Reserch Of Cooperative Spectrum Sensing Technology Based On Double Threshold In Cognitive Radio

As one of the key technologies, spectrum sensing is the first step for realization of cognitive radio. Now the research on spectrum sensing technology is mainly focused on the field of single node spectrum detection and multi-node spectrum detection. The service condition of the spectrum can be judged accurately by dealing with the detection information of cognitive users for the cooperative detection. In order to improve the spectrum detection performance, the cooperative spectrum detection and decision fusion algorithm are studied further based on analyzing the existing research results, and the main work of this thesis is as follows.In this thesis, firstly, the developing summary of cognitive radio is introduced; secondly, the technology of spectrum sensing is presented detailedly through the concept of spectrum sensing, the study status at home and abroad, and performance assessment. And then, single-user local spectrum sensing method is analyzed, including the transmitter spectral detection and receiver spectral detection. In order to deal with the limitation of individual node spectrum sensing, cooperative spectrum sensing is introduced, and several conventional soft decision methods and hard decision methods in cooperative spectrum sensing are discussed in this thesis. The detection performance of various classical algorithms are compared and analyzed by the simulation.For the soft-decision fusion algorithm, the tug-of-war-based cooperative spectrum sensing is improved in this thesis. In order to further improve reliability, the probability of local detection is used in credibility factor; to reduce the interference between the secondary user and the authorized user and low the BER, the threshold of tug-of-war-based cooperative spectrum sensing is improved in this thesis. A kind of performance evaluation standard, which are pcollision probability and limit-using probability, is proposed and used. Effectiveness of its improvement is proved by the simulation under each node with different Signal to Noise Ratio.For the hard-decision fusion algorithm, a novel "use-to-idle ratio" rule cooperative spectrum sensing based on double-threshold for cognitive radio is proposed in this thesis. In this algorithm, the energy detection method based on double threshold is used in local detection and the "use idle rate" rule detection algorithm with high flexibility is adopted by the fusion center, selecting users through updating the weights. Compared to traditional detection algorithm, this algorithm can effectively reduce the bit numbers of the transmission and increase the detection probability in some degree.