of the conventional fully passive reflecting surface. This motivates us to investigate the application of the HR-RIS in improving the secrecy capacity of millimeter wave multiple-input-multiple-output (MIMO) systems with the presence of multi-antenna eavesdropper. The joint optimization of the transmit beamformer and the relay-reflecting coefficients at RIS is tackled via alternating optimization. In the proposed solution, a closed-form expression for the optimal transmit beamformer at the transmitter is derived, and a metaheuristic solution based on particle swarm optimization is proposed to optimize the active and passive elements at the HR-RIS. The simulation results verify that under various scenarios, the HR-RIS provides significant improvement in the secrecy capacity with respect to the conventional passive reflecting surface.
翻译:最近引入了混合中继反射智能表面(HR-RIS),作为克服双轨路损耗和常规完全被动反射表面的有限波形多样性的有效解决办法,这促使我们调查HR-RIS在利用多电脉冲窃听器提高毫米波多输入-多输出输出(MIMO)系统的保密能力方面的应用,通过多电波多输出-多输出(MIMO)系统;通过交替优化处理传输光谱仪和RIS中继反射系数的联合优化问题。在拟议的解决方案中,生成了发射机最佳传输光谱的封闭式表达式表达式,并提议了以粒子温优化为基础的光学解决方案,以优化HR-RIS的主动和被动元素。模拟结果证实,在各种情景下,HR-RIS为常规被动反射表面的保密能力提供了重大改进。