Contents I. Introduction
INtelligent reflecting surface (IRS), a passive planar array with cost-efficient and energy-efficient, has received significant consideration as a leading technology in the sixth-generation (6G) wireless communication networks [1]. Different from the transmitter and wireless relay, an IRS planar consists of a large number of inexpensive passive reflecting elements, each of which is able to induce a controllable phase shift to the incident signal independently [2]. Thus, IRS is able to enhance the desired signals and suppress the interference by designing the phase shift of each reflecting element. Since security issues become increasingly prominent, extensive research work has been devoted to the study of IRS in secure communication system. A novel idea in physical layer secrecy is to transmit artificial noise (AN) from the base station (BS) to interfere the received signals of eavesdropper was investigated in [3]. However, the energy efficiency is limited by the channel conditions when we take physical layer security into consideration. To deal with this issue, the IRS-assisted multiple input single output (MISO) network with independent cooperative jamming has been investigated in [4]. Besides, by employing IRS into a simultaneous wireless information and power transfer (SWIPT) system, the security performance of the system can be enhanced significantly [5]. Moreover, multiple IRSs-assisted multiusers MISO secure communication system has been proposed in [6], which multiple IRSs were shown to be more efficient in decreasing information leakage to potential eavesdroppers.
