ABSTRACT
A reconfigurable intelligent surface (RIS) is an interdisciplinary technology that combines two main fields: material science and wireless communications. More specifically, in the field of material science, a RIS involves designs and manufacturing of programmable metasurface devices. In the field of wireless communications, a RIS is highly related to multi-antenna technology and relay technology. In this chapter, metamaterial and metasurface devices are briefly discussed, followed by the fundamentals of wireless technologies that are related to a RIS, including multi-antenna technology; coordinated multi-point processing; and heterogeneous networks such as micro cells, pico cells, femto cells, and relay nodes. As a RIS is considered a strong candidate technology for 6G future mobile networks, in this chapter we also discuss the application scenarios, key performance requirements, basics about the performance evaluation methodologies of 6G, and pinpoint the importance of a RIS to fulfill those performance requirements.
