VANET中基于捎带确认机制的自适应数据传播策略

车载自组网（VANET）通过自组织分散环境传播交通数据,交通数据的特点使得VANET数据传播方法更适合依赖广播。然而,当在高密度场景下广播数据时,可扩展问题和数据传播冗余问题变得尤为突出,可能导致广播风暴的发生。针对数据传播冗余和广播开销等问题,以最远转发策略和捎带确认机制为基础,提出一种捎带确认的自适应最远转发策略（AckAMFR）,根据存储转发的概念进行信息的传输和存储,降低了数据冗余,具有较强的可靠性和较小的广播开销。仿真结果表明,该转发策略具有低广播开销和高数据传输率的特性。     

软件定义车联网的数据转发策略和路由选择技术

针对目前车联网（VANET）数据转发效率低的问题,提出了软件定义网络（SDN）的数据转发策略和路由选择技术。首先,采用了软件定义车联网的分层控制结构,由局部控制器和全局控制器组成,实现数据转发和控制分离,可灵活控制数据转发的方向;然后,设计了单条路段的车辆路由机制,该机制预测车辆节点位置并采用贪心策略,实现数据的稳定传输;其次,设计了多个需求间的路段路由机制,该机制采用广度优先搜索（BFS）算法和边集相结合的方式,实现多个需求间路径不相交,缓解带宽瓶颈问题;最后,通过仿真验证,对比无线自组网按需平面距离向量（AODV）路由,所提出的数据转发策略和路由选择算法在数据分组接收率上提高40%以上,平均延迟时间降低60%左右。实验结果表明,软件定义车联网的数据转发策略和路由选择技术能够提高数据转发效率,减少平均收包延时。     

一种基于地理位置的车载自组网快速可靠广播算法

针对车载自组织网络VANET(Vehicular Ad Hoc Networks)中广播信息发送所面临的延迟大、不可靠的问题,提出一种基于车辆位置信息的快速、可靠的多跳广播算法LFRB(A Location-based Fast and Reliable Multi-hop Broadcast Algorithm)。提出的LFRB算法从车辆定期交换的Hello消息中获取邻居车辆的位置信息,建立邻居信息表,根据转发车辆所处位置选择距离该车辆最远(单一路段)或距离路口最近(路口)的若干车辆作为下一跳转发车辆的候选者,并采用指数退避机制选择一个候选车辆作为转发车辆来转发数据包。为了保证信息传输的可靠性,引入确认机制来提高成功转发的概率,同时还使用了缓存机制来避免数据包的重复转发,减少了网络冗余。NS2仿真结果表明,与现有的多跳广播算法相比,该算法具有较好的可靠性和较低的传输时延。     

车联网中基于距离的多转发者广播协议

为实现安全信息在车载自组织网络中快速、有效的传播,提出一种基于距离的多转发者广播协议.将上一跳转发节点信号边缘处的节点作为最优转发节点,以增加单次转发覆盖新节点的数量.选择信号覆盖范围中点处节点和次接近信号覆盖范围边缘处节点作为备选转发节点,以降低因隐蔽站或车辆脱离信号覆盖范围导致转发失败的概率,并通过反向车辆存储转发广播分组恢复路由.仿真结果表明,该协议能够适应多种车辆密度的车载自组织网络,满足不同交通流密度情况下紧急信息的分发要求,降低车辆间通信的平均端到端延时和转发率,提高转发效率,并且负载上升缓慢,能有效抑制广播风暴.     

基于优先级的数据广播内容选择算法

在以无线网络为代表的移动计算环境中,数据广播是一种有效的数据访问方式。为响应最多用户数据请求,提出了优先级计算模型,进而提出了一种基于优先级的广播内容选择算法。该算法综合考虑了事务存取多个数据项和满足定时限制的要求,根据用户请求队列状态动态选择广播内容,并应用剪枝机制减少了选择开销。实验结果表明它比现有算法有明显的优越性。     

移动分布感知的车载自组网络数据分发

提出了一种面向发布/订阅系统基于车辆移动分布感知的事件分发策略MDA(mobile distribution-aware data dissemination).基于车流的自组织性及自稳性的特点,建立VANET(vehicular ad hoc network)下的发布/订阅模型,通过计算车辆与移动订阅者的相遇概率,预测订阅者的移动分布,并以此为依据实时部署和调度广播令牌在网络中的转发,从而有效地控制事件代理的分布,保证了数据传递的有效性.与已有相关研究相比,MDA采用的启发式算法,能够使事件代理的分布更好地适应网络环境的动态变化.此外,MDA采用了一种基于概率预测密度的令牌控制算法,通过实时地调整令牌的数量,进而控制事件代理的数量,降低了整个网络的负载.模拟实验结果表明,与现有的几种消息分发算法相比,MDA能以较低的网络负载和传输延迟获得较高的数据传输成功率.     

基于模糊C均值聚类和模糊逻辑的车辆信息传输组网研究

针对在车联网中车辆间共享道路信息和车辆状态信息而出现的广播风暴、信息冗余等问题，结合模糊逻辑和模糊聚类，提出一种改善VANET广播的组合方法。方法是基于全局分簇的方案，利用模糊C均值聚类对车辆进行分簇，并在此基础上建立簇间传输，再利用模糊逻辑算法考虑车辆密度、速度、距离三个影响因素去寻找稳定的簇头。仿真结果表明与传统的方案相比，本组合方法能够减少不必要的网络传输，提高了分组传输效率，使车辆间的信息传输更加安全可靠。     

软件定义车联网的数据转发机制

针对现有车联网（VANET）中数据转发效率低的问题,提出了软件定义网络（SDN）的数据转发机制。首先,设计了软件定义车联网的分层次网络模型,该模型由局部控制器和车辆组成,实现控制与数据转发分离,具有可扩展性、独行性等特点;其次,设计了车辆路由转发机制,该机制采用动态规划和二分搜索的方法,以实现高效的数据转发;最后,通过仿真验证,对比无线自组网按需平面距离向量路由（AODV）、目的节点序列距离矢量路由（DSDV）、动态源路由（DSR）和最优链路状态路由（OLSR）算法,所提的数据转发机制在传递成功比上提高大约100%,而端到端延迟时间降低大约20%。实验结果表明,软件定义车联网的数据转发机制能够提高路由转发效率、减小延迟。     

VANET中一种基于概率转发的AODV路由协议

泛洪被作为实现广播通信的最简单的技术,广泛应用于车联网VANET(vehicular Ad Hoc network)路由.然而,由于VANET中节点的快速移动以及网络拓扑动态变化,简单的泛洪容易导致大量的冗余数据包,并引发广播风暴.为此,以典型的按需式距离矢量路由协议AODV (Ad Hoc on-demand distance vector)为基础,提出基于概率转发的AODV路由协议,记为AODV_P.AODV_P协议利用概率转发机制替代AODV中的泛洪.节点利用距离、密度信息计算转发概率,并依据转发概率设置计时器.计时器时间越短,成为下一跳转发节点的可能性越大.仿真结果表明,提出的AODV_P能够有效降低冗余数据包,缓解广播风暴问题.与AODV协议相比,AODV_P在传输时延、数据包传输率方面得到了有效提高.     

无线传感器网络中的优先级数据转发攻击检测方法

优先级队列是一种先进先出的数据结构，在优先级数据转发过程中，一旦其遭受攻击，整个队列中的数据将都会受到影响。为保证无线传感网络中优先级数据转发的安全性，提出一种优先级数据转发攻击检测方法。首先采用监督判别算法对传感网络中的优先级数据做降维处理；其次采用主成分分析法提取优先级网络数据中的特征；最后将提取的特征输入到构建的攻击检测模型中，通过设立的攻击检测阈值判定被攻击的数据，完成无线传感器网络中的优先级数据转发攻击检测。仿真结果显示：所提方法的数据包传输率为0.95bps，网络吞吐量均高于90，路由开销小于19，能量消耗约500J，攻击检测误报率低于4.76%。因此所提方法具有较好的优先级数据转发效果，能准确检测攻击。     

An adaptive and opportunistic broadcast protocol for vehicular ad hoc networks

A primary goal of broadcasting in vehicular ad hoc network (VANET) is to improve the road safety by transmitting alert messages to all surrounding vehicles as soon as possible. In this paper, we adopt the concept of opportunistic routing and propose a multiple candidate relays opportunistic broadcast (MCROB) protocol for VANET. The MCROB protocol is a sender-driven broadcast scheme independent of node density. The packet delivery ratio (PDR) is derived and an expected transmission speed (ETS) for the MCROB is proposed. A priority rule for selecting a proper candidate relay and an adaptive algorithm for forwarding timers of candidate relays are also presented in this paper. Simulations show that MCROB is adaptive to the rapid changing of network conditions. It keeps a low communication overhead introduced by the broadcast and increases the average transmission speed by around 40%.     

Dynamic priority scheduling of periodic queries in on-demand data dissemination systems

As an important wireless data broadcast technique, on-demand broadcast has been widely used for dynamic and large-scale data dissemination. An important class of emerging data broadcast applications requires monitoring multiple data items continuously in order to support data-driven decision making. Since wireless bandwidth is a precious shared medium, an important problem to solve is how to disseminate data to periodic queries, so that all the requests can be satisfied while the bandwidth consumption is minimized. In this paper, we first propose a new real-time scheduling algorithm called EDFS, which is a variant of the classic EDF [24] algorithm. Based on EDFS, we propose a novel on-line broadcast scheduling algorithm, called EDFS-BS. To our best knowledge, EDFS-BS is the first dynamic priority based broadcast scheduling algorithm that can be utilized to satisfy the timing constraints of periodic queries. We also propose a bandwidth utilization based schedulability test for EDFS-BS, which is used to ensure timing predictability of a periodic query set. Extensive experiments have been conducted to compare EDFS-BS versus existing solutions with comparable quality. The results show that EDFS-BS outperforms them considerably in terms of wireless bandwidth consumption and query service ratio.     

WSLA在WebQos分级问题上的应用

分析了区分Web服务及衡量服务级别的重要因素,介绍了WSLA的结构,提出了一种动态分配Web服务优先权的方法,尽可能满足了Web服务级协议(SLA)的要求,保证用户在Web服务质量(WebQos)的需求。     

基于命名数据网络的车载自组织网络数据分发机制

车载自组织网络（VANET）是一个高度动态的通信网络,设计稳定的数据分发机制是一个很大的挑战。将关注数据内容的命名数据网络（NDN）应用于车载自组织网络中,能有效缓解网络拓扑频繁变化所带来的问题。首先,优化命名数据网络的消息类型和数据结构;然后,结合车载自组织网络的特性,提出根据路段建立路由的方式,减少数据分发的开销。仿真实验结果表明,所提出的基于命名数据网络的车载自组织网络数据分发机制与应用于车载自组织网络数据分发的传统命名数据网络算法对比,数据转发平均命中率（AHR）提高大约53个百分点,平均转发次数减少大约0.4。因此提出的基于命名数据网络的车联网数据分发机制,采用新的路由方式,能够提高数据分发效率。     

Restricted usage of anonymous credentials in vehicular ad hoc networks for misbehavior detection

The automobile industry is entering a new era of digitalization with major impact on human mobility and transportation infrastructures. A result of such a convergence between the automobile and information technologies is vehicular ad hoc network (VANET), a type of mobile ad hoc networks that has recently enjoyed a lot of attention from the industry, the research community, lawmakers and privacy activists. In VANET, vehicles frequently broadcast various types of messages, including location data. This enables innovative applications and improvements in safety and driving experience. As messages broadcasted in the VANET are digitally signed and the receiver must be able to verify the sender’s authentication and message integrity, there is a need to ensure broadcast authentication and protect driver’s anonymity. However, communication in VANETs takes place with high frequency, and malicious vehicles can hide behind anonymity in order to duplicate packets and get advantage over other vehicles in the network. Indeed, state-of-the-art approaches to privacy-preserving messages broadcast in the VANET typically ensure that each vehicle has a number of pseudonymous certificates that are changed regularly in order to thwart an automated tracing of its activities. However, the possibility of uncontrolled simultaneous use of pseudonyms by misbehaving vehicles remain unaddressed. This paper proposes a set of anonymous credential system based protocols for VANET that enables the detection and limitation of pseudonym/credential overspending. The revocation of the misbehaving vehicle can be also achieved through the proposed solutions. With the prototypical implementation of the proposed protocols, it has been shown that the successful detection of fraud, i.e., pseudonyms overspending and the subsequent revocation of credentials are possible in VANET.     

一种多向链路感知的车载Ad Hoc网络传播协议

为了提高车辆自组织网络（Vehicular Ad Hoc Network,VANET）的数据传输效率,并使车辆间的数据通信能够持续进行,提出一种多向链路感知的车载Ad Hoc网络传播协议。为了保证车辆节点在执行通信任务的过程中实现数据的持续传输,防止通信链路频繁断连影响传输质量,提出了车辆网络的时间关联模型来讨论车辆间的速度差与通信持续时间的关系。为了缩短VANET中用于数据传输任务的总时间,协议基于改进蚁群的方法进行了多向链路感知,从而寻找在保证通信需求时间下的最短传输路径。实验结果分析表明,相比基于改进地理信息路由和基于优化链路状态路由的VANET数据传输算法,该算法的数据传输任务完工时间分别缩短了38.4%和27.3%,平均传输延迟分别降低了25.5%和12.1%。     

自适应紧急消息广播协议在VANET中的应用

车联网VANET(vehicular ad hoc network)被认为是智能交通系统最有前景技术之一,能够提出不同的应用服务,其中安全预警是最为重要的应用.可靠、有效地广播紧急消息是实现安全预警的关键.为此,提出面向不同应用的自适应紧急消息广播DAEMB(different application-self-adaption emergency messages broadcasting)协议.DAEMB协议依据应用的不同特性,采用Reliable和Dissemination两种紧急消息传输模式,并利用非均匀化基于时间和距离的段(segment)策略选择转发节点.仿真结果表明,提出的DAEMB协议平均传输时延、吞时量和紧急消息传输成功率方面具有良好的性能.     

Multiple hypothesis tracking for data association in vehicular networks

The introduction of Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communications in Intelligent Transportation Systems of the future brings new opportunities and new challenges into the automotive scene. Vehicular communications broaden the information spectrum that is available to each vehicle, allowing the enhancement of existing applications and the introduction of new ones. Undoubtedly, the impact of this new technology in transportation safety, efficiency and infotainment is expected to be very important.A significant part of research in vehicular networks (VANETs) is dedicated to networking issues like routing and safety. However, perception systems which until now were based on onboard sensors only, need to incorporate the wirelessly received information in order to extend the situation awareness of the vehicle and the driver. This paper presents an algorithm for associating targets tracked from an onboard radar sensor with the position and motion data received from the VANET. The core of the algorithm is a track oriented multiple hypothesis tracker that is modified for incorporating information included in VANET messages. The algorithm is tested in real scenarios using two experimental vehicles and then compared with two other algorithmic approaches. One is using a simpler single hypothesis algorithm for association of VANET messages and the second is using only the onboard sensors for environment perception. As a result, the advantages of the Multiple Hypothesis Algorithm regarding association performance and the added value of wireless information in the perception system are highlighted.