Research On Spectrum Allocation Algorithm In Cognitive Radio Network Based On Graph Theory

With the rapidly development of wireless mobile communication technology, an increasingly severe problem of scarceness of wireless spectrum placed in front of us. But on the other hand, there are different levels of idle in Space and time. Therefore people proposed cognitive radio technology. Users in Cognitive radio networks can sense the wireless environment, and accesses the spectrum opportunistically, so the technology can improve spectrum efficiency and use spectrum in flexibility.This paper mainly researches dynamic spectrum allocation algorithm in cognitive radio network. The flexible application of spectrum expects the cognitive radio system dynamically allocate the spectrum resource, at the same time, to help retreat and switch when primary users to present themselves. Therefore, the spectrum allocation becomes the key technology to use idle spectrum efficiently.This paper first introduces cognitive radio briefly, including the concept, function and development, and then introduces the existing model of the spectrum allocation and the spectrum allocation algorithm based on graph coloring theory. After that, this paper analyzes the advantages and disadvantages of existing algorithms.According to the disadvantages of the existing algorithms, this paper proposes a modified algorithm considering user demand and a spectrum allocation algorithm based on users waiting time. This paper describes the design process and algorithm steps of the two algorithms in detail, and has done a qualitative analysis for the performance of the two algorithms. Simulation results show that modified algorithm considering user demand can make total unsatisfied demand decrease greatly and satisfy the user demand better. Under the premise of little loss in total utility, spectrum allocation algorithm based on users waiting time can improve the system fairness and keep users will not fall into a long wait, when the Spectrum resources is short.