【作者】 文莉；

【导师】 谭晓衡；

【作者基本信息】 重庆大学 ， 电子科学与技术， 2019， 硕士

【摘要】 车载GPS通信是实现车辆定位的一种重要方式,车辆与GPS卫星的通信质量好坏影响了车辆定位的准确性。车联网技术的发展对汽车定位的精准度提出了更高的要求。为了确保GPS卫星在车辆导航中的定位更加精准,本文对汽车行驶状态下GPS卫星与汽车通信信道衰落特性进行了深入研究,并建立了有效的车载GPS卫星信道模型及其确定性仿真模型。在车载GPS卫星移动通信系统中,车辆作为接收端具有高速移动、行驶区域局限于道路、周围的散射体环境时常发生切换等特点。本文根据GPS卫星与汽车在不同环境下信道衰落特性的不同,将汽车行驶的环境归纳为三种场景,分别是:空旷的高速公路、郊区小路和复杂环境的城市公路,并对三种场景下的经典车载GPS卫星通信信道模型进行了分析。由于车辆行驶区域局限于道路,大多数场景下周围的散射体分布是非均匀的,因此本文首先提出了扩展莱斯过程,然后在扩展莱斯过程的基础上,对三种不同场景下的经典信道模型均进行了扩展。上述的三种扩展模型均基于实际情况,假设接收终端的散射环境不均匀,从而多径散射造成的多普勒扩展功率谱密度呈现双端不对称,因此可通过双端截断频率的配置来反映实际的散射环境。此外,本文对三个扩展模型的一阶统计量和二阶统计量进行了详细的推导,并将经典模型、扩展模型以及实测数据进行了拟合对比。相比于经典模型,三种扩展模型与实测数据具有更好的拟合程度,能够更加准确的反映实际信道的衰落特性,验证了扩展模型的可行性和精确性。本文基于有色高斯随机过程对三种场景下的扩展车载GPS卫星通信信道模型进行确定性建模,并采用精确多普勒扩展法对确定性模型中多普勒参数进行计算。本文将三种确定性模型的仿真结果与其概率统计模型理论值进行了对比和分析,三种确定性模型的仿真结果曲线与其理论值曲线拟合程度均较高,验证了确定性模型的正确性。为了模拟汽车行驶状态下不同场景的信道环境的切换,本文引入三状态马尔可夫模型对不同场景下三种扩展单状态信道模型的切换过程进行描述。然后根据特定区域车行道路的地形场景随行驶距离变化的Markov状态转移矩阵对引入的三状态马尔可夫模型进行了分析和仿真实现。本文建立的车载GPS卫星信道Markov模型实现了不同模型之间的切换,实现了特定场景下采用特定模型进行描述的目的,为准确描述车载GPS卫星信道的传输特性提供了理论参考。更多还原

【Abstract】 Vehicle-borne GPS communication is an important way to realize vehicle positioning.The quality of communication between vehicles and GPS satellites affects the accuracy of vehicle positioning.In order to achieve more precise positioning and navigation of vehicles through application of GPS satellite and make communication between vehicles and GPS satellite efficiently when used in Internet of Vehicles,fading characteristics of the communication channel between GPS satellite and vehicles in driving state were studied thoroughly and the correct and effective communication channel model between GPS satellites and vehicles together with its deterministic model were established in this thesis.In the vehicle-borne GPS satellite mobile communication system,the vehicle which is the receiving end has the characteristics of high-speed movement,limited driving area to the road,and frequent switching of scatterers around the environment.Considering the difference of fading characteristics of communication channel between GPS satellites and vehicles in diverse environment,the scene of vehicles driving was divide into three parts which were open expressways,suburban roads and complex urban highways respectively.Three classical vehicle GPS satellite communication channel models in three scenes were analyzed.Because the driving area of vehicles is limited to the road and the scatterer environment around most scenes is inhomogeneous,a extended Rice channel model was proposed according to analysis of fading characteristics of the communication channel in this thesis.Besides extended classical channel models in three scenes were proposed based on the extended Rice channel model.Considering real condition of transmission,these models proposed above assumed that the scattering environment of receiving end is nonuniform and the Doppler spread power density spectrum is asymmetric caused by multipath scattering.Therefore the actual scattering environment could be simulated by configuring the two-terminal truncation frequency.Furthermore,first-order statistics and second-order statistics of these three extended models were induced in detail.These extended models were fitted well with the measured data which verified the feasibility and accuracy of these extended models.On the top of that,deterministic models of three extended satellite channel models were implemented based on the colored Gaussian random process.Method of Exact Doppler Spread was also introduced to calculate Doppler parameters of deterministic models.Simulation results of the deterministic models were fitted well with its theoretical values,which verified the validity.Finally,to simulate the switching of channel of vehicles running in different environment,a three-state Markov model was introduced and analyzed in this thesis.By statistic of the change of terrain scene in the selected area,the Markov transfer matrix of scene change can be calculated,which contributes to predicting the fading characteristic change of vehicle GPS satellite communication channel.The established vehicle GPS satellite mobile communication channel model in this thesis achieved the purpose of describing specific scenarios using specific models,which could provide a theoretical reference for accurately describing the transmission characteristics of vehicular GPS satellite channels.更多还原