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
software-defined radio,
IoT,
M2M,
802.11ah,
802.11af and
802.22.