Outage Analysis and Realization Challenges of RIS-enabled Underlay CR Networks over Nakagami-m Fading

Metamaterials, i.e., reconfigurable intelligent surfaces (RISs), have become very promising and advancing rapidly due to the ability to manipulate electromagnetic (EM) waves. This feature essentially ensures the versatile application area such as various imaging techniques, cloaking devices, wireless power transfer systems, holography, and cross-radar section reduction. The control of EM waves, within the idea of digital metamaterials, can be realized by employing binary coding with 1-, 2-, or more bits. In general, the programmable metasurface can assure the modification of reflected wave amplitude and phase in a certain frequency band. In another development, cognitive radio has become an effective approach for improving spectrum efficiency. Possessing promising features, this work investigates the concept of adopting both RIS and CR within a network for the purpose of increasing the possible benefits available. We simulate the practical realization of the digital metasurface using different coding elements. We obtain the exact and numerical solutions for the system's outage probability and validate the expressions via Monte Carlo simulations. Furthermore, the impacts of the Nakagami- m fading parameter, interference temperature constraint, and number of reflective elements on the system performance are examined and discussed.