| Under the pressure of the rapid growth of the wireless services and the increased requirements of the wideband as well as high-speed multimedia service, wireless network demands for more spectrum bands assignment to satisfy all kinds of services and to handle the challenge of better customer experience. Meanwhile, new born wireless technologies also apply for spectrum bands assignment. Consequently, the contradiction between the limited spectrum resource and the fast increased spectrum requirement becomes more and more serious. Fortunately, cognitive radio technology can settle the problem by opportunistically accessing to the license band on the premise of not causing any interference to the license system, based on the fact that the current spectrum bands are not fully utilized. Hence, cognitive radio technology has aroused extensive research interests.This thesis mainly focuses on the measurement of the data fusion algorithm of cooperative spectrum sensing and the research of adaptive spectrum sensing scheme in cognitive radio. And spectrum sensing is the process that cognitive equipment senses its wireless environment and finds out the unoccupied spectrum band. It is the basic function of realizing efficient spectrum utilization and is critical to cognitive radio. Cooperative spectrum sensing is an important guarantee of accurately and swiftly sensing spectrum resources under complicated spectrum circumstance. In general, the contents of this thesis include following aspects:Firstly, the definition and the background of cognitive radio are envisaged. The cognitive radio is identified as a feasible and effective solution to the contradiction between the limited spectrum resource and the rapidly increased spectrum demand. Afterward, the paper demonstrated that as the implementation prerequisite of cognitive radio technology, spectrum sensing is significant for cognitive radio. Then, related researches home and abroad are also investigated. Detailed analysis produces two emphases of this thesis-the measurement of the data fusion algorithm of cooperative spectrum sensing and the research of adaptive spectrum sensing scheme in cognitive radio.The research of cooperative sensing fusion algorithm, this paper extracted the necessity of cooperative sensing from the limitation of local sensing, and then made a comparison with synchronous sensing, finally locked on the research of asynchronous cooperative fusion algorithm as the study orientation. After that, analyzed the current asynchronous cooperative fusion algorithm, proposed one novel triggered asynchronous sensing scheme, which is suitable for cognitive users' administration of fusion center in heterogeneous network environment. While reduced calculation in fusion center, this scheme improved the timeliness and accuracy of cooperative sensing by analysis of sensing period and cognitive user credit level.Corresponding to centralized adaptive cooperation scheme, this thesis firstly analyzed the feature of spectrum which is suitable for cognitive network system, combined with the spectrum distribution in China and the actual spectrum sensing result, determined the workable spectrum for the system. Afterwards, the thesis determined the centralized spectrum sharing network architecture according to the characteristics of the primary authorized services in the specific spectrum. Meanwhile, designed one local sensing algorithm applicable to this spectrum, and also studied every function module and related problems that should be taken into consideration in cooperative scheme designation. Ultimately described function module, working process, interface parameter and adaptive requirement of centralized adaptive cooperation sensing scheme in the design.A summary of the whole thesis is given at the end, where the future research directions related to this thesis are also pointed out. |
