The Analysis And Simulation Of Cooperative Spectrum Sensing Technologies In Cognitive Radios

In the past decade, with the growth of the wireless communication business, the wireless communication technologies are getting more extensive and in-depth studies. In wireless communications, the management of the spectrum is particularly important. Under the current policies, the allocation of the spectrum are fixed to the specific services. These services are authorized to use the relevant frequency bands, while others are prohibit to use them. Therefore the use of the spectrum resources is becoming more tension. In order to meet the current needs of the growing wireless business, cognitive radio(CR) technology emerged, which mainly use the related spectrum sensing technology and spectrum management technology to improve the spectrum efficiency for the current underutilization of the spectrum.In this paper, the spectrum sensing technology in cognitive radio is mainly studied, we first introduce the definition of cognitive radio and the basic spectrum sensing techniques, then carry out the research in two areas.First, we study the cooperative spectrum sensing technology of the SNR-based weighted algorithm. On the basis of various proposed weighted algorithms, we focus on the SNR-based weighted algorithm, and then construct a new model based on it. In the new algorithm, we calculation and distribution the weights before the CRs(cognitive radios) send the singals to the fusion center. After the theoretical analysis, we get that this algorithm can effectively avoid the two drawbacks of the previous weighted algorithms. First, as the fusion center must receive the energy values,the SNR value, and calculate the weights, Its's load is large; On the other hand, because of the complexity of the transmission of various values and the fading in the transmission process, the final judgments will be affected. In addition, the detection performance is also improved compared to conventional cooperative sensing algorithm, which can be seen from the simulation results.Second, we discuss the influence of different manner of random clustering on the coordination performance. When the channels between cognitive users and fusing center are suffered fading, the sensing performance may be severely degraded. In the paper, the cluster-based cooperative spectrum sensing technology is proposed firstly, which can effectively overcome the fading phenomenon. Then surrounding this clustering algorithm, we conduct further analysis. We analyze the effects with different ways of random clustering on the detection performance to find the best clustering method. We discuss several typical cases, and provide the corresponding theoretical simulation for each one. At last we conclude according to the simulation results that in random clustering, the best detection performance can be obtained when the cognitive users are divided into two clusters, with same or two approximately same number per cluster.