基于车载通信标准街道场景的电磁散射信道模型

An electromagnetic street scattering channel model for outdoor vehicular-to-vehicular communication systems

针对室外无线信道视距(line of sight,LOS)/非视距(non-line of sight,NLOS)传输环境下的车到车(vehicular-to-vehicular,V2V)通信系统,本文提出了一种基于标准街道散射的统计信道模型,其移动发射机(mobile transmitter,MT)与移动接收机(mobile receiver,MR)处于运动状态,街道两旁分布的散射体固定.由几何模型出发又引入了一种随机的参考信道模型,其散射体有无穷多个,均以平行于街道两侧的散射条纹形式均匀分布在三维(three dimensional,3D)空间的一个二维(two dimensional,2D)矩形内部.在室外街道通信环境下,模型推导了散射信道中发射角(angle of departure,AOD)以及到达角(angle of arrival,AOA)的概率密度函数(probability density functions,PDFs)解析式;研究了多普勒功率谱密度(power spectral density,PSD)及其时间自相关函数(autocorrelation function,ACF);分析了模型多普勒参数以及街道散射体等因素对V2V通信系统性能的影响.与城市、农村的测量信道对比分析,表明本模型仿真的统计特性符合理论与实际,拓宽了室外V2V无线通信信道建模的研究.为评估室外V2V通信系统的传输特性、仿真无线通信系统提供了有力的研究工具.

The vehicular-to-vehicular（V2V） communications have recently received great attention due to some traffic telematic applications that make transportation safer, more efficient, and more environmentally friendly. Reliable traffic telematic applications and services require V2 V wireless communication systems to be able to provide robust connectivity. To develop such wireless communication systems and standards, accurate channel models for the V2 V communication systems are required. In this paper, a geometric street scattering channel model for a V2 V communication system is presented under line-of-sight（LOS） and non-LOS（NLOS） propagation conditions. Starting from the geometric model,a stochastic reference channel model is developed, where the scatterers are uniformly distributed in rectangles in the form of stripes parallel to both sides of the street. A typical propagation scenario for the proposed model is presented,where the buildings and the trees can be considered as scatterers. Analytical expressions for the probability density functions（PDFs） of the angle-of-departure（AOD） and the angle-of-arrival（AOA） are derived. By obtaining the PDF of the total Doppler frequency, the Doppler power spectral density（PSD） and the autocorrelation function（ACF） of the proposed model are also investigated and computed, assuming that the mobile transmitter（MT） and the mobile receiver（MR） are moving, while the surrounding scatterers are fixed. In this respect the underlying radio channel model differs from the traditional cellular channels. We can draw the conclusion that the PDFs of AOD and AOA first increase and then decrease within a certain angle range; the Doppler power spectral density of the signal in the outdoor street environment presents the peak value in fmax. In addition, while the Rice distribution factor is larger, the value of the autocorrelation function increases relatively, the stability of the fluctuation increases correspondingly as well. To validate the reference channel model, its Doppler parameters are compared with those of a real-world measured channel for urban and rural areas. The numerical results show a good fitting of the theoretical results to the computer simulations. In the proposed geometry-based channel model, we not only study the influence of the street scatterers on the performance of V2 V communication system, but also broaden the research of the channel modeling of outdoor wireless communication in turn. To evaluate the propagation characteristics of the outdoor V2 V communication systems and the simulation of wireless communication system, this paper provides a powerful research tool.