Relay-assisted spectrum sensing

A cooperative spectrum-sensing problem has been considered here, in which a network of secondary users (SUs) assists a fusion centre (FC) in detecting the presence of a primary user (PU). Assuming communication links with unlimited capacity of the SUs and FC and known channel gains and noise variances, the optimal Neyman-Pearson detector is derived. Assuming limited capacity between the SUs and FC and unknown channel gains and noise variances, three different spectrum-sensing protocols have been studied; namely, amplify-and-forward (AF), compress-and-forward (CF) and detect-and-forward (DF), where each SU transmits an amplified or compressed version of its observed signal, or its local binary decision to the FC, respectively. The Edgeworth expansion is used to obtain novel expressions for the performance of these detectors. The theoretical analysis and numerical results show that the CF and OR detectors outperform the other proposed detectors. In addition, the simulation results show that the performance of the coded protocols (CF and DF) improves as the number of samples increases or as the noise variance at the SUs decreases, whereas such a behaviour cannot be guaranteed in the uncoded AF protocol.