Double threshold-based cooperative spectrum sensing for a cognitive radio network with improved energy detectors

We investigate the performance of cooperative spectrum sensing (CSS) in a cognitive radio (CR) network, where each of the N numbers of CR nodes uses an improved energy detector (IED) to sense the primary user (PU), and makes a local decision regarding the presence of PU using double thresholds. The local decisions are utilized to attain a global decision at the fusion centre (FC) through hard decision fusion. The advantage of a double threshold based system over a single threshold based one is, in the former case, a CR node can opt for no decision when the decision variable lies in the fuzzy zone between two thresholds. Such censoring reduces transmission overhead between CR and FC without significantly affecting the receiver operating characteristics (ROC). In this paper, the performance of the above-mentioned CR network has been assessed in terms of the average number of normalized transmitted sensing bits (knor) and the total error probability (Pe,n). It was observed that knor increases as the signal power raise factor (SPRF), p, of IED increases or failed sensing probability, b0, decreases. Next, optimal number of CR users (nopt) that ensures minimum total error has been found. Further, it was noted that the agility of the network improved when PU death rate increased. The impact of reporting channel on the sensing performance has also been studied. The simulation results indicate that fading and noise of the reporting channel reduced the agility gain of the network significantly.