Research On Spectrum Sensing And Transmit Power Allocation In Cognitive Radio Network

With the development of wireless communication technologies, an important development trend of mobile communications is broadband multimedia communication in the future, limiting it to develop of the main reasons is the lack of spectrum resources, and the spectrum allocation inflexibly. At present, the vast majority of the band for radio communication has been fully allocated, the U.S. Federal Communications Commission study found that the existing use of licensed spectrum, especially in the frequency needs very tense from megahertz to three Gigahertz band spectrum utilization is very low, ranging from15%to85%.Current fixed spectrum allocation method is the main reason for the low frequency utilization.In fixed spectrum allocation, even if the authorized user at a certain time, location, not using its authorized band, other non-authorized users are not permit to use the band, resulting spectrum resource waste.Cognitive radio provides a viable idea to solve the problem of spectrum resources scarcity and meet additional demand for wireless access by "secondary use" of licensed bands to improve the utilization of the spectrum. Unauthorized users how to detect spectrum "white space" and successfully access authorized "white space", is the most critical and fundamental challenges in cognitive radio network.First, the paper describes the development of cognitive radio network, elaborated the concept of cognitive radio networks, research progress and potential practical application scenarios. Specific description of the composition and structure of the cognitive radio networks, cognitive radio network system should have three main functional modules of access to information, learning, decision-making and adjustment. In this chapter, also introduce the classic architecture of the cognitive radio network model:the center control architecture, distributed control architectures and net control architecture.Secondly, the paper describes the existing spectrum sensing cognitive radio technology, analyzes the advantages and disadvantages of various existing detection technology. In accordance with the energy detection method, the author propose a multi-user collaborative scheme based on dual thresholds energy detection, in this scheme, each secondary user’s detection decision has a weight value, which is characterized by the secondary user’s distance from the Node (e.g. base station).Simulation results and analysis show that the proposed improvement program can increase the accuracy and reliability of the collaborative detection.Thirdly, the paper describes the method of the dynamic spectrum management in cognitive radio networks. The paper also discusses spectrum allocation strategy for cognitive radio networks, focusing on analysis of the orthogonal spectrum access spectrum allocation the colored graph theory model, introducing a list graph coloring algorithm, color sensitive graph coloring algorithm and improved parallel algorithm based on color sensitive graph coloring algorithm. At last, author describes the channel assignment in the shared spectrum access mode, i.e. power control problem.Finally, the paper introduces the existing power allocation algorithms for cognitive radio networks, game theory power control method and power control method based on water-filling algorithm. In this chapter the author also made some improvements on conventional water-filling power control algorithm, experiment simulations and results show that the improved scheme can reduce the interference which is brought in by secondary users access, also keep the system data rates the same with optimal water-filling algorithms. The analysis showed that the improved algorithm having a lower complexity, it is possible to reduce the time consuming of the power allocation. That is the system pursuit.