Resech On Spectrum Allocation Algorithm In Cognitive Radio Based On Graph Theory

With the development of wireless communication technology, it becomes more and more lack of spectrum resources. One of the problems we have to face is the lack of spectrum resources. However, fixed spectrum allocation has led to the phenomenon of uneven distribution and even waste of spectrum resources, which is in contradiction with the status of lack with spectrum resources. Cognitive radio can effectively alleviate the contradictions. Cognitive radio could adaptive the change of the external wireless environment, and has the ability to "opportunistic exploration of the white space" to access the spectrum, thereby improve the utilization of spectrum resources.Dynamic spectrum allocation is a way to improve the utilization of spectrum resources. In this paper, the dynamic spectrum allocation algorithms which based on graph coloring have been researched to alleviate the low utilization of fixed spectrum allocation.Because of the disadvantages of list-coloring and color-sensitive graph coloring algorithm, a modified distributed greed algorithm based on user’s demand and a modified color-sensitive graph coloring algorithm also based on user’s demand are introduced. The simulation results indicate that the modified algorithms improved user’s satisfaction, spectrum resource utilization, but increased the time cost of the system. Then by comparising the two modified algorithms, it is found that the modified distributed greed algorithm based on user’s demand significantly improved user’s satisfaction and spectrum utilization, but also greatly enhanced the system time cost, however, the modified color-sensitive graph coloring algorithm based on user’s demand is less obvious increased the system time cost, but also improved user’s satisfaction and spectrum utilization.