The Research On Cooperative Spectrum Sensing In Cognitive Radio Network

With more limited spectrum resource, cognitive radio technology becomes a new paradigm in wireless communications which can resolve the contradiction between allocation and utilization of the spectrum effectively. As an important issue in cognitive radio, spectrum sensing technology is under extensive research. As to distributed cognitive network, cognitive users exchange sensing information to each other, and sense the primary user by cooperating. As to centralized cognitive network, each cognitive user senses the primary user independently. The decision results made by each one are transmitted to the fusion center for final decision.In this paper, the definition, research situation of cognitive radio and the important function of cooperative spectrum sensing are introduced. According to analysis on research situation of cooperative spectrum sensing technology, basic issues and main targets are proposed. Then two aspects are under research.The first one is about the distributed cooperative sensing network. Ganesan cooperative sensing model on single-antenna cognitive user and model on multi-antenna cognitive user are introduced, then cooperative spectrum sensing algorithm on multi-antenna cognitive users is proposed which based on optimal power allocation and cooperative diversity. It used SVD to implement power water-filling on each antenna based on channel condition, and the detection process of the cooperative spectrum sensing for the primary user was considered in the two-user network with multi-antenna. The ergodic capacity, detection probability and detection time in cognitive network with multi-antenna were analyzed with path-loss model based on exponential attenuation. Theoretical analysis and computer simulation results show that cognitive users with multi-antenna can not only make the cognitive network have maximal ergodic capacity, but also improve detection performance of the system through optimal power allocation and cooperative spectrum sensing: increases detect probability and decreases detection time.The other one is about the centralized cooperative cognitive network. Conventional single threshold sensing scheme is first introduced. To resolve the problem existing in conventional sensing scheme, improved two-threshold sensing scheme is proposed. The close-form expression between detect probability and false alarm probability is also derived. Simulation results show that the improvement of sensing performance for two two-threshold sensing scheme depends on the size of interval between the two thresholds, and fusion bits number can be reduced effectively which save the band resources.