Research On Models Of The 3D Channel And Interference Of Vehicle-to-vehicle Communications

Vehicle-to-vehicle(V2V)communication is one of the basic elements that make up vehicular networks.Its performance is directly constrained by the signal propagation environment.Appropriate channel models and interference models are of great significance to the design and performance enhancement of V2 V communication systems,and they are also research hotspots and difficulties in the field of communication.However,the complex and changeable signal propagation environment brings severe challenges to the study of the three-dimensional(3D)channel and interference model of V2 V communication,making the existing models less adaptable: the existing channel models generally assume that the transceiver moves with a constant velocity in a constant direction,and the transmitted signals reach the receiver after undergoing only one or two scatterings,without considering the effect of the non-linear variation in the moving speed and direction of the transceiver and multiple dynamic scattering in the 3D space;the existing channel models in the angular domain are mostly two-dimensional omni-directional azimuth channel models,which cannot characterize the spatial selectivity of channels in 3D angular domain caused by the non-uniform distribution of scatterers;the interference model in 3D angular domain has not yet been developed in the existing literature.For the signal propagation environment of V2 V communication,the thesis first models the 3D channel and interference of V2 V communication,and then studies statistics of the channel,interference and signal-to-interference ratio(SIR)in order to provide a theoretical basis for improving the performance of V2 V communication.The main research contents and achievements of the thesis are summarized as follows:(1)A 3D multiple-input-multiple-output(MIMO)V2V channel model with multiple moving scatterers was proposed,and a model of the transceiver movement with nonlinearly varying velocities in nonlinearly varying directions was developed.The corresponding channel statistics such as space-time correlation function(ST-CF)and Doppler power spectral density(D-PSD)were derived,and the effect of various factors of the signal propagation environment of V2 V communication such as maximum bounces,scattering forms,scatterer velocity distributions and roadway scenarios on the channel statistics was analyzed.In the models,transceiver could move with nonlinearly varying velocities in nonlinearly varying directions,each scatterer could move with a random velocity in a random direction,and the signal could be multiple bounced by moving scatterers.Time correlation functions and space correlation functions of several notable existing channel models such as the Jakes model,single-ring moving scattering model and two-ring fixed scattering model became the special cases of ST-CFs of the proposed channel model,which indicated the proposed channel model was generalized.The D-PSD of the proposed channel model could match with the D-PSD of the existing channel model and the available measured data of D-PSD,which confirmed the effectiveness of the proposed channel model.(2)Two 3D multipath angular power density(APD)models of Rice channel were proposed for two communication scenarios,i.e.,the power of non-line-of-sight waves was evenly distributed in 3D sphere space,the power of non-line-of-sight waves was evenly distributed in the horizontal plane and the vertical plane,respectively.Based on 3D multipath shape factors theory,the closed-form expressions of some spatial statistics of Rice channel like the unnormalized complex spherical harmonic coefficients,multipath shape factors,fading rate variance,level crossing rate,average fade duration,spatial correlation,coherence distance and minimum separation distance of antenna arrays were derived in two communication scenarios.The proposed multipath APD models and these spatial statistics could characterize the spatial selectivity that the multipath signal power of V2 V communication had different fading patterns in different 3D angular directions.Simulation analysis showed that 3D spatial angular directions had significant effect on these channel statistics,and the results could effectively simplify the design and optimization of transmission technologies of V2 V communication such as 3D antenna array and beamforming technologies.(3)A 3D Gaussian interference distribution model was proposed,and the corresponding interference APD was given.Based on 3D multipath shape factors theory,the closed-form expressions of some spatial statistics of interference like the interference shape factors,fading rate variance and level crossing rate were derived.The proposed interference distribution model,interference APD and these spatial statistics of interference could characterize the spatial selectivity that the power of co-channel interference of V2 V communication had different sizes in different 3D angular directions.The closed-form expressions of the probability density function and spatial correlation function of SIR were derived based on the 3D multipath APD model and spatial statistics of Rice channel in(2).Simulation analysis showed that 3D spatial angular directions had significant effect on these spatial statistics of interference and the spatial correlation function of SIR,and the results could provide theoretical support for study of anti-interference technologies.