面向城市道路的车联网紧急消息可靠传输机制研究

发布时间：2018-04-30 00:17

本文选题：车联网 + 城市道路环境　；参考：《北京交通大学》2017年博士论文

【摘要】：随着新一代的网络技术在智能交通领域的应用,车联网关键技术的研究受到了广泛关注。车联网在缓解城市交通拥堵,提高道路使用效率,促进交通智能化信息化建设等方面具有重要的研究意义和应用价值。鉴于道路异常事件通常会对城市路况造成严重影响,设计可靠的紧急消息传输机制,及时有效地向目标群体传递异常事件信息,将有助于提升道路交通的自我调节和应急处理能力。车联网网络拓扑会随着车辆的高速移动而动态变化,并且受到路网拓扑限制。而城市道路环境的特殊性将为紧急消息传输机制的设计带来新的挑战。本论文主要围绕如何在城市车联网环境中传输紧急消息开展研究工作,以提高消息传输可靠性保障消息传输效率为研究目标。在车联网中,隐藏终端问题和链路频繁中断等因素是导致数据包丢失,损害紧急消息传输可靠性的主要原因。本文首先从这两方面出发,提出了适用于城市车联网的紧急消息可靠传输机制和转发策略。然后,在有路边单元(RSU)辅助的情况下,考虑如何有效利用RSU传递消息,并提出混合式紧急消息多跳广播机制,解决RSU稀疏部署对消息传输性能的影响。本文的主要工作与创新点如下:(1)针对消息碰撞导致的数据包丢失问题,提出了一种基于道路布局感知的紧急消息可靠传输机制。首先,研究紧急消息发生碰撞丢失的原因,建立不饱和条件下马尔可夫链模型,分析紧急消息发生碰撞的概率。然后,分析城市道路环境和布局特点,考虑多方向传输和障碍物遮挡等因素的影响,提出了基于布局感知的消息碰撞避免机制。该方法针对不同道路场景采用不同的传输策略,并解决场景变换时消息传输的过渡问题。利用RBEM/CBEM握手机制避免隐藏终端问题,并且通过简化握手过程来减少控制消息对紧急消息传输效率的影响。在此基础上,利用上述握手机制提供的反馈信息,设计了自适应冗余中继节点调整机制。该方法可以根据链路质量动态调整广播冗余,进一步提高消息传输可靠性。仿真结果表明,所提的可靠传输机制能够提供较高的消息覆盖率,同时维持较低的传输时延。(2)针对车联网中通信链路不稳定性导致的数据包丢失问题,提出了一种基于链路寿命预测的消息转发机制。首先,分析城市道路场景和车辆移动对链路持续时间的影响,考虑车辆节点的位置、速度、方向、传输范围以及有无交通灯等因素,设计了基于移动场景感知的剩余链路寿命预测方法。然后,权衡消息传输的可靠性和效率,设计了两种链路效用值计算方法,用来反映车辆间通信链路的使用价值。结合链路寿命预测和效用值计算,提出了新的转发节点选择方法,旨在选择稳定的通信链路,建立可靠的传输路径,实现消息的可靠传输。仿真结果表明,该方案可以有效缓解链路中断对消息传输的影响,获得较高的消息覆盖率和传输效率。(3)针对如何有效利用RSU通信提高紧急消息传输可靠性的问题,提出了一种基于软件定义车联网的混合紧急消息多跳广播机制。首先,将软件定义网络(SDN)技术引入车联网,通过部署支持SDN功能的中心控制器、混合式RSU和公交车辆,构建基于公交车辆辅助的新型软件定义车联网架构。其次,借助SDN控制器的逻辑集中和全局掌控能力,建立整数规划模型,设计目的地RSU、VBT-RSU和目的地公交车选择算法。提出通信覆盖率、车辆迁移率、移动性熵的计算方法,合理规划RSU的使用,减少广播冗余。然后,针对RSU稀疏部署问题,设计了车辆间多跳广播触发机制,在RSU无法完全覆盖的区域促使车辆使用车辆间通信传递紧急消息,提高消息的覆盖率。最后,在车辆间通信部分提出了一种权力下放式的转发节点选择方法。仿真结果表明,与传统ITS架构相比,新架构下的混合多跳广播机制具有更高的消息覆盖率和更低的控制器开销。
[Abstract]:With the application of the new generation of network technology in the field of intelligent transportation, the research on the key technologies of the vehicle network has been widely concerned. The vehicle network has important research significance and application value in alleviating urban traffic congestion, improving the efficiency of road use, and promoting the information construction of traffic intelligence. The urban road conditions have a serious impact. The design of a reliable emergency message transmission mechanism and the timely and effective transmission of abnormal event information to the target group will help to improve the self-regulation and emergency handling capacity of road traffic. The network topology of the vehicle network will change dynamically with the high-speed movement of the vehicle, and will be restricted by the topology of the road network. The particularity of city road environment will bring new challenges to the design of emergency message transmission mechanism. This paper focuses on how to transmit emergency messages in the network environment of urban vehicles to carry out research work to improve the efficiency of message transmission reliability guarantee message transmission. The main cause of the packet loss is the loss of data packet and the reliability of the emergency message transmission. First, this paper, starting from these two aspects, proposes an emergency message reliable transmission mechanism and forwarding strategy suitable for urban vehicle networking. Then, under the condition of the roadside unit (RSU), we consider how to use RSU to transmit messages effectively, and propose a method to deliver the message effectively. A hybrid emergency message multi hop broadcast mechanism is proposed to solve the impact of RSU sparse deployment on message transmission performance. The main work and innovation points of this paper are as follows: (1) to solve the data packet loss caused by message collision, an emergency message transfer mechanism based on road layout awareness is proposed. First, the study of emergency message collision is carried out. The cause of the loss is to establish a Markov chain model under unsaturated conditions, analyze the probability of the collision of emergency messages. Then, analyze the urban road environment and layout characteristics, consider the influence of multi direction transmission and obstacle occlusion, and propose a collision avoidance mechanism based on layout awareness. This method is used for different road scenes. Using different transmission strategies and solving the transition problem of message transmission when the scene is transformed. Using the RBEM/CBEM handset to avoid the hidden terminal problem, and reducing the influence of the control message to the efficiency of the emergency message transmission by simplifying the handshake process. On this basis, the adaptive feedback information provided by the handset system is designed. Redundant relay node adjustment mechanism. This method can dynamically adjust broadcast redundancy according to link quality to further improve the reliability of message transmission. The simulation results show that the proposed reliable transmission mechanism can provide high message coverage and maintain low transmission delay. (2) the communication link instability in the vehicle network is caused by the instability of the communication link. A message forwarding mechanism based on link life prediction is proposed. Firstly, the impact of urban road scene and vehicle movement on link duration is analyzed, and the location, speed, direction, transmission range and traffic lights of vehicle nodes are considered, and the residual link life based on mobile scene perception is designed. Then, weighing the reliability and efficiency of message transmission, two methods of link utility value calculation are designed to reflect the use value of communication links between vehicles. A new method of forwarding node selection is proposed, which is designed to select a stable communication link and establish a reliable transmission path by combining link life prediction and utility value calculation. The simulation results show that the scheme can effectively alleviate the impact of link interruption on message transmission and obtain high message coverage and transmission efficiency. (3) a hybrid emergency message based on software definition of vehicle networking is proposed in view of the problem of how to effectively utilize RSU communication to improve the reliability of emergency message transmission. Multi hop broadcasting mechanism. First, software definition network (SDN) technology is introduced into the network of vehicles. By deploying a central controller that supports SDN functions, hybrid RSU and bus vehicles, a new software definition vehicle network architecture based on bus vehicle assistance is constructed. Secondly, the integer programming model is established by using the logic centralization of the SDN controller and the overall control ability of the SDN controller. Type, design destination RSU, VBT-RSU and destination bus selection algorithm. Put forward communication coverage, vehicle mobility, mobility entropy calculation method, rationally plan the use of RSU and reduce broadcast redundancy. Then, aiming at the problem of RSU sparse deployment, a multi hop broadcast trigger mechanism between vehicles is designed to promote vehicles in the area where RSU is not fully covered. In the end, a decentralized forwarding node selection method is proposed in the communication part of the vehicle. The simulation results show that the hybrid multi hop broadcast mechanism under the new architecture has higher message coverage and lower controller overhead compared with the traditional ITS architecture.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN929.5;U495

【参考文献】