Cooperative Spectrum Sensing and Optimization on Multi-Antenna Energy Detection in Rayleigh Fading Channel

In order to reduce the problem that the spectrum resources are not allocated uniformly, we adopt spectrum sensing of cognitive radio technology to find spectrum holes so that the cognitive users can legally use the licensed band, and reduce the waste of spectrum resources. In this paper, the simulation of cognitive radio system works as follows: First, the system creates transmit signal by a single antenna. Then several multiple antenna energy detectors are used as cognitive relays. The architecture becomes single-input multi-output system. In cooperative spectrum sensing method, each cognitive relays receives signal energy from primary user, and we assume the simulation in Rayleigh fading channel environment. Not only will we investigate the effect with multiple paths for cognitive radio system, but we also examine cognitive relays at distinct position to detect primary user signal. Cognitive relays enhance cognitive performance by beamforming technology. After spectrum sensing, we get the results transferred to decision center by multi-input multi-output system. Then decision center uses decision fusion method to obtain the final result. We propose the rounding down method that abandons relays with the worst signal before decision fusion. The proposed method is able to improve system performance.