Flexible distributed wideband cognitive radio network with double threshold energy detector combining cooperative and spatial diversity

To improve the radio spectrum utilization, cognitive radio (CR) technology, which can dynamically use frequency bands detected as free, has been proposed. To provide this detection with sufficiently security for the licensed primary user (PU) and without a loss of CR capacity, spectrum sensing is a fundamental requirement in CR. Also, if this spectrum sensing is addressed for wideband, a current idea is to distribute it among all CRs in the network by dividing the wideband sensing into several sub-bands sensing. However, this physical spectrum division can be too wide to detect narrow band PU. In this paper, we propose to analyse digitally these sub-bands by using a numerical fast Fourier transform (FFT). This analysis is then made, in each sub-sub-bands, by a double threshold energy detection method. For a targeted probability of PU detection, simulation results show the possibilities of the proposed system when a multi-optimization problem is addressed.