一维车载Ad Hoc网络连接度分析

In this paper we analyze connectivity of one-dimensional Vehicular Ad Hoc Networks where vehicle gap distribution can be approximated by an exponential distribution. The probabilities of Vehicular Ad Hoc Network connectivity for difference cases are derived. Furthermore we proof that the nodes in a sub-interval [z1,z1 +Δz] of interval [0, z], z>0 where all the nodes are independently uniform distributed is a Poisson process and the relationship of Vehicle Ad hoc Networks and one-dimensional Ad Hoc networks ...     

ACAR: Adaptive Connectivity Aware Routing for Vehicular Ad Hoc Networks in City Scenarios

Multi-hop vehicle-to-vehicle communication is useful for supporting many vehicular applications that provide drivers with safety and convenience. Developing multi-hop communication in vehicular ad hoc networks (VANET) is a challenging problem due to the rapidly changing topology and frequent network disconnections, which cause failure or inefficiency in traditional ad hoc routing protocols. We propose an adaptive connectivity aware routing (ACAR) protocol that addresses these problems by adaptively selecting an optimal route with the best network transmission quality based on statistical and real-time density data that are gathered through an on-the-fly density collection process. The protocol consists of two parts: 1) select an optimal route, consisting of road segments, with the best estimated transmission quality, and 2) in each road segment of the chosen route, select the most efficient multi-hop path that will improve the delivery ratio and throughput. The optimal route is selected using our transmission quality model that takes into account vehicle densities and traffic light periods to estimate the probability of network connectivity and data delivery ratio for transmitting packets. Our simulation results show that the proposed ACAR protocol outperforms existing VANET routing protocols in terms of data delivery ratio, throughput and data packet delay. Since the proposed model is not constrained by network densities, the ACAR protocol is suitable for both daytime and nighttime city VANET scenarios.     

Connectivity Analysis of Vehicular Ad Hoc Networks from a Physical Layer Perspective

This paper investigates the network connectivity properties of a vehicular ad hoc network (VANET) from a physical layer perspective. Specifically, we investigate the minimum transmit power used by all vehicles, sufficient to guarantee network connectivity. As opposed to the conventional graph-theoretic approach, in this paper, the network connectivity problem is analyzed according to a physical layer-based quality of service constraint. Under this approach, a multi-hop path joining a pair of vehicles in a VANET is said to be connected if and only if the average route BER meets a target requirement. We derive closed form analytical expression for the minimum transmit power sufficient to ensure network connectivity. We also derive analytical expression for the maximum number of hops, a packet can traverse satisfying the route BER constraint, for a given transmit power. The validity of our theoretical analysis is verified by extensive simulation studies. The analysis provides a framework for investigating the impact of traffic dependent parameters such as vehicle arrival rate, vehicle density, mean and standard deviation of vehicle speed, highway length and physical layer-based parameters such as path loss exponent, fading factor, Doppler spread, and data rate on VANET connectivity characteristics.     

Analytical Model of Cooperation in Ad Hoc Networks

The problem of cooperation among selfish nodes in ad hoc networks has gained recently a considerable attention. In this paper we propose a dynamic game theoretical model of cooperation in ad hoc networks, based on evolutionary game theory. Our model enables us to make predictions about possible equilibrium points of the network composed of the selfish and learning nodes, which can dynamically adjust their strategy in order to maximize their own payoff. In particular, we show that if an ad hoc network implements a reputation mechanism, all long term equilibrium points of the system will include cooperating nodes. In fact, in most of the equilibrium points, the cooperators will constitute a majority of the nodes. We believe that this new approach, borrowing from biological research, can have broader applications for studying dynamics of distributed communication systems.     

Internet Connectivity for Ad Hoc Mobile Networks

The growing deployment rate of wireless LANs indicates that wireless networking is rapidly becoming a prevalent form of communication. As users become more accustomed to the use of mobile devices, they increasingly want the additional benefit of roaming. The Mobile IP protocol has been developed as a solution for allowing users to roam outside of their home networks while still retaining network connectivity. The problem with this solution, however, is that the deployment of foreign agents is expensive because their coverage areas are limited due to fading and interference. To reduce the number of foreign agents needed while still maintaining the same coverage, ad hoc network functionality can cooperate with Mobile IP such that multihop routes between mobile nodes and foreign agents can be utilized. In this work, we present a method for enabling the cooperation of Mobile IP and the Ad hoc On-Demand Distance Vector (AODV) routing protocol, such that mobile nodes that are not within direct transmission range of a foreign agent can still obtain Internet connectivity. In addition, we describe how duplicate address detection can be used in these networks to obtain a unique co-located care-of address when a foreign agent is not available.     

车载网络中的数据分发策略

通过车载网络(VAETNs)能够有效提高交通管理系统(TMS)的数据传输。然而,由于通信距离短以及车辆的移动,完成VANETs中的数据传输是一项挑战任务。为此,提出基于复杂网络指标的数据传输(MCDD)策略。MCDD策略依据二跳邻居的信息,并通过介数中心性和度中心性两项性能指标选择转发节点,进而降低开销和缩短传输时延。仿真结果表明,相比于基于区划分的全-分布式流量管理系统(FTMS),MCDD策略的交通拥塞时间缩短了约48.95%,平均行驶速度提高了约8%。     

Routing in Sparse Vehicular Ad Hoc Wireless Networks

A vehicular ad hoc network (VANET) may exhibit a bipolar behavior, i.e., the network can either be fully connected or sparsely connected depending on the time of day or on the market penetration rate of the wireless communication devices. In this paper, we use empirical vehicle traffic data measured on 1-80 freeway in California to develop a comprehensive analytical framework to study the disconnected network phenomenon and its network characteristics. These characteristics shed light on the key routing performance metrics of interest in disconnected VANETs, such as the average time taken to propagate a packet to disconnected nodes (i.e., the re-healing time). Our results show that, depending on the sparsity of vehicles or the market penetration rate of cars using Dedicated Short Range Communication (DSRC) technology, the network re-healing time can vary from a few seconds to several minutes. This suggests that, for vehicular safety applications, a new ad hoc routing protocol will be needed as the conventional ad hoc routing protocols such as Dynamic Source Routing (DSR) and Ad Hoc On-Demand Distance Vector Routing (AODV) will not work with such long re-healing times. In addition, the developed analytical framework and its predictions provide valuable insights into the VANET routing performance in the disconnected network regime.     

Extending Global IP Connectivity for Ad Hoc Networks

Ad hoc networks have thus far been regarded as stand-alone networks without assumed connectivity to wired IP networks and the Internet. With wireless broadband communications and portable devices with appropriate CPU, memory and battery performance, ad hoc connectivity will become more feasible and demand for global connectivity through ad hoc networking is likely to rapidly grow. In this paper we propose an algorithm and describe a developed prototype for connectivity between an ad hoc network running the ad hoc on-demand distance-vector protocol and a wired IP network where mobile IP is used for mobility management. Implementation issues and performance metrics are also discussed.     

基于车载自组织网络的消息发送时机研究

车载自组织网络(VANET)是一种节点迅速移动的无线自组织网络,网络的动态密度变化具有明显的特征,呈现出疏密相间的"手风琴"现象。利用汽车之间相遇的机会进行通信需要考虑到网络动态变化对传输的影响。文章利用仿真软件SUMO生成的跟踪轨迹文件,在仿真软件ONE下做网络参数的对比实验。通过模拟道路交通的网络动态密度变化,文章得到结论:最佳发送时机随网络参数不同而变化。     

Privacy Addressing-Based Anonymous Communication for Vehicular Ad Hoc Networks

Vehicle ad-hoc network (VANET) technology is a basic component of the future intelligent transportation system. With the advances in modern information society, privacy issues have become important considerations. However, most routing proposals for VANETs lack privacy support, namely anonymity or pseudonymity and unlinkability aspects. This paper presents a novel privacy addressing-based anonymous communication approach for VANETs, which prevents eavesdroppers from identifying a particular vehicle by its address. The proposed scheme is a kind of end-to-end solution, so it can potentially be extended to work with many traditional routing protocols. Finally, the simulation results show that the proposed scheme outperforms previous approaches with privacy support in terms of protocol overhead and packet latency.     

一种基于可靠性的车载自组织网络路由算法

提出了一种改进的GPSR路由算法.该算法在选择转发节点过程中同时考虑位置和方向,进而提高转发节点选择的正确性来增加通信链路可靠性.用VanetMobisim交通仿真软件构建真实的VANETs网络城市场景,结合NS-2进行仿真研究,结果表明,和传统GPSR算法相比,改进的GPSR路由算法在端到端时延影响不大的条件下,能够有效地提高数据包传递率,降低数据丢包率.因此,改进的GPSR协议更适用于对实时性要求不高、而对可靠性要求较高的VANETs网络.     

Trustworthy Privacy-Preserving Car-Generated Announcements in Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANETs) allow vehicle-to-vehicle communication and, in particular, vehicle-generated announcements. Provided that the trustworthiness of such announcements can be guaranteed, they can greatly increase the safety of driving. A new system for vehicle-generated announcements is presented that is secure against external and internal attackers attempting to send fake messages. Internal attacks are thwarted by using an endorsement mechanism based on threshold signatures. Our system outperforms previous proposals in message length and computational cost. Three different privacy-preserving variants of the system are also described to ensure that vehicles volunteering to generate and/or endorse trustworthy announcements do not have to sacrifice their privacy.     

车载自组网中的网络与信息安全

因自组织网络无中心的特点,传统有中心网络中成熟的安全保障机制无法得到直接应用。为了使车载通信技术得到更加广泛的应用,安全问题必须得到很好的解决。文章对车载自组网的安全需求及目标进行分析,然后从安全路由、密钥管理和入侵检测3个方面对车载自组网安全研究的现状进行介绍。在这3个方面中,安全路由研究最为广泛,而密钥管理则是保障车载自组网安全的关键。     

An Analytical Model for the Node Degree in Wireless Ad Hoc Networks

Node degree is regarded as an important and convenient metric to measure the connectivity of wireless ad hoc networks. Existing studies are mainly based on the assumption that nodes are static and do not provide closed-form expressions for node degree. In this paper, we investigate three fundamental characteristics of a wireless ad hoc network: Its node degree distribution, its average node degree and its maximum node degree experienced by the nodes during their movement. We introduce a novel mathematical model to derive analytical expressions in the presence of radio channel fading. Furthermore, our results reveal that the node degree distribution follows a binomial distribution regardless of the initial distribution of nodes?? location. The results of this paper are useful to study node connectivity and to improve the algorithmic complexity of incentive protocols.     

基于身份的车联网消息认证方案

本文对车联网中常用的椭圆曲线消息认证方法进行比较分析,对现有的方案改进,并对该方案进行了性能分析,在安全性不变的前提下,仿真结果表明增加了19％通信开销,但是消息验证阶段计算开销提升80％以上,签名阶段提升22％.     

A Pairing-Free Certificateless Signcryption Scheme for Vehicular Ad Hoc Networks

Vehicular ad hoe networks (VANETs) cre-ate an vital platform for communication between vehicles,which can realize accident warning,auxiliary driving,road traffi...     

An Intelligent Scheme for Slot Reservation in Vehicular Ad Hoc Networks

Vehicular ad hoc network is a solution for increasing road traffic demand.Non-safety messages are sent during the service channel interval.The slots during whic...     

Ad Hoc网中链路连通性的概率评估

Ad Hoc网将在未来的商用和军用通信方面起着非常重要的作用.网内节点的随机移动将会导致网络拓扑的动态变化.任一对节点之间链路连通性的分析对提前预测网络拓扑变化起着关键作用.文中基于不同的初始条件通过数学推导的方法来分析任一对节点之间随时间变化的链路连通性空间平均概率.