| With the rapid development of communication technologies,the requirements of the communication business are higher.Spectrum resources become more and more scarce with an explosive growth of the terminal communication devices.Some studies have indicated that the shortage of radio spectral resource is getting serious day by day,because the spectrum allocation policy is not adequate.To improve the utilization of spectrum allocation,Joseph Mitola proposed the concept of Cognitive Radio(CR)in 1999,which has attracted much attention in the international communication community.The basic idea of CR is to make the wireless terminals have the abilities to detect the "spectrum holes" and to take full advantage of them without affecting any other primary users.As a communication technology,due to the open and dynamic features of CRN(cognitive radio network),the CR systems are vulnerable to various malicious attacks,both traditional wireless security and some new classes of security threats.Thus,it is essential to strengthen its security to make CR viable and reliable.The thesis mainly includes five aspects about the work and research in this area.Firstly,a comprehensive introduction and review on traditional radio,software defined radio and cognitive radio is provided.This section describes the core technology of these radio network and compare the differences between them.It highlights the key technologies and main issues of cognitive radio.Secondly,as a communication technology,cognitive radio faces security issues as traditional radio network does,it faces new security risks or threats because of the dynamic and cognitive features.These security threats become a major obstacle to the development of cognitive radio network.Discussion and research of the security issues of cognitive radio and spectrum sensing are provided in the thesis.Thirdly,spectrum sensing is the key technology in cognitive radio and is the basis of the implementation of cognitive radio network;however,it is the most vulnerable node to be attacked.To better understand cognitive radio and the security issues,starting from spectrum sensing,the thesis analyzes the key technologies of cognitive radio and implement the functionality of spectrum sensing.With Sora platform,using the SDK,a spectrum sensing system is designed and implemented to obtain the statistic information about the spectrum resources around the users.Fourthly,cognitive radio network system security analysis is proposed and a method of applying comprehensive judgement based on fuzzy mathematics to analyzing security situation of cognitive radio network is proposed.Fifthly,based on fuzzy mathematics,a detailed analysis of security situation of cognitive radio network is explored.The detailed processes and algorithms are described and the safety assessment results are analysed.The innovations of the research topics in the thesis are summarized as follows:Firstly,a new method of safety assessment analysis for systems with different scales and infrastructure based on fuzzy mathematics is proposed.Secondly,the evaluation system and evaluation index sets of the security situation of cognitive radio network is constructed.Thirdly,a fuzzy mathematical model of security assessment method for cognitive radio network system is proposed.It provides theoretical base for studying security situation of these kinds of systems.Fourthly,the method can be used in the safety analysis of a running system and can also be used in the design and planning of a new system.Fifthly,regarding system security,especially for security comparison,there is no exact basis,and the conclusion is not quantifiable.The new method proposed in the thesis can provide quantified results on the fuzzy idea of safety,so the results are more convincing.As can be seen from the above description,the research of this subject not only has certain theoretical value,but also has a very broad application prospects. |
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