Reconfigurable intelligent surfaces (RIS)

RIS is a novel technology that uses network nodes to utilize intelligent radio surfaces capable of adjusting their response to match the propagation environment’s conditions through control signaling. It is a reconfigurable intelligent surface designed to have properties which enable the dynamic control of electromagnetic waves on its planar structure. An RIS generally consists of a large number of low-cost, passive (and thus low-energy) elements, each of which reflects the incident signal with a certain phase shift to collaboratively achieve beamforming and suppress interference at one or more designated receivers. The building blocks of such an RIS are known as metamaterials. In contrast to materials with properties based on their atomic constituents, these are engineered structures designed to interact with electromagnetic radiation in a desired fashion and afford special properties. They usually comprise an array of structures smaller than the wavelength of interest.

Metamaterials are key to any RIS, as RIS are composed of numerous small metamaterials capable of dynamically altering their electrical or magnetic properties. Through precise control of these properties, the RIS can selectively manipulate the reflection, refraction and scattering of radio waves. By adjusting the phase shift and amplitude of the reflected waves, the RIS can fine-tune signal strength, direction and other parameters to facilitate optimal wireless communication. RIS essentially functions as an intelligent medium for shaping and directing radio waves according to specific requirements.