基于时序网络的VANETs拓扑特征分析

动态性是车载自组织网络（VANETs）拓扑结构的重要特征之一,研究拓扑结构的时序特征对VANETs协议开发和网络管理具有重要意义。采用复杂网络理论研究VANETs拓扑结构的时序特性。建立了VANETs时序网络模型- 可达图模型,该模型不仅考虑了信息传输时间,而且能够刻画VANETs中信息的存储转发机制。通过仿真实验研究VANETs时序网络的拓扑特征,分析信息传输时间 和最大可容忍延迟时间 与网络的节点出度、非对称性、数据包到达率等时序拓扑参数之间的关系。研究结果表明与瞬时和静态网络模型相比,本文提出的时序网络模型能更合理的刻画VAENTs中信息传输过程,并且降低信息传输时间 和增大最大可容忍时间 有利于提高整个网络的时序连通性,从而提高数据包传输效率,该结论可为优化VANETs拓扑控制和网络协议开发提供新的指导。     

A social network approach to trust management in VANETs

In the past few years, vehicular ad hoc networks(VANETs) was studied extensively by researchers. VANETs is a type of P2P network, though it has some distinct characters (fast moving, short lived connection etc.). In this paper, we present several limitations of current trust management schemes in VANETs and propose ways to counter them. We first review several trust management techniques in VANETs and argue that the ephemeral nature of VANETs render them useless in practical situations. We identify that the problem of information cascading and oversampling, which commonly arise in social networks, also adversely affects trust management schemes in VANETs. To the best of our knowledge, we are the first to introduce information cascading and oversampling to VANETs. We show that simple voting for decision making leads to oversampling and gives incorrect results in VANETs. To overcome this problem, we propose a novel voting scheme. In our scheme, each vehicle has different voting weight according to its distance from the event. The vehicle which is more closer to the event possesses higher weight. Simulations show that our proposed algorithm performs better than simple voting, increasing the correctness of voting.     

关于VANETs路由协议的研究现状与进展

随着车载自组网络(VANETs)应用的不断深入,有关VANETs技术研究已成为众多学者关注的热点。由于VANETs节点的高速移动、不稳定的无线信道等显著特点,导致网络拓扑结构变化快、节点通信呈机会性、路径可用的持续时间短,因此,设计稳定可靠的消息路由方案成为VANETs应用的核心问题。阐述了路由协议研究的重要性,并对VANETs的各种路由协议的进行了比较,分析各自优缺点,同时将现有的VANETs路由协议根据其性质分为五类,并研究了每类协议的特点。最后分析了VANETs的未来研究方向。     

Improved authentication in vanets using a connected dominating set-based privacy preservation protocol

The Journal of Supercomputing - Vehicular ad hoc networks (VANETs) provide real-time communication between vehicle units for comfortable and safe driving. VANETs are driven by the concept of...     

Detecting sybil attacks in vehicular ad hoc networks using fuzzy logic and arithmetic optimization algorithm

The Journal of Supercomputing - In vehicular ad hoc networks (VANETs), Sybil attacks are serious security problems that can seriously affect the operations of the VANETs by producing fake...     

PS-PPF:一个基于代理签名簇的VANETs隐私保护框架

车辆自组网(VANETs)是一种物联网在智能交通领域的重要应用形态,近年来已经成为学术界和工业界共 同研究的重点。VANE Ts具有诱人的发展前景,但其应用受到安全性和隐私保护的严格制约,因此有关VANE`I's的 安全性和隐私保护的文献逐渐成为研究的一个热点,涌现了一大批研究成果,这些成果对VANETs的实用化具有重 要意义。代理签名是现实世界中应用领域非常广泛的一种数字签名技术。在不同的场景下,代理签名有大量的变体, 其可形成一个代理签名簇。提出了一个基于代理签名簇的VANE I's隐私保护框架(PS-PPF);在VANE`I's系统体系 架构层面上提出了一个面向实用的VANE Ts隐私保护框架;划分了4个级别设置;分析了7个关键角色;探讨了4关键代理签名:条件隐私保护型代理签名、身份认证授权型代理签名、防追溯滥用授权型代理签名、业务前置授权型代 理签名。该框架不仅能对车辆身份隐私和位置隐私进行安全保护,还具备良好的实际部署能力和可扩展能力。最后, 指出了一些该框架的实际扩展说明。PS-PPF可用于规范和指导实际运营系统的规划和建设。据悉,这是第一个面向 实用的基于代理签名簇的VANETs隐私保护框架设计方案。     

基于演化图论的可靠的VANETs路由协议

车载网络（VANETs）属于移动无线网络的特例,具有鲜明的特性。传统无线网络的路由协议难以直接应用于VANETs。节点的高速移动,引起网络拓扑动态变化,导致VANETs的通信链路频繁断裂。高动态网络的链路可靠性问题引起广泛的关注。为此,针对高速公路VANETs的路由可靠性进行分析,对演化图论进行扩展,建立扩展后的演化图论模型（EEGM）,并利用EEGM获取VANETs拓扑的动态信息,从而预先获取可靠路由的信息。在此基础上,提出基于演化图论的可靠路由协议（EG-RAODV）。仿真结果表明,与同类的其他协议相比,提出的路由协议在分组传输率、端到端传输时延、路由请求消息率以及链路断裂数方面得到了提升。     

衰落信道下车载自组织网络连通性分析

以孤立节点数、最大连通长度、全局网络效率等参数为连通性量化指标,应用VanetMobisim车辆仿真软件建立车载自组织网络,详细研究在Nakagami衰落信道模型和确定信道模型下VANETs连通性随时间的演化特征。结果表明当VANETs全连通时,网络时间相关性较弱,当网络连通性比较差时,各项连通性指标均呈现重尾现象,网络连通性具有很强的时间相关性。分析车辆节点密度、路径损耗指数和衰落因子等因素对网络连通性的影响。     

Unicast routing protocols for vehicular ad hoc networks: A critical comparison and classification

Vehicular Ad hoc NETworks (VANETs) allow vehicles to form a self-organized network without the need for a permanent infrastructure. As a prerequisite to communication, an efficient route between network nodes must be established, and it must adapt to the rapidly changing topology of vehicles in motion. This is the aim of VANET routing protocols. In this paper, we discuss the design factors of unicast routing protocols for VANETs, and present a timeline of the development of the existing unicast routing protocols. Moreover, we classify and characterize the existing unicast routing protocols for VANETs, and also provide a qualitative comparison of them. This classification and characterization gives a clear picture of the strengths and weaknesses of existing protocols in this area and also throws light on open issues that remain to be addressed. Multicast routing protocols are also very important in VANETs; however, they are outside the scope of this paper.     

稀疏交通环境下基于轨迹的车联网数据分发

在稀疏交通环境下,车联网的数据转发机会较少,车辆携带数据时间较长,从而造成较大的数据传输时延.针对该问题,提出了基于车辆轨迹信息的数据转发协议（data dissemination based on trajectory,简称DDBT）.协议采用“携带+连通组件”思想,通过分析双向交通路段延迟特征,建立了端对端传输延迟模型,提出了在路口接入点协助下基于最小传输延迟期望的车辆留存副本多径转发原则.理论分析及仿真实验结果表明,提出的DDBT协议在稀疏交通环境下表现出较好的数据传输延迟性能.     

An adaptive approach for information dissemination in Vehicular Ad hoc Networks

Vehicular Ad hoc Networks (VANETs) appeared as a subclass of MANETs for inter-vehicle communication. However, VANETs have a relatively more dynamic nature as compared to MANETs concerning the network topology. The design and implementation of an efficient and scalable algorithm for information dissemination in VANETs constitutes a major issue that should be tackled. Indeed, in this dynamic environment, an increasing number of redundant broadcast messages will increase resource utilization, which would indirectly affect the network performance. In the past few years, several statistical-based broadcasting schemes, such as counter-based protocol, for information dissemination have been proposed in the context of MANETs. These schemes are based on various threshold parameters to help nodes to decide whether to rebroadcast or discard received messages. However, in dynamic networks, such as in VANETs, it is difficult even impossible to determine a priori these threshold values. Dynamically changing these values, to minimize the number of redundantly received messages while maintaining good latency and reachability, is a complex issue in the absence of centralized controllers or constant threshold parameters. This paper presents a decentralized and adaptive approach for information dissemination (AID) in VANETs. Simulations are conducted and results are presented to show that adaptive approaches have a better performance over statistical-based approaches.     

PAACP: A portable privacy-preserving authentication and access control protocol in vehicular ad hoc networks

Recently, several studies addressed security and privacy issues in vehicular ad hoc networks (VANETs). Most of them focused on safety applications. As VANETs will be available widely, it is anticipated that Internet services could be accessed through VANETs in the near future. Thus, non-safety applications for VANETs would rise in popularity. This paper proposes a novel portable privacy-preserving authentication and access control protocol, named PAACP, for non-safety applications in VANETs. In addition to the essential support of authentication, key establishment, and privacy preservation, PAACP is developed to provide sophisticated differentiated service access control, which will facilitate the deployment of a variety of non-safety applications. Besides, the portability feature of PAACP can eliminate the backend communications with service providers. Therefore, better performance and scalability can be achieved in PAACP.     

基于NS-3的VANETs路由协议性能仿真研究

分析了车用自组织网络(VANETs)仿真工具的应用现状,讨论了将NS -3引入VANETs仿真领域的优势.针对VANETs的实际特点,研究了基于NS -3的VANETs仿真平台的构建方法与步骤.依据真实的车辆间通信环境,设计并实现了AODV和OLSR两种路由协议的网络仿真测试方案,并进一步分析了端到端平均时延、分组投递率、吞吐量和时延抖动4项网络性能参数.仿真结果表明,在VANETs应用场景当中,节点运动速度对网络性能的影响较大,而节点密度对网络性能的影响较小;OLSR协议的性能总体要优于AODV协议.     

An advanced security scheme based on clustering and key distribution in vehicular ad-hoc networks

Preservation of security is an essential requirement in vehicular ad hoc networks (VANETs) as vehicular communication is vulnerable to attacks. Attackers may exploit VANETs to send bogus information to deceive other vehicles which leads to serious issues. In this paper, we describe an advanced Secure scheme based on Clustering and Key Distribution (SCKD) among members and cluster-heads in VANET. The SCKD is a coordination based algorithm in which nodes are located within different clusters and their cluster heads are chosen from trusty nodes. For a secure end-to-end communication, our scheme deploys the proxy signature, blind proxy signature, hashed message authentication code, and symmetric cryptography. Results show that our scheme preserves security requirements including authentication, confidentiality, data-integrity, non-repudiation, and unforgeability. Since the cost and time computation of key generation and distribution decreases by SCKD compared with other algorithms, our algorithm will be applicable for VANETs.     

COBRA:车载网络中基于协作的大数据传输增强机制

车载网络利用车载无线通信设备在车辆移动过程中组网.研究者们已提出了大量的路由算法用于车载网络中的多跳数据传输,但是这些算法大都假设车辆间传输带宽不受限制,从而其性能会随转发数据量的增加而降低.车载网络中用于大数据量传输的路由增强机制COBRA,利用同向行驶车辆间的拓扑稳定特性延长数据在车辆间的传输时间,利用擦除编码增加传输可靠性.实验证明,当传输数据量较大或带宽受限时,COBRA机制能以较低的开销提升现有典型车载网络路由协议的传输延时与可靠性能.     

The selective use of redundancy for video streaming over Vehicular Ad Hoc Networks

Video streaming over Vehicular Ad Hoc Networks (VANETs) offers the opportunity to deploy many interesting services. These services, however, are strongly prone to packet loss due to the highly dynamic topology and shared wireless medium inherent in the VANETs. A possible strategy to enhance the delivery rate is to use redundancy for handling packet loss. This is a suitable technique for VANETs as it does not require any interaction between the source and receivers.In this work, we discuss novel approaches for the use of redundancy based on the particularities of video streaming over VANETs. A thorough study on the use of redundancy through Erasure Coding and Network Coding in both video unicast and video broadcast in VANETs is provided. We investigate each strategy, design novel solutions and compare their performance. We evaluated the proposed solutions from the perspective not only of cost as bandwidth utilization, but also the offered receiving rate of unique video content at the application layer. This perspective is fundamental to understanding how redundancy can be used without limiting the video quality that can be displayed to end users.Furthermore, we propose the selective use of redundancy solely on data that is more relevant to the video quality. This approach offers increases in overall video quality without leading to an excessive overhead nor to a substantial decrease in the receiving rate of unique video content.     

车载自组织网络中的数据分发机制

车载自组织网络（vehicular ad-hoc network,简称VANET）作为一种新型的移动自组织网络,应用前景广阔.鉴于长距离数据分发机制是支撑VANET应用的一个不可或缺的机制,提出了一种VANET下路边单元（roadsideunit,简称RSU）辅助的数据分发机制Ara,并在不同的交通场景下对其性能进行了评估.实验结果表明,即使在有RSU出现故障的情况下,Ara也可以保证较高的数据到达率、较小的延迟和较低的消息开销.同时,通过建立分析模型对Ara的数据传递延迟进行了理论分析.该分析模型建立在车辆的微观流模型之上,可以推导出不同RSU 部署场景下的数据传递延迟.模拟实验结果验证了模型的正确性,因此该分析模型可以对Ara数据传递的性能进行预测.     

车载自组网中最远转发机制的可靠性改进

车载自组网是传统的移动自组织网络在交通道路上的应用。在车载自组网中,最远转发机制[1]能够有效降低数据传播跳数,减少冗余发送,但最远转发机制的可靠性将因最远节点失效而受到影响。在分析和实验验证节点高速运动将导致严重的最远节点失效问题的基础上,提出了两种对最远转发机制进行改进的方法:安全距离法和失效预测法。安全距离法选择最接近计算出的安全距离的邻居作为转发节点;失效预测法通过邻居的状态参数对其位置进行预测,进而避免选择那些可能已经脱离通信半径的邻居作为转发节点。多个仿真实验表明,两种改进方法都能不同程度地降低转发节点失效的比例,提高消息传播的可靠性。     

车联网中beacon消息传输频率研究

车联网(VANETs)提供车与车之间的车间通信(V2V)和车与路旁设施(V2I)间的通信.VANETs中存在两类消息:beacon消息和安全消息.车辆周期地交互车辆的beacon消息,仅在紧急情况下才广播安全消息;而beacon消息的传输频率受多个因素影响.为此,提出基于模糊逻辑的自适应beacon传输频率方案,利用模...     

自组织车联网中GPSR路由协议的研究进展

由于贪婪周边无状态路由(GPSR)对于拓扑结构频繁变化的自组织车联网(VANETs)具有最适性,为此,针对GPSR提出了许多改进协议。首先对VANETs网络层路由协议进行分类比较,然后分析和总结近年来基于位置路由协议的核心路由机制和优缺点,重点分析典型的基于位置的路由协议GPSR在城市场景中存在的问题。最后,提出了GPSR未来可能的研究策略和发展方向。