| Cognitive Radio (CR) has been considered to be the key technology to solve the shortage of spectrum resources in the future. However, how to apply CR is still a big challenge especially with the rapid development of communications and stringent requirements. The key problem we should address when applying CR is to avoid interference to authorized network.This thesis focused on the interference modelling and interference elimination from the perspective of the interference introduced by the CR users. The first part of this thesis introduced the significance of interference modelling and summarized the background, theories and applications from two aspects, i.e., spectrum sensing and network application. The validity and practical significance had been verified by simulation. Then we used the previous models and analysis method to solve the parameters matching of CR networks. From the simulation results, networks can quickly choose suitable parameters according to the environment.Through the study of the first part, interference to authorized network cannot be fully avoided. Coupled with diversity and mobility of CR applications, harmful interference is also unavoidable. Therefore, the second part presented a non-cooperative interference elimination scheme based on Game theory. When interference is too large to authorized user, the non-cooperative interference elimination scheme helps CR users to eliminate the interference with local information. Simulation results showed that this scheme can effectively protect the authorized users'communications.The utility of elimination in the above scheme can not be maximized because of the lack of overall planning and the accurate amount of the interference elimination. To solve this problem, the third part of this paper presents a cooperative interference elimination scheme based on bargaining game. The cooperative scheme can not only solve the problems in non-cooperative game, but also can improve the link qualities of CR users. |
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