Research On Cooperate Spectrum Sensing Algorithm In Cognitive Vehicular Ad Hoc Networks

As people pay more and more attention to road safety and in-vehicle entertainment,vehicular communication business type and quantity are surging,which make the demand of spectrum increase rapidly.This increase leads to the shortage of spectrum resources in vehicular ad hoc networks.In order to alleviate the contradiction between the growing demand of vehicular communication services and the increasingly tense spectrum resources,cognitive radio is proposed to apply to vehicular ad hoc networks to provide additional spectrum resources,and effectively solve the problem of scarcity spectrum.Spectrum sensing is the primary task in cognitive radio.However,in the high-speed vehicular environment,the performance of spectrum sensing is seriously affected,so it is necessary to design an efficient and reasonable spectrum sensing algorithm.In this paper,we mainly study the spectrum sensing algorithm in cognitive vehicular ad hoc networks.Firstly,we study the traditional single-user spectrum sensing and cooperative spectrum sensing algorithms,then a simulation analysis and comparison is carried out.Secondly,we analyze the influence of high speed motion on the traditional spectrum sensing algorithm.Finally,we propose a cooperative spectrum sensing algorithm for high speed vehicular environment.The main work of this paper is as follows:Firstly,this paper studies the single-user spectrum sensing algorithm for cognitive vehicular ad hoc networks.Considering the complexity of the channel in high speed vehicular environment,the signal-to-noise ratio is low and the received signal is too weak,this paper proposes a double threshold cyclic spectrum energy detection algorithm.The double threshold can reduce the influence of noise uncertainty on the detection performance.The Doppler shift of the high-speed motion causes the cyclic spectrum to shift and disperse,this lead to decrease of the detection performance.Thus,a Doppler shift estimation algorithm based on the correlated conjugate cycle auto-correlation function is proposed in this paper.Before the detection,received signal is Doppler shift compensated to eliminate the impact of Doppler shift.Secondly,the cooperative spectrum sensing algorithm in cognitive vehicular ad hoc networks is studied.Considering the limitations of single-user spectrum sensing,acooperative spectrum sensing algorithm based on secondary user correlation is proposed.Cognitive vehicles are selected to cooperate according to the double threshold,that is,the cognitive vehicles with test statistic outside the two thresholds is selected while the test statistic is between the two thresholds,the corresponding cognitive vehicles are directly discarded without judgment.Considering the existence of certain shadow correlation between the cognitive vehicles,the position-dependent linear weighted-K rank fusion scheme is used for data fusion,the weights dynamic change with the real-time change of vehicles' relative position.Simulation results show that compared with the existing algorithm,the proposed algorithm has a better detection performance.