Cognitive radio (CR) may be a sort of wireless communication during which a transceiver can intelligently detect which communication channels are in use and which aren't . It instantly moves into vacant channels while avoiding occupied ones. It doesn't cause any interference to the licensed user. In cognitive radio networks, two sorts of antennas are needed: sensing and communicating antennas. The sensing antenna, which is typically an Ultra Wide Band (UWB) antenna, is employed to sense the spectrum and find the spectrum holes, and therefore the communicating antenna is employed to transmit at the frequencies of those holes.

Cognitive radio system (CRS) may be a radio system which is conscious of its operational and geographical environment, established policies, and its internal state. it's ready to dynamically and autonomously adapt its operational parameters and protocols and to find out from its previous experience. Cognitive-radio networks aim to use the spectrum during a dynamic manner by allowing radio terminals to work within the best available waveband , maintaining seamless communication requirements during transitions to raised spectrum.A user who has higher priority or. legacy rights on the usage of a selected a part of the. spectrum. â–¡ Secondary User: A user who features a lower priority.