User Cooperation for RIS-aided Secure SWIPT MIMO Systems under the passive eavesdropping

In this paper, reconfigurable intelligent surface (RIS) is proposed to enhance the physical layer security in the Rician fading channel where the angular direction of the eavesdropper is aligned with a legitimate user. In this scenario, we consider a two-phase communication system under the passive eavesdropping. Particularly, in the first phase, the base station avoids direct transmission to the attacked user. While, in the second phase, other users cooperate to forward signals to the attacked user with the help of RIS and energy harvesting technology. An average secrecy rate maximization problem is formulated, which is addressed by a low complexity algorithm. Numerical results show that the negative effect of the eavesdropper’s channel error is greater than that of the legitimate user.