Spectrum Sensing for Half and Full-Duplex Cognitive Radio

According to the Federal Communications Commission (FCC) [1–3], the typical radio channel occupancy is less than 15%. The Dynamic Spectral Access has been proposed as a solution to increase the spectrum usage, and to solve the problem of the scarcity in the frequency resources due to the increasing in the demand on the wireless technologies. The Cognitive Radio (CR) technology is presented as a good candidate for applying the Dynamic Spectral Access. According to FCC, CR is an aware system, that can detect its own electromagnetic environment, so it can intelligently detect which communication channels are occupied and which are in use, and instantly move into vacant channels while avoiding occupied ones. This optimizes the use of available radio-frequency (RF) spectrum while minimizing interference. The CR idea is based on the sharing of the spectrum between users: licensed users are called Primary Users (PU) and unlicensed users are called Secondary Users (SU). SU can use the channel only when PU is idle. Generally, this activity is done in a non-cooperative context. In other words, PU is not obligated to notify SU on its activity.