The Research Of Dynamic Specteum Access In Cognitive Radio Network

With the rapid development of mobile communication technology, the requiring bandwith is also increasing rapidly. In order to satisfy the increasing needs for wideband wireless communication, scientists have developed lots of effective wireless communication technologies. However, we cannot meet the needs for wireless communication simply by developing new transmission technology. Otherwise, the spectrum resources which have been allocated to the existing wireless system are not fully utilized due to the current spectrum allocation method. Cognitive Radio and Cognitive Radio Network as a smart spectrum-sharing technology will be effective in alleviating these contradictions. Through sensing frequency environment, using the free licensed spectrum, a new way on how to improve sectrum utilization of the wireless communications under the conditions of limited spectrum resources has been addressed.Chapter 1 of this thesis introduced the background of cognitive radio, cognitive radio network and the development situation and trend of them. The application scene was also briefly introduced to clear the significance of cognitive radio network.Chapter 2 introduced the key technologies and dynamic spectrum access of cognitive radio network in detail, mainly including dynamic authorizing and dynamic spectrum access sharing. The research center in this thesis was—dynamic spectrum access in cognitive radio network.Chapter 3 introduced the principle of dynamic spectrum access in detail. This chapter also described the mathematical modeling of multiple unlicensed users resue the same frequency range and dynamic spectrum access. This modeling mainly took the efficiency and fairness of different second users into consideration, which provided theory basis for the later design of efficient and reliable dynamic spectrum access mechanism.In chapter 4 and chapter 5, on the basis of the above theory knowledge, centralized and distributed cognitive radio network structures were presented and the detail design of dynamic spectrum access mechanism for the above two network strutrues was introduced. Next the simulation results of the performace of dynamic spectrum access for two network structures were given. In these two chapters, delay transmiting in cognitive radio network was also defined and a dynamic spectrum access mechanism was designed for it. The simulation results showed the benefits of this mechanism and channel selectiong algorithm.Chapter 6 perceived the future development of cognitive radio network and wireless communication.