Nowadays, traffics on the roads are getting more and more congested due to the fast-rising number of vehicles and the increasing need of citizens for mobility. Accidents happen frequently and result great loss of lives and properties. Internet of Vehicles (IoVs), as an important part of Internet of Things (IoTs), is placed high hope for enhancing traffic safety and controlling the damage caused by traffic accidents. According to statistics, most accidents can be avoided if drivers can be notified of a danger timely, so the key to minimize the damage introduced by road traffic accidents is the realization of fast and efficient data dissemination. However, great challenges exist due to the transmission characteristics of IoVs, such as high-speed movement of vehicles and dynamic changing network topologies. In this paper, we propose a vehicle-to-vehicle cooperative video alert dissemination mechanism for transmitting accident video in the highway scenario of IoVs. A two-way cooperative transmission strategy is designed. Vehicles in the same direction of accident vehicle are formed into clusters and communicate within clusters, while vehicles in the opposite direction select relay vehicles to help spreading video fast and reliably. The difficulties brought in by the characteristics of IoVs are solved through careful considerations of multiple factors such as vehicles' speeds, locations, distances, channel conditions and data receiving statuses in the design of the mechanism. Moreover, Scalable Video Coding (SVC) technology is used for encoding the original accident video, to take care of the performance degradation caused by the heterogeneity of vehicles in different locations. Instantly Decodable Network Coding (IDNC) technology is adopted during the cooperative transmission to further improve the transmission efficiency and reliability. Simulation results justify the proposed mechanism that it effectively shortens the accident video transmission delay, increases the success warning ratio, enhances the reconstructed video quality and improves the user satisfaction.

如今，由于车辆数量的快速增长和市民对出行的需求不断增加，道路上的交通越来越拥挤。事故频发，造成重大生命财产损失。车联网（IoVs）作为物联网（IoT）的重要组成部分，对于提高交通安全和控制交通事故造成的损失寄予厚望。据统计，如果能及时将危险告知驾驶员，大多数事故是可以避免的，因此将道路交通事故造成的损失降到最低的关键是实现快速高效的数据传播。然而，由于车联网的传输特性，例如车辆的高速运动和动态变化的网络拓扑，存在很大的挑战。在本文中，我们提出了一种车对车协作视频警报传播机制，用于在 IoV 的高速公路场景中传输事故视频。设计了一种双向协作传输策略。事故车辆同向车辆组成集群，集群内通信，相反方向车辆选择中继车辆，帮助视频快速可靠传播。解决了车联网特性带来的难点，在机制设计时，通过对车速、位置、距离、信道条件、数据接收状态等多方面因素的综合考虑，解决了车联网特性带来的困难。此外，可扩展视频编码（SVC）技术用于对原始事故视频进行编码，处理由于车辆在不同位置的异构性导致的性能下降。协同传输采用即时可解码网络编码（IDNC）技术，进一步提高传输效率和可靠性。仿真结果证明所提出的机制有效地缩短了事故视频传输延迟，提高了成功预警率，增强了重建视频质量，提高了用户满意度。