CSI acquisition in RIS-assisted mobile communication systems

This paper gives an overview of the work on CSI acquisition in RIS-assisted mobile communication systems with a focus on various categories of RISs, implicit and explicit CSI acquisition, and different channel estimation targets and algorithms. Reconfigurable intelligent surface- (RIS) assisted mobile communication is a promising technological paradigm thanks to the attractive advantages of low cost and flexible control of electromagnetic waves. However, the low-cost features of RISs entail some fundamental challenges to the acquisition of channel state information (CSI), which is essential for the optimal RIS design. To tackle this problem, there have been extensive studies on CSI acquisition in RIS-assisted mobile communication systems, from the perspective of architectural improvement as well as specific mathematical solutions. This article aims to overview the existing works on CSI acquisition in RIS-assisted mobile communication systems.