窃听CSI未知场景下基于可重构智能表面的物理层安全传输方案

近些年来,人们一直在开发可重构智能表面(Reconfigurable Intelligent Surface,RIS),它是一种由许多无源反射器组成的低成本结构,可以自由地改变每个元素的反射系数,并重新配置无线传输环境以改变入射信号的传播。由于具有若干新型和独特的优势,RIS应用场景广泛,关于其在物理层安全中应用的研究蓬勃发展。与此同时,物理层安全研究中窃听者的信道状态信息(Channel State Information,CSI)一直是人们讨论的热点,实际通信场景中窃听CSI通常是不易获取或未知的。因此本文考虑了一个更接近现实的情况,即针对窃听CSI未知的场景,考虑存在一个合法接收者以及多个非法窃听者,从功率分配的角度出发,结合波束成形,设计一种多RIS辅助的人工噪声与功率分配方案,通过对基站波束成形矩阵和RIS反射系数的交替优化,并应用二分法,使得在合法接收用户信号质量不变的前提下,降低基站处发送保密信息至合法用户所需的功率,降低其接收信号的信干噪比,进而提高系统的保密容量。同时考虑到了多个RIS协作辅助保密通信不一定最优,并可能增加系统优化的复杂度,设计了多个RIS的选择方案,...

A Physical Layer Security Transmission Scheme Based on Reconfigurable Intelligent Surfaces for Eavesdropping CSI Unknown Scenarios

? ?In recent years， people have been developing reconfigurable intelligent surface （RIS）， which is a low-cost structure composed of many passive reflectors. It can freely change the reflection coefficient of its each element and reconfigure the wireless transmission environment to change the propagation of the incident signal. Due to several novel and unique advantages， RIS has a wide range of application scenarios， and research on it in physical layer security flourishes. At the same time， eavesdropping channel state information in the physical layer security has always been a focus of people while the actual communication scenario eavesdropping channel state information is usually unknown. Therefore， this article considered a more realistic situation and aimed at the scenario of unknown eavesdropping channel state information， considering the existence of a legitimate receiver and multiple illegal eavesdroppers. From the perspective of power allocation， combined with beamforming， a multiple RISs auxiliary artificial noise and power allocation scheme was designed. Through the alternate optimization of the base station beamforming matrix and the RIS reflection coefficient and dichotomy， the power required to send confidential information to the legitimate user at the base station could be reduced， under the premise that the signal quality of the legally received user remains unchanged. Then signal to interference plus noise ratio of the received signal was reduced， by which the security capacity of the system was increased. Meanwhile， considering that the cooperative assisted confidential communication of multi-RIS may not be necessarily optimal， and may increase the complexity of system optimization， a multi-RIS selection scheme was proposed to improve energy efficiency while maintaining the secrecy of the communication system. The complexity of the designed algorithm was analyzed to prove the feasibility and effectiveness of the designed scheme. Then， the artificial noise scheme assisted by the joint beamforming RIS was simulated and analyzed. Finally， it is concluded that when the eavesdropping channel state information is unknown， rational joint optimization of RIS and base station beamforming for power allocation， combined with multi-RIS selection technology， can suppress the signal quality at the eavesdroppers， improve the energy efficiency of the communication system， and finally achieve confidentiality communication.