Routing Algorithm Based On Real-Time Road Segment Evaluation And Its Implementation For Vehicular Delay Tolerant Network In Urban Scenario

With the rapid development of automobile industry,electronic communication technology,cloud computing and other fields,intelligent transportation system and "urban brain" have been proposed to solve the urban traffic problems facing mankind.Vehicle Ad-hoc Network(VANET)as an important part of intelligent transportation has attracted more and more attention from academia and industry.In urban environment,VANET is different from traditional Ad-Hoc network and has more complex and changeable challenges.Therefore,the routing algorithm design of VANET in urban environment is more challenging.This thesis studies and analyses the classical VANET routing algorithm,summarizes the advantages and disadvantages of several types of VANET,and analyses the characteristics and challenges of VANET in urban environment.In this thesis,a new Routing Algorithm based on real-time road Segment Evaluation in urban scenario(RASE)is proposed,It combines macro route planning with micro-forwarding mechanism between vehicles to achieve reliable and efficient delivery of messages.The main contributions of this thesis are as follows:(1)A real-time road segment evaluation method is proposed.Firstly,the section is divided into two parts,and the link connectivity of the nodes on the two sections is evaluated in real time.Then,the concepts of link connectivity and road network connectivity are defined on the basis of this evaluation method,which are used to describe the real-time link connectivity of the nodes in the whole road segmen and the real-time link connectivity of the whole road network respectively.Finally,a real-time scoring method based on link connectivity is proposed.(2)Improved greedy perimeter strategy for message forwarding between vehicles.Including: Improving the perception mechanism of vehicle driving information.In the next hop node selection of messages,the node link lifetime calculation method is added,which reduces the possibility of message forwarding failure between vehicles.A message balanced allocation method is proposed to avoid the excessive number of messages cached by some nodes,which results in the delay of message delivery and even the failure of message delivery.(3)RASE is proposed.In RASE,the macro-planning and maintenance of message routing path is based on(1)the real-time road segment evaluation method.Micro-forwarding of messages between vehicles uses(2)an improved greedy perimeter strategy in message forwarding between vehicles.In addition,according to the different forwarding modes of Road Side Unit(RSU),RASE has two routing modes: RSU direct forwarding mode and RSU assisted forwarding mode,which make RASE adapt to the periodic drastic changes of node density in urban environment,and have better adaptability and robustness.(4)The simulation system of RASE is realized by SMUO and NS-3.By comparing RASE with other similar algorithms in different parameter scenarios,the experimental results show that RASE has superior performance.