Fast Handover Approach In MmWave Vehicular Networks

With the development of the vehicular networks,more and more sensors data and new entertainment video service data in connected cars requires higher data rates.Millimeter wave can provide extremely high data rates because of its wide frequency band.Therefore,mmWave vehicular networks,which combined the mm Wave and vehicular networks,can meet its data rate needs.Antenna arrays are widely used in mm Wave vehicular networks and they use beamforming strategy to form beams.Connected cars consume more time in beam alignment during handover between mmWave base stations because of the narrow beam-based communication mechanism.Handover also becomes more frequent due to the high mobility of connected cars.The higher handover time and more frequent handover is against with the requirements for low handover latency.Therefore,it is necessary to optimize the handover process in mmWave vehicular networks.The thesis first models the channel and the codebooks for mmWave vehicular networks.And the thesis models the beam searching stage,which is most time-consuming in handover process,as an optimal beam selection problem.Then,the thesis analyzes the outdated beam connection and creatively extracts the context information of handover direction.This context information is more stable and its delay is smaller than any other approach.The thesis proposes the Fast Beam Handover algorithm which uses this context information to predict the possible handover location and greatly reduces the subset of beam selection and the beam searching time.Simulation results prove that the proposed method reduces the complexity of the beam alignment process.Then,a time model of the handover process and a beam selection model in three-dimensional space is established for the first time for the three-dimensional handover process in mmWave vehicular networks.Based on the proposed beam selection model,three-dimensional codebooks and the channel model are established.And the thesis proposes the Reduced Beam Space Searching algorithm and extract the angle information by analyzing the outdated beam.The thesis reduces the possible handover area and the size of searching beam space based on the geometric relationship.Simulation results prove that the proposed method have better performance on handover duration and communication capability of selected beam than many other algorithms in multiple base stations handover scenario.