Communication framework for vehicle ad hoc network on?freeways

Providing an efficient and stable communication framework of Vehicular Ad hoc Network (VANET) is an emerging issue. Most of conventional VANET communication schemes only support short range transmission, vehicles need to relay traffic data or frequently switch to different roadside units. Such an ad hoc-based method suffers a high jitter delay and makes it difficult to develop travel and real-time multimedia services, such as traffic information dissemination and fleet management. Fortunately, existing novel wireless technologies, e.g. WiMAX mobile multi-relay (MMR), provide long transmission range and high transmission rate in mobile environments. This study presents a Safety/Vehicular Information Delivery (SVID) framework, an application-layer VANET communication protocol. A power-abundant, large size vehicle, called SIP-based relay vehicle (SRV), e.g. long distance transportation bus, plays as a relay station (RS) providing the connectivity to other small vehicles around it. To provide VANET services in SVID, this work adopts a SIP-based mechanism. The proposed scheme can provide more efficient communication than conventional VANET ad hoc mode. Simulation results show that the proposed scheme achieves a low SIP transaction time, jitter delay, frame loss rate while avoiding the broadcast storm problem.     

Data relationship degree–based clustering data aggregation for VANET

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.     

SEAD: A simple and efficient adaptive data dissemination protocol in vehicular ad-hoc networks

Vehicular ad-hoc network (VANET) is becoming a promising technology for improving the efficiency and the safety of intelligent transportation systems by deploying a wide variety of applications. Smart vehicles are expected to continuously exchange a huge amount of data either through safety or non-safety messages dedicated for road safety or infotainment and passenger comfort applications, respectively. One of the main challenges posed by the study of VANET is the data dissemination design by which messages have to be efficiently disseminated in a high vehicular speed, intermittent connectivity, and highly dynamic topology. In particular, broadcast mechanism should guarantee fast and reliable data delivery within a limited wireless bandwidth in order to fit the real time applications’ requirements. In this work, we propose a simple and efficient adaptive data dissemination protocol called “SEAD”. On the one hand, the originality of this work lies in its simplicity and efficiency regardless the application’s type. Simplicity is achieved through a beaconless strategy adopted to take into account the surrounding vehicles’ density. Thanks to a metric locally measured, each vehicle is able to dynamically define an appropriate probability of rebroadcast to mitigate the broadcast storm problem. Efficiency is manifested by reducing excessive retransmitted messages and hence promoting the network capacity and the transmission delay. The simulation results show that the proposed protocol offers very low packet drop ratio and network load while still maintaining a low end-to-end delay and a high packet delivery. On the other hand, SEAD protocol presents a robust data dissemination mechanism which is suitable either for safety applications or for other kinds of application. This mechanism is able to adapt the protocol performance in terms of packet delivery ratio to the application’s requirements.     

A new type of blockchain for secure message exchange in VANET

In the Vehicular Ad-hoc NETworks (VANET), the collection and dissemination of life-threatening traffic event information by vehicles are of utmost importance. However, traditional VANETs face several security issues. We propose a new type of blockchain to resolve critical message dissemination issues in the VANET. We create a local blockchain for real-world event message exchange among vehicles within the boundary of a country, which is a new type of blockchain suitable for the VANET. We present a public blockchain that stores the node trustworthiness and message trustworthiness in a distributed ledger that is appropriate for secure message dissemination.     

A Street Broadcast Reduction Scheme (SBR) to Mitigate the Broadcast Storm Problem in VANETs

In urban vehicular wireless environments, several vehicles can send warning messages and so every vehicle within the transmission range will receive the broadcast transmission, possibly rebroadcasting these messages to other vehicles. This increases the number of vehicles receiving the traffic warning messages. Hence, redundancy, contention, and packet collisions due to simultaneous forwarding (usually known as the broadcast storm problem), can occur. In the past, several approaches have been proposed to solve the broadcast storm problem in wireless networks such as Mobile ad hoc Networks MANETs. In this paper, we present Street Broadcast Reduction SBR, a novel scheme that mitigates the broadcast storm problem in VANETs. SBR also reduces the warning message notification time and increases the number of vehicles that are informed about the alert.     

Adaptive information dissemination: an extended wireless data broadcasting scheme with loan-based feedback control

The dissemination of numerous information broadcast services, gives rise to the scalability issue in wireless networks. Previous researchers have shown that the push-based data broadcast mechanism is efficient in reducing message traffic. However, most research efforts are dedicated to the dissemination of static information contents. In practice, information broadcast services can produce and deliver dynamic information contents. To efficiently convey the dynamic data, we device, in this paper, an adaptive information dissemination mechanism by exploiting the functionality of data broadcasting, to support the dissemination of static and dynamic information services simultaneously. In our design, both static and dynamic information services are subsumed as service groups, i.e. the building blocks with the uniform representation of structure and group popularity and, thus, the conventional scenario becomes a special case of our framework. Furthermore, in order to tolerate the broadcast traffic dynamics, we design an online load-based slot allocation and feedback control technique to deal with the adaptation of the service group classification, bandwidth allocation, and broadcast schedule so as to avoid performance degradation. It is shown by the experimental study that the proposed adaptive information dissemination mechanism associated with the online loan-based feedback control is able to achieve a substantial reduction of message traffic for dynamic dissemination in wireless networks.     

Broadcast storm mitigation techniques in vehicular ad hoc networks

Several multihop applications developed for vehicular ad hoc networks use broadcast as a means to either discover nearby neighbors or propagate useful traffic information to other vehicles located within a certain geographical area. However, the conventional broadcast mechanism may lead to the so-called broadcast storm problem, a scenario in which there is a high level of contention and collisions at the link layer due to an excessive number of broadcast packets. While this is a well-known problem in mobile ad hoc wireless networks, only a few studies have addressed this issue in the VANET context, where mobile hosts move along the roads in a certain limited set of directions as opposed to randomly moving in arbitrary directions within a bounded area. Unlike other existing works, we quantify the impact of broadcast storms in VANETs in terms of message delay and packet loss rate in addition to conventional metrics such as message reachability and overhead. Given that VANET applications are currently confined to using the DSRC protocol at the data link layer, we propose three probabilistic and timer-based broadcast suppression techniques: weighted p-persistence, slotted 1-persistence, and slotted p-persistence schemes, to be used at the network layer. Our simulation results show that the proposed schemes can significantly reduce contention at the MAC layer by achieving up to 70 percent reduction in packet loss rate while keeping end-to-end delay at acceptable levels for most VANET applications.     

VANET: A novel service for predicting and disseminating vehicle traffic information

The arrival of cloud computing technology promises innovative solutions to the problems inherent in existing vehicular ad hoc network (VANET) networks. Because of the highly dynamic nature of these networks in crowded conditions, some network performance improvements are needed to anticipate and disseminate reliable traffic information. Although several approaches have been proposed for the dissemination of data in the vehicular clouds, these approaches rely on the dissemination of data from conventional clouds to vehicles, or vice versa. However, anticipating and delivering data, in a proactive way, based on query message or an event driven has not been defined so far by these approaches. Therefore, in this paper, a VANET‐Cloud layer is proposed for traffic management and network performance improvements during congested conditions. For the traffic management, the proposed layer integrates the benefits of the connected sensor network (CSN) to collect traffic data and the cloud infrastructure to provide on‐demand and automatic cloud services. In this work, traffic services use a data exchange mechanism to propagate the predicted data using a fuzzy aggregation technique. In the evaluation phase, simulation results demonstrate the effectiveness of the proposed VANET‐Cloud layer to dramatically improve traffic safety and network performance as compared with recent works.     

Cognitive Agent Based Critical Information Gathering and Dissemination in Vehicular Ad hoc Networks

Next generation vehicles will have capability of sensing, computing, and communicating capabilities. Different components in a vehicle have to constantly exchange available information with other vehicles on the road and cooperate for the purpose of ensuring safety and comfort using a Vehicular Ad hoc Network (VANET). Critical information like navigation, cooperative collision avoidance, lane-changing, speed limit, accident, obstacle or road condition warnings, etc. play a significant role for safety-related applications in VANET. Such kind of critical information gathering and dissemination is challenging, because of their delay-sensitive nature. This paper proposes an agent based model that consists of heavy-weight static cognitive (based on Belief Desire Intention : BDI) and light-weight mobile agents. Proposed model executes push (gather/store and disseminate) and pull (gather/store) operations on information gathered based on information relevance, criticalness and importance. The simulation results show that BDI based information gathering and dissemination scheme performs better than the reliable broadcast scheme in terms of bandwidth utilization, packet delivery ratio, push latency (information saturation time) and push/pull decision latency.     

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。     

Fireworks: an intelligent location discovery algorithm for vehicular ad hoc networks

Searching for and locating a certain destination in a vehicular ad-hoc network (VANET) are fundamental issues to ensure routing and data dissemination under high mobility and lack of fixed infrastructure. However, naive-flooding searching is too expensive and takes a considerable amount of valuable bandwidth in the network. To overcome this, GPS information of the vehicles can be exploited, which can aid searching and routing in VANETs. In this paper, we present a novel position-based searching algorithm—called Fireworks—that can be used as a location discovery algorithm in VANETs. The proposed scheme is purely reactive and has a limited usage of beacons. Fireworks algorithm provides the position of the destination vehicle without having a Location Information System infrastructure or a proactive mechanism. We show that the method is efficient and reliable while greatly reducing the searching overhead. The simulations show that the algorithm covers as many nodes as naive-flooding with less than one-fifth of the broadcast messages and with less than one-third of the Dynamic Source Routing (DSR). It also performs better than Acknowledgement-Based Broadcast Protocol (ABSM) in terms of total number of broadcast messages, node coverage speed and query success rate.     

基于概率策略逻辑的VANET信息广播模型定量验证方法研究

VANET网络中信息的发送和接收具有随机性和不确定性,IEEE 802.11p广播协议无法适应VANET网络拓扑动态变化,于是研究者们根据不同环境中的具体应用需求提出了各种VANET广播协议,如何对新提出的协议的性能以及可靠性进行分析与验证是一个关键性问题.自动化的定量验证技术能够针对系统需要满足的多个性质进行分析,并给出满足需求的最大或者最小概率.然而研究人员在进行定量验证过程中使用的PTCL、rPATL等逻辑语言都不能够明确描述用户的策略是什么,因此本文提出基于概率策略逻辑的模型定量验证方法.该方法首先对系统中的多个角色使用概率时间接口自动机对其行为建模,然后使用概率策略逻辑语言对系统需要满足的性质进行描述,最后基于定量验证算法自动给出系统相关性质的分析结论.本文将该方法应用到VANET信息广播协议性能分析上,能够针对外界环境的变化选择合理的策略,从而分析出不同环境下信息广播发送成功的最大概率.     

Broadcasting safety information in vehicular networks: issues and approaches

A primary goal of intelligent transportation systems is to improve road safety. The ability of vehicles to communicate is a promising way to alleviate traffic accidents by reducing the response time associated with human reaction to nearby drivers. Vehicle mobility patterns caused by varying traffic dynamics and travel behavior lead to considerable complexity in the efficiency and reliability of vehicular communication networks. This causes two major routing issues: the broadcast storm problem and the network disconnection problem. In this article we review broadcast communication in vehicular communication networks and mechanisms to alleviate the broadcast storm problem. Moreover, we introduce vehicular safety applications, discuss network design considerations, and characterize broadcast protocols in vehicular networks.     

AMOEBA: Robust Location Privacy Scheme for VANET

Communication messages in vehicular ad hoc networks (VANET) can be used to locate and track vehicles. While tracking can be beneficial for vehicle navigation, it can also lead to threats on location privacy of vehicle user. In this paper, we address the problem of mitigating unauthorized tracking of vehicles based on their broadcast communications, to enhance the user location privacy in VANET. Compared to other mobile networks, VANET exhibits unique characteristics in terms of vehicular mobility constraints, application requirements such as a safety message broadcast period, and vehicular network connectivity. Based on the observed characteristics, we propose a scheme called AMOEBA, that provides location privacy by utilizing the group navigation of vehicles. By simulating vehicular mobility in freeways and streets, the performance of the proposed scheme is evaluated under VANET application constraints and two passive adversary models. We make use of vehicular groups for anonymous access to location based service applications in VANET, for user privacy protection. The robustness of the user privacy provided is considered under various attacks.     

Location aided probabilistic broadcast algorithm for mobile Ad-hoc network routing

On-demand routing protocols are widely used in mobile Ad-hoc network (MANET). Flooding is an important dissemination scheme in routing discovering of on-demand routing protocol. However, in high-density MANET redundancy flooding packets lead to dramatic deterioration of the performance which calls broadcast storm problem (BSP). A location-aided probabilistic broadcast (LAPB) algorithm for routing in MANET is proposed to reduce the number of routing packets produced by flooding in this paper. In order to reduce the redundancy packets, only nodes in a specific area have the probability, computed by location information and neighbor knowledge, to propagate the routing packets. Simulation results demonstrate that the LAPB algorithm can reduce the packets and discovery delay (DD) in the routing discovery phase.     

QoS‐aware broadcasting in VANETs based on fuzzy logic and enhanced kinetic multipoint relay

Vehicular ad hoc networks (VANETs) are emergent concepts in terms of infrastructure‐less communication. The data dissemination is usually done using broadcast schemes. Data broadcast in VANETs is a challenging issue due to the high mobility vehicles and the varying density. On one hand, these vehicles have to share and disseminate the safety‐critical information, in real time, to other intended vehicles. On the other hand, the existing broadcast solutions do not succeed, till now, to fulfill VANETs requirements especially in terms of performance and QoS. In this paper, we propose a new QoS‐aware broadcast method in order to face VANETs communications challenges. We choose to adapt a concept originally devoted to mobile ad hoc networks (MANETs) and join it to other specific VANET techniques to introduce a new broadcasting protocol in the aim of optimizing QoS fulfilment. The proposed solution is fundamentally based on enhanced kinetic strategy assisted with fuzzy logic for QoS‐aware multipoint relay (MPR). The protocol efficiency is eventually tested through an experimental study and compared with existing methods. The results prove the over‐performance of the proposed solution.     

在VANETs城市场景下的基于自适应时延的Geocast路由协议

基于广播式的Geocast路由协议能够在特定的地理区域内高效地发布数据。然而,广播模式引起冗余重播,易导致广播风暴问题。另外,由于城市场景下建筑物的影响,现有的多数广播抑制方案难以应用于城市环境。为此,提出面向城市的基于自适应时延的Geocast路由协议UGAD(Urban Geocast based on Adaptive Delay)。UGAD采用了基于自适应时延的广播抑制方案,降低发生广播风暴的概率。同时,考虑到交叉路口的地理优势,给位于交叉路口的车辆 “优惠”的时延,使其具有优先转发数据包权力,从而提高数据包到达率。此外,考虑到城市道路的复杂性,UAGD采用基于交叉路口转发IF(Intersection forwarding)和贪婪转发GF(Greedy forwarding)两个模式,依据不同的道路情况选择不同的转发模式,从而降低冗余重播,并保持高的数据包到达率。最后,针对城市场景进行仿真,结果表明提出的UGAD具有高的数据包到达率,低的数据包重播率。     

SOBP: a sender-designated opportunistic broadcast protocol for VANET

Two problems existing in highway vehicular ad hoc networks (VANET), i.e., the slow reaction problem (SRP) and the local broadcast storm problem (LBSP), are investigated. In SRP, a candidate forwarder (CF) close to a sender always rebroadcasts a packet with a low probability or rebroadcasts a packet after a long delay in sparse network, while LBSP occurs when vehicles contending for accessing channel in a local dense network. To solve these problems, a Sender-designated Opportunistic Broadcast Protocol (SOBP) is proposed, which has multiple CFs to broadcast packets and is irrelevant to node density. A sender designates a fixed number of CFs and assigns priorities to them before broadcasting a packet so that possible collisions in the receivers are avoided. To enhance the efficiency of a single transmission, the sender chooses the CFs separated with a certain distance to alleviate the effect of hidden node. The average number of transmissions in a successful broadcast is analyzed and the retransmission strategy to enhance the reliability is presented. One of the main features of SOBP is that it is able to keep broadcasting overhead at a low level. Simulations show that SOBP is able to effectively solve the SRP and the LBSP.     

Cluster based emergency message broadcasting technique for vehicular ad hoc network

Broadcasting is one of the major emergency services of Vehicular ad hoc network, since the number of vehicles increases every day. Because of the high density of the vehicles, it is necessary to broadcast emergency messages to all the vehicles to avoid traffic jam and vehicle accidents. Reliable broadcasting of messages in self-organizing Ad hoc networks is a promising research field. In this paper a cluster based emergency message broadcasting algorithm is proposed. In this regard we have proposed cluster based architecture for emergency message dissemination and collision avoidance in VANET. In this paper, first the formation of cluster is done in such a way that it avoids any kind of collision. Once cluster head is selected it takes the responsibility of intra cluster management to avoid interference between the clusters. To increase the reliability during emergency message dissemination two MAC layer broadcasts protocol is used. This assures that message is delivered on time without any hazards. The proposed model is simulated for DSDV, AODV, and DSR protocols with the standards 802.11 and 802.11p in SHWM, Manhattan and freeway mobility models.     

DDDRC: decentralised data dissemination in VANET using raptor codes

The design of data dissemination protocol has been a great challenge due to the highly dynamic and unreliable wireless channel in vehicular ad hoc networks (VANET). In literature, several interesting solutions are proposed to perform data dissemination for this environment. But these solutions either use architectures requiring centralised coordination or global network knowledge or large intermediate buffers. In this paper, we propose a decentralised technique that overcomes above requirements and provides reliable and scalable communication in both dense and sparse traffic for VANET. Random walks are used in the proposed technique to disseminate data from one vehicle to other vehicles in the network. We use raptor codes to provide low decoding complexity and more scalability for data dissemination. Simulation results demonstrate that the proposed technique has better fault tolerance with lower complexity than general random-walk-based dissemination process and more scalability as compared to the other protocols.