Surveys on the intelligent surface: an innovative technology for wireless networks beyond 5G

With the rapid development of wireless communication technology and the explosive growth of mobile data traffic, more and more users are eager to get faster and better internet access. In order to meet the needs of users, energy and spectrum utilization are becoming more and more important as new challenges in wireless communication networks. In recent years, reconfigurable intelligent surface(RIS) technology has been proposed in a programmable intelligent way to improve the performance and quality of wireless communication systems. In addition, the RIS performs better in terms of energy efficiency than other technologies. Therefore, the RIS has become research hotspot rapidly because of its unique wireless communication ability. This paper aims to review the RIS, including channel model, design for transmitter and receiver, information theory, and the latest development of RIS-assisted multiple-input multiple-output(MIMO) systems. The applications of RISs in physical layer security, device to device(D2 D) and cell coverage extension are also introduced in detail. In addition, we discuss major research challenges related to the RIS. Finally, the potential research directions are proposed.