Theoretical analysis of combination and detection for short-term cooperative sensing in cognitive radio systems

In cognitive radio systems, one of the main requirements is to detect the presence of the primary users´ transmission. Cooperative sensing is used to improve the detection performance when the number of nodes increasing. In this paper, short-term cooperative sensing based energy detection is considered. The theoretical detection probability of equal gain combination has been analyzed with different SNR on each cooperative node. The combined variable for different SNR based cooperative sensing is proved to follow central and non-central chi-square distribution. Simulation results show that the derived theoretical ROC curve precisely matches the simulated curve.