Reconfigurable Intelligent Computational Surfaces: When Wave Propagation Control Meets Computing

The envisioned sixth-generation (6G) of wireless networks will involve an intelligent integration of communications and computing to meet the urgent demands of task-oriented applications. To realize the concept of the smart radio environment, reconfigurable intelligent surfaces (RISs) are becoming promising options for offering programmable propagation of impinging electromagnetic signals via external control. However, the purely reflective nature of conventional RISs induces significant challenges in supporting a variety of computation tasks, such as wave-based calculation and signal processing. To fulfill such computing demands, new metamaterials are needed to complement the existing technologies of reconfigurable surfaces, enabling further diversification of electronics and their applications. In this event, we introduce the concept of reconfigurable intelligent computational surface (RICS), which is composed of two reconfigurable multifunctional layers: the reconfigurable beamforming layer, which is responsible for tunable signal reflection, absorption, and refraction, and the intelligence computation layer, which concentrates on meta-materials-based task-oriented computing. By exploiting the recent trends in computational metamaterials, RICSs have the potential to make joint computation and communication a reality. We further demonstrate two typical tasks of RICSs, in particular a spectrum learning task for intelligent communications and a signal processing task for physical layer security. Future research challenges arising from the design and operation of RICSs are finally highlighted.