Research On Spectrum Allocation Algorithm For Cognitive Radio Networks

In recent years, the limited spectrum resources become increasingly crowded with the rapid growth of wireless services. However, most of licensed spectrums are scarcely used. This contradiction restricts the development of wireless communication. Therefore, how to improve spectrum utilization has attracted considerable attention. Cognitive radio(CR) technology has emerged as a promising technology to improve the utilization efficiency of radio spectrum, which can search and use licensed spectrum automatically, through sensing spectrum environment of frequency domain, time domain and space domain. However, many critical technologies have not been resolved in cognitive radio network based on CR technology, one of which is the spectrum allocation.In this paper, we study the spectrum allocation of cognitive radio network by means of centralized structure and distributed structure separately. It entails three main jobs. The first is about spectrum allocation algorithm based on graph coloring theory, the second is about spectrum allocation and power control joint optimization algorithm based on fairness, and the third is about distributed channel allocation and power control joint optimization algorithm based on game theory.For the centralized network structure, an improved spectrum allocation algorithm based on proportional fairness is proposed according to graph coloring theory, in which an adjusting factor of a channel quality is introduced. The adjusting factor not only has effective inhibitory functions for cognitive users who occupy high priority throughout but also provides the opportunities of channel allocation for more users. The simulation results show that the improved algorithm can improve the users'fairness on service capacity and bandwidth gain compared with previous algorithms. Then, a channel allocation and power control joint optimization algorithm is proposed considering Qos and fairness. We introduce the nash bargaining solution(NSB) to construct the utility function of network performance. The simulation results show that the proposed algorithm makes a good trade-off between system throughout and fairness.For the distributed network structure, a distributed joint channel and power allocation algorithm is proposed based on game theory. Most game algorithms are based on nash equilibrium(NE), but the existence of NE multiplicity has influenced system performance. We use pricing mechanism to improve the NE to enhance the performance of the algorithm. The simulation results show that the proposed algorithm improves the system throughout and reduces the average power consumption of cognitive users.