基于IEEE802.11p的车联网MAC层算法研究

发布时间：2018-01-16 17:35

本文关键词：基于IEEE802.11p的车联网MAC层算法研究　出处：《哈尔滨工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着城市交通堵塞状况的日益加重以及交通事故的频繁发生,VANET(Vehicle Ad hoc Network,车联网)的概念越来越频繁的被提起并且逐步开始应用。VANET网络设备由能自由移动的车载通信单元和固定的路边接入设备构成,VANET网络架构是由车辆节点间通信的车间网络和车辆节点与路边接入点通信的车对设施网络构成的。VANET因其重要的现实意义,逐步成为移动自组网络研究的一大热点。VAN ET以车辆作为节点,由于车辆节点的移动轨迹受制于道路,所以其节点的分布和信息的交互受交通流的影响。网络中节点因高动态变化导致节点频繁加入和退出通信,网络的拓扑变化剧烈。如何设计出有效的MAC层接入协议,保证车联网成员在高动态拓扑结构下和接入竞争激烈的环境中及时有效合理的接入信道一直是车联网的研究热点。本文着重对面向车联网提出的IEEE 802.11p标准MAC层协议作出分析,研究如何结合车联网的交通移动特性来达到优化接入协议的目的。本文结合交通移动性对车辆网进行分析,以由此定义的位移趋向作为标准将单播模式下车辆节点双方的运动趋向类型分类,并根据IEEE 802.11p中EDCA的服务区分机制针对不同类型提供不同的信道接入优先级,改善因交通移动性引起的车联网内节点通信不公平现象,并以此为支点提升网络性能。本文应用交通流理论中的重要参数密度将车联网中车辆节点所处的环境分为两类,并针对车辆节点所处不同疏密环境调整IEEE 802.11p中退避算法,用能根据节点所处环境的疏密调节竞争窗口变化机制的退避算法VBA替换了原有的二进制指数退避算法,降低了了稀疏环境下节点出现的无效退避的可能性,减少了密集环境下节点发送消息碰撞的概率,从而提高了网络性能。最后本文以Vanet Mobisim与NS2搭建了仿真平台,在城市V2V单播场景下实现了两种改进算法,并分别对比了更新过两种改进算法的IEEE802.11p协议与原始协议在丢包率、公平性、时延、吞吐量上的差异,并分析原因。仿真结果表明VEDCA算法与VBA算法能提高网络公平性、减小接入时延,有效改善了网络性能,通过本文的研究,为VANET网络协议与交通特性的联系和VANET网络协议的优化等提供一定的参考依据。
[Abstract]:With the increasing aggravation of urban traffic jam and the frequent occurrence of traffic accidents, vehicle Ad hoc Network. The concept of "vehicle networking" has been brought up more and more frequently and gradually began to be applied. The VANET network equipment consists of mobile vehicle-mounted communication units and fixed roadside access devices. The VANET network architecture is composed of the workshop network of communication between vehicle nodes and the vehicle-to-facility network where the vehicle node communicates with the roadside access point because of its important practical significance. It has gradually become a hot topic in the research of mobile ad hoc networks. Van et takes the vehicle as the node because the moving path of the vehicle node is restricted by the road. So the distribution of nodes and the interaction of information are affected by the traffic flow. The nodes in the network frequently join and exit communication because of the high dynamic change. The topology of the network changes dramatically. How to design an effective MAC layer access protocol. It has always been a research hotspot to ensure the timely, effective and reasonable access channel of the vehicle network members in the high dynamic topology structure and in the environment of fierce competition for access. This paper focuses on the IEEE for vehicle networking. The 802.11p standard MAC layer protocol is analyzed. This paper studies how to optimize the access protocol by combining the traffic mobility characteristics of the vehicle network. This paper analyzes the vehicle network combined with the traffic mobility. The moving trend types of both sides of vehicle nodes in unicast mode are classified by the displacement trend defined in this paper. According to the service differentiation mechanism of EDCA in IEEE 802.11p, different channel access priorities are provided for different types. Improve the traffic mobility caused by the intranet node communication unfair phenomenon. This paper applies the important parameter density in traffic flow theory to divide the environment of vehicle nodes into two categories. The Backoff algorithm of IEEE 802.11p is adjusted according to the different density environment of vehicle nodes. The original binary exponential Backoff algorithm (VBA), which can adjust the change mechanism of competition window according to the environment of nodes, is replaced by the original binary exponential Backoff algorithm, which reduces the possibility of invalid Backoff of nodes in sparse environment. It reduces the probability of message collision in dense environment and improves the network performance. Finally, a simulation platform based on Vanet Mobisim and NS2 is built. Two improved algorithms are implemented in the city V2V unicast scenario, and the packet loss rate, fairness, delay of the original protocol and the IEEE802.11p protocol, which have been updated by the two improved algorithms, are compared respectively. Simulation results show that VEDCA algorithm and VBA algorithm can improve network fairness, reduce access delay, and effectively improve network performance. Some references are provided for the connection between VANET network protocol and traffic characteristics and the optimization of VANET network protocol.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U495;TN929.5;TP391.44

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