Research On Digital MAP Based Channel Modeling In Vehicular Network

Vehicular communications is characterized by its high mobility,relatively low antenna height and short propagation distance.These characteristics make the traditional cellular wireless channel model no longer suitable for vehicular network communications system.Most of existing system-level vehicular ad hoc network simulation platforms employ simple statistical channel models without considering influences of environmental objects on ray propagation.Deterministic modeling simulation platforms based on ray tracing technology often rely on the open-source geographic environment data provided by OpenStreetMap or other platforms,but the accuracy and integrity of these data are relatively low.In this thesis,a vehicular network(VANET)simulation platform which supports the access of a shape-file format digital map is developed,and has built-in complete data of Nanjing three-dimensional digital map.The ray tracing technology is used in this platform to provide accurate channel model and a visual user graphical interface is also developed.The main works of this thesis are as follows:Firstly,several general performance specifications are adopted to evaluate a VANET channel model.Some representative VANET channel models are introduced and classified according to their modeling methods.The theory and classical algorithms of ray tracing technology are studied.The core ideas and representative implementation algorithms of various ray tracing acceleration technologies are discussed respectively.Secondly,the implementation of the VANET channel simulation platform is described in detail in this thesis.The development environment of the simulation platform is Qt framework.The software uses C++ language to realize the core functions of digital map access,channel modeling,coordinate data conversion,link budget and so on.The software uses BootStrap framework to build a user-friendly visual graphical interface and realizes the rendering of interactive 3D model by three.js framework.The platform's channel modeling is based on ray tracing technology.Vertical plane launch algorithm and ray crossing algorithm are used to accelerate ray tracing and the vertical plane launch algorithm is improved according to the characteristics of vehicular network communications.Finally,several typical scenarios are selected to simulate the vehicular communication on the platform,and the key channel performances,such as ray propagation path,path loss,delay and Doppler frequency shift are analyzed.Meanwhile,moving scenarios are supported by the developed platform and the time-varying characteristics of the channel are analyzed.