Reconfigurable Intelligent Surface for Near Field Communications: Beamforming and Sensing

Reconfigurable intelligent surface (RIS) can improve the communications between a source and destination. Recently, continuous aperture RIS is proved to have better communication performance than discrete has received much attention. However, conventional designed convert incoming planar waves into outgoing waves, which not optimal reflecting scheme when receiver array located in near field of RIS. In this paper, we consider two types receivers radiating RIS: (1) equipped with uniform linear (ULA), design coefficient cylindrical waves; (2) single antenna, spherical waves. We then propose maximum likelihood (ML) method focal scanning (FS) sense location based on analytic expression reflection coefficient, derive corresponding position error bound (PEB). Simulation results demonstrate that proposed reduce energy leakage thus enlarge channel capacity compared scheme. Moreover, could be accurately sensed by ML large computation complexity or roughly FS small complexity.