车联网中基于消息时间戳和路边设施的广播协议研究

发布时间：2018-07-09 22:46

本文选题：车联网 + 网络断开　；参考：《天津科技大学》2014年硕士论文

【摘要】：到现在为止,大多数的车载自组网研究一直专注在高密度网络拓扑结构下的广播风暴问题的协议,这些研究都是基于过于简单的VANET网络连接良好的情形下进行的。然而,网络断开问题是VANET中普遍存在的问题,因此需要开发一个可靠高效的广播协议,用以支持多样化网络拓扑结构。本文通过对SCF(Store-Carry-Forward)、SCB(Store-Carry-Broadcast)机制流程进行分析,由于它们是单纯借助反方向行驶的车辆实现断开连接的车-车通讯,无法保证簇尾车辆遇到反方向转发者的等待时间,因此消息传播的时延就可能会很长。在此基础上,利用固定设施RSU(roadside unit),提出旨在缩短节点间的重新愈合时间的广播协议。论文中涉及到的主要问题有：首先,基于路边设施的广播协议模型：当研究VANET中的数据包传送问题时,根据需要不同区分开以下2种情形是很重要的：第1种源车辆检测到事故可以产生一个警告信息,并将其传播给后方车辆,在后方车辆到达潜在危险区之前能够得到此警告信息；当目标远离源车辆(即几公里至几十公里远的发送者)就会发生第2种情况—需要将消息发送到远方的特定节点。其次,基于消息时间戳的退避时延τ计算：该算法主要思想是源节点在发送消息中加入发送时间戳,每个节点在接收到消息之后,计算相应的退避时延τ,并在等待τ时间后,对此消息进行确认和下一步广播；如果在τ时间内,节点收到了其他节点的确认,则放弃再次广播。消息的确认机制用于在广播前抑制中间其他节点的广播。最后,重新愈合时间(re-healing time,简称tr)的计算：重新愈合时间是两个相邻簇间传递消息的时间。通过QualNet进行仿真实验,与SCB、SCF机制进行对比。结果表明应用RSU之后重新愈合时间大大的减少,提高了广播的实时性和可靠性。
[Abstract]:Up to now, most of the studies of vehicle-mounted ad hoc networks have focused on the broadcast storm protocols under the topology of high-density networks. These studies are based on the case that the VANET network is too simple and well connected. However, the problem of network disconnection is a common problem in VANET, so it is necessary to develop a reliable and efficient broadcast protocol to support diverse network topologies. In this paper, the flow of SCF (Store-Carry-Forward) SCB (Store-Carry-broadcast) mechanism is analyzed. Because they are simply disconnected vehicle-vehicle communication with the aid of vehicles driving in the opposite direction, it is impossible to guarantee the waiting time for the vehicles with cluster tails to meet the reverse direction repeater. Therefore, the delay of message propagation can be very long. On this basis, a broadcast protocol designed to shorten the time of rehealing between nodes is proposed by using the fixed facility RSU (roadside unit),. The main problems involved in this paper are as follows: first, the broadcast protocol model based on roadside facilities: when the packet transmission problem in VANET is studied, It is important to distinguish between the following two situations depending on the need: the first source vehicle detects an accident that generates a warning message and disseminates it to the rear vehicle. This warning message can be obtained before the rear vehicle reaches the potential danger area; a second situation occurs when the target is far from the source vehicle (i.e. the sender several to several kilometers away)-messages need to be sent to a specific node in the distance. Secondly, the Backoff delay 蟿 calculation based on message timestamp: the main idea of this algorithm is that the source node adds the sending time stamp to the sending message. After receiving the message, each node calculates the corresponding Backoff delay 蟿, and after the waiting time 蟿, This message is confirmed and broadcast next. If the node receives confirmation from other nodes within 蟿 time, it will give up broadcasting again. The message confirmation mechanism is used to suppress the broadcast of other intermediate nodes before broadcast. Finally, the calculation of re-healing time (tr): the time of recuperation is the time of passing messages between two adjacent clusters. The simulation experiment is carried out by QualNet and compared with the SCB / SCF mechanism. The results show that the time of re-healing after RSU is greatly reduced, and the real-time and reliability of broadcast is improved.
【学位授予单位】：天津科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U495;TN915.04

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