Research On Information Reconstruction And Routing Optimization Mechanism Based On Radio Environment Map In Cognitive Radio Networks

With the rapid development of wireless communication technology,radio spectrum resources which can be allocated for future wireless communication services are decreasing.However,the radio spectrum that has been allocated is under-utilization.Cognitive radio networks are the research hotspots in the field of wireless communication,which can improve the utilization ratio of the allocated frequency band.Radio environment map contains multidimensional information of the radio environment which can be widely used in cognitive radio networks.However,radio environment map is facing the threat of Spectrum Sensing Data Falsification(SSDF)attack.Therefore,the research on how to resist SSDF attack is an important subject of radio environment map reconstruction.Routing technology is the basis for achieving end-to-end data transmission and is one of the key technologies of cognitive radio networks.Therefore,the thesis' s research points are radio environment map reconstruction and routing optimization in cognitive radio networks.Firstly,due to the presence of SSDF attack,the difference between the reconstructed radio environment map and the real radio environment is huge,resulting in the reduction of the availability of radio environment map.To solve this problem,radio environment map reconstruction scheme based on trust mechanism is proposed.Firstly,the trust level of the data is determined through the clustering method.And the calculating and updating scheme of the trust value of the sensing node is described.Then,the weight of each data is calculated according to the trust value of every sensing node.Finally,the radio environment map is reconstructed through spatial interpolation algorithms.The simulation results indicate that the proposed scheme is able to resist SSDF attack and guarantee the accuracy of the radio environment map.Secondly,in cognitive radio networks,when comes to the design of routing algorithm,primary user protection and routing performance should be take into consideration at the same time.Radio environment map is able to provide secondary user with radio environment data which relates to primary user protection.As a result,in order to improve the end-to-end performance of routing between secondary users in cognitive radio networks,a route optimization mechanism based on radio environment map is proposed.First of all,radio environment map sends the availability and power control information about each authorized frequency band back to the secondary user which forwarded the request.Then,secondary user calculates the stability of the link and the delay between the previous hop user and itself.Finally,the destination secondary user calculates the expected value of the end-to-end throughput of each route and selects the route with the maximum expected value.The simulation results show that the proposed routing mechanism is superior to the contrast routing algorithms in average packet delivery ratio,average end-to-end throughput and average end-to-end delay.