摘要
量子信息学是一门新兴的交叉学科，它在信息领域中有着独特的性能，在提高运算速度、确保信息安全、增大信息容量和提高检测精度等方面可突破现有经典信息系统的极限。特别是近年来，基于量子并行计算的量子智能算法有效地降低了一些经典难解算法的计算复杂度问题。
近年来，随着无线通信技术的不断发展，频谱资源的使用日趋频繁，整个无线电频谱空间被划分的所剩无几。然而，从一些研究结果可以看到，频谱资源的缺乏更多是由于对不同无线接入技术的频谱分配不合理引起的。认知无线电技术在这样的背景下应运而生，它能够主动检测频谱使用情况，自适应的改变自身通信参数，择机的选择主用户暂不使用的频段进行通信，具有灵活、频谱利用率高等优点。
但是，对频谱的灵活应用要求认知无线电系统能够准确的检测并动态的分配频谱资源，其间还要为主用户的出现实现退避和切换功能，因此，频谱分配问题是认知无线电无线资源管理中的核心问题之一。目前，对认知无线电中的频谱分配问题研究己较为广泛，出现了基于图论理论等频谱分配问题模型，但是本领域的研究还刚刚开始。
本文首先介绍了量子遗传算法的主要思想、机理，并对算法进行了改进且对改进的量子遗传算法进行了性能测试分析。
其次对认知无线电系统的网络构架和系统平台进行了分析介绍，并给出了动
态频谱分配算法的四种模型。接着，研究了现有的基于图论模型的频谱分配算法，
针对原有算法中分配时间开销过大的不足，给出了一种改进的算法。
最后针对原有算法的另一个不足——未考虑不同用户的不同需求，给出了基于用户需求的改进QGA算法。通过仿真，改进算法与原有算法相比在系统公平性和频谱有效利用率方面有了提高。
关键词：量子遗传算法、认知无线电、频谱分配、图论着色模型
Abstract
Quantum information science is a rising cross subject. Due to unique features in information field, it may break the limitation of classic information system, currently available in several aspects, namely, speeding computation, ensuring information security, expanding the capacity of information, improving the accuracy of detection. Particularly in recent years, quantum algorithms, based on the parallel quantum computation, simplify some classic information systems which are not easy to solve on the background of classic system.
In recent years，with the development of radio communication technology ,spectrum resource has been more widely employed,after which very few of the whole radio spectrum space is left.However, according to some researches,the decrease of spectrum resource is largely caused by illegitimate radio technologies,which can automatically examine the employment of spectrum,self-adaptively change communication parameters,and opportunely switch to the bands which are not being used by the primary users.Good agility and high utilization are some of its merits.
Yet,the flexible application of spectrum expects the cognitive radio system to precisely detect and dynamically allocate the spectrum resource,and,at the same time,to help retreat and switch when primary users present themselves.Therefore,spectrum allocation is one of the key issues of the radio resource management in cognitive radio.Nowadays,the spectrum allocation study in cognitive radio has become a hotspot,and some theories,such as the allocation model based on graph theory,have thrived this research field.
However,they are still tiny progess.
Firstly, the dissertation introduces the basic principle of quantum genetic algorithm, and has made the improvement to it.
Secondly,the network architecture and the system platform are analyzed，and the four models of the dynamic spectrum allocation algorithm are introduced.introduced．Then it mainly studies the existing spectrum allocation
algorithm，which based on graph coloring theory,and an improved spectrum allocation algorithm is given.
Finally,aiming at the disadvantage of that the intrinsic algorithm does not take the different needs from different users into account in the process of distribution，another improved QGA algorithm is given．which considers user’s demand．The simulation shows that the improved algorithm could increase the fairness of the allocation and the utilization of spectrum comparing with the existing algorithm．
Key words:Quantum Genetic Algorithm、cognitive radio、 spectrum allocation、 graph coloring theory model
