Power Minimization for the IRS-Aided SWIPT Secure Communication System with Imperfect Cascaded Channel

Abstract

Intelligent reflecting surface (IRS)-assisted simultaneous wireless information and power transfer (SWIPT) is a promising technology for prolonging the lifetime of the users and improving system performance. However, it is challenging to obtain the perfect channel state information (CSI) at the base station (BS) due to the lack of radio frequency (RF) chains at the IRS, which becomes even harder when eavesdroppers (Eves) exist. In this paper, we study the power issues in the IRS-aided SWIPT system under the imperfect CSI of BS-IRS-Eves links. We aim to minimize the transmitting power at the BS by jointly designing transmit beamforming and reflective beamforming with subject to the rate outage probability constraints of the Eves, the energy harvesting constraints of the energy receivers (ERs), and the minimum rate constraints of the information receivers (IRs). We use Bernstein-type inequality to solve the rate outage probability constraints. Afterward, the formulated non-convex problem can be efficiently tackled by employing alternating optimization (AO) combined with semidefinite relaxation (SDR) and penalty convex-concave procedure (CCP). Numerical results demonstrate the effectiveness of the proposed scheme.