Research On Message Broadcast Strategy And Technology In VANET-cellular Network

In vehicular ad hoc networks(VANETs),efficient message dissemination is critical to improve road safety and traffic efficiency.However,Due to the high dynamic of vehicles and constant changing of vehicular networks topology,the communication link between vehicles in traditional DSRC-based VANET suffers from low life time,which obviously increase the transmission delay and severly impact the tansmission ratio.Rencently,with the rapid development of next generation netwroks and telecom market,3G network are widely deployed around us and 4G/5G keep a fast growth,which provide an ideal environment for the integration of VANET and cellular networks.Accordingly,the new approach for dealing with the data transmission in VANET.Based on the heterogeneous VANET-cellular network,we propose a novel data transmission strategy which include two procedures:the uplink strategy and downlink strategy.Lastly,we explore an infrastructure-assisted message dissemination strategy for supporting heterogeneous driving patterns.The details of our strategy are as follows:(1)The selection method of safety message broadcast relay in VANET-cellularIn traditional DSRC-based VANET,the communication opportunity only appears when vehicles enter in each others' communication range.The transmission delay and success ratio can not be granteed when the vehicle density is low.However,vehicles can transmit the data to the server through the vehicles which are equiped with cellular network interface,then the server can send the data to the target vehicles.Data transmission through mobile gateway can definitely extend the broadcast area and significantly reduce the remote transmission delay.Based on the VANET-cellular architecture,a selection method of safety message broadcast relay(VRSM)was proposed.We first introduce a metric for relay selection by jointly considering link stability,cellular signal strength and its variation,geographical locations and physical-layer channel conditions.Then,using this metric,a unique relay vehicle is selected to transmit the safety message to server by cellular network.The server will disseminate the safety message to the vehicles in target area afterward.Simulations and mathematical analysis demonstrate that the proposed method can minimize the message redundancy,improve the resource utilization and message transmission efficiency.What's more,the encouraging results do not depend too much on the traffic density and infrastructures deployment.(2)Data Uplink Strategy in Mobile Cloud Service Based VANETNowadays,with the fast development of vehicular ad hoc network(VANET),mobile cellular networks,and cloud computing,VANET based on cellular network and cloud computing has attracted great attention from both acadamic and industry.What's more,the cloud computing provide new sight for the data transmission in VANET.This paper proposes a novel VANET architecture and data uplink method(CDUL)accordingly,which combines the idea of mobile cloud computing.We first provide the registration procedure of gateway server(GWS).Then,by jointly considering the historical data and real-time information,a GWS selection method by cloud is proposed to dynamically decide the participating GWSs and their service area.After acquiring the service information from GWS,the gateway consumer(GWC)could choose the optimal GWS from its GWS list by jointly considering communication load,link stability,channel quality,e.g.and transmit the data to the selected GWS which will then sends the data to cloud.Simulations with different scenarios in OMNeT++ and mathematical analysis demonstrate that the proposed method can achieve lower transmission delay and higher delivery success ratio.(3)Cloud-assisted safety message dissemination in VANET-cellular heterogeneous wireless networkIn vehicular ad hoc networks(VANETs),efficient message dissemination is critical to improve road safety and traffic efficiency.Since many VANET-based schemes suffer from high transmission delay and data redundancy,the integrated VANET-cellular heterogeneous network has been proposed recently and attracted significant attention.However,most existing studies focus on selecting suitable gateways to deliver safety message from the source vehicle to a remote server,whereas rapid safety message dissemination from the remote server to a targeted area has not been well studied.In this paper,we propose a framework for rapid message dissemination that combines the advantages of diverse communication and cloud computing technologies.Specifically,we propose a novel Cloud-assisted Message Downlink dissemination Scheme(CMDS),with which the safety messages in the cloud server are first delivered to the suitable mobile gateways on relevant roads with the help of cloud computing,and then being disseminated among neighboring vehicles via vehicle-tovehicle(V2V)communication.To evaluate the proposed scheme,we mathematically analyze its performance and conduct extensive simulation experiments.Numerical results confirm the efficiency of CMDS in various urban scenarios.(4)Infrastructure-Assisted Message Dissemination for Supporting Heterogeneous Driving PatternsTo support the message dissemination for cooperative vehicle and individual vehicles in Heterogeneous Driving Patterns,we propose a general framework for Infrastructure-assisted Beacon and Safety message Dissemination(IBSD)that takes advantages of centralized and decentralized approaches to support the heterogeneous driving pattern.Based on the collected traffic dynamics and communication situations through V2I and cellular communication,we select RSUs as the coordinators to arrange beacon schedule for multiple CDSs in bidirectional roads to avoid communication collisions.Weutilize CSMA-based MAC protocols for the safety message to maximize the channel utilization.We validate the efficiency of the proposed infrastructureassisted message dissemination algorithms by analytical model and extensive simulation experiments under various traffic scenarios with different vehicular networking settings.