| The Internet of Vehicle technology is the application of 5G mobile communication technology in the field of intelligent transportation.It can realize real-time vehicle-tovehicle(V2V)and vehicle-to-roadbed equipment information interaction,which is of great significance in safety,intelligence,environmental protection,etc.V2V is also a solution for unmanned driving,intelligent transportation planning,etc.It is necessary to describe and model the characteristics of wireless channel accurately to build a good wireless communication system.However,the characteristics of the wireless channel are easily affected by the actual environment.The key point of channel modeling is whether the measurement environment can be fully identified and the appropriate modeling method selected.Therefore,massive actual measurement activities must be carried out in some specific scenarios to collect data.Tunnel is an indispensable scene in the traffic system,but the previous research and measurement activities are inadequate,and there is no standardized tunnel channel model at present.Therefore,this paper chooses two special tunnel scenarios in Xi’an and Germany,conducts actual V2V wireless communication channel measurement activities,and analyzes and models the wireless channel characteristics from multiple angles.Firstly,this paper explains the principles of wireless transmission and detection and builds a channel measurement system.Then measurement activities were planned and carried out in two tunnel scenarios based on the 5.9 GHz and 5.2 GHz bands,respectively.After preprocessing the high precision measurement data,the plute form channel impulse response and location,time and other information are obtained.Based on this information,the channel characteristics are analyzed and studied.Secondly,the analysis and modeling of the large and small-scale fading characteristics of wireless channels are made outside,inside and at the connection of the tunnel,for example,path loss and shadow fading,small-scale amplitude distribution,Rician K-factor,power delay spectrum,root mean square delay spread,delay doppler and diffuse multipath component.A distance-based path loss model was established based on the near logarithmic path loss model,the α-β-γ model and the ITU-RP1411 model.The received power inside and outside the tunnel in the two scenarios were evaluated and compared.The α-β-γ model has a higher goodness-offit.The logarithm of shadow fading in the two scenarios can be well fitted with the normal distribution.In addition,the characteristics of the small-scale fading amplitudes are more similar to the Rice distribution with the minimum goodness of fit value when compared with the five typical theoretical fading distributions.The Rician K-factor inside the tunnel is smaller that outside the tunnel.The distance based Rician K-factor model inside the tunnel is given.The K-factor inside the tunnel decreases as the range increase.The statistical properties of Rucian K-factor follow Gaussian distribution.For delay spread,the generalized extreme value distribution is more common in the inside and outside of the Xi’an tunnel,while the lognormal distribution is more common inside and conjunction of the German scene tunnel,and the generalized extreme value distribution is more common outside the tunnel.At the same time,the change of Doppler spectrum in the German tunnel is given,and its influencing factors are analyzed.In addition,the diffuse multipath component is estimated based on the SAGE algorithm and the AR filter.The ratio of diffuse components to total power in the tunnel does not exceed 0.5 and follows the Log-normal distribution of the number. |
