Abstract: In cognitive radio systems, cognitive users require a accurate and real-time judgment of the busy or free of the spectrum. But it is usually very difficult if the cognitive user stations in severe fading or interference. According to these facts,we proposed to use statistical difference value of the primary user and the noise to revise the energy detection.Then we further used cyclostationay detection in the confused area to get more reliable result. The final result is based on the joint judgment of the both detection. Simulation result shows that the proposed method excels energy detection in higher reliability, and cyclostationary detection in lower computation. It presents accurate real-time detection performanc'e even when the noise is in major fluctuation.

Key words: Cognitive radio,Difference value, Cyclostationary detection, Energy detection