Dans le cadre du développement des innovations dans les Systèmes de Transport Intelligents, les véhicules connectés devront être capables de télécharger des informations basées sur la position sur et depuis des serveurs distants. Ces véhicules seront équipés avec des différentes technologies d’accès radio, telles que les réseaux cellulaires ou les réseaux véhicule-à-véhicule (V2V) comme IEEE 802.11p. Les réseaux cellulaires, avec une couverture presque omniprésente, fournissent un accès à internet avec garanties de qualité de service. Cependant, l’accès à ces réseaux est payant. Dans cette thèse, un algorithme de clustering multi-saut est proposé avec pour objectif de réduire le coût d’accès au réseau cellulaire en agrégeant des données sur le réseau V2V. Pour faire ceci, le leader du cluster (CH, de l’anglais Cluster Head) est utilisé comme passerelle unique vers le réseau cellulaire. Pour le test d’une application d’exemple pour télécharger du Floating Car Data agrégé, les résultats des simulations montrent que cette approche réduit l’utilisation du réseau cellulaire de plus de 80%, en s’attaquant à la redondance typique des données basées sur la position dans les réseaux véhiculaires. Il y a une contribution en trois parties : Premièrement, une approche pour déléguer la sélection du CH à la station de base du réseau cellulaire afin de maximiser la taille des clusters, et par conséquent le taux de compression. Deuxièmement, un algorithme auto-adaptatif qui change dynamiquement le nombre maximum de sauts afin de maintenir un équilibre entre la réduction des coûts d’accès au réseau cellulaire et le taux de perte de paquets dans le réseau V2V. Finalement, l’incorporation d’une théorie de la justice distributive, afin d’améliorer l’équité sur la durée concernant la distribution des coûts auxquels les CH doivent faire face, améliorant ainsi l’acceptabilité sociale de la proposition. Les algorithmes proposés ont été testés via simulation, et les résultats montrent une réduction significative dans l’utilisation du réseau cellulaire, une adaptation réussie du nombre de sauts aux changements de la densité du trafic véhiculaire, et une amélioration dans les métriques d’équité, sans affecter la performance des réseaux. / For the development of innovative Intelligent Transportation Systems applications, connected vehicles will frequently need to upload and download position-based information to and from servers. These vehicles will be equipped with different Radio Access Technologies (RAT), like cellular and vehicle-to-vehicle (V2V) technologies such as LTE and IEEE 802.11p respectively. Cellular networkscan provide internet access almost anywhere, with QoS guarantees. However, accessing these networks has an economic cost. In this thesis, a multi-hop clustering algorithm is proposed in the aim of reducing the cellular access costs by aggregating information and off-loading data in the V2V network, using the Cluster Head as a single gateway to the cellular network. For the example application of uploading aggregated Floating Car Data, simulation results show that this approach reduce cellular data consumption by more than 80% by reducing the typical redundancy of position-based data in a vehicular network. There is a threefold contribution: First, an approach that delegates the Cluster Head selection to the cellular base station in order to maximize the cluster size, thus maximizing aggregation. Secondly, a self-adaptation algorithm that dynamically changes the maximum number of hops, addressing the trade-off between cellular access reduction and V2V packet loss. Finally, the incorporation of a theory of distributive justice, for improving fairness over time regarding the distribution of the cost in which Cluster Heads have to incur, thus improving the proposal’s social acceptability. The proposed algorithms were tested via simulation, and the results show a significant reduction in cellular network usage, a successful adaptation of the number of hops to changes in the vehicular traffic density, and an improvement in fairness metrics, without affecting network performance.

[ES] La disponibilidad y el rendimiento de las actuales tecnologías inalámbricas como WiFi o 4G, pueden tener serios problemas de congestión y propagación, especialmente en espacios muy concurridos, o bien ser inaccesibles en sitios remotos o con baja densidad de personas. La utilización de las Redes Oportunistas en este tipo de escenarios puede ser la solución a estos problemas. Estas redes se basan en la oportunidad de intercambiar mensajes utilizando algún tipo de tecnología de comunicación directa entre dispositivos móviles como son Bluetooth o WiFi. El rendimiento de las Redes Oportunistas depende principalmente de la movilidad de los nodos y los protocolos de enrutamiento utilizados, siendo estos últimos los encargados de decidir como son intercambiados los mensajes cuando un contacto ocurre, intentando encontrar la mejor ruta para que un mensaje alcance su destino. Por otra parte, la eficiencia de la difusión en estas redes está ligada especialmente a la movilidad de los usuarios y al comportamiento humano. Entonces, para el análisis y la evaluación del rendimiento de las Redes Oportunistas es necesario considerar tanto los aspectos técnicos relacionados con los protocolos de encaminamiento, como los aspectos de la movilidad humana. Esta tesis doctoral se centra principalmente en evaluar la diseminación de la información usando redes oportunistas en escenarios urbanos, en los que existen diferentes densidades y tasas de renovación de personas, es decir, con usuarios que puedan entrar y salir del escenario evaluado. Dado que la existencia de este tipo de trazas reales es muy limitada, en esta tesis se plantea la generación de este tipo de trazas de forma sintética. Para ello, mediante el uso de un simulador de movilidad peatonal, se han generado trazas realistas de movilidad con diferentes grados de densidad y tasas de renovación de usuarios con el objeto de evaluar diferentes aspectos de la difusión de mensajes en las Redes Oportunistas. El análisis de las características temporales y espaciales de estas trazas generadas refleja el realismo de los escenarios que se han considerado. Además, los experimentos relativos a la difusión de mensajes realizados con estas trazas, confirman que la tasa de renovación tiene un gran impacto en el rendimiento de los protocolos, lo que es particularmente evidente cuando el tamaño de los mensajes es mayor. Por otra parte, también se ha realizado el estudio, utilizando en este caso trazas reales, de la difusión de información a través de las Redes Oportunistas Vehiculares. Ya que de la misma manera la movilidad de estos vehículos está ligada al comportamiento humano, nos hemos centrado en la diseminación de la información en determinadas horas del día dependiendo del número de vehículos en circulación, debido a que este aspecto tiene un gran impacto en el reenvío de datos. Los resultados de estos experimentos confirman que los dos principales factores que afectan a la difusión de información son el grado de movilidad y el tamaño de mensaje. Aunque es bien sabido que al aumentar la densidad de nodos aumenta la velocidad de difusión, mostramos que, al mantener la densidad de nodos fija, las tasas de renovación más altas hacen que la relación de entrega disminuya. Además, descubrimos que la relación entre el tamaño del mensaje y la duración del contacto también es un factor clave, lo que demuestra que la transmisión de los mensajes grandes puede llevar a un rendimiento general muy bajo. Basándonos en todo lo expuesto anteriormente, se ha propuesto una mejora al protocolo Epidemic, a la que hemos denominado EpidemicX2, que se basa en la fragmentación de los datos a ser enviados con el fin de aprovechar la corta duración de los contactos para aumentar así la posibilidad de su entrega. Este protocolo es particularmente efectivo para la difusión de los mensajes grandes. Los resultados muestran que la tasa de entrega se increment / [CA] La disponibilitat i el rendiment de les actuals tecnologies sense fil com WiFi o 4G, poden tindre seriosos problemes de congestió i propagació, especialment en espais molt concorreguts, o bé ser inaccessibles en llocs remots o amb baixa densitat de persones. La utilització de les Xarxes Oportunistes en este tipus d'escenaris pot ser la solució a estos problemes. Estes xarxes es basen en l'oportunitat d'intercanviar missatges utilitzant algun tipus de tecnologia de comunicació directa entre dispositius mòbils com són Bluetooth o WiFi. El rendiment de les Xarxes Oportunistes depén principalment de la mobilitat dels nodes i els protocols d'enrutamiento utilitzats, sent estos últims els encarregats de decidir com són intercanviats els missatges quan un contacte ocorre, intentant trobar la millor ruta perquè un missatge abast el seu destí. D'altra banda, l'eficiència de la difusió en estes xarxes està lligada especialment a la mobilitat dels usuaris i al comportament humà. Llavors, per a l'anàlisi i l'avaluació del rendiment de les Xarxes Oportunistes és necessari considerar tant els aspectes tècnics relacionats amb els protocols d'acarrerament, com els aspectes de la mobilitat humana. Esta tesi doctoral se centra principalment a avaluar la disseminació de la informació usant xarxes oportunistes en escenaris urbans, en els que hi ha diferents densitats i taxes de renovació de persones, és a dir, amb usuaris que puguen entrar i eixir de l'escenari avaluat. Atés que l'existència d'este tipus de traces reals és molt limitada, en esta tesi es planteja la generació d'este tipus de traces de forma sintètica. Per a això, per mitjà de l'ús d'un simulador de mobilitat de vianants, s'han generat traces realistes de mobilitat amb diferents graus de densitat i taxes de renovació d'usuaris amb l'objecte d'avaluar diferents aspectes de la difusió de missatges en les Xarxes Oportunistes. L'anàlisi de les característiques temporals i espacials d'estes traces generades reflectix el realisme dels escenaris que s'han considerat. A més, els experiments relatius a la difusió de missatges realitzats amb estes traces, confirmen que la taxa de renovació té un gran impacte en el rendiment dels protocols, la qual cosa és particularment evident quan la grandària dels missatges és major. D'altra banda, també s'ha realitzat l'estudi, utilitzant en este cas traces reals, de la difusió d'informació a través de les Xarxes Oportunistes Vehiculares. Ja que de la mateixa manera la mobilitat d'estos vehicles està lligada al comportament humà, ens hem centrat en la disseminació de la informació en determinades hores del dia depenent del nombre de vehicles en circulació, pel fet que este aspecte té un gran impacte en el reexpedició de dades. Els resultats d'estos experiments confirmen que els dos principals factors que afecten la difusió d'informació són el grau de mobilitat i la grandària de missatge. Encara que és ben sabut que a l'augmentar la densitat de nodes augmenta la velocitat de difusió, mostrem que, al mantindre la densitat de nodes fixa, les taxes de renovació més altes fan que la relació d'entrega disminuïsca. A més, descobrim que la relació entre la grandària del missatge i la duració del contacte també és un factor clau, la qual cosa demostra que la transmissió dels missatges grans pot portar a un rendiment general molt davall. Basant-nos en tot el que exposa anteriorment, s'ha proposat una millora al protocol Epidemic, a la que hem denominat EpidemicX2, que es basa en la fragmentació de les dades a ser enviats a fi d'aprofitar la curta duració dels contactes per a augmentar així la possibilitat del seu entrega. Este protocol és particularment efectiu per a la difusió dels missatges grans. Els resultats mostren que la taxa d'entrega s'incrementa, el temps mitjana en l'entrega es reduïx, sense un substancial increment en termes de sobrecàrrega. / [EN] The availability and performance of current wireless technologies such as WiFi or 4G, can have severe problems of congestion and information diffusion, especially in crowded spaces, or, on the other side, be inaccessible in places with a low density of people. The use of Opportunistic Networks in these types of scenarios can be a solution to these problems. These networks are based on the opportunity to exchange messages using some type of direct communication technology between nearby mobile devices such as Bluetooth or WiFi. The performance of these networks depends mainly on the mobility of the nodes and the routing protocols used. The goal of these protocols is to decide how messages are exchanged when a pair of nodes are in contact, trying to find the best route for a message to reach its destination. The efficiency of the diffusion in these networks is related mainly to the mobility of users and human behaviour. Therefore, for the analysis and evaluation of the performance of the Opportunistic Networks, it is necessary to consider both the technical aspects related to the routing protocols, as well as the aspects of human mobility. This thesis mainly focuses on evaluating the dissemination of information using Opportunistic Networks in urban scenarios, in which there are different densities and renewal rates of people, that is, with users who can enter and leave the evaluated scenario. Given that the existence of this type of real traces is very limited, this thesis proposes the generation of realistic traces. For this, through the use of a pedestrian mobility simulator, realistic traces of mobility have been defined with different degrees of density and renewal rates of users to evaluate different aspects of the Opportunistic Network with this approach. The analysis of the temporal and spatial characteristics of these generated traces reflects the realism of the scenarios that have been considered. The experiments related to the diffusion of messages made with these traces, confirm that the renewal rate has a high impact on the performance of the protocols, which is particularly evident when the message size is longer. Furthermore, considering vehicular scenarios, a study has also been carried out using real traces, following the same methodology to evaluate the dissemination of information. Since in the same way the mobility of these vehicles is linked to human behaviour, we have focused on the dissemination of information at certain times of the day depending on the number of vehicles in circulation, since this aspect has a significant impact on data diffusion. The results of all these experiments show that the diffusion of contents is affected mainly by two factors: degree of mobility and message size. Although it is well known that increasing the density of nodes increases the speed of diffusion, we show that, by maintaining the density of fixed nodes, the higher renewal rates cause the delivery ratio to decrease. In addition, we discovered that the relationship between message size and contact duration is also a key factor, showing that large messages can lead to very reduced overall performance. Based on these results, an improvement to the Epidemic protocol has been proposed, called EpidemicX2, which is based on the fragmentation of the data to be sent in order to take advantage of the short duration of the contacts. This protocol is particularly effective for the dissemination of large messages. The results show that the delivery rate increases, the average time in the delivery is reduced, without a substantial increase in terms of overload. / Finalmente, quiero agradecer a la República del Ecuador junto con la “Secretaría de Educación Superior, Ciencia y Tecnología e Innovación” - SENESCYT, por su programa de apoyo y financiar mis estudios. / Chancay Garcia, LJ. (2019). Evaluación y Modelado de Redes Oportunistas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124339

O trabalho tem por objetivo desenvolver um veículo com massa inferior a 500 kg e que atenda aos requisitos estruturais e biomecânicos conforme regulamentações das Nações Unidas referentes a segurança dos ocupantes, para tal serão aplicadas metodologias de otimização usando metamodelos, que são modelos substitutos aos modelos em elementos finitos. O trabalho apresenta o desenvolvimento de um veículo completo para dois ocupantes, o mesmo é conceitual pois é mais curto e estreito se comparado a um veículo convencional, propiciando a redução do espaço ocupado em centros urbanos. Por meio de simulação numérica computacional será avaliada a capacidade da estrutura em proteger os ocupantes, bem como serão utilizados manequins virtuais para obter as respostas do corpo humano aos diferentes eventos de colisão veicular. São apresentadas técnicas para criação dos metamodelos e definida a melhor aproximação que foi aplicada no processo otimização da estrutura do veículo, objetivando atingir a menor massa possível. Além disto, o veículo precisa cumprir aos requisitos de proteção dos ocupantes em casos de impacto frontal, lateral e traseiro. Também serão avaliadas as respostas biomecânicas dos ocupantes, respostas do corpo humano a forças internas e externas, em impactos veiculares não regulamentados pelas Nações Unidas, mas são procedimentos de teste empregados para avaliar e comparar os resultados entre diferentes veículos. O estudo é inovador pois na formulação dos problemas de otimização são utilizadas funções objetivo e restrições tanto estruturais quanto biomecânicas. O veículo projetado servirá de base para o desenvolvimento de futuros estudos em diferentes áreas e disciplinas da Universidade, podendo ser utilizado na definição, aplicação e validação de novos conceitos. Finalmente, por meio da otimização numérica computacional baseada em metamodelos, demonstra-se que o veículo pode ser melhorado, satisfazendo os requisitos estabelecido e promovendo redução no tempo e no custo de desenvolvimento de um novo veículo. / The work aims to develop a vehicle with mass less than 500 kg and it meets the structural and biomechanical requirements according to the United Nations regulations regarding the occupant protection. To achieve these goals will be applied optimization processes based on metamodels that are surrogate models for finite elements models. The work presents the development of a conceptual full vehicle for two occupants, it is shorter and narrower compared to a conventional vehicle, allowing the reduction of occupied space in urban centers. Through computational numerical simulation will evaluate the ability of the structure to protect the occupants and will be used virtual mannequins to assess the human body responses to different types of vehicular collisions. Techniques to create metamodels will be presented and setting the best approximation that was applied to the optimization process of the vehicle structure with the objective to obtain the lowest possible mass. Furthermore, the vehicle must meet the occupants\' protection requirements in events of frontal, lateral and rear impact. Also, it will be evaluated the occupants\' biomechanical responses in case of vehicular impacts not regulated by United Nations. However, these test procedures are applied to assess and comparing results among different vehicles. The study herein developed presents significant contributions since in the optimization problems are used both structural and biomechanical responses as objective and constraint functions. The vehicle designed will be a basis for the development of future studies in different areas and disciplines of the University. It will be used in the definition, implementation and validation of new concepts. Finally, it is shown that the application of numerical optimization based on metamodels is an effective process to improve the vehicle performance by meeting the requirements and promoting a reduction in time and cost of developing.

[pt] Apresentam-se nesta dissertação os principais modelos para análise e simulação de colisões e reconstituição de acidentes, desenvolvidos especialmente para reproduzir a dinâmica de uma colisão de forma adequada. Esse tipo de tratamento está se tornando uma indispensável ferramenta de auxílio nas perícias judiciais e para uma melhor interpretação de problemas de colisão em geral. Os programas desenvolvidos em MATLAB são baseados na implementação das equações relacionadas à interação entre os veículos, supostos rígidos, que ocorre durante uma colisão e são aplicáveis aos casos de colisões centrais e oblíquas, gerando resultados válidos e compatíveis aqueles obtidos através da teoria de conservação da quantidade de movimento, e com as medições realizadas após os acidentes. / [en] It is shown in this dissertation the main models for collisions analysis and simulation and accidents reconstruction, developed specially to reproduce the collision dynamics by an appropriated approach. This approach are becoming an indispensable tool of help for a better interpretation of collision and forensic problems. The MATLAB programs developed are based on implementation of equations related to rigid vehicles interaction in a collision, and are applicable for the central and oblique collisions, supplying valid and compatible results to those obtained by momentum conservation theory, and accidents experimental data.

[pt] É apresentado um procedimento para simulação de colisões de veículos terrestres deformáveis, cuja entrada são as condições imediatamente anteriores ao choque, produzindo como saída a evolução das variáveis ao longo do tempo de duração do impacto. Foram feitas simulações de casos semelhantes aos apresentados na literatura, e os resultados obtidos validaram os modelos criados. O procedimento foi implementado em Simulink/MatLab, seguindo a mesma estrutura dos demais programas em desenvolvimento nesta linha de pesquisa, de modo a futuramente integrá-lo aos pré- processadores e pós-processadores gráficos do programa SVDV - Simulação e Visualização da Dinâmica de Veículos. / [en] A procedure for the simulation of flexible ground vehicles collisions is presented, which uses the conditions at the instant just before the impact as input variables and the evolution of the dynamic variables during the collision as output. Various simulations are presented and compared to similar cases found in the literature, what validates the proposed models. The algorithm was implemented using Simulink/Matlab software and used the same structure of the other programs under development in this area, in order to integrate it to graphic pre-processors and post-processors available in SVDV program - Simulation and Visualization of Vehicle Dynamics.

This work presents the implementations of three adaptive broadcast protocols for vehicular ad hoc networks (VANET) using the Network Simulator 3 (Ns-3). Performing real life tests for VANET protocols is very costly and risky, so simulation becomes a viable alternative technique. Ns-3 is one of the most advanced open source network simulators. Yet Ns-3 lacks implementations of broadcast protocols for VANET. We first implement the Distance to Mean (DTM) protocol, which uses the distance to mean to determine if a node should rebroadcast or not. We then implement the Distribution-Adaptive Distance with Channel Quality (DADCQ) protocol, which uses node distribution, channel quality and distance to determine if a node should favor rebroadcasting. The third protocol, Statistical Location-Assisted Broadcast protocol (SLAB), is an improvement of DADCQ which automates the threshold function design using machine learning. Our NS-3 implementations of the three protocols have been validated against their JiST/SWANS implementations. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

A Vehicular Ad-hoc Network (VANET) is a wireless ad-hoc network that provides communications among vehicles with on-board units and between vehicles and nearby roadside units. The success of a VANET relies on the ability of a routing protocol to ful ll the throughput and delivery requirements of any applications operating on the network. Currently, most of the proposed VANET routing protocols focus on urban or highway environments. This dissertation addresses the need for an adaptive routing protocol in VANETs which is able to tolerate low and high-density network tra c with little throughput and delay variation. This dissertation proposes three Geographic Ad-hoc On-Demand Distance Vector (GEOADV) protocols. These three GEOADV routing protocols are designed to address the lack of exibility and adaptability in current VANET routing protocols. The rst protocol, GEOADV, is a hybrid geographic routing protocol. The second protocol, GEOADV-P, enhances GEOADV by introducing predictive features. The third protocol, GEOADV-PF improves optimal route selection by utilizing fuzzy logic in addition to GEOADV-P's predictive capabilities. To prove that GEOADV and GEOADV-P are adaptive their performance is demonstrated by both urban and highway simulations. When compared to existing routing protocols, GEOADV and GEOADV-P lead to less average delay and a higher average delivery ratio in various scenarios. These advantages allow GEOADV- P to outperform other routing protocols in low-density networks and prove itself to be an adaptive routing protocol in a VANET environment. GEOADV-PF is introduced to improve GEOADV and GEOADV-P performance in sparser networks. The introduction of fuzzy systems can help with the intrinsic demands for exibility and adaptability necessary for VANETs. An investigation into the impact adaptive beaconing has on the GEOADV protocol is conducted. GEOADV enhanced with an adaptive beacon method is compared against GEOADV with three xed beacon rates. Our simulation results show that the adaptive beaconing scheme is able to reduce routing overhead, increase the average delivery ratio, and decrease the average delay. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Dans le cadre des systèmes de transport intelligents (STI), les véhicules peuvent avoir beaucoup de capteurs (caméras, lidars, radars, etc.) et d’applications (évitement des collisions, surveillance du trafic, etc.) générant des données. Ils représentent alors une source d’information importante. Les applications locales peuvent augmenter considérablement leur efficacité en partageant une telle information au sein du réseau. La précision des données, la confiance et la pertinence peuvent être vérifiées lors de la réception de données provenant d’autres nœuds. Par conséquent, nous croyons qu’une question importante à répondre dans ce contexte est: “Comment partager efficacement les données dans un tel environnement?” Le partage de données est une tâche complexe dans les réseaux dynamiques. De nombreuses problèmes telles que les connexions intermittentes, la variation de la densité du réseau et la congestion du médium de communication se posent. Une approche habituelle pour gérer ces problèmes est basée sur des processus périodiques. En effet, un message envoyé plusieurs fois peut atteindre sa destination même avec des connexions intermittentes et des réseaux à faible densité. Néanmoins, dans les réseaux à haute densité, ils peuvent entraîner une congestion du médium de communication. Dans cette thèse, nous abordons le problème du partage de données dans des réseaux dynamiques en nous appuyant sur des horizons de pertinence. Un horizon est défini comme une zone dans laquelle une information devrait être reçue. Nous commençons par nous concentrer sur le partage de données au sein des voisins directs (à 1 saut de distance). Ensuite, nous proposons une solution pour construire une carte des voisins, centrée sur le nœud ego, dans un horizon à n sauts. Enfin, nous relâchons la définition de l’horizon pour la définir de façon dynamique, où différents éléments de données peuvent atteindre des distances différentes (sauts). En ce qui concerne la solution pour les horizons à 1 saut, notre technique adaptative prend en compte la dynamique des nœuds et la charge du réseau. Afin d’assurer une diffusion efficace des données dans différents scénarios, la fréquence d’envoi des messages est définie en fonction des mouvements des véhicules et d’une estimation du taux de perte du réseau. Après, nous nous concentrons sur la carte des voisins jusqu’à n sauts de distance. Comme la communication avec des nœuds éloignés apporte des problèmes supplémentaires (actions de transfert, retards plus importants, informations périmées), une évaluation de confiance des nœuds identifiés et une estimation de fiabilité du chemin vers chaque voisin sont ajoutées à la carte. Au lieu d’exécuter des processus de diffusion séparés, notre troisième contribution porte sur une stratégie de coopération dont l’objectif principal est de diffuser des données tout en satisfaisant la plupart des nœuds. À cette fin, une trame unique est transmise de nœud en nœud. Sa charge utile est mise à jour localement afin qu’elle contienne les éléments de données les plus pertinents en fonction de certains critères (par exemple, urgence, pertinence). Une telle stratégie définit ainsi un horizon centré sur les données. Nous validons nos propositions au moyen d’émulations de réseaux réalistes. De toutes nos études et des résultats obtenus, nous pouvons affirmer que notre approche apporte des perspectives intéressantes pour le partage de données dans des réseaux dynamiques comme les VANET. / In the context of Intelligent Transportation Systems - ITS, vehicles may have a lot of sensors (e.g. cameras, lidars, radars) and applications (collision avoidance, traffic monitoring, etc.) generating data. They represent then an important source of information. Local applications can significantly increase their effectiveness by sharing such an information within the network. Data accuracy, confidence and pertinence can be verified when receiving data from other nodes. Therefore, we believe that an important question to answer in this context is: “How to efficiently share data within such an environment?” Data sharing is a complex task in dynamic networks. Many concerns like intermittent connections, network density variation and communication spectrum congestion arise. A usual approach to handle these problems is based on periodic processes. Indeed, a message sent many times can reach its destination even with intermittent connections and low density networks. Nevertheless, within high density networks, they may lead to communication spectrum scarcity. In this thesis we address the problem of data sharing in dynamic networks by relying in so-called horizons of pertinence. A horizon is defined as an area within which an information is expected to be received. We start focusing on data sharing within direct neighbors (at 1-hop of distance). Then we propose a solution to construct a map of neighbors, centered in the ego-node, within a horizon of n-hops. Finally, we relax the horizon definition to a dynamic defined one where different data items may reach different distances (hops). Regarding the solution for 1-hop horizons, our adaptive technique takes into account nodes’ dynamics and network load. In order to ensure an effective data dissemination in different scenarios, the sending messages frequency is defined according to vehicles movements and an estimation of the network loss rate. Following, we focus on the map of neighbors up to n-hops of distance. As communicationwith distant nodes brings additional concerns (forwarding actions, larger delays, out-of-date information), a trust evaluation of identified nodes and a reliability estimation of the multi-hop path to each neighbor is added to the map. Instead of running separated disseminating processes, our third contribution deals with a cooperative strategy with the main goal of disseminating data while satisfying most of the nodes. For this purpose a unique frame is forwarded from node to node. Its payload is locally updated so that it contains the most relevant data items according to some criteria (e.g. urgency, relevance). Such a strategy defines thus a data-centered horizon. We validate our proposals by means of realistic network emulations. From all our studies and achieved results we can state that our approach brings interesting insights for data sharing in dynamic networks like VANETs.

Neste trabalho, é desenvolvido um estudo sobre o uso de alertas auditivos e hápticos dentro do ambiente veicular. É proposto um sistema de assistência ao motorista para alertá-lo de que uma colisão lateral com outros veículos pode ser iminente, quando a observação do espelho retrovisor é insuficiente ou o motorista está desatento. O sistema é composto por um módulo de ativação e um módulo de alerta. O módulo de ativação detecta a condição de perigo por sensores posicionados ao redor do veículo e na tendência de abandono de faixa. Esse trabalho enfoca o módulo de alerta, para o qual se propõe o uso de som tridimensional juntamente com estímulo de vibração. Um ambiente de simulação é proposto para se reproduzir em laboratório o ambiente em que o motorista atua. Nesse ambiente, o sujeito deve utilizar um jogo de corrida projetado na parede à sua frente usando um volante e pedais para acelerar e frear. O motorista se mantém ocupado na tarefa de conduzir o veículo pela trajetória do jogo enquanto é submetido a situações em que um outro veículo se aproxima pela região lateral-traseira velozmente. O assento utilizado é equipado com os elementos geradores dos estímulos vibratórios e auditivos. No primeiro experimento, estuda-se o comportamento de 12 participantes na situação crítica sem o uso do sistema de alerta e conclui-se que a reação preferencial em tal situação é o esterçamento do volante. No segundo experimento, 23 participantes são submetidos ao mesmo cenário adicionando-se o sistema de alertas auditivo e háptico. São coletados os dados de tempo de reação, esterçamento do volante, pressionamento dos pedais e distância entre os carros. Também são registradas as percepções dos participantes sobre o sistema de alerta utilizado. A análise dos dados indica que o sistema de alerta é elegível para uso e pode auxiliar em termos de tempo de reação, devendo-se, entretanto, revisar as características dos alertas utilizados, especialmente o auditivo, para se reduzir o desconforto e evitar prejuízo significativo no controle do veículo. / In this work, we develop a study about the usage of auditive and haptic alerts in the vehicular environment. It is proposed a driver assistance system to warn the driver that a lateral collision with other vehicle may be imminent, when the rear mirror observation is insufficient or the driver is distracted. The system is composed by an activation module and a warning module. The activation module detects the dangerous condition using sensors placed around the vehicle and on the identification of a lane departure tendency. This work focuses on the warning module, which proposes the usage of three-dimensional sound together with vibration stimulus. A simulation environment is proposed to reproduce in laboratory the environment where the driver actuates. In this environment, the subject is requested to play a driving game projected in the frontal wall using a steering wheel and pedals to accelerate and brake. While the driver conducts the vehicle over the game route, he is submitted to the situation where another vehicle approaches very fastly from behind. The seat is equipped with the vibration and auditory stimuli generator elements. In the first experiment, it is assessed the behavior of 12 subjects in the critical situation without the usage of the warning system and it is concluded that the major reaction in such situation is the steering of the wheel. In the second experiment, 23 subjects are submitted to the same scenario adding the auditory and haptic warning system. The following data are collected: reaction time, wheel steering, pedal pressing and distance between the vehicles. The perception of the participants about the used warning system is registered. The analysis of all data indicates that the system is eligible to be used and is able to help regarding reaction times. Nevertheless, it is still necessary to review the characteristics of the used warnings, specially the auditory, to reduce discomfort and avoid loss of control during driving.

There is an increasing interest in the deployment of wireless communication systems in vehicles. The motivation for this work is to provide a fundamental characterisation of the in-vehicle Electromagnetic (EM) wave propagation environment, and to demonstrate how this can be used to aid the deployment of wireless communication systems in vehicles. The fundamental characterisation of the in-vehicle EM wave propagation environment presented in this dissertation yields a number of useful outcomes. The instantaneous impulse response of the in-vehicle channel is characterised, which is presented in the form of a statistical model for arriving rays. Noticing that it is impractical to undertake a full statistical characterisation of the time-varying impulse response, the time variation of the in-vehicle channel is instead characterised as a Doppler spread. This approach provides parameters which are sufficient to perform an information theoretic analysis to lower bound the capacity of the in-vehicle channel. For typical operating conditions, it is found that the channel capacity is approximately equal to that of the same channel with perfect channel state information available at the receiver. Having established the fundamental EM wave propagation characteristics for a single in-vehicle wireless channel, the EM properties of the cavity itself are characterised. This is achieved through a thorough investigation into the analogy between vehicle cavities and reverberation chambers, specifically considering the quality factor (and hence time constant), EM isolation, and electric field uniformity of typical vehicle cavities. This approach yields the important insight that the root mean square delay spread is approximately the same for all wireless links in a typical vehicle cavity. Also, that the angular spread of energy received at any given location (away from the cavity boundaries) is approximately uniform, and that over short distances the coherence distance is well defined, and hence Multiple Input Multiple Output antenna arrays should work well in vehicles. To what extent a typical wireless system can exploit this characterisation depends on how well the parameters can be estimated by a typical wireless communication system. This is also addressed, specifically investigating the estimation of the cavity time constant, and channel time variation. It is found that both of these can be estimated well using a typical wireless sensor network system.