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Connected vehicles continuously reveal their location information to the potential observers that then track vehicles over time and space. However, safety applications require disseminating such location information to the vicinity, which essentially urges to develop the awareness ability of the exposed location-privacy quantity. We propose an analytic framework to quantify location privacy from the perspective of temporal and spatial correlation, which permits connected vehicles to flexibly configure their preferential location-privacy sensitivity extent. We offer a novel approach so as to make the disclosure of location privacy more human-understandable and independent of the suffered attack pattern. This paradigm enables users to customize the location-privacy protection mechanisms for adapting to the frequently varying traffic context. Moreover, we put forward an adaptive lived-term pseudonym scheme for exampling how to utilize the presented quantitative framework. Finally, we move from theory to practice by applying the proposed theoretical framework to a simulation vehicular mobility data set TAPASCologne composed of more than two hundred and fifty thousand vehicles and a real trace set of more than ten million location sample points obtained from the Roman taxis. We investigate the accuracy and applicability of the presented quantification model and effects of combinations of various concerned parameters. The results show that the quantification model can identify the real-time exposure of location privacy efficiently and effectively as vehicles move and then provide quantitative control feedback to privacy protection mechanisms, which facilitates restrict the location privacy to a target value and tradeoff between the location privacy and service enjoyment.

Over the last decade, vehicular ad-hoc networks (VANETs) have received a greater attention in academia and industry due to their influence in intelligent transportation systems. Providing reliability and security to the VANET is essential in order to guarantee the efficiency of its applications. Anomaly detection has become a challenging problem due to the unique environment of VANETs with quick movement and short-lived link. In this paper, a method using the spatio-temporal feature of network traffic is proposed to implement network traffic estimation at first, and on this basis, an anomaly detection algorithm is put forward. The convolutional neural network is employed to extract the spatio-temporal features of the traffic matrix. In terms of the extracted features, network traffic is estimated by using a fully connected architecture as the output layer. Then, a threshold-based separation method is used to implement anomaly detection. The preliminary experiments comparing the proposed method with other machine learning-based methods show the effectiveness of the proposed anomaly detection method.

Vehicles travelling and communicating with each other and infrastructure is the basis of the future of vehicular transportation. There are many possible applications of communication in a vehicular network. One of the more important applications is for safety. Safety messages exchanged between vehicles can possibly be life-saving. However, if such messages are not received in a timely or reliable manner, a safety application’s effectiveness could suffer. As such, network congestion control is a popular topic in vehicular networks. Various methods of controlling the message transmission rate and power have been explored to-date. In this thesis we propose an algorithm which manipulates the transmission power based on a density estimation derived from the vehicle’s driving speed, and compare it to methods observing only speed, only density, or other factors. Analysis of the results was done through simulation software. Results showed that the proposed algorithm reduced symptoms of channel congestion at least as effectively as the related density-based algorithm, and much better than using no congestion control algorithm at all. This thesis also adds “relevance” as a new measurement of performance by observing the proportion of packets received from certain distances at each vehicle.

Submitted by Marisa Figueiredo (marisa@ua.pt) on 2020-10-30T15:39:08Z No. of bitstreams: 1 Documento_Ana_Tavares.pdf: 13443520 bytes, checksum: 075fa209bc9239bfdac84f8b109ae2ad (MD5) Made available in DSpace on 2020-10-30T15:39:08Z (GMT). No. of bitstreams: 1 Documento_Ana_Tavares.pdf: 13443520 bytes, checksum: 075fa209bc9239bfdac84f8b109ae2ad (MD5) Previous issue date: 2019-07 Mestrado em Engenharia Informática

Com o crescimento da população global a mobilidade urbana emerge como um desafio. Como consequência deste crescimento mais dados se tornaram disponíveis, o que permite que novas tecnologias surjam para melhorar os sistemas de mobilidade, especialmente o sistema de transporte. Uma estratégia de baixo custo para lidar com problemas na mobilidade urbana, é o conceito de Sistemas de Transporte Inteligentes -- Intelligent Transportation System (ITS). O desenvolvimento de novas aplicações e serviços para o ambiente ITS, com o objetivo de melhorar a mobilidade, depende da disponibilidade de grandes quantidades de dados, que atualmente demostra-se limitada. Esta proposta tem como objetivo o uso de diversas fontes de dados para promover a melhora da mobilidade atual nas cidades. No entanto, um desafio substancial surge quando combinamos várias fontes de dados, aumentando os problemas de cobertura espaço-temporal que afetam o desenvolvimento de soluções para Mobilidade Inteligente -- Smart Mobility (SM). Nesse sentido, investigamos soluções para melhorar a qualidade dos dados do sistema de transporte, fornecendo aplicações e serviços, permitindo que a fusão entre Dados Intra-Veiculares -- Intra-Vehicular Data (IVD) e Dados Extra-Veiculares -- Extra-Vehicular Data (EVD) melhore a mobilidade. Projetamos uma plataforma de fusão de dados heterogêneos para SM, com o objetivo de analisar os dados do Espaço de Dados Veiculares -- Vehicular Data Space (VDS), considerando seus aspectos espaço-temporais e identificar metodos e técnicas para aplicar a fusão desses dados. Introduzimos o conceito VDS, que mapea os dados disponíveis e usados pela comunidade acadêmica para desenvolver soluções para ITS. Depois disso, desenvolvemos um conjunto de abordagens para fundir vários conjuntos de dados em benefício da SM. Inicialmente, realizamos estudos com o objetivo de fundir IVD economizando combustível, reduzindo as emissões de gases e garantindo a segurança no compartilhamento de carros em Redes Veiculares -- Ad-hoc Networks (VANETs). Além disso, fundindo EVD desenvolvemos um modelo baseado em dados de mídia social, para enriquecer as informações atuais de transito, oferecendo mais opções para as pessoas se locomoverem na cidade. Finalmente, desenvolvemos uma abordagem para fundir Dados Intra-Extra-Veículares -- Intra-Extra-Vehicular Data (IEVD), permitindo melhorar a qualidade dos dados de tráfego e enriquecer a atual cobertura espaço-temporais do dados. Urban mobility aspects have become a challenge with the constant growth of the global population. As a consequence of this increase, more data has become available, which allows new information technologies to improve the mobility systems, especially the transportation system. Thus, a low-cost strategy to handle these issues rises as an Intelligent Transportation System (ITS) concept. However, the development of new applications and services for the ITS environment, improving the mobility, depending on the availability of vast amounts of data, despite its currently slow availability. In this proposal, we aim to use data from a vast number of sources to provide directions to improve the current mobility in cities. However, a substantial challenge emerges when we combine multiple data sources, increasing the spatiotemporal coverage issues which affect the development of Smart Mobility (SM) solutions. In this sense, we investigate solutions to improve the transportation system data quality, providing applications and services, enabling Intra-Vehicular Data (IVD) and Extra-Vehicular Data (EVD) fusion to improve mobility. We design a heterogeneous data fusion platform for SM, aiming to analyze each data type from the Vehicular Data Space (VDS), considering its spatiotemporal aspects. We introduced the concept of VDS, which map the data available and used by the community to design solutions for ITS. After that, we develop a set of approaches to fuse various datasets in benefit of SM. Initially, we conducted studies to fusing IVD saving fuel, reducing emissions and ensuring the security of car-sharing in Vehicular Ad-hoc Networks (VANETs). Moreover, fusing the EVD, we developed a model, based on social media data to enrich the current traffic information, offering more options to people moves in a city. Finally, we developed an approach to fusing Intra-Extra-Vehicular Data (IEVD), allowing to enhance the road traffic data quality and enriching the current spatiotemporal data coverage.

Time synchronization is critical for the operation of distributed systems in networked environments. It is also demanded in vehicular ad-hoc networks (VANETs), which, as a special type of wireless networks, are becoming increasingly important for emerging cooperative intelligent transport systems. Global navigation satellite system (GNSS) is a proven technology to provide precise timing information in many distributed systems. It is well recognized to be the primary means for vehicle positioning and velocity determination in VANETs. However, GNSS-based time synchronization is not well understood for its role in the coordination of various tasks in VANETs. To address this issue, this paper examines the requirements, potential benefits, and feasibility of GNSS time synchronization in VANETs. The availability of GNSS time synchronization is characterized by almost 100% in our experiments in high-rise urban streets, where the availability of GNSS positioning solutions is only 80%. Experiments are also conducted to test the accuracy of time synchronization with 1-PPS signals output from consumer grade GNSS receivers. They have shown 30-ns synchronization accuracy between two receivers of different models. All these experimental results demonstrate the feasibility of GNSS time synchronization for stringent VANET applications., 10 pages

Vehicular Ad-Hoc Network (VANET), a vital component of Intelligent Transportation Systems (ITS) technology, relies on communication between dynamically connected vehicles and static Road Side Units (RSU) to offer various applications (e.g., collision avoidance alerts, steep-curve warnings and infotainment). VANET has a massive potential to improve traffic efficiency, and road safety by exchanging critical information between nodes (vehicles and RSU), thus reducing the likelihood of traffic accidents. However, this communication between nodes is subject to a variety of attacks, such as Man-In-The-Middle (MITM) attacks which represent a major risk in VANET. It happens when a malicious node intercepts or tampers with messages exchanged between legitimate nodes. In this paper, we studied the impact on network performance of different strategies which attackers can adopt to launch MITM attacks in VANET, such as fleet or random strategies. In particular, we focus on three goals of MITM attacks&mdash, message delayed, message dropped and message tampered. The simulation results indicate that these attacks have a severe influence on the legitimate nodes in VANET as the network experience high number of compromised messages, high end-to-end delays and preeminent packet losses.

This paper addresses the development of a system that facilitates the formation of a road train by informing in real-time the drivers of commercial vehicles, especially trucks with cargo, with information about position-related data, the speed of a road train and the necessary conditions to become part of such a train. By collecting information from fleets of trucks, the communication interface between the vehicle and the fleet monitoring server will be extended. The server will receive data from the vehicles and after a specific processing stage, a extended map will be generated with real-time information collected from the cars in traffic. The optimal route generation algorithm will be also extended, by using data received in real time. The data collected by the fleet monitoring server will be provided through a communication protocol to the ITS traffic server.

Проведен анализ принципов формирования потоков сообщений в децентрализованной самоорганизующейся автомобильной сети. Аналитическое описание процесса формирования суммарного потока выполнено на основе теоремы Бёрка. Рассмотрен вариант описания параметра потока на основе теории просеянных потоков. Оценка справедливости суждений о структуре суммарного потока в сети и принципов его формирования произведена посредством имитационного моделирования на основе среды NS-2. Разработанные на языке Perl скрипты обработки выходной статистики позволили выполнить оценку принадлежности потока распределению Пуассона при низкой плотности транспортных средств и гамма-распределению при высокой. Вследствие высокой интенсивности поступления требований о передаче сообщений происходит перегрузка сетевого ресурса, что приводит к резкой деградации функционала системы безопасности дорожного движения. На основе результатов оценки полезной загрузки канала удалось сформировать предложения к режиму ретрансляции сообщений с целью повышения эффективности использования сетевого ресурса.

International audience; Intelligent Transportation System (ITS) is an intelligent system which can make the road traffic safer, more efficient, and more comfortable. The prerequisites of ITS are positioning, perception and networking. Different ITS infrastructures and applications are built by a large society from academia and industry. Nevertheless, the state-of-the-art network application simulators lack the capabilities to access the position and perception related information. In this paper, we proposed one extension to NS- 3 network simulator and two to DCE application simulator, to bring the positioning and perception sensors to the simulated application. Both positioning and perception were designed fully experimental reproducible, and the simulated perception sensor can be adjusted to accommodate different types of devices. With the proposed work, much more scenarios of ITS applications can be tested, including Position Based Routing, Cooperative Awareness, etc.

Nowadays, increasing number of vehicles on the streets are causing congestion at the intersections and consequently resulting in disruptions in traffic flows. Overall responsibility for preventing congestion in intersections is on traffic light control systems. In order to provide an enhanced traffic light controlling system, we utilized VANET technology for accessing vehicles’ travelling data and consequently traffic flow information. Our dynamic cycle traffic light management proposal provides an intelligent and real-time mechanism to choose the trafic lanes that will be allowed to pass through the intersection and adjust the green light duration in each cycle according to the traffic situation. The traffic density and short-term future traffic density computing in each road are two important steps of our proposed scheme. The broadcasted vehicles travelling data by using V2R communication helps us to compute traffic density values. Also, weather condition and important sites in the roads that make roads crowded are other key parameters in our scheme. The proposed scheme for choosing traffic light cycle and adjusting traffic light is evaluated against the existing static and other intelligent systems using our developed simulation web application. We found that our introduced scheme has better performance than the other approaches by significantly reducing delay time and accordingly decreasing number of the stopped vehicles behind traffic lights. Keywords: Traffic light controlling, Intersection congestion, Vehicular ad-hoc Network, Intelligent traffic light, Vehicle to infrastructure broadcasting. ÖZ: Günümüzde, sayıları artan araçlar kavşaklarda tıkanıklığa yol açmakta ve bu nedenle tarafik akışında aksamalara neden olmaktadır. Kavşaklardaki tıkanıklığı önlemenin genel olarak sorumluluğunu trafik ışık kontrol sistemi almıştır. Gelişmiş bir trafik ışık kontrol sistemlerini elde etmek için, araçların seyehat bilgilerine ve dolayısı ile trafik akış bilgisine erişim şağlayan VANET teknolojisi kullandık. Dinamik döngü trafik ışık yönetimi önerimiz trafiğin o anki durumuna göre hangi şeritlerin kavşaktan geçmesine izin verileceğini kararlaştıran ve yeşil ışık süresini ayarlayan akıllı ve gerçek zamanlı bir mekanizma sağlamaktadır. Her bir yoldaki o andaki ve sonraki trafik yoğunluğu hesaplamaları önerilen planın iki önemli adımını oluşturmaktadır. Seyahat halindeki araçların V2R altyapısına gonderdikleri veriler trafik yoğunluğu değerlerini hesaplamamıza yardımcı oluyor. Buna ek olarak, hava koşulları ve yolların kalabalık olmasına neden olan önemli yerler planımızdaki diğer önemli faktörlerdir. Trafik ışık döngüsünü belirlemek ve trafik ışıklarını ayarlamak için önerilen plan, geliştirilmiş olan simülasyon web uygulaması kullanılarak varolan statik ve diğer akıllı sistemlerle mukayese edilmiştir. Önerdiğimiz sistemin bekleme zamanını ve dolayısı ile trafik ışıkları arkasında bekleyen arabaların sayısını önemli ölçüde azaltması nedeniyle diğer yöntemlere göre daha iyi perfromans gösterdiği gözlemlenmiştir. Anahtar Kelimeler: Trafik ışık kontrolü, Kavşak tıkanıklığı, Akıllı trafik ışıkları, Araçtan altyapıya yayın. Master of Science in Computer Engineering. Thesis (M.S.)--Eastern Mediterranean University, Faculty of Engineering, Dept. of Computer Engineering, 2017. Supervisor: Assoc. Prof. Dr. Zeki Bayram.

Vehicular ad hoc networks (VANETs) are an upcoming technology that is gaining momentum in recent years. That may be the reason that the network attracts more and more attention from both industry and academia. Due to the limited bandwidth of wireless communication medium, scalability is a major problem. Data aggregation is a solution to this. The goal of data aggregation is to combine the messages and disseminate this in larger region. While doing aggregation integrity of the information can not be easily verified and attacks may be possible. Hence aggregation must be secure. Although there are several surveys covering VANETs, they do not concentrate on security issues specifically on data aggregation. In this paper, we discuss and analyse various data aggregation techniques and their solutions.

A proof-of-concept demonstrator of a cooperative integrity monitoring concept, called “local integrity” and tailored to terrestrial applications, is presented in this paper. The idea is to take advantage of a collaborative Vehicular Ad-hoc NETwork (VANET) architecture in order to perform a spatial/temporal characterization of possible local degradations of Global Navigation Satellite System (GNSS) signals in an urban context. Such characterization enables the computation of the so-called “Local Protection Levels”. Starting from the theoretical concepts, this paper describes the experimental validation, the implementation of the algorithm on a vehicular prototype for real-time demonstration purposes, and the obtained results from a measurement campaign. The effectiveness and the performance of the proposed approach are demonstrated in a real scenario.

International audience; Vehicular Ad hoc NETworks (VANETs) play a key role in the design and development of Intelligent Transportation Systems (ITS) that aim to improve road safety and transportation productivity. VANETs cover vehicle-to-vehicle and vehicle-to-roadside communications. One of the most important challenges of this type of network is the timely and reliable dissemination of messages among vehicular nodes that enable drivers to take appropriate decisions to improve road safety. In the past decade, many routing protocols for VANETs that can support reliability and safety requirements have been proposed. These protocols suffer from several limitations, including complexity, lack of scalability to large scale networks, routing overheads, etc. To address these limitations, various bio-inspired approaches have been proposed to route packets among vehicular nodes in an optimized manner. We survey recent proposed bio-inspired routing algorithms for the VANET environment. In particular, we identify the key features, strengths, and weaknesses of these algorithms and compare them by using various criteria. Moreover, we propose a unified formal model of the bio-inspired multimodular approaches applied to VANET routing. We highlight main future research directions in this area.

Ova disertacija istražuje načine učinkovitog rasprostiranja poruka u ad-hoc mrežama vozila kako bi se postiglo pravovremeno rasprostiranje hitnih poruka, pokrivanje velikog geografskog područja, učinkovita komunikacija u situacijama s malom gustoćom prometa i sprječavanje širenja zalihosnih poruka. Ad-hoc mreže vozila imaju vrlo dinamičnu mrežnu topologiju zbog konstantnog i brzog kretanja vozila. To zahtijeva inovativne pristupe i metode u rješavanju problema u komunikaciji. U disertaciji je predstavljen algoritam za učinkovito rasprostiranje poruka u ad-hoc mrežama vozila korištenjem V2V i SCF modela komunikacije koji na temelju geografskog položaja vozila i lokalne gustoće prometa smanjuje kašnjenja i broj zalihosnih poruka te povećava pokrivenost mreže. Za scenarije s malom gustoćom prometa na cestama izrađen je model učinkovitog rasprostiranja poruka korištenjem parkiranih vozila koja imaju visoki stupanj vremenske i prostorne pravilnosti te poboljšavaju komunikaciju i pokrivenost u ad-hoc mrežama vozila u okolinama gradskih područja s rijetkim prometom i brojnim preprekama. Da bi vrednovanje performansi različitih aplikacija i protokola za ad-hoc mreže vozila u stvarnom svijetu bilo jednostavnije i pristupačno, razvijena je metoda za vrednovanje temeljena na korištenju pametnih mobilnih uređaja. Za implementaciju, testiranje, prikupljanje eksperimentalnih rezultata i vrednovanje protokola i aplikacija za ad-hoc mreže vozila u stvarnoj okolini razvijen je okvir u kojemu je ključna komponenta mVANET mobilna aplikacija otvorenog izvornog koda koja je dostupna svima za korištenje i testiranje. This doctoral thesis explores methods for efficient message dissemination in VANETs in order to achieve the timely propagation of urgent information, coverage of a large geographical area, efficient communication in sparse networks and to prevent the propagation of redundant messages. VANETs have highly dynamic network topology due to the constant and rapid movement of vehicles. This requires an innovative approaches and methods for solving communication problems. In doctoral thesis, an algorithm for efficient message dissemination in VANETs, using V2V and SCF communication models that based on a vehicle geographic location and local traffic density reduces delays and number of redundant messages and increases network coverage, is presented. For scenarios with low traffic density on the roads, efficient message dissemination model based on using parked vehicles, is developed. Parked vehicles have a high degree of temporal and spatial regularity and they enhance communication and network coverage in VANETs in urban areas with sparse traffic and obstacles. In order to enable simpler and inexpensive evaluation of various VANETs applications and protocols in a real world, an evaluation method based on using smartphones is developed. For implementation, testing, experimental results collection and evaluation of applications and protocols in a real world a framework is developed. A key component of developed framework is an open source mVANET mobile application available for everyone for using and testing.

In this paper, we analyze the combination of Vehicular Ad-hoc NETworks (VANETs) with the Social Internet of Things (SIoT), i.e., the Social Internet of Vehicles (SIoV). In the SIoV every vehicle is capable of establishing social relationships with other vehicles in an autonomous way with the intent of creating an overlay social network that can be exploited for information search and dissemination in VANET applications. The contribution of this paper is two-fold: firstly, we define some relationships which can be established between the vehicles and between the vehicles and the road side units (RSUs); secondly, we propose a SIoV middleware which extends the functionalities of the Intelligent Transportation Systems Station Architecture (ITS SA), defined by ISO and ETSI standards, to take into account the elements needed to integrate VANETs in the SIoT. Additionally, we present results of software simulations analyzing realistic vehicular mobility trace in order to study the characteristics of the resulting social network structure.

International audience; Vehicular ad-hoc networks (VANETs) can be considered as complex dynamic systems where simulation modeling plays a crucial role in conducting research due to the difficulties in the realization of such a network, like high costs, risks and dangers. During the last decade, the results of VANET simulations were considered successful and acceptable however, most prior VANET simulators were based on non realistic mobility when describing node positions, distribution, frequency and movement, model paths, traffic signals etc. To deal with this challenge, we propose in this paper a Markov-History based modeling for realistic mobility of vehicles in VANETs. It starts with a geographic area digitization, followed by a vehicle positions initialization. The proposed model predicts directions of the vehicles using a Markov chain, as well as it predicts the vehicle velocities using a History-based sub-model. Moreover, the density of the network is updated according to the peak or off-peak hours. The emerged model can be used as mobility model to simulate VANET scenarios. To validate our proposal, a concrete mobility model has been designed using the proposed model that represents the downtown of Biskra City located in Algeria. The performances of the resulting network have been proved against the others obtained using Random Waypoint as a standard mobility model in terms of packet delivery ratio, network overhead, average end-to-end delay, and dropped packets.

Piggybacking on beacons is a forwarding technique in vehicular ad-hoc networks (VANET) as a means to disseminate data. With this technique data is attached to and transmitted along with scheduled beacons. Nodes are assumed to beacon asynchronously. In this paper we present a first version of an analytical model that is able to accurately capture the performance of a piggybacking protocol inside a VANET in a number of closed-form expressions, assuming some simplifications. For a given forwarding distance, transmission range, node density, and beacon frequency, the model is able to give the stochastic distribution of the end-to-end delay. The model also provides the distribution of the per-hop delay, the hop length, and the position of the ith forwarder. We have verified our analytical model using a simulation study. The most relevant assumptions in our model are a fixed inter-node distance and a fixed deterministic transmission range. Having completed this stage of our work, our next goal is to extend our model so that we can drop these assumptions. © 2012 ACM.

Piggybacking on beacons is a forwarding technique in vehicular ad-hoc networks (VANET) as a means to disseminate data. With this technique data is attached to and transmitted along with scheduled beacons. Nodes are assumed to beacon asynchronously. In this paper we present a first version of an analytical model that is able to accurately capture the performance of a piggybacking protocol inside a VANET in a number of closed-form expressions, assuming some simplifications. For a given forwarding distance, transmission range, node density, and beacon frequency, the model is able to give the stochastic distribution of the end-to-end delay. The model also provides the distribution of the per-hop delay, the hop length, and the position of the ith forwarder. We have verified our analytical model using a simulation study. The most relevant assumptions in our model are a fixed inter-node distance and a fixed deterministic transmission range. Having completed this stage of our work, our next goal is to extend our model so that we can drop these assumptions. © 2012 ACM.

Despite the push for using mass transit, the number of vehicles on the road is growing at a steady rate and traffic congestion has become a daily problem that most people suffer. This not only impacts the productivity of the population but also poses a safety risk. Most of the technologies for intelligent highways focus on safety measures and increased driver awareness, and expect a centralized management for the traffic flow. We present a new approach for enabling autonomous and adaptive traffic management through vehicular networks. By allowing data exchange between vehicles about route choices, congestion and traffic alerts, a vehicle makes a decision on the best course of action. Unlike centralized schemes that provide recommendations, our VANET-based Autonomous Management (VAM) approach factors in the destination and routes of nearby vehicles in deciding on whether rerouting is advisable. In addition, VAM leverages the presence of smart traffic lights and enables coordination between vehicles and light-controllers in order to ease congestion. The collective effect of all vehicles will be an autonomous reshape of the traffic pattern based on their destinations and road conditions. To validate our approach we have developed a graphical tool that not only enables the collection of performance statistics but also allows visualizing the effect on traffic. The implementation also supports smart traffic lights and configurable roads. The simulation results demonstrate the advantage of VAM and there is up-to 40% increase in overall throughput for fully cooperative drivers.

En redes Ad-hoc vehiculares, se requiere acceso al medio por parte de los vehículos de forma constante. El hecho de ser una red inalámbrica totalmente distribuida en la que los distintos vehículos transmiten a intervalos aleatorios implica la necesidad de disponer de un protocolo MAC (Medium Access Control) adecuado a las circunstancias de estas redes. En este artículo se presenta un protocolo MAC que consiste en el establecimiento periódico de diálogos entre los distintos vehículos (hosts), con el fin de intercambiar información topológica que permita a cada host establecer un intervalo de tiempo de transmisión que no coincida con el de ningún otro vehículo presente dentro de su respectivo rango de cobertura.

International audience; In this paper, we address the rate control, the Medium Access Control (MAC) and the routing problem for cooperative Vehicular Ad-Hoc Network (VANET) in the framework of cross-layer design. At first, we introduce the cooperative communication conception to VANET, and propose an opportunistic cooperation strategy to improve the system performance. And then, we develop a cross-layer solution which consists of the link capacity detection with adjusting persistence probability at the MAC Layer, the flow rate control with the maximal utility at the Transport Layer and the routing design at the Network Layer. This proposal is designed in distributed manner in order to support a simple and efficient implementation for VANET. Furthermore, some practical issues, such as fairness and network cost, are presented for implementing the proposed solution and improving the system performance. Simulation results show that the proposed opportunistic cooperation strategy combined with joint control algorithm achieves the desired performance over VANET.