Research On Cluster-Based Cooperative Spectrum Sensing Technology In Cognitive Radio

As an important nature resource, the electromagnetic radio spectrum is licensed by the government. The study found that some licensed bands are largely unoccupied most of the time, even only1%to6%, and some public frequency bands in the spectrum are very heavily used. Therefore, people turned attention to how to use spectrum resources efficiently. The cognitive radio, defined as an intelligent system that is aware of surrounding environment and learns from the environment and adjusts its parameters to share radio spectrum resources with authorization cognitive users, then improving the utilization of spectrum resources. The spectrum detection technology is one of the key technologies of cognitive radio. Only through the detection of the spectrum, the cognitive network can find spectrum holes, and then adjust parameters, share radio spectrum but not to the detriment of the primary users.This paper first introduces several local spectrum detection methods, and we focuses on energy detection method which does not require any priori information, and the energy detection method is very simple and has been widely used. But single cognitive user is liable to be affected by the environment, so people proposed cooperative spectrum sensing scheme, the system performance can be improved by dealing with the information of multiple cognitive users in cognitive network. In order to reduce the adverse impact of the imperfect channel, we introduce the cluster-based cooperative spectrum sensing scheme, and some correlative theories are introduced too.Secondly, considering the channel between cognitive users in one cluster, we propose a dynamically clustering based cooperative spectrum sensing with STBC scheme. The base station is no longer simply grouping users with their positions, but based on the signal-to-noise ratio between the cognitive users in one cluster. And this scheme makes good use of the inter-channel information and dynamically selects the users to form the clusters. Simulation results show that the proposed scheme has better sensing performance.Finally, by combing different sensing duration and two thresholds, we propose a weighted collaborative spectrum sensing scheme. This scheme is divided into two parts. Part I considering the sensing environment of the cognitive users, assign different weight factor to different users, in other words, we assign high value to the cognitive users who has high detection probability, while assigning low value to the cognitive users who has low detection probability. The simulation results and theoretical analysis show that this scheme can reduce the impact of cognitive users under adverse environment and the sensing performance of the proposed scheme can be improved significantly. Considering there will be some malicious nodes in cognitive network, and these malicious nodes deliberately sent the error message to the base station for some purpose, lead the base station make a wrong judgment, we propose a credibility-weighted cooperative spectrum sensing scheme. This scheme adjusts the weight factor by updating the reputation value, and then weakens the adverse effects of the malicious nodes. The simulation results show that sensing performance of the proposed scheme is better than traditional cooperative spectrum sensing with different sensing durations.