ABSTRACT
The Energy detector is optimal to detect the unknown signal if the noise power is known. In the energy detection, CR users sense the presence/absence of the PUs based on the energy of the received signals. To enhance the sensing performance by exploiting the spatial diversity in the observations of spatially located CR users. Modulated signals are combined with sine wave carriers, pulse trains, repeating spreading, hopping sequences or cyclic prefixes which end up in built in periodicity. Cooperative detection schemes permit mitigation of multipath fading and shadowing effects, thereby improving the detection probability in a heavily shadowed ambience. Universal Software Radio Peripheral (USRP) is a range of software-defined radios designed and vended by Ettus Research and its parent company, National Instruments. Some USRP models also integrate the general functionality of a host computer with an embedded processor that enables operation of the USRP device in a stand-alone fashion.
