Research On Spectrum Sensing In Cognitive Vehicular Networks

As a reliable way to improve road traffic safety and communication efficiency,vehicular network has become a research hotspot in the development of smart cities and intelligent transportation.Vehicular network needs to ensure the safety of collision warning,blind spot warning and other business applications in order to improve the driving safety.At the same time,vehicular network also need to realize conveniently and efficiently accessing to the Internet,providing information and entertainment service in order to meet our requirements.Research shows that both the safety applications and the business applications require a lot of band widths.On the other hand,with the explosive growth of vehicular network communication requirements,a large number of vehicle nodes will have serious delay and packet loss rate when they compete the limited bandwidth.Thus,vehicular network needs more spectrum to provide a reliable transmission.To apply the cognitive radio technology into vehicular network becomes an effective method to solve the shortage of spectrum opportunistic.The research topic is supported by Chinese National Nature Science Foundation Project "Sensing and utilization of polarization resource in dense heterogeneous wireless environment"(No.61571062)and the project of Beijing supports Central Government Programs"The development of application technology in public bus network based on cognitive radio network" This paper carried out the study of the spectrum sensing technology in cognitive vehicular network in order to find new theories and new methods.And it has improved the spectrum utilization rate in this paper.The main contents and achivements of this research are summarized as follows:(1)This paper summarizes and analyzes the technology of vehicular network,cognitive radio,cognitive vehicular network and spectrum sending in cognitive vehicular network.First of all,this paper summarizes the current situation of the development of the vehicular network,and points out the contradiction between the high demand of the spectrum resources in vehicular network and the shortage of current spectrum resources.Secondly,the research gives a survey of cognitive radio technology and spectrum sensing technology,and it point out the necessity of constructing cognitive vehicular network.Then,the research progress and the challenges of cognitive vehicular network are analyzed.Finally,this paper summarizes the current situation of spectrum sensing technology in cognitive vehicular network,and points out the shortcomings of the existing research.The three factors of theoretical research and simulation analysis in the dynamic vehicular network environment has important guiding significance for spectrum sensing algorithm research.(2)The cognitive vehicular network environment is dynamic,which is embodied in three aspects:cognitive user mobility,fast fading of channel and dynamic changing of vehicle flow in space and time.The current majority of spectrum sensing technology researches often assume that cognitive users in static state,and few papers consider to model cognitive user mobility as a random walk model,or a random waypoint model.These researches are not appropriate to actual vehicle movement.Considering the cognitive user mobility,some papers respectively investigate the random mobility model and mobility model under limited area.The performance are deduced by analyzing the spatial-temporal spectrum opportunity.And the capability of spectrum access is studied.In view of the time-varying fading characteristics of the vehicular netwokd,this paper analyzes the spectrum sensing performance of four typical time-varying channel scenarios,namely Rayleigh channel,Nakagami channel,log-normal channel and Suzuki channel.In this paper,the spectrum sensing performance of traffic flow is analyzed based on the correlation between users.(3)Under the dynamic channel of cognitive vehicular network,the high speed mobility of cognitive users causes a deviation between the cycle frequency received by cognitive users and the main user cycle frequency.In order to compete the loss of spectrum sensing performance caused by cyclic frequency offset,a spectrum sensing algorithm based on the Fourier expansion channel model is proposed in this paper.Compared with the traditional spectrum sensing algorithm,the analysis and simulation results show that the proposed spectrum sensing algorithm based on Fourier expansion channel model accurately estimate the channel,and effectively overcome the cycle frequency offset problem.The algorithm improves the reliability of spectrum sensing under dynamic channel.(4)In order to solve the problem of inaccurate cooperative spectrum sensing data caused by the interference users,this paper proposes a spectrum sensing algorithm under the dynamic traffic flow in the cognitive vehicular network.In this paper,the LRMR-RCSS algorithm under the scenario of low traffic density is proposed to eliminate the influence caused by the error of spectrum sensing data.The LRMR-RCSS algorithm recoverys the real low-rank spectrum sensing data.Considering the dense vehicular environment,this paper established a WLRMR-RCSS algorithm based on the diversity effect of cooperative users.Analysis and simulation results show that both the proposed LRMR-RCSS algorithm and WLRMR-RCSS algorithm can effectively compete the interference of error spectrum sensing results.The weighing mechanism in WLRMR-RCSS can effectively reduce the cooperation overhead in dense traffic environment.