Study Of Cognitive Radio Spectrum Sensing Technology

In 1999, for resolving the problem of low spectrum utilization Dr. Mitola presented a viable solution-Cognitive Radio (CR). CR is a novel wireless communication technology, which has speeded up to develop in recent years. The core idea of CR is the secondary user reliably senses the environment in the broadband spectrum for inspection primary user and occupies available local spectrum adaptively to avoid the interference between the primary user and the secondary user in the communication process. Because of its intelligence and flexibility in spectrum use, CR is considered as one of the key technologies to meet the case of broadband wireless communications in the future, and will become an important part of future wireless ubiquitous network. At present, CR has been an excellent candidate for a next broadband wireless communication system. Therefore, establish and improve the basic theory of CR system to address its key technology, has a very important scientific and practical sense. This study mainly discusses the key techniques of spectrum detection and the issues can be divided into three parts:optimal low-power spectrum detection algorithm design, CR interference detection and analysis based on spatial spectrum estimation, and real-time interference detection and analysis based on spatial spectrum changes.This study includes 6 chapters. The main content and innovation can be summarized as following:Chapter 1 is the introduction. In this chapter, the notion, the characteristics, prospect of deployment, and the key techniques of CR system are introduced. Then, the main research content and innovation of this dissertation are summarized.In chapter 2, the general issues of CR spectrum sensing technologies are described. The important spectrum sensing technologies of CR are introduced, their basic principles, methods and advantages and disadvantages to achieve such a detailed analysis and discussion.Chapter 3 introduces a two-threshold primary user detection algorithm based on energy detection. Firstly, time domain and frequency domain primary user detection algorithms based on energy detection are introduced and carried out a detailed theoretical analysis, and pointed out the advantages and disadvantages of algorithms respectively. Then, from the perspective of reducing the power consumption of detection system, a two-threshold detection algorithm based on both time domain and frequency domain energy detection and its improvement are proposed, and the proposed algorithm is analysed theoretically in detail. Finally, with a large number of simulation experiments, the performance of the proposed algorithm is compared with the traditional algorithm, and simulation results show the effectiveness of the algorithm.In chapter 4, a novel interference temperature estimation model based on directions of arrival is expatiated. Firstly, background and significance of this model are analysed and the specific algorithm is derivated in detail. Then, the spatial spectrum estimation theory which is involved in the broadband signals interference temperature estimation is discussed fully. Finally, the simulation shows that the proposed algorithm can reduce the interference temperature estimation valuation and improve spectrum efficiency under the directed communication conditions.In chapter 5, a novel Multi-Taper Method Combined with Singular Value Decomposition (MTM-SVD) interference temperature algorithm based on neural network in the electromagnetic spectrum environment which changes slowly is presented. Firstly, the traditional MTM-SVD of the interference temperature method is introduced, and pointed out the lack of the traditional numerical methods for changes of the electromagnetic spectrum environment. Then, from the adaptive changes of spectrum environment and improving the accuracy of the interference temperature estimation valuation perspective, the interference temperature model based on neural network is established, and the new neural network model is analyzed and discussed thoroughly. Finally, the proposed algorithm is compared with the traditional algorithm in algorithm complexity, interference temperature estimation valuation accuracy and performance to adapt to changes in spectral characteristics. The simulation results show that the proposed algorithm can response real-timely the changes of the electromagnetic spectrum environment and the interference temperature estimation valuation is much more accurate and effective.In the last chapter, the whole study is concluded and succeeding works in the future researches are pointed out.