Wireless communications techniques that can sense the signals in the environment and change channels in real time. Such systems must accurately detect the type and bandwidth of the channels transmitting in the vicinity. Cognitive radio (CR) has become an important issue in order to allow the same limited spectrum to be shared with the increasing number of wireless devices in the home, office and industrial facilities. See Internet of Things, M2M, 802.11ah, 802.11af and 802.22.
A radio that is able to acquire knowledge of the condition of the spectrum to which it has access, determine which channels and services are in use and the intensity of the usage patterns, and avoid those channels in order to optimize performance. Cognitive radio is especially advantageous in applications using unlicensed spectrum such as the ISM band, as that spectrum is often and unpredictably subject to congestion. See also channel, ISM, radio, and spectrum.