Data Dissemination Strategy Based On Network Coding For Vehicular Ad Hoc Networks

Intelligent transportation system is an effective way to alleviate the traffic problem.Vehicular ad hoc networks as the main part of intelligent transportation system has been widely concerned.In traditional mobile communication protocol,the relay nodes only store and forward the received data information.When there are a large amount of data needing to be transmitted,this way will make the relay nodes become bottleneck nodes.If we apply network coding in vehicular ad hoc networks,the large data stream is compressed,so that we can achieve the purpose of further enhance quality of service in vehicular ad hoc networks.The data transmission technology based on network coding were mainly discussed in this paper.In order to improve the network throughput and the efficiency in vehicular ad hoc networks,a data delivery protocol named Data Dissemination Based on Network Coding and Clustering(DDNCC)was proposed for dense vehicular ad hoc networks.In the protocol,packets were divided into many blocks,and the packets in the same block were performed random linear network coding in order.The number of redundant encoding packets updated dynamically according to the quality of communication link.The specific elements of encoding matrix were equal to 1,which not only reduced the complexity of decoding but also improved the decoding rate.What's more,the paper proposed a transmission strategy based on clustering and vehicle nodes' collaborative forwarding.In the strategy,in order to improve the decoding rate further,a deterministic retransmission mechanism with Ack to confirm step by step was adopted.Theoretical analysis and simulation experiments show that the DDNCC protocol has preferable performance in the efficiency of data transmission,forwarding latency and network throughput.In sparse traffic vehicular ad hoc networks environment,vehicles usually have limited data forwarding opportunities.Packets are carried by vehicles for a long time,and as a result there is larger data transmission delay in sparse vehicular ad hoc networks.In order to alleviate the problem,a data delivery protocol named Data Dissemination Based on Trajectory(DDBT)is proposed for sparse vehicular ad hoc networks.In this protocol,packets are delivered according to trajectory of vehicles and forwarded under the assistance of connected component of vehicular ad hoc networks.The concept of carry and connected component is employed.In addition,link delay model of road segment is deduced under two-way traffic environment,and based on that,end-to-end delivery delay model of packets is established.According to the delay model,multi-path forwarding strategy is proposed by using the minimal expected delivery delay.Theoretical analysis and simulation experiments show that the DDBT protocol has preferable performance in data delivery delay in sparse vehicular ad hoc networks.