Research On Spectrum Sensing For Malicious User Attacks In Cognitive Radio

The rapid development of wireless communication technology has caused a huge conflict between the growing wireless communication service volume and the limited spectrum resources on which wireless communication depends.It is necessary to find a feasible scheme and strategy to alleviate the contradiction.To solve this problem,cognitive radio technology was born.It allows secondary users to dynamically access the main user’s frequency band without affecting the communication of the main user and exit in time when the primary user is ready to use it.Spectrum sensing technology is a key technology in cognitive radio,which helps secondary users determine the state of the target frequency band,and helps secondary users find spectrum holes.In the collaborative spectrum sensing method,there is often a problem of data tampering attacks initiated by malicious users,which causes other users to misjudge by sending false sensing data to surrounding users,so as to achieve their own purpose of monopolize the frequency band or cause the communication conflicts in sensing network.This thesis makes a specific research on different types of malicious user attacks and defense algorithms in topology-based sensing networks.The main technological innovations are as follows:(1)Aiming at the continuous RD Attack(IRDA)of malicious users,a trust value estimation algorithm based on the path inclusion criterion,the originating node criterion and the number comparison criterion is proposed.These three criteria update the trust values of each node in the topological network by utilizing three fields of the information.Then the outlier elimination algorithm is used to eliminate the collected data with large differences.Finally the new fusion method is proposed to substitute the traditional primary fusion.The new fusion method not only considers the credibility of the origin node,but also considers the possibility of data tampering by the path node to reduce the fusion weight of tampered information in the fusion stage.The simulation results show that the algorithm has a high detection probability and a low false alarm probability.It shows a good defense ability in the face of IRDA attacks by malicious users.(2)Aiming at the collaborative attack method of malicious users,a trust value estimation algorithm based on sliding window and data comparison is introduced.The sliding window algorithm divides multiple sensing time slots into different windows and assigns different fusion weights to them,counts the historical sensing data and the performance of each node under each window,so as to update the trust value of the sensing users.The data comparison algorithm utilizes consistency of data sent by malicious users when they perform coordinated attacks.The nodes with a large degree of similarity and large differences from the perception data of the collecting node are regarded as suspicious nodes.Their trust values are appropriately reduced,and the final trust value is used as the fusion weight of the next perception stage.The simulation result shows that the algorithm has a high detection probability and a low false alarm probability.The new algorithm shows better performance against coordinated attack in sensing networks...