Research On Cooperative Spectrum Sensing Algorithm In Cognitive Radio

In recent years,with the 3G and 4G began to mature and commercial and the rapid development of 5G,people's demand for wireless spectrum resources growing,which put forward a huge challenge to the original tight and limited wireless spectrum resources.On the other hand,the traditional fixed spectrum allocation method leads to the utilization rate of authorized spectrum resource is very low.In order to solve this contradictions,cognitive radio(CR)technology has been proposed,and become a research hotspot in the field of wireless.The cooperative spectrum sensing(CSS)algorithm in CR has been studied in this thesis.Spectrum sensing technology is the prerequisite and basis of CR technology,which the accuracy of detection performance directly affects the reliability of the cognitive system.Therefore,this technology has been studied extensively.In this thesis,the existing spectrum sensing algorithms have been improved under the background of the difference of sensing channel and the difference of notification channel between second user(SU).The main contents are as follows:Firstly,an adaptive double-threshold energy detection algorithm based on noise variance estimation has been proposed for the noise variance uncertainty problem of the sensing channel influence on the sensing performance.Firstly,the uncertainty interval of the noise variance has been estimated in the fast sensing stage and obtains the interval estimation value.Then,the double threshold value is adaptively set with the upper and lower boundary estimates.Finally,sending the double threshold value to the precise sensing stage for double threshold energy detection.The simulation results show that,the sensing performance of this algorithm is very close to the theoretical value.Then,a new double-threshold CSS algorithm has been proposed to solve the problem that the sensing environment of cooperative SU is different in CSS.Firstly,the optimal single threshold is obtained by constructing the error detection probability function.Then,the double thresholds are set by the difference of the SU-sensing channel.Finally,the sensing performance is analyzed by the optimized fusion criterion.The simulation results show that the proposed algorithm has higher sensing performance than single threshold detection and traditional double threshold detection.Finally,combined with the weighted CSS technique and the CSS technology based on the clustering structure,a multi-cluster weighted CSS algorithm has been proposed under the condition that the fusion center(FC)relative to the SU is in the notification channel fading.The algorithm can effectively improve the performance of the CSS system under the fading channel,and effectively saves the spectrum resources of the control channel,reduces the overhead of the system,shortens the convergence decision delay and responds to the call of green communication.