Research Of Routing Protocol In Software Defined-based Vehicular Ad Hoc Networks

Vehicular Ad-hoc Network(VANET)is a system of vehicles that being connected with each other by wireless technologies.Usually the vehicles are moving with very high speeds,thus the topology is unpredictable and frequently changing.VANETs'characteristics,such as multi-hop paths,vehicle mobility and large network size make the design of routing protocols a major challenging.The SDVN(the software defined Vehicular Ad-hoc Network)integrates SDN and VANET.By separating the data plane and the control plane of the network devices of the vehicles,centralizing the control logic on the centralized controller,it can use the global network information to make the optimal policy,which improves network resource utilization.First,the differences between the traditional VANET and the SDVN,the characteristics and advantages of SDVN are described in this paper.We also describe the operational principles,characteristics and deficiencies of some classical routing protocols in the VANET.Then,combining the characteristic of SDVN,a map-based software-defined routing protocol(MBSDR)in SDVN is proposed.The design of MBSDR consists of four parts:information collection and routing request,the optimal forwarding path selection,data forwarding strategy and route repair mechanism.The first part describes the process of collecting network information and routing request in the SDVN.The second part takes full of advantage of the rich map information(such as intersection location,road position and the length of road segments,etc.)and the vehicles'movement information to obtain a data forwarding path with good connection and optimal length.In the third part,in order to avoid the impact of intersection building on the communication quality,it is divided into two cases:road segment forwarding and intersection forwarding.In addition,in order to reduce impact of the intersection forwarding,the intersection sequence in the path is simplified.The last part is used to repair route when the link does not work as expected.Finally,through the simulation experiments,the packet delivery rate(PDR)and the average end-to-end delay(AEED)were estimated under the different vehicle numbers,limited maximum speeds and data transmission rates.The simulation results show that the proposed MBSDR routing protocol outperforms DSDV,AODV and GPCR in terms of both PDR and AEED.