The Research Of Reliable Link Maintenance Methods In Cognitive Radio Systems

Cognitive radio is viewed as a novel approach for improvingthe utilization of a precious natural resource: the radio electromagnetic spectrum. The cognitive radio, based on a software-defined radio, is defined as an intelligent wireless communication system. It is aware of its environment and uses the methodology of understanding-by-building to learn from the environment and adapt to statistical variations in the input stimuli.Firstly, this dissertation introduces the background, development, and research significane of cognitive radios. Then its basic concept, key technologies, applications settings, main functions and important technologies are presented.Secondly, the dissertation summarizes link transfer technology for current mobile communications. It is found that this technology in cognitive radios is absolutely different, for that cognitive users are just sub-users not primary users The so-called cognitive radio link technology is a general model for link maintenance in secondary usage scenarios. This dissertation systematically investigated two theoretical spectrum sharing, negotiated spectrum sharing and opportunistic spectrum sharing, the later of which is more adaptable in cognitive radios. As regards to opportunistic spectrum sharing theory, a link maintenance model is established for primary user interference, whose parameters are also detailed.Thirdly, with respect to primary user interference problem in link maintenance model, this dissertation shows Meta- Content redundancy code solutions. Coding theory, process, as well as redundancy code method are also presented. Through deeply analysis and simulation, this redundancy code method is found to be effective compensation primary user interference.Finally, as regards that primary users have priority rights on spectrum access, in order to fully guarantee communication quality, this dissertation makes simulation analysis from three aspects of the link maintenance model, then detailed investigates the relationships among actual channel goodout, channel sub-band, channel redundancy sub-band, and sub-band to sub-band interference, at last finds the best compromise points between them.