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1.
    
Traffic congestion, air pollution, fuel wastage, and car accidents are all exacerbated by increased traffic. Thus, vehicular communications, which refer to information transmission between cars, pedestrians, and infrastructures, have lately gained popularity and been extensively explored due to their enormous potential to enable intelligent transportation and various safety applications. Manually piloted cars and automated vehicles can acquire relevant information via vehicular communications to enhance traffic security and boost entertainment services. The basic concept of automobile clouds was originally published in the literature not long ago, and several suggested structural approaches have been presented in this study thus far. Several academics have concentrated on the structural layout to address various problems and, as a result, satisfy user expectations in order to give dependable services. We examined various vehicular cloud topologies in this study. We also offered a complete summary of current network layer research on allowing efficient vehicle communications and examined specific security, architectural, and reliability concerns in vehicular clouds. Also, the taxonomy of vehicular networks was discussed in terms of the service link between vehicular networks and cloud computing. Ultimately, we discussed the research prospects available. The results showed that security and privacy challenges are among the most important challenges.  相似文献   

2.
    
Recently, intelligent transportation systems (ITS) is becoming an important research topic. One goal of ITS is to exchange information among vehicles in a timely and efficient manner. In the ITS research community, inter‐vehicle communications (IVC) is considered a way that may be able to achieve this goal. An information network built on the top of vehicles using IVC can be viewed as a type of mobile ad hoc networks (MANETs). In the past, several unicast routing protocols for MANET have been proposed. However, most of them are designed for general MANETs rather than for IVC networks. In this paper, we first used more realistic vehicle mobility traces generated by a microscopic traffic simulator (VISSIM) to understand the characteristics of routing paths in an IVC network. Based on the insights gained from the derived path characteristics, we designed and implemented an intelligent flooding‐based routing protocol for small‐scale IVC networks. Via several field trials conducted on highways, we compared the performance of ad hoc on‐demand distance vector (AODV) and our protocol. Our experimental results show that (1) our protocol outperforms AODV greatly in IVC networks and (2) our protocol can provide text, image, audio, and video services for small‐scale IVC networks (e.g., a platoon) quite well. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

3.
This paper explains trajectory-based data forwarding schemes for multihop data delivery in vehicular networks where the trajectory isthe GPS navigation path for driving in a road network. Nowadays, GPS-based navigation is popular with drivers either for efficient driv-ing in unfamiliar road networks or for a better route, even in familiar road networks with heavy traffic. In this paper, we describe howto take advantage of vehicle trajectories in order to design data-forwarding schemes for information exchange in vehicular networks.The design of data-forwarding schemes takes into account not only the macro-scoped mobility of vehicular traffic statistics in road net-works, but also the micro-scoped mobility of individual vehicle trajectories. This paper addresses the importance of vehicle trajectoryin the design of multihop vehicle-to-infrastructure, infrastructure-to-vehicle, and vehicle-to-vehicle data forwarding schemes. First, weexplain the modeling of packet delivery delay and vehicle travel delay in both a road segment and an end-to-end path in a road net-work. Second, we describe a state-of-the-art data forwarding scheme using vehicular traffic statistics for the estimation of the end-to-end delivery delay as a forwarding metric. Last, we describe two data forwarding schemes based on both vehicle trajectory and vehicu-lar traffic statistics in a privacy-preserving manner.  相似文献   

4.
    
Vehicular Ad‐hoc Networks (VANETs) that are characterized by frequently changed topology, worse signal noise ratio, and non‐negligible Doppler effect introduce new non‐trivial challenges to Quality‐of‐Service (QoS) provisioning. The methodology of cross‐layer optimization aims to jointly optimize the working behaviors over different layers to achieve a better network performance, eg, throughput and transmission latency. This paper presents a novel cross‐layer optimization method based on Partially Observed Markov Games (POMG) to improve optimization decision against the inaccurate observed context caused by high‐speed movement, sensor errors, and other unavoidable reasons. POMG extends Markov Decision Process (MDP) and Partially Observed Markov Decision Process (POMDP) to dynamically adjust the concerned actions (eg, transmission range, contention window, and bit rate) according to the observed traffic density and thus can improve optimization performance at several aspects, eg,, throughput, channel utilization, delay, and total number of neighbor nodes. The extensive simulations show that POMG could harvest a high entire gain compared with the traditional fixed policy and the other cross‐layer optimization schemes.  相似文献   

5.
陈振  韩江洪  杨勇  刘征宇  陆阳 《通信学报》2015,36(7):92-101
车载自组网中的分布式TDMA方法没有利用节点的空闲TDMA时隙,未能充分利用无线信道资源,基于此,提出了一种利用空闲TDMA时隙的MAC层数据重发方法,当节点发送数据失败时,附近节点利用空闲的TDMA时隙重新发送传输失败的数据。理论分析和仿真结果表明,所提方法显著提高了分布式TDMA方法的数据发送成功概率和网络吞吐量。此外,通过仿真比较所提方法与IEEE802.11p的性能,结果表明,由于以确定的方式访问信道,所提方法能够及时稳定地传输车载自组网中的实时安全信息。  相似文献   

6.
Data aggregation is one of the major needs of vehicular ad hoc networks (VANETs) due to the constraints of resources. Data aggregation in VANET can reduce the data redundancy in the process of data gathering and thus conserving the bandwidth. In realistic applications, it is always important to construct an effective route strategy that optimises not only communication cost but also the aggregation cost. Data aggregation at the cluster head by individual vehicle causes flooding of the data, which results in maximum latency and bandwidth consumption. Another approach of data aggregation in VANET is sending local representative data based on spatial correlation of sampled data. In this article, we emphasise on the problem that recent spatial correlation data models of vehicles in VANET are not appropriate for measuring the correlation in a complex and composite environment. Moreover, the data represented by these models is generally inaccurate when compared to the real data. To minimise this problem, we propose a group-based data aggregation method that uses data relationship degree (DRD). In the proposed approach, DRD is a spatial relationship measurement parameter that measures the correlation between a vehicle’s data and its neighbouring vehicles’ data. The DRD clustering method where grouping of vehicle’s data is done based on the available data and its correlation is presented in detail. Results prove that the representative data using proposed approach have a low distortion and provides an improvement in packet delivery ratio and throughput (up to of 10.84% and 24.82% respectively) as compared to the other state-of-the-art solutions like Cluster-Based Accurate Syntactic Compression of Aggregated Data in VANETs.  相似文献   

7.
彭鑫  李仁发  付彬  李文  刘志鹏 《电子学报》2017,45(9):2195-2201
针对车联网的容迟特性造成通信资源受限的问题,提出了满足副本抑制要求的数据分发方案.方案利用马尔可夫链,通过交通网络的车辆概率分布建立路段的期望传输时延,并结合车辆的轨迹与目标位置的匹配度确定车辆的转发优先级.车辆为转发的每个数据包插入转发参数字段并通过同步反馈机制确定最终的转发车辆,确保由优先级最高的车辆完成转发.考虑到链路的稳定性,还推导了当前丢包率前提下,车辆接收数据包与发送次数之比,避免不必要的发送尝试产生大量副本.实验结果显示,提出的方案与基于轨迹预测的算法相比,有效提高了网络吞吐量和时延性能.  相似文献   

8.
    
Vehicular Ad Hoc Networks (VANETs), designed to ensure the safety and comfort of passengers via the exchange of information amongst nearby vehicles or between the vehicles and Roadside Units (RSUs), have attracted particular attention. However, the success of many VANET applications depends on their ability to estimate the vehicle position with a high degree of precision, and thus, many vehicle localization schemes have been proposed. Many of these schemes are based on vehicle‐mounted Global Positioning System (GPS) receivers. However, the GPS signals are easily disturbed or obstructed. Although this problem can be resolved by vehicle‐to‐vehicle communication schemes, such schemes are effective only in VANETs with a high traffic density. Accordingly, this paper presents a VANET localization scheme in which each vehicle estimates its location on the basis of beacon messages broadcast periodically by pairs of RSUs deployed on either side of the road. In addition, three enhancements to the proposed scheme are presented for the RSU deployment, RSU beacon collisions, and RSU failures. Overall, the ns‐2 simulation results show that the localization scheme achieves a lower localization error than existing solutions on the basis of vehicle‐to‐vehicle communications and is robust toward changes in the traffic density and the vehicle speed. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

9.
    
Vehicular ad hoc networks (VANETs) have been a research focus in recent years. VANETs are not only used to enhance the road safety and reduce the traffic accidents earlier but also conducted more researches in network value‐added service. As a result, the security requirements of vehicle communication are given more attention. In order to prevent the security threat of VANETs, the security requirements, such as the message integrity, availability, and confidentiality are needed to be guaranteed further. Therefore, a secured and efficient verification scheme for VANETs is proposed to satisfy these requirements and reduce the computational cost by combining the asymmetric and symmetric cryptology, certificate, digital signature, and session key update mechanism. In addition, our proposed scheme can resist malicious attacks or prevent illegal users' access via security and performance analysis. In summary, the proposed scheme is proved to achieve the requirements of resist known attacks, non‐repudiation, authentication, availability, integrity, and confidentiality. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

10.
车载自组织网中基于蚁群算法的延迟感知路由协议   总被引:1,自引:0,他引:1       下载免费PDF全文
吴敏  章国安  蔡蓉 《电讯技术》2016,56(10):1086-1092
针对城市道路环境下车载自组织网( VANETs)中通信性能下降以及数据传输失败的问题,提出了一种基于蚁群算法的延迟感知路由( ACDR)协议。首先,建立双向车道的数学延迟模型;然后,根据提出的端点十字路口( EI)的概念,ACDR利用蚁群优化( ACO)寻找最佳路线,其中前向蚂蚁根据本地路段延迟以及当前十字路口与目的节点的端点十字路口之间的全局时延来选择路径,后向蚂蚁则负责在返回路径时更新信息素,同时,相邻十字路口之间利用贪婪转发算法进行数据包的传递。最后仿真比较了ACDR协议与连通性感知路由( CAR)协议的性能,结果表明提出的ACDR协议的数据包的传输延迟小,丢包率低,通信性能好。  相似文献   

11.
车载自组织网络关键技术   总被引:1,自引:0,他引:1  
车载自组织网络(VANET)是一种自组织、结构开放的车辆间通信网络,随着无线通信技术与交通业联系的日益密切,VANET得到了大力发展。本文从VANET的基本概念和发展进程出发,综述VANET的关键技术。首先介绍VANET的网络模型、主要特点及体系结构,然后对VANET的物理层、MAC层、路由协议及应用层的研究内容和研究现状进行了系统阐述,最后对VANET今后的研究方向和应用前景进行了展望。  相似文献   

12.
    
This paper presents a comprehensive study of the performance of routing protocols in distributed vehicular networks. We propose a novel and efficient routing protocol, namely cross‐layer, weighted, position‐based routing, which considers link quality, mobility and utilisation of nodes in a cross layer manner to make effective position‐based forwarding decisions. An analytic hierarchy process approach is utilised to combine multiple decision criteria into a single weighting function and to perform a comparative evaluation of the effects of aforementioned criteria on forwarding decisions. Comprehensive simulations are performed in realistic representative urban scenarios with synthetic and real traffic. Insights on the effect of different communication and mobility parameters are obtained. The results demonstrate that the proposed protocol outperforms existing routing protocols for vehicular ad hoc networks, including European Telecommunications Standards Institute (ETSI's) proposed greedy routing protocol, greedy traffic aware routing protocol and advanced greedy forwarding in terms of combined packet delivery ratio, end‐to‐end delay and overhead. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

13.
Recently, the routing problem in vehicular ad hoc networks is one of the most vital research. Despite the variety of the proposed approaches and the development of communications technologies, the routing problem in VANET suffers from the high speed of vehicles and the repetitive failures in communications. In this paper, we adjusted the well‐known K‐medoids clustering algorithm to improve the network stability and to increase the lifetime of all established links. First, the number of clusters and the initial cluster heads will not be selected randomly as usual, but based on mathematical formula considering the environment size and the available transmission ranges. Then the assignment of nodes to clusters in both k‐medoids phases will be carried out according to several metrics including direction, relative speed, and proximity. To the best of our knowledge, our proposed model is the first that introduces the new metric named “node disconnection frequency.” This metric prevents nodes with volatile and suspicious behavior to be elected as a new CH. This screening ensures that the new CH retains its property as long as possible and thus increases the network stability. Empirical results confirm that in addition to the convergence speed that characterizes our adjusted K‐medoids clustering algorithm (AKCA), the proposed model achieves more stability and robustness when compared with most recent approaches designed for the same objective.  相似文献   

14.
为了提高VANET中节点的吞吐量性能,提出基于协议序列平均分配算法的信道接入机制。在高速公路场景下,规划IEEE 802.11p业务信道与竞争区段的映射,并根据用户保障序列的特性设计帧结构。通过少量反馈确定竞争区段的节点数,并提出循环轮流分配法实现平均意义上非整数个序列的分配。仿真结果证明了理论分析的有效性,在实际路况中均分法与经典方法相比吞吐量性能明显改善,并且节点越稀疏、物理层数据传输速率越高,吞吐量性能提升越明显,同时可保持较低的网络开销和较好的信道接入公平性。  相似文献   

15.
    
In vehicular ad hoc networks, vehicles may use a routing protocol to inform emergent events, for example, car accidents or traffic jams. Hence, many of the researchers are focused on minimizing the end‐to‐end delay of the routing protocol. However, some applications, for example, email or ftp, are not time critical, and radio spectrum is a limited resource. Hence, delay‐bounded routing protocol, whose goal is to deliver messages to the destination within user‐defined delay and minimize the usage of radio, has become an important issue. The delay‐bounded routing protocols deliver message to the destination by the hybrid of data muling (carried by the vehicle) and forwarding (transmitted through radio). When the available time is enough, the message will be delivered by muling; otherwise, it will be delivered by forwarding. However, in an urban area, there are many traffic lights, which may greatly affect the performance of the delay‐bounded routing protocols. Existing works do not consider the effect of traffic lights, and hence, it may adopt an improper delivery strategy and thus wastes much available time. To improve previous works, we propose a novel delay‐bounded routing protocol, which has considered the effect of traffic lights. Whenever a vehicle passes an intersection, it will gather the information of the traffic light and traffic load of the next road section, and thus, it can make a more accurate prediction and adopt a more proper strategy to deliver message. Simulation results show that the proposed protocol can make a better usage of the available time and uses less radio resource to deliver the message in time. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

16.
在对车载自组织网络的特点和研究现状分析的基础上,文章给出了车载自组织网络(VANET)中多维多层的理论模型和网络体系结构,讨论了物理层技术及其相关标准以及MAC层、网络层协议设计的重点和难点,阐述了广播协议的设计思路。  相似文献   

17.
    
Routing protocols for vehicular ad hoc networks (VANETs) have attracted a lot of attention recently. Most of the researches emphasize on minimizing the end‐to‐end delay without paying attention to reducing the usage of radio. This paper focuses on delay‐bounded routing, whose goal is to deliver messages to the destination within user‐defined delay and to minimize the usage of radio because radio spectrum is a limited resource. The messages can be delivered to the destination by the hybrid of data muling (carried by the vehicle) and forwarding (transmitted through radio). In the existing protocol, a vehicle may only switch the delivery strategy (muling or forwarding) at an intersection according to the available time of the next road segment, which is between the current intersection and the next intersection. To improve previous works, our protocol uses linear regression to predict the available time and the traveling distance, and thus, the vehicle can switch to a proper delivery strategy at a proper moment and can reduce the number of relays by radio. Our protocol contains two schemes: the greedy and centralized schemes. The greedy scheme uses only the current sampling data to predict the available time and decide when to switch the delivery strategy, whereas the centralized scheme uses the global statistical information to choose a minimum‐cost path. Simulation results justify the efficiency of the proposed protocol. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

18.
    
While authentication is a necessary requirement to provide security in vehicular ad hoc networks, user's personal information such as identity and location must be kept private. The reliance on road side units or centralized trusted authority nodes to provide security services is critical because both are vulnerable, thus cannot be accessed by all users, which mean security absence. In this paper, we introduce a self‐organized secure framework, deployed in vehicular ad hoc networks. The proposed framework solution is designed not only to provide an effective, integrated security and privacy‐preserving mechanism but also to retain the availability of all security services even if there are no road side units at all and/or the trusted authority node is compromised. A decentralized tier‐based security framework that depends on both trusted authority and some fully trusted nodes cooperated to distribute security services is presented. Our approach combines the useful features of both Shamir secret sharing with a trust‐based technique to ensure continuity of achieving all security services. Mathematical analysis of security issues that the proposed framework achieves as well as the availability of offering security services is provided. Proposed framework examination was done to show the performance in terms of storage, computation complexity, and communication overhead as well as its resilience against various types of attacks. Comparisons with different types of security schemes showed that the protocol developed gave better results in most comparison parameters while being unique ensuring continuity of security services delivery.  相似文献   

19.
基于自组织映射神经网络的VANET组网算法   总被引:1,自引:0,他引:1  
吴怡  杨琼  吴庆祥  沈连丰  林潇 《通信学报》2011,32(12):136-145
研究了应用于汽车辅助驾驶、无人驾驶等智能交通领域的车辆组网方法,提出一种将自组织映射神经网络算法应用于车辆自组织网络进行车辆组网的算法,该算法根据车辆定时发出的消息中位置、行驶方向等信息对车辆按目的地、行驶方向的相似性进行组网,组网后的车辆主要接收并处理与之在同一个网络中的车辆的信息。理论分析和仿真结果表明,组网后的系统传输时延远低于未组网通信情况,吞吐量有显著提高。  相似文献   

20.
针对车载自组织网络的特点,该文利用双线性对提出了一个新的基于身份的签密方案,并在随机预言模型中给出了安全性证明.在假设Bilinear Diffie-Hellman问题是困难的条件下,该方案被证明是安全的.与已有的基于身份的签密方案相比,该方案计算量和传输代价小,适合用于车载网安全通信.  相似文献   

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