Research And Application Of Network Coding For Video Distribution In VANETs

In recent years,Vehicular Ad hoc Networks(VANETs)have become a hot topic in intelligent transportation research.In VANETs,due to the high-speed movement of nodes,the information transmission among nodes is intermittent,which increases the difficulty of distributing video files among nodes.In the traditional network,the intermediate nodes only store and forward the data packets.However,the technology called network coding changed this status,its core technical feature is that the performance gain can be obtained by coding through the intermediate devices in the networks.In VANETs,mobile nodes re-encode data with network coding technology,which can improve network throughput and quality of service of the VANETs.For a high-speed and mobile VANETs environment,this paper proposes a video distribution scheme based on Random Linear Network Coding(RLNC)for D2D(Device-to-Device)communication.The source node equally splits the video file into multiple segments,and then linearly encodes the segments with RLNC.Each mobile device receives a segment from the source node,and then distributes the segments to other devices after the data has been re-encoded.Only when the device receives a fixed number of linearly independent segments,can it decode the original data.In order to reduce the delay of data distribution,this paper designs three strategies,including mode switching strategy,access point(AP)selection strategy,and proactive re-encoding strategy.Compared to the traditional replication-based transmission scheme and the transmission scheme based on Instantly Decodable Network Coding(IDNC),the experimental result shows that the proposed scheme provides the highest distribution efficiency.In addition,the communication links among vehicles in VANETs unpredictably disappear,resulting in the loss of the video file being transmitted.So it is necessary to ensure the validity of the video transmission within a short link duration.To solve this problem,a classical link duration model is introduced in this paper,which can estimate the amount of data that can be transmitted within the link duration,and calculate the number of fragments required for network coding based on the estimated value,thereby improving the efficiency of video distribution.The simulation platform of VANETs is established by OMNeT++ simulation software,which simulates the scene situation of video distribution based on network coding in VANETs.The simulation result shows that the proposed scheme outperforms traditional replication-based and erasure-coding-based scheme in highway environment.Based on the above research results and the software development tool Android Studio,the research on the application of network coding based on network coding in VANETs is carried out,video file segmentation coding and re-encoding are designed and realized.Moreover,when the nodes receive a fixed number of linearly independent segments,it can decode the video file.By comparing with the replication-based and IDNC-based schemes,it is verified that the proposed system provides higher distribution efficiency.