Research On Spectrum Handover In Cognitive Radio Networks

Cognitive radio (CR) is a hot technology to solve the current shortage of wireless spectrum resources, it can make use of every bit of spectrum to improve the utilization of spectrum resources and avoid the interference to the authorization system. Spectrum handover is one of the key technologies in cognitive radio. In this paper, we study the spectrum handover mechanism deeply and design spectrum handover mechanism based on weather it have available spectrum resources reaching to the target node.At first ,this paper introduces the theoretical basis for the study, namely, the basic concept of cognitive radio,related protocols and key technologies. Then it analyzes and summarizes the concept, triggering causes, common processes, performance analysis of spectrum handover and its challenges under cognitive environment. Finally, the representative strategy and analysis models of spectrum handover are introduced. Based on analyzing the shortcomings of them, the main research motivation and start point of this article is indicated.In allusion to the case of exiting the available spectrum which can cover the goal nodes, chapter 3 proposed a spectrum handover mechanism based on grading and multi-attribute making decision theory. In this chapter, the available spectrum and second users are graded, and different types of business option available spectrum at different levels and adopts multi-attribute making decision mechanism to select the target switching channels in the corresponding types of spectrum. The simulation results show that: when the business loads increase, the algorithm ensures the link maintenance probability of all second users according to the order of priority. Compared with the first matching selection algorithm, the comprehensive performance of target channel is better.When there is no available spectrum that can cover the goal nodes, chapter 4 proposed a spectrum handover mechanism based on multi-channel collaboration relay, which quote the thinking of relay, and designed the mechanism of relay node selection and spectrum reservation considering user demand with cognitive radio features. The simulation results show that: for the reservation mechanism, the improved algorithm is better on the spectrum utilization compare to the original algorithm, while the transmit power of the selected spectrum is lower. On the whole, the mechanism proposed greatly reduces the link interruption probability.