The Spectrum Allocation Of Cognitive Radio Based On The Reliable Of The Spectrum Holes

In wireless communication systems, the fixed spectrum allocation method is using by the existing spectrum management and allocation strategies. As the types of users services and the network speed and bandwidth requirements are increasing, the existing spectrum distribution ways are not proper any more.For the spectrum, resources became increasingly intense and the fixed spectrum allocation methods are used, the cognitive radio technology brought to improve the low spectrum efficiency. Cognitive Radio technology could sense the environment, search for available spectrum resources and access spectrum dynamically without influencing the primary users.The spectrum allocation method determines the wireless network spectrum utilization, and it plays a decisive role of the performance of cognitive radio network. The cognitive radio network structure we used is centralized topology and we use overlay sharing to avoid interference. The secondary users choose the spectrum for communication with the minimum interference to the primary uses. Once the primary users appear, the secondary users have to handover to other idle spectrum.For the absolute priority of the primary users, the "collision" problem probably happened between the primary users and the secondary users. The instability and uncertainty of the spectrum holes caused the "collision" problem. In this paper, the time-varying characteristic of the spectrum holes is emphatically analysed. In the research, we find that the service load of the primary system, the arrival rates and the leaving rates of the primary users decide the time-varying characteristic. Therefore, we give the definition of the reliability of the spectrum holes, and quantitative analysis of the difference of time-varying characteristic during the time length the secondary users need. It helps to improve the spectrum efficiency.Accoring to the summarize and analyze of the current spectrum allocation algorithms, on the basis of graph coloring theory, a new spectrum allocation algorithm based on the eliability of the spectrum holes is proposed. Though the simulation, it proves that the new algorithm could decrease the "collision" probability, and improve the spectrum efficiency.