An Optimized Cooperative Spectrum Sensing Technology Algorithm Based On Double-threshold Energy Detection

With the rapid development of information technology, wireless communicationtechnology is gradually changing to the high speed and the large downloads tendency.The contradiction between business needs and limited frequency resources becomebigger than before. The limited wireless spectrum resources have been becomingshorter and shorter. Nowadays, static spectrum allocation leads to the low spectrumutilization. In order to solve this problem, the theory of cognitive radio has been putforward. The theory of cognitive radio is intended to get and use the best availablefrequency band to increase spectrum resources utilization with the cognitive users’ability of perception and reset. To improve the utilization of spectrum resourcesdynamically.As a kind of intelligent communication system, cognitive radio can detect theexistence of spectrum hole in authorized frequency bands through the spectrumperception technique, and then adjust its transmission power, carrier frequency,modulation mode to take up authorized frequency band. When finding the authorizeduser, the cognitive users will change the parameter of themselves in order not todisturb the authorized user. Spectrum sensing technology is one of the most importantprerequisites depending on which the cognitive radio can work efficiently. Therefore,this topic will focus on the research of how to improve the accuracy of spectrumsensing algorithm effectively in cognitive radio system.Based on the authorized transmitters in spectrum sensing technology, energydetection algorithm is widely used in cognitive radio due to its low complexity. It hasthe advantage of detecting without the users’ prior knowledge. But it is easy to beinflunced with the noise and the fading channel.In order to overcome the disadvantage, this paper combines an energy detection algorithm based on the double-threshold with SNR wall theory and the spectrumsensing algorithm based on differential energy detection to optimize energy detectionalgorithm. As to overcome the effects of the noise in the environment. In the low SNRcommunication conditions, the organized algorithm can enhance the accuracy ofspectrum sensing.The thesis’s main work is as follows:Firstly, an energy detection algorithm based on the double-threshold comes overthe traditional energy detection algorithm. Analysis on the theory in detail andcompare the performance of the double-threshold with the traditional one. As a result,demonstrate the superiority of the double-threshold one.Secondly, single user detection has been proved vulnerable to the noiseuncertainty, which causes the existence of an SNR wall theory below which thedetector can not robustly achieve the given detection requirements. By analysing thephenomenon that SNR wall theory in this paper, combine it with the cooperativesensing to preliminary screening to improve the detection performance.Thirdly, combine the three algorithms which are introduced in detail above inorder to modify the differential energy detection. It becomes a new kind ofcollaborative spectrum sensing model. Compared with the simulation, the proposedscheme which has lower computational complexity and it is easy to be implemented.It can be used to detect different kinds of unknown signals. Especially in the low SNRenvironment, it obviously improves the accuracy of spectrum detection and reducesthe operation time of the system.