Research On Spectrum Sensing Based On Secondary User Node Selection In Cognitive Radio

Due to the rapid development of communication technology,there has been a huge conflict between the limited spectrum resources and increasing communication needs,and it is urgent to improve the utilization of spectrum resources.Therefore,cognitive radio technology comes into being.It can allow secondary users to dynamically access the frequency spectrum for communication without affecting the primary user's communication,then improving spectrum utilization and easing the problem of lack of spectrum resources.Spectrum sensing technology is an important prerequisite for the realization of cognitive radio technology,so that secondary users can independently sense the spectrum holes in the target frequency band and use the spectrum holes.The single-node spectrum sensing technology is greatly affected by multipath fading and shadow effects,so cooperative spectrum sensing technology has become an important research direction.This thesis studies and optimizes the secondary user selection problem of cooperative spectrum sensing.The specific work is as follows:Firstly,this thesis introduces several common detection techniques in single-node spectrum sensing,and analyzes the principles,advantages,and disadvantages.Then it describes two common cooperative spectrum sensing technologies and decision criteria.Secondly,this thesis proposes a distance-based secondary user node selection method.First,using a short distance from the primary user and a good channel environment as a standard,a set of secondary users with a high signal-to-noise ratio is selected.These secondary users can receive a stronger primary user signal,and then show better perception performance.Then,by taking the distance between two secondary users as the standard,a group of secondary users with low correlation are selected to avoid the shadow effect caused by spatial correlation when the distance between secondary users is too close.Aiming at the problem of poor perceptual performance under low signalto-noise ratio of the energy detection method,noise uncertainty is introduced for optimization.Simulation results show that this method can improve system detection performance and reduce detection overhead.Finally,a selection method based on the credibility of the secondary user group is proposed.In view of the existence of malicious users in the wireless environment,the secondary users are evenly divided into several secondary user groups,and a head node within each secondary user group is responsible for reporting judgment information and integrating the judgment information within the group.By analyzing the credibility of each secondary user,the credibility of the secondary user group is obtained.When the credibility of the secondary user group is greater than the preset credibility threshold,the judgment information will be reported.Then analyzes the energy consumption model when sensing and reporting information in units of sub-user groups.Simulation results show that this method can reduce system energy consumption when the confidence threshold is increased,and the detection performance of the system is also improved when there are malicious users.