Cognitive radio can dynamically adj ust its spectrum allocation according to secondary users'needs, while the analysis of different levels of service demand are still lacking in existed studies.Aiming at the prob-lem,an improved dynamic spectrum allocation algorithm was proposed based on different levels of service de-mand.In this part,the problem of dynamic spectrum allocation was formulated as a 0-1 integer programming. An improved dynamic spectrum allocation algorithm based on genetic algorithm with t distribution mutation was proposed.The simulation results showed the superiority of the classification model in dealing with the problem of DSA with different levels,the classification model had higher system profits than the common model,and the algorithm proposed could get spectrum allocation efficiency close to the optimal solution,which had a high value of practical application.%认知无线电系统要根据次用户的需求进行动态频谱分配，而现有研究中缺乏对次用户不同需求等级的分析，针对该问题，提出了一种基于不同需求等级改进的动态频谱分配算法。该算法将频谱资源分配建模为0-1整数规划问题，提出了一种基于t分布变异 GA 的认知无线电频谱分配算法。仿真结果表明：该分级模型相比于普通模型在处理不同需求等级DSA分配问题时可获得更高的网络效益，且所提算法的频谱分配效率接近最优分配效率，具有较高的应用价值。
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