Study Of Cognitive Radio Spectrum Allocation Algorithm

The scarceness of wireless spectrum hampers the sustainable development of wireless communication services. Cognitive radio (CR) technology is a revolutionary technology of wireless mobile communication, which is considered as a novel method to solve the problem of the shortage of wireless spectrum. Smart users can use CR technology to sense the environment, search for available spectrum resources and access spectrum dynamically, so that the efficiency of spectrum is improved and the capacity of wireless communication system is increased.Recently, there are two scenarios of using CR technology to access spectrum dynamically. One is that CR users share spectrum on unlicensed band, such as Wireless Local Area Network (WLAN) on 2.4GHz and IEEE 802.16h/g Wireless Metropolitan Area Network (WMAN). The other is that CR users opportunisticly use licensed spectrum, such as IEEE 802.22 Wireless Regional Area Network (WRAN), whose users opportunisticly use the spectrum licensed to DVB. The latter scenario involves sensing licensed spectrum and avoiding interference to licensed users, which are the key points of cognitive radio.Our studies mainly focus on dynamic spectrum allocation algorithm in CR system. This thesis firstly summarizes spectrum allocation model in the two senarios mentioned above, including allocation model based on graph colorling theory, game theory and auction theory in economics. Moreover, an important model for measuring interference is introduced, which is called interference temperature model. Then we dedicate to investigating spectrum allocation using graph coloring theory and interference temperature model.This thesis firstly focuses on spectrum allocation based on graph colorling theory. A summary of exsisted algorithms is presented and then a parallel spectrum allocation algorithm is proposed to adapt to a rapidly changing environment in cognitive radio system. Compared with the original algorithm, the parallel algorithm can reduce the temporal cost of spectrum allocation, achieveing near or the same performance. Furether more, a modified algorithm is proposed by introducing a demand factor to meet the needs of the system. Simulation analyses show that the modified algorithm would better meet the system requirements.Based on interference temperature model, we propose a concept of Hierarchical Spectrum Sharing (HSS) firstly and then investigate the architecher and communication modes of HSS as well as the method of spectrum identification in HSS. Simulation analyses show that HSS can extend available spectrum set so that the efficiency of spectrum is improved further.Cognitive radio is a revolutionary technology of wireless mobile communication, which is considered as a novel method to solve the problem of the scarceness of wireless spectrum. In this thesis, by studying spectrum allocation model in cognitive radio, a parallel algorithm and a modified algorithm considering user demand are proposed based on graph coloring theory. Moreover, a novel concept called HSS is proposed based on interference temperature model. The research of HSS in this thesis include network architecher, communication mode and spectrum identification. Analyses show that HSS can extend available spectrum and improve spectrum ulitization.