Date Added: Oct 2010
Radio spectrum has become a precious resource, and it has long been the dream of wireless communication engineers to maximize the utilization of the radio spectrum. Dynamic Spectrum Access (DSA) and Cognitive Radio (CR) have been considered promising to enhance the efficiency and utilization of the spectrum. In current overlay cognitive radio, spectrum sensing is first performed to detect the spectrum holes for the secondary user to harness. However, in a more sophisticated cognitive radio, the secondary user needs to detect more than just the existence of primary users and spectrum holes. For example, in a hybrid overlay/underlay cognitive radio, the secondary use needs to detect the transmission power and localization of the primary users as well.