  Over the last decade, cognitive radios (CRs) have emerged as a technology for
improving spectrum efficiency through dynamic spectrum access techniques. More
recently, as research interest is shifting beyond 5G communications, new
technologies such as reconfigurable intelligent surfaces (RISs) have emerged as
enablers of smart radio environments, to further improve signal coverage and
spectrum management capabilities. Based on the promise of CRs and RISs, this
paper seeks to investigate the concept of adopting both concepts within a
network as a means of maximizing the potential benefits available. The paper
considers two separate models of RIS-based networks and analyzes several
performance metrics associated with the CR secondary user. Monte Carlo
simulations are presented to validate the derived expressions. The results
indicate the effects of key parameters of the system and the clear improvement
of the CR network, in the presence of a RIS-enhanced primary network.
