Perception Spectrum Detection In Wireless Networks With Dynamic Access Technology

With the rapid growth of wireless technologies, spectrum scarcity has become a serious problem. Cognitive radio technology can effectively solve the spectrum tense actuality. Cognitive radio technology is a revolutionary technology of wireless mobile communication, and the secondary users can use CR technology to sense all available spectrum opportunity at present communication environment, and access spectrum dynamically,so that the efficiency of spectrum is improved and the capacity of wireless communication system is increased.There are two scenarios of using CR technology to access spectrum dynamically. One is that the secondary users share spectrum on unlicensed band,and achieves the dynamic sharing the goal. The other is that the secondary users opportunisticly use licensed spectrum. The latter scenario involves sensing licensed spectrum and avoiding interference to licensed users,which are the key points of cognitive radio. What this paper discusses is the second scenarios.The essential requirements that the secondary users access licensed spectrum opportunisticly is to avoide interference to licensed users, therefore the second dynamic spectrum access way's most important work is to detect the available spectrum hole. None but searched the spectrum hole, the secondary users could access licensed spectrum opportunisticly.This paper first makes an overview of the background, the research present situation and concept for CR, then focused on spectrum sensing, and investigate three spectrum sensing technology: transmitter detection, cooperation detection and interference-based detection. In this paper ,we propose collaborative sensing method based on energy detection and user's cooperation (EDAUC) . Simulation and analyse results show that the method can effectively improve detecting spectrum holes probability.On the basis of detecting spectrum holes premise, in the fourth chapter, we propose a spectrum access model to analyze this problem using markov theory on the basis of CR and OFDM. Then, we propose a dynamic spectrum access scheme based on the system of concession mechanism. In our scheme,cognitive users are allowed to adaptively select available frequency bands,which may use some of the temporarily unused spectral bands of the primary users,so as to effectively improve the spectrum utilization without interference to the primary users.Aiming at deficiencies of the dynamic spectrum access scheme based on the system of concession mechanism(BCM),in the fifth chapter,we propose a dynamic spectrum access scheme based on minimizing interference and maximizing demand. The feature of this scheme is that the cognitive users can select the best available spectrums,which has the most successful access rate,as their candidate access spectrum,after the study of former spectrum access experience. When a primary user appears,the cognitive users will handoff to these candidate spectrums through certain algorithm. Simulation and analyses shows that this scheme can further improve the efficiency of spectrum compared with the BCM scheme.