Abstract:

Aiming at the problem of physical layer security transmission when there is no direct transmission link between transmitter and desired user,a physical layer transmission scheme based on the reconfigurable intelligent surface (RIS) is proposed.This dissertation first establishes an RIS array antenna system model.The secure communication of the wireless system is completed through the array antenna direct transmission link and the RIS reflection link.Furthermore,in view of the situation that eavesdropers passively receive information and cannot determine the specific location of eavesdropers,the dissertation optimizes the transmitting beamforming vector and the RIS coefficient matrix to maximize artificial noise interference power while ensuring reliable signal reception for the desired user.The non-convex quadratic problem is transformed into an equivalent convex problem by using auxiliary variables and semidefinite relaxation methods.The transmitting beamforming vector and reflection coefficient matrix of the intelligent reflector are optimized jointly,which can restrain the eavesdropper from receiving information and ensure the reliable and secure communication of expected users.Finally,simulation results show that the secure transmission scheme based on the RIS improves the reliability and security of information transmission.

Key words: physical layer security, reconfigurable intelligent surface, non-line-of-sight