基于协议序列的车辆自组织网络信道接入控制算法

 针对如何提高车辆自组织网络无线信道资源利用率问题,提出了一种分布式车辆间通信信道接入控制算法,该算法具体表示为利用中国余数定理设计一种用户保障协议序列,车辆节点(亦称用户)依据该协议序列决定其对通信信道的接入,无需基站或中心节点的协调,所设计的协议序列确保每个车辆节点在一个序列周期内至少成功发送一次数据.仿真结果表明,采用本文提出的协议序列控制算法比无反馈时隙ALOHA接入控制算法具有更小的传输时延,能够满足车辆自组织网络通信实时性的要求.     

基于车载自组网的动态交通信息的挖掘和利用

动态交通信息系统是智能交通系统中重要的组成部分,作为一种新兴的车辆间无线通信网络技术,车载自组网可有效提高高速行驶车辆间的信息共享能力。文章阐述利用基于车载自组网的交通信息采集和交通事件协同检测算法、大规模海量交通信息的分布式组织和实日寸处理方法、基于位置的交通信息分发协议等技术,构建一个动态交通信息系统,实现改进交通信息系统中的事件检测的准确性和实时性,提高大规模交通信息处理的实时性,改善交通信息分发的针对性。     

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.     

Cross-Layer Congestion and Contention Control for Wireless Ad Hoc Networks

We consider joint congestion and contention control for multihop wireless ad hoc networks, where the goal is to find optimal end-to-end source rates at the transport layer and per-link persistence probabilities at the medium access control (MAC) layer to maximize the aggregate source utility. The primal formulation of this problem is non-convex and non-separable. Under certain conditions, by applying appropriate transformations and introducing new variables, we obtain a decoupled and dual-decomposable convex formulation. For general non-logarithmic concave utilities, we develop a novel dual-based distributed algorithm using the subgradient method. In this algorithm, sources at the transport layer adjust their log rates to maximize their net benefits, while links at the MAC layer select transmission probabilities proportional to their conceived contribution to the system reward. The two layers are connected and coordinated by link prices. Our solutions enjoy the benefits of cross-layer optimization while maintaining the simplicity and modularity of the traditional layered architecture.     

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。     

面向高动态移动自组织网络的生物启发分簇算法

分簇可以有效地提高大规模移动自组织网络的性能.但高动态的移动自组织网络具有节点移动性强、网络拓扑变化快的特点,应用传统的分簇算法会造成网络性能迅速下降,频繁的簇拓扑更新造成了簇结构的不稳定和控制开销的增加.为了解决传统分簇算法无法适应高动态的大规模移动自组织网络的问题,提出了一种基于生物启发的移动感知分簇算法,该算法对多头绒泡菌的觅食模型进行了改进,使其适用于移动自组织网络领域.由于该算法与节点的移动特性进行了结合,所以该算法可以有效地在高动态移动自组织网络中进行簇的建立与维护.实验结果表明,相较于其他传统分簇算法,本文算法提高了平均链路连接保持时间和平均簇首保持时间,使得簇结构更加稳定,提高了对高动态、大规模移动自组织网络的适应能力.     

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%。     

Collaboration of Trusted Node and QoS Based Energy Multi Path Routing Protocol for Vehicular Ad Hoc Networks

In the recent past information transmission through the vehicular ad hoc network (VANET) playing a vital role due to increase in accident statistics. There are numerous networking and VANET protocols helpful to control the trust while transmitting the data from source to destination nodes in traffic environment. In spite of many existing protocols for analyzing the trust in the network, the challenge of routing overhead, high energy consumption and malicious attacks issues still continue in the communication. This research introduces the trust collaboration nodes and Quality of Service (QoS) with energy multipath routing protocol for transmitting the information through VANET. Initially, the trusted nodes have been collected for analyzing the neighbouring nodes and the information are transmitted using the proposed QoS based energy efficient multipath routing protocol. During this transmission, the multi path protocol eliminates the intermediate attacks effectively when compared with the other existing protocols. The Proposed protocol maintains the QoS while routing the information from source to destination and further the efficiency has been analyzed through simulation experiments and Montgomery multiplier based Elliptic Curve Cryptography (ECC) will be used in future for better security and privacy.     

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.     

Analytical Model for Connectivity in Vehicular Ad Hoc Networks

We investigate connectivity in the ad hoc network formed between vehicles that move on a typical highway. We use a common model in vehicular traffic theory in which a fixed point on the highway sees cars passing it that are separated by times with an exponentially distributed duration. We obtain the distribution of the distances between the cars, which allows us to use techniques from queuing theory to study connectivity. We obtain the Laplace transform of the probability distribution of the connectivity distance, explicit expressions for the expected connectivity distance, and the probability distribution and expectation of the number of cars in a platoon. Then, we conduct extensive simulation studies to evaluate the obtained results. The analytical model that we present is able to describe the effects of various system parameters, including road traffic parameters (i.e., speed distribution and traffic flow) and the transmission range of vehicles, on the connectivity. To more precisely study the effect of speed on connectivity, we provide bounds obtained using stochastic ordering techniques. Our approach is based on the work of Miorandi and Altman, which transformed the problem of connectivity distance distribution into that of the distribution of the busy period of an equivalent infinite server queue. We use our analytical results, along with common road traffic statistical data, to understand connectivity in vehicular ad hoc networks.      

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。     

Congestion Control Performance of R-DSDV Protocol in Multihop Wireless Ad Hoc Networks

Ad hoc wireless networks are composed of mobile nodes communicating through wireless links, without any fixed backbone infrastructure. Frequent topology changes due to node mobility make routing in such dynamic networks a challenging problem. Moreover, successful message routing implies every mobile node is potentially capable of acting as a router, thus supporting store-and-forward mechanisms. However, resource limitations on these nodes also require a control on congestion due to message forwarding. In this paper, we consider our recently proposed randomized version of the well-known Destination-Sequenced Distance Vector (DSDV) routing protocol, referred to as R-DSDV, and validate its performance through extensive simulation experiments. Our results demonstrate that a probabilistic control on message traffic based on local tuning of protocol parameters is feasible, and that R-DSDV outperforms the basic DSDV protocol by significantly reducing the average queue size associated with each mobile node and hence the average packet delay.     

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 ...     

Detecting Hot Road Mobility of Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks (VANETs) can provide value-added services to both drivers and passengers with on-board vehicular communication systems. Node mobility and volatile wireless connection in VANETs affect inter-contact time (T _I ) between mobile nodes, which greatly degrades the performance of vehicular applications. Nevertheless, the node spatial distribution in VANETs is another important factor especially in real applications. It positively affects the inter-contact time of vehicular nodes. By leveraging it, we can significantly improve the performance of data transmissions and inter-vehicle communication. To this end, we investigate the data collected from around 4,000 taxisin Shanghai and propose in this paper an efficient hot road mobility model. We find that most taxis distribute on some hot roads, which makes the node spatial distribution follow the power law. Based on this observation, we propose the concepts of indirect contact and heterogeneous inter-contact time (T _H ) to reveal how hot roads can change the distribution of inter-contact time. We find that the tail distribution of T _H also appears the power law, and both node spatial distribution and T _H distribution decay at least as the power law. We further propose a model for detecting vehicle mobility in hot roads, which can generates synthetic traces that captures both spatial and temporal features of nodes in VANETs.     

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.