Research Oncognitive Radio Cooperate Spectrum Sensing

With the rapid development of wireless communication technology, spectrum resources are increasingly strained, the statistics find that the utilization of the licensed spectrum is low. Cognitive radio technology is considered to be an effective technique to solve the problem, and the first step of its implementation is the spectrum sensing of the licensed bands for white spaces. Spectrum sensing technology can be divided into single-user spectrum sensing technology and multi-user cooperative spectrum sensing technology.According to the shortage that the existing single-user sensing algorithms need to known the noise variance and have the problem of noise variance uncertainty, this thesis proposed an improved algorithm, which is based on the combing of the fractal dimension and third-order cycle accumulation. We used fractal dimension algorithm when the signal to noise (SNR) is high, and used third-order cycle accumulation algorithm when the SNR is low. At the same time, considering the high computational complexity of the third-order cycle accumulation, we proposed an improved third-order cycle accumulation algorithm. The simulation result showed that the improved algorithm can guarantee a good probability of detection in the case of high SNR and low SNR.Because the control channel is not ideal, the cognitive radio user's sensing data may be transmitted to the fusion center falsely on the control channel, and the system detection result may be wrong, which lead to the sensing performance decreases. This thesis proposed a cooperated spectrum sensing solution which based on a relay. That we used a relay to cooperate to transmit the cognitive radio user's sensing data to the fusion center, which makes the bit error of user's sensing data decreases when it transmits. At last it verified that the method can improve the system detection performance.