Coverage Area Based Opportunistic Forwarding Algorithm in VANETs

The highly mobility of vehicles, intermittent communication between the vehicles and the requirements of real time applications are some of the main challenges of multi-hop message delivery in Vehicular Ad Hoc Networks （ VANETs ）. There are also additional challenges, especially when the destination for the message delivery is a moving vehicle. In this paper, we propose a novel multihop message delivery method, called the Coverage Area-based oPportunistic message forwarding algorithm （CAP）. The main idea of CAP is to cover the potential area of a moving target vehicle as much as possible with the reachable area of the required delivery messages, so that the message can be delivered successfully. Because the success ratio and overhead of the multi-hop message delivery are two important but incompatible parameters in CAP, two tunings are discussed in the algorithm in order to maintain the balance of the two parameters. The simulation results show that compared with other reference approaches, CAP provides an efficient message delivery with a higher success ratio and a shorter message deNNy.

Opportunistic Unicast and Multicast Routing Protocol for VANET

Vehicular Ad Hoc Network (VANET) is a new paradigm of wireless network. Reliable and efficient unicast and multicast routing protocols are critical for VANETs. As a possible solution, opportunistic routing (OR) has received much attention recently. This paper focuses on the aspect of soft security by building trust opportunistic forwarding model in VANET. It incorporates the trust mechanism into OR to enhance the security of routing in resisting malicious attacks. In this paper, we proposed a trusted minimum cost opportunistic unicast routing protocol (TMCOR) and a multicast routing protocol (TMCOM). The simulation results show TMCOR and TMCOM have good throughput, average delay and security gains compared with existing protocols.

Void Aware Position Based Opportunistic Routing for QoS in Mobile Ad Hoc Networks

The unique anywhere, anytime wireless communication support offers, tremendous potential for the next generation of applications in a Mobile Ad-hoc Network (MANET). The Quality of Service (QoS) has been the ever demanding task of wireless communication to satisfy the application requirements. Geographical routing employs a greedy forwarding technique to deliver the packets to the destination and to owe the communication void, it fails to render the expected level of QoS. Opportunistic routing technique effectively utilizes the advantages of broadcasting nature of the wireless medium and selects a set of forwarding candidates instead of relying on a greedy node. To improve the efficiency of QoS routing in sparse and highly dynamic network topology, this paper proposes the Void-Aware Position based Opportunistic Routing (VAPOR). The VAPOR maintains 2-hop neighbor information to take a routing decision, but it is limited to 1-hop information when the node density is high. It efficiently balances the storage overhead and communication delay due to void and it increases the network throughput even under a sparse network. To provide a certain assurance level for packet reachability, VAPOR decides the potential forwarders based on the forwarding probability that measures link stability, capacity, and connectivity factor. It adaptively favors a path that avoids frequent link failure and unreliable link usage. By limiting the propagation area of duplicate packets, VAPOR reduces wastage of network resources, and ittakes the advantage of concurrent batch forwarding to avoid further duplication and unnecessary delay.

Road traffic and geography topology based opportunistic routing for VANETs

The message delivery .ratio and transmission delay is affected deeply by road traffic flow in vehicular ad hoc networks （VANETs）. An opportunistic routing based on geography and road traffic flow for VANETs （ORRIS） was proposed. ORRIS leverages the knowledge of geography positions, motion vectors and road traffic flows. In order to estimate the traffic flow density, the history of encounter number of the vehicles in the opposite direction is considered in ORRIS. The forwarding decisions are made by distributed vehicles based on the geography topology and the road traffic flow. The real map based simulation results show that ORRIS has a better performance than other algorithms, especially when the road traffic is busy or the traffic flow rates have great differences between roads.

一种基于连接性的VANETs地理机会路由协议

针对车载自组织网络(VANETs)中道路拓扑的限制和车辆的高速移动导致VANETs路由协议面临频繁的连接中断问题而效率低下的问题,综合考虑车辆行驶轨迹和该轨迹上的车流分布信息,动态地选择转发机会最大、预期时延最小的节点作为下一跳,提出了基于道路连接性的地理机会路由协议(CGOP)。仿真结果显示,相比GeOpps和GPSR,提出的CGOP具有更低的平均端到端时延,更高的分组投递率,在连接频繁中断的VANETs中具有良好的鲁棒性。

VANET环境下基于历史行为的消息路由方案

通过分析车用自组织网络(VANET)在道路交通领域中的应用现状,根据VANET的特点及其消息传输过程中面临的挑战,针对以往算法较难准确进行空间建模并较少考虑社会行为的规律性特征的问题,提出了一种基于车辆历史行为统计的消息路由方案——HBSR,具体分为计算车辆之间的连通性的节点连通算法,计算源节点和目的节点间可达时段数的拓扑重叠算法,选择消息转发路径的路径选择算法和丢包策略四部分。通过在ONE仿真平台上将其和一些典型的路由算法进行比较,实验证明HBSR方案能够更有效地在VANET中找到消息转发路径,在送达时延明显降低的同时交付率有显著提高,并且表现相对稳定。

基于VANETs下的决策树多副本机会路由协议

在车载自组织网络(vehicular Ad hoc networks,VANETs)中,当节点缓存和消息副本数目被限制的情况下,如何合理地选择车载网络的路由节点是实现VANETs高效转发和投递的关键问题。为此提出了一种基于学习方法的决策树理论的多副本VANETs机会路由协议(D-Tree)。D-Tree将VANETs中节点间的传输和连接因素看做多个属性的集合,并与决策树方法得到一个消息转发规则,同时结合多副本路由与机会路由的"存储─携带─转发"优势进行消息投递。真实数据集上的实验结果表明,在场景密集的情况下,D-Tree相比于Bubble和S&W路由算法投递成功率提高了近10%,同时在投递延迟等方面也具有明显优势。

VANET中考虑节点质量的机会路由协议

提出一种车载自组织网络(VANET)中考虑节点质量的机会路由协议——QAOR(Quality of node based Adaptive Opportunistic Routing Protocol)。针对以往协议均没考虑到节点历史接触频繁性的问题,该协议在路口根据距离目的最近和反映节点接触频繁性的质量两个指标机会选择下一跳,改善了GPSR在路口下一跳没有后续节点的情况;在直路上运用加入携带转发机制的贪婪算法。NS-2仿真显示,在城市场景中,QAOR自适应选路,比传统贪婪算法GPSR投递率增加,延时减少。

一种基于三角模糊数的VANETs机会路由算法

分析了现有车用自组织网络(VANETs)的路由算法,提出一种新的基于三角模糊数的机会路由算法。新算法将转发节点与目标节点的距离、到达目标节点的方向、行驶速度向量、重传次数、车流状况等因素作为目标函数进行分析计算,采用熵权系数法确定各因素权重。路由过程中,贪婪选择向量值最大的节点转发数据包;遇到网络不连续时,将采用存储—携带—转发的机会路由策略。仿真结果表明,该算法能够较好地适用于VANETs各种场景。

基于链路预测和能量感知的机会路由协议研究

在无线传感器(Wireless Sensors Networks,WSN)中,由于节点能量有限,可能导致节点过早死亡,引起网络结构发生变化,链路稳定性变差。针对该问题文中提出了一种基于链路预测和能量感知的机会路由协议ELPOR(Opportunistic Routing Protocol Based on Link Prediction and Energy Sensing,ELPOR).该协议综合考虑节点能量和各节点之间链路连接的概率,从潜在的候选转发集中选择一个中继节点,以实现能量的高效利用和数据的可靠传输。仿真结果表明,该协议能够有效均衡网络能耗、提高吞吐量和延长网络生存周期。

VANETs中的基于最小传输选择的局部机会路由

机会路由充分利用无线网络的广播特性,极大地提高单播吞吐量。然而,现有的机会路由依赖拓扑的全局信息,而且收集全局信息增加了系统开销,这将限制了机会路由在大型无线网络的应用。为此,提出基于最小传输选择MTS-B(minimum transmission selection)算法的局部机会路由LOR(localized opportunistic routing)协议,记为MTS-BLOR。提出的MTS-BLOR采用分布式最小传输选择算法MTS-B,并利用局部信息将网络拓扑划分小的邻近节点集CNS(close-node-set),拓宽了机会路由在大型的无线网络中的应用。由于无需使用全局动态信息,MTS-BLOR降低了系统开销,减少了系统复杂度。同时,分析了转发清单的全局优化与因开销受限的可扩展性之间的权衡。实验仿真表明,与ExOR(extremely opportunistic routing)、MORE(MAC-independent opportunistic routing protocol)相比,MTS-BLOR在时间复杂度、端到端传输时延和吞吐量方面得到明显的提升。

Utilizing the dropped packets for data delivery in VANETs

Timely and cost-efficient multi-hop data delivery among vehicles is essential for vehicular ad-hoc networks （VANETs）, and various routing protocols are envisioned for infrastructure-less vehicle-to-vehicle （V2V） communications. Generally, when a packet （or a duplicate） is delivered out of the routing path, it will be dropped. However, we observe that these packets （or duplicates） may also be delivered much faster than the packets delivered along the original routing path. In this paper, we propose a novel tree based routing scheme （TBRS） for ultilizing the dropped packets in VANETs. In TBRS, the packet is delivered along a routing tree with the destination as its root. And when the packet is delivered out its routing tree, it won＇t be dropt immediately and will be delivered for a while if it can arrive at another branch of the tree. We conduct the extensive simulations to evaluate the performance of TBRS based on the road map of a real city collected from Google Earth. The simulation results show that TBRS can outperform the existing protocols, especially when the network resources are limited.

基于自适应选路策略的VANETs路由协议

基于车载自组织网络特性,提出一种基于自适应选路策略的VANETs路由协议ASVP。协议针对VANETs的链路频断性,引入携带-转发(carry-forward)机制,使协议能够适用于间断性连接的延迟容忍网络。通过对道路模型分析计算,获得路段连通性度量指标,用于选取最优路径。协议基于道路拓扑将数据包的转发过程分为直路模式和路口模式,并对比分析VANETs中边界模式是否有必要性,路口模式下采用辅助设施进行转发。仿真结果表明,ASVP应用于城市场景中在时延和投递率方面有一定的优势。

基于链路持续时间控制的VANET路由协议

在车辆自组织网络中,车辆的快速移动会使网络拓扑呈现高动态性,造成链路频繁断裂、路径不稳定。针对该问题,提出一种控制链路持续时间的路由协议。采用相同行驶方向且链路持续时间最长的节点组建路径,在路由维护阶段,设置定时器提前触发路由寻路,找到可替代的有效链路组建新路径。如果未能找到有效链路,则在链路两端节点增大发射功率,延长链路持续时间,扩大寻路搜索范围,最大限度减小链路断裂的概率。仿真实验结果表明,与AODV及LED-AODV协议相比,该路由协议在路径持续时间、传输延迟和吞吐率方面性能较好,具有更稳定的链路。

一种基于区域广播的VANET机会路由协议

对VANET网络中现有的路由协议进行了系统的分析和研究,提出了一种基于区域广播的VANET机会路由协议。基于安全消息在网络割裂情况下的传播需求,新协议结合地理信息和机会转发算法,提出了不同于点对点的新的基于区域广播的消息传播模式,以实现安全消息在稀疏车辆环境下的有效传播。理论分析和仿真实验表明,该协议相比传统路由协议具有更优异的网络性能和可靠性。

VANET城市场景下一种优化的地理信息路由协议

车辆的高速移动以及城市场景中的障碍物使得车辆间的通信链路变得异常脆弱。而现有的多数地理信息并没有考虑链路的稳定、可靠性,产生了高的数据包丢失率和高的数据包传输时延,降低了网络性能。为此,提出了一种优化的地理信息路由协议IGR(Improved geographical)。IGR协议在数据包转发过程中,考虑了源车辆离候选车辆间的相对移动方向、候选车辆离目的车辆的距离以及beacon接收率,尊重车辆间无线链路的不稳定性事实。IGR协议择优选择具有稳定链路的车辆作为下一跳数据包转发节点。最后,评估了提出的IGR协议,并与现有的地理信息路由进行比较分析。结果表明,提出的IGR协议在数据包传输时延、数据包传输率性能优于GPCR和RBVT-R协议。

考虑相遇强度的约束扩散路由算法

为了提高机会网络的转发效率,论文提出了一种考虑相遇强度的约束扩散路由算法(EICD)。该算法针对概率路由中预测不准确导致的投递率低,提出了相遇强度并给出了其计算公式。相遇强度将时间作为计算的重要依据,更能准确反映两个节点下次相遇的可能性。同时,针对多拷贝算法中过多的消息副本和已投递消息的冗余副本占用大量的网络资源等问题,通过约束扩散和去冗余两种方法来降低网络负载和转发时延。仿真实验结果表明,与其它经典路由算法相比,EICD算法能够提高消息投递率,降低网络负载和转发时延。

移动机会网络路由问题研究进展

移动机会网络基于节点接触形成的通信机会逐跳转发数据,是满足物联网透彻感知与泛在互联的一种重要技术手段.机会路由作为实现间歇式连通环境下节点通信的基本方法,具有十分重要的研究意义,引起了研究人员的广泛关注.首先介绍了移动机会网络的概念、体系结构、典型应用以及所面临的一些挑战;然后详细阐述了机会路由算法的评价指标、设计需求与转发机制,并介绍了研究进展;最后,对机会路由未来的研究趋势进行了分析与展望.

基于网络编码的多播车载网路由算法研究

多播与网络编码的融合,可以实现网络的最大流最小割值,增加网络吞吐量.针对车载网拓扑变化频繁、链路寿命短暂的特点,利用网络编码,结合车内GPS系统提供的地理位置信息,提出一种事件驱动的车载多播路由算法:NCMR.NCMR算法依据车载节点的局部拓扑信息,确定数据发送速率和局部网络最大流最小割值,结合最大距离可分码,计算最小有限域,并按域值构造满足线性无关特性的全局编码矩阵,指导下游节点编码,从而在保证目标节点解码成功率的前提下有效减少有限域信息的传输量.仿真实验表明,算法有效减少了节点通信次数,降低了通信干扰,实现了网络负载均衡.

时延容忍网络中基于效用转发的自适应机会路由算法

提出了一种基于效用转发的自适应机会路由算法URD,并从理论上对该算法的有效性进行了分析。通过DTN仿真软件ONE进行了具体实现和验证,并与其他的经典协议:Epidemic,PRoPHET和SprayAndWait进行了性能对比。仿真结果表明,URD算法能够增加节点相遇的可能性,提高数据分组转发的效率,减少了网络的时延开销。