Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-04-19T13:47:30Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Aleciano_Lobo_Junior_Dissertacao.pdf: 9925931 bytes, checksum: bcf8228c8e29cef0e7302ea7716436ec (MD5) / Made available in DSpace on 2017-04-19T13:47:31Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Aleciano_Lobo_Junior_Dissertacao.pdf: 9925931 bytes, checksum: bcf8228c8e29cef0e7302ea7716436ec (MD5) Previous issue date: 2016-08-24 / CNPQ / A implantação de sistemas de transportes inteligentes (Intelligent Transportation System (ITS)) representa um desafio para a comunidade científica e industrial. As melhorias na segurança e eficiência do tráfego de veículos são os principais objetivos de sistemas ITS. Em 2014, acidentes de trânsito foram responsáveis por 32.765 mortes e mais de dois milhões de feridos somente nos Estados Unidos. O Brasil teve resultados piores em 2014: foram 52.226 pessoas mortas em acidentes de trânsito. A Administração Nacional de Segurança em Tráfego de Autoestradas (National Highway Traffic Safety Administration (NHTSA)) estima que sistemas de comunicações veiculares possam reduzir a ocorrência e severidade de 22 de 37 tipos comuns de acidentes. Assim, comunicações Vehicle-to-Vehicle (V2V) e Vehicle-to-Infrastructure (V2I) podem melhorar a segurança por meio da complementação, ou em alguns casos, provendo alternativas aos equipamentos ativos tradicionais baseados no sensoriamento como radares, Light Detection And Ranging (LIDAR) ou por visão. Sobre a eficiência do tráfego de veículos, sistemas ITS implantados via Vehicular Ad-Hoc Networks (VANETs) irão também contribuir para as melhorias nestes índices por meio de ferramentas de monitoramento de tráfego, rotas dinâmicas e alertas sobre as condições da via. Em algumas localidades, estas características de tráfego variam ao longo de um mesmo dia, portanto, engenheiros ITS e pesquisadores devem estar preparados para este comportamento dinâmico de maneira efetiva enquanto analisam o desempenho do sistema. Por outro lado, uma vez que sistemas ITS dependem de serviços de rede, estudos específicos são necessários para considerar os parâmetros de comunicação e de mobilidade veicular. Este trabalho apresenta um modelo de desempenho que considera parâmetros de mobilidade e comunicação para guiar a tomada de decisões no planejamento e gerência de infraestruturas VANETs. As Redes de Petri Estocásticas (SPN) são o formalismo adotado. A dissertação também adota uma metodologia de avaliação. Para representar o comportamento das estações sem fio, foram empregadas distribuições expolinomiais. Os resultados mostram que o modelo proposto produz resultados que podem auxiliar engenheiros e projetistas a implantar e gerenciar infraestruturas VANETs. / The deployment of Intelligent Transportation System (ITS) is a challenge for industry and scientific community. Improvements on safety and vehicular traffic efficiency are the main ITS goals. In 2014, car accidents were responsible for 32,675 deaths and over two million injuries in the United States alone. Brazil had worse results: in 2014, 52,226 people died in car accidents. The National Highway Traffic Safety Administration (NHTSA) estimates that vehicular communications may reduce the severity of 22 of 37 common types of accidents. Thus, V2V and V2I wireless communications may enable improved safety system effectiveness by complementing or, in some instances, providing alternative approaches to the traditional active safety equipment based on autonomous sensing, such as radar, lidar, or vision. Regarding vehicular traffic efficiency, ITS deployed through Vehicular Ad-Hoc Networks (VANETs) will also contribute to improvements in these indices by traffic monitoring tools, dynamic routes, and road condition alerts. In some locations, those traffic characteristics change widely within a single day, therefore, ITS engineers and researchers must deal with that dynamic behavior in an effective manner while analyzing the system performance. On the other hand, once the ITS depends on networking services, specific studies are required to consider the communication parameters along with vehicle mobility. This work presents a performance model that considers both mobility and communication parameters to guide decision-making during the design and management of VANETs infrastructures. The Stochastic Petri Net (SPN) is the adopted formalism. This dissertation also adopts an evaluation methodology. We employed expolynomial distributions to represent the service rates of the wireless stations. Results show that the proposed model provides results that may assist engineers to design and manage VANETs infrastructures.

De nos jours, la filiale automobile connait une évolution énorme en raison de la croissance évolutive des technologies de communication, des aptitudes de détection et de perception de l’environnement, et des capacités de stockage et de traitement présentes dans les véhicules. En effet, une voiture est devenue une sorte d'agent mobile capable de percevoir son environnement et d’en collecter des informations, de communiquer avec les autres véhicules ou infrastructures présentes sur la route, et de traiter les données collectées. Ces progrès stimulent le développement de plusieurs types d'applications qui vont permettre d'améliorer la sécurité et l'efficacité de conduite et de rendre le voyage des automobilistes plus confortable. Cependant, ce développement repose beaucoup sur les données collectées et donc ne pourra se faire que via une collecte sécurisée et un traitement efficace de ces données détectées. La collecte de données dans un réseau véhiculaire a toujours été un véritable défi en raison des caractéristiques spécifiques de ces réseaux fortement dynamiques (changement fréquent de topologie, vitesse élevée des véhicules et fragmentation fréquente du réseau), qui conduisent à des communications opportunistes et non durables. L'aspect sécurité, reste un autre maillon faible de ces réseaux sans fils vu qu'ils sont par nature vulnérables à diverses types d'attaques visant à falsifier les données recueillies et affecter leur intégrité. En outre, les données recueillies ne sont pas compréhensibles par eux-mêmes et ne peuvent pas être interprétées et comprises si montrées directement à un conducteur ou envoyées à d'autres nœuds dans le réseau. Elles doivent être traitées et analysées pour extraire les caractéristiques significatives et informations pour développer des applications utiles et fiables. En plus, les applications développées ont toujours des exigences différentes en matière de qualité de service (QdS). Plusieurs travaux de recherche et projets ont été menées pour surmonter les défis susmentionnés. Néanmoins, ils n'ont pas abouti à la perfection et souffrent encore de certaines faiblesses. Pour cette raison, nous focalisons nos efforts durant cette thèse au développement d’une plateforme de collecte efficace et sécurisée de données dans un réseau de véhicules ainsi que l’exploitation de ces données par des applications améliorant le voyage des automobilistes et la connectivité des véhicules. Pour ce faire, nous proposons une première solution visant à déployer de manière optimale des véhicules, qui auront la tâche de recueillir des données, dans une zone urbaine. Ensuite, nous proposons un nouveau protocole de routage sécurisé permettant de relayer les données collectées vers une destination en se basant sur un système de détection et d'expulsion des véhicules malveillants. Ce protocole est par la suite amélioré avec un nouveau mécanisme de prévention d'intrusion permettant de détecter des attaquants au préalable en utilisant les filtres de Kalman. En deuxième partie de thèse, nous nous sommes concentré sur l’exploitation de ces données en développant une première application capable de calculer de manière fine l’itinéraire le plus économique pour les automobilistes ou tout gestionnaire de flottes de véhicules. Cette solution est basée sur les données influents sur la consommation de carburant et collectées à partir des véhicules eux mêmes et aussi d’autres sources d’informations dans l’Internet et accessibles via des API spécifiques. Enfin, un mécanisme spatio-temporel permettant de choisir le meilleur médium de communication disponible a été développé. Ce dernier est basé sur la logique floue et considère les informations recueillies sur les réseaux, les utilisateurs et les applications pour préserver de meilleure qualité de service. / Nowadays, automotive area is witnessing a tremendous evolution due to the increasing growth in communication technologies, environmental sensing & perception aptitudes, and storage & processing capacities that we can find in recent vehicles. Indeed, a car is being a kind of intelligent mobile agent able to perceive its environment, sense and process data using on-board systems and interact with other vehicles or existing infrastructure. These advancements stimulate the development of several kinds of applications to enhance driving safety and efficiency and make traveling more comfortable. However, developing such advanced applications relies heavily on the quality of the data and therefore can be realized only with the help of a secure data collection and efficient data treatment and analysis. Data collection in a vehicular network has been always a real challenge due to the specific characteristics of these highly dynamic networks (frequent changing topology, vehicles speed and frequent fragmentation), which lead to opportunistic and non long lasting communications. Security, remains another weak aspect in these wireless networks since they are by nature vulnerable to various kinds of attacks aiming to falsify collected data and affect their integrity. Furthermore, collected data are not understandable by themselves and could not be interpreted and understood if directly shown to a driver or sent to other nodes in the network. They should be treated and analyzed to extract meaningful features and information to develop reliable applications. In addition, developed applications always have different requirements regarding quality of service (QoS). Several research investigations and projects have been conducted to overcome the aforementioned challenges. However, they still did not meet perfection and suffer from some weaknesses. For this reason, we focus our efforts during this thesis to develop a platform for a secure and efficient data collection and exploitation to provide vehicular network users with efficient applications to ease their travel with protected and available connectivity. Therefore, we first propose a solution to deploy an optimized number of data harvesters to collect data from an urban area. Then, we propose a new secure intersection based routing protocol to relay data to a destination in a secure manner based on a monitoring architecture able to detect and evict malicious vehicles. This protocol is after that enhanced with a new intrusion detection and prevention mechanism to decrease the vulnerability window and detect attackers before they persist their attacks using Kalman filter. In a second part of this thesis, we concentrate on the exploitation of collected data by developing an application able to calculate the most economic itinerary in a refined manner for drivers and fleet management companies. This solution is based on several information that may affect fuel consumption, which are provided by vehicles and other sources in Internet accessible via specific APIs, and targets to economize money and time. Finally, a spatio-temporal mechanism allowing to choose the best available communication medium is developed. This latter is based on fuzzy logic to assess a smooth and seamless handover, and considers collected information from the network, users and applications to preserve high quality of service.

Indiana University-Purdue University Indianapolis (IUPUI) / Autonomous Emergency Braking (AEB) system uses vehicle’s on-board sensors such as radar, LIDAR, camera, infrared, etc. to detect the potential collisions, alert the driver and make safety braking decision to avoid a potential collision. Its limitation is that it requires clear line-of-sight to detect what is in front of the vehicle. Whereas, in current V2V (vehicle-to-vehicle communication) systems, vehicles communicate with each other over a wireless network and share information about their states. Thus the safety of a V2V system is limited to the vehicles with communication capabilities. Our idea is to integrate the complementary capabilities of V2V and AEB systems together to overcome the limitations of V2V and AEB systems. In a V2V-AEB system, vehicles exchange data about the objects information detected by their onboard sensors along with their locations, speeds, and movements. The object information detected by a vehicle and the information received through the V2V network is processed by the AEB system of the subject vehicle. If there is an imminent crash, the AEB system alerts the driver or applies the brake automatically in critical conditions to prevent the collision. To make V2V-AEB system advance, we have developed an intelligent heart Monitoring system and integrated it with the V2V-AEB system of the vehicle. The advancement of wearable and implantable sensors enables them to communicate driver’s health conditions with PC’s and handheld devices. Part of this thesis work concentrates on monitoring the driver’s heart status in real time by using fitness tracker. In the case of a critical health condition such as the cardiac arrest of a driver, the system informs the vehicle to take an appropriate operation decision and broadcast emergency messages over the V2V network. Thus making other vehicles and emergency services aware of the emergency condition, which can help a driver to get immediate medical attention and prevent accident casualties. To ensure that the effectiveness of the V2V-AEB system is not reduced by a time delay, it is necessary to study the effect of delay thoroughly and to handle them properly. One common practice to control the delayed vehicle trajectory information is to extrapolate trajectory to the current time. We have put forward a dynamic system that can help to reduce the effect of delay in different environments without extrapolating trajectory of the pedestrian. This method dynamically controls the AEB start braking time according to the estimated delay time in the scenario. This thesis also addresses the problem of communication overload caused by V2V-AEB system. If there are n vehicles in a V2V network and each vehicle detects m objects, the message density in the V2V network will be n*m. Processing these many messages by the receiving vehicle will take considerable computation power and cause a delay in making the braking decision. To prevent flooding of messages in V2V-AEB system, some approaches are suggested to reduce the number of messages in the V2V network that include not sending information of objects that do not cause a potential collision and grouping the object information in messages.

Dans de proches années, les véhicules électriques (VEs) vont faire leur apparition massive sur les marchés. Cela peut avoir un impact important sur le fonctionnement des réseaux d’électricité actuels qui devront ajuster leur fonctionnement à la nouvelle demande massive d'électricité provenant des VEs. Par contre, les VEs peuvent aussi être vus comme une nouvelle opportunité dans le futur marché d’électricité. En effet, une décharge/recharge intelligente peut permettre aux VEs d’être un support de stockage d’électricité important, valable, et permanent dont la capacité croit en fonction du nombre des VEs. Ce projet a comme objectifs de : (1) proposer un schéma d’interaction V2G (Vehicle-to-Grid) intégrant des techniques permettant de : (a) adapter le fonctionnement de la grille aux contraintes temporelles et spatiales relatives au processus de recharge des VEs dans un milieu résidentiel. On cherchera à satisfaire de différentes demandes en puissance des VEs branchés au secteur sans trop stresser la grille intelligente, (b) optimiser les opérations de chargement/déchargement entre les VEs et la grille dans les deux sens. (2) Proposer de nouveaux schémas de communication sans fil, entre les VEs et la grille intelligente loin des bornes de recharge, qui soient basés sur les standards de communications véhiculaires (VANETs) ainsi que sur d’autres standards de communication à grande échelle. On introduira des techniques d’accès à la grille intelligente pour négocier le coût de recharge/décharge des batteries, le temps d’attente du service, les emplacements et aussi pour planifier la motivation du consommateur afin de favoriser la stabilité de la grille.

Tragically, traffic accidents involving drivers, motorcyclists and pedestrians result in thousands of fatalities worldwide each year. For this reason, making improvements to road safety and saving people's lives is an international priority. In recent years, this aim has been supported by Intelligent Transport Systems, offering safety systems and providing an intelligent driving environment. The development of wireless communications and mobile ad hoc networks has led to improvements in intelligent transportation systems heightening these systems' safety. Vehicular ad hoc Networks comprise an important technology; included within intelligent transportation systems, they use dedicated short-range communications to assist vehicles to communicate with one another, or with those roadside units in range. This form of communication can reduce road accidents and provide a safer driving environment. A major challenge has been to design an ideal system to filter relevant contextual information from the surrounding environment, taking into consideration the contributory factors necessary to predict the likelihood of a crash with different levels of severity. Designing an accurate and effective pre-crash system to avoid front and back crashes or mitigate their severity is the most important goal of intelligent transportation systems, as it can save people's lives. Furthermore, in order to improve crash prediction, context-aware systems can be used to collect and analyse contextual information regarding contributory factors. The crash likelihood in this study is considered to operate within an uncertain context, and is defined according to the dynamic interaction between the driver, the vehicle and the environment, meaning it is affected by contributory factors and develops over time. As a crash likelihood is considered to be an uncertain context and develops over time, any usable technology must overcome this uncertainty in order to accurately predict crashes. This thesis presents a context-aware pre-crash collision prediction system, which captures information from the surrounding environment, the driver and other vehicles on the road. It utilises a Dynamic Bayesian Network as a reasoning model to predict crash likelihood and severity level, whether any crash will be fatal, serious, or slight. This is achieved by combining the above mentioned information and performing probabilistic reasoning over time. The thesis introduces novel context aware on-board unit architecture for crash prediction. The architecture is divided into three phases: the physical, the thinking and the application phase; these which represent the three main subsystems of a context-aware system: sensing, reasoning and acting. In the thinking phase, a novel Dynamic Bayesian Network framework is introduced to predict crash likelihood. The framework is able to perform probabilistic reasoning to predict uncertainty, in order to accurately predict a crash. It divides crash severity levels according to the UK department for transport, into fatal, serious and slight. GeNIe version 2.0 software was used to implement and verify the Dynamic Bayesian Network model. This model has been verified using both syntactical and real data provided by the UK department for transport in order to demonstrate the prediction accuracy of the proposed model and to demonstrate the importance of including a large amount of contextual information in the prediction process. The evaluation of the proposed system delivered high-fidelity results, when predicting crashes and their severity. This was judged by inputting different sensor readings and performing several experiments. The findings of this study has helped to predict the probability of a crash at different severity levels, accounting for factors that may be involved in causing a crash, thereby representing a valuable step towards creating a safer traffic network.

Current geocasting algorithms for VANETs are being designed to enable either private or reliable communications, but not both. Existing algorithms preserve privacy by minimizing the information used for routing, and sacrifice message delivery success. On the other hand, reliable protocols often store node information that can be used to compromise a vehicle's privacy. We have designed two private and reliable geocasting protocols for VANETs that ensure confidentiality. One is a probabilistic algorithm that uses direction-based dissemination, while the other is a deterministic algorithm that uses transmission-coverage dissemination. To preserve privacy, we create unlinkable and pseudonymous channels of communication with geocasting. For encryption and authentication, we use a public key technique. Our probabilistic forwarding model depends on message rate and cumulative payload, as well as the value of the angle of spreading of the direction-based scheme. To reduce message duplication, we apply dynamic traffic restriction and probabilistic forwarding techniques. The deterministic forwarding algorithm delays forwarding messages based on its uncovered transmission area after neighbouring nodes have broadcast the message. We prove that both algorithms ensure node privacy with appropriate message encryption security, and we ran simulations to demonstrate that both meet the message delivery requirements. From the gathered data, we observe that both algorithms behave differently depending on the scenario, with node density affecting the deterministic algorithm, while the angle of spreading does have a significant impact on the probabilistic protocol.

O desenvolvimento de redes veiculares possibilita o surgimento de sistemas inteligentes de transporte que podem aumentar a segurança nas vias, aperfeiçoar o controle de tráfego e fornecer entretenimento aos passageiros. O avanço e padronização de tecnologias de comunicação inter-veicular permitem que veículos compartilhem informações de forma colaborativa de maneira a viabilizar o estabelecimento de sistemas de transporte inteligentes cooperativos (C-ITS, Cooperative Intelligent Transportation Systems). Na comunicação veicular, cada nó compartilha periodicamente uma mensagem que contém informações sobre seu estado como posição, velocidade e aceleração. Estas mensagens são denominadas Cooperative Awareness Messages (CAMs) e podem ser utilizadas por veículos vizinhos para a operação de aplicações, sendo a formação de comboios um exemplo. Em um comboio veicular, um grupo de veículos viaja com distância reduzida entre cada membro através da operação de um controlador que utiliza informações compartilhadas por CAMs. O posicionamento compartilhado através de CAMs por cada veículo é crucial para a operação dos controladores de nós vizinhos, dado que este será utilizado para a condução do veículo. Embora os controles criptográficos padronizados para troca de mensagens em VANETs ofereçam contramedidas contra ataques como roubo de identidade e adulteração de pacotes, um atacante interno que possua credenciais válidas do sistema ainda pode mentir sobre as informações que são transmitidas para outros veículos. Em modelos atuais de redes veiculares, cada veículo é responsável por obter sua localização, normalmente através de GPS (Global Positioning System). A dependência de aplicações VANET na posição correta dos nós introduz a necessidade de mecanismos de garantia de localização. Nesta dissertação são identificados os riscos associados com a falsificação de posição em comboios veiculares. Através de simulações utilizando o ambiente de simulação Veins, mostramos que colisões em alta velocidade podem ser causadas por nós que atuam em conluio na falsificação de mensagens para um comboio. Dado que posicionamento legítimo é essencial para o funcionamento adequado das aplicações VANET, investigamos mecanismos de prova de localização propostos na literatura. Então, projetamos um mecanismo de prova de localização adaptado para VANETs usando equipamentos de estrada (RSUs, roadside units), com a capacidade de usar diferentes freqüências de prova de acordo com os requisitos de precisão de detecção e sobrecarga. Através de simulações usando os ataques estudados neste trabalho, mostramos que o mecanismo pode detectar ataques de falsificação de mensagens e Sybil. / In vehicular communication, nodes periodically share Cooperative Awareness Messages (CAMs) in order to convey information such as identity, velocity, acceleration and position. The positioning of nodes in a vehicular network is a key factor that directly affects how applications operate, being the formation of platoons a major case. In vehicular platooning, a group of vehicles travels closely together and leverages information shared through CAMs to operate lateral and longitudinal control algorithms. While the standardised cryptographic mechanisms counteract threats such as identity hijacking and packet tampering, an internal member who holds valid credentials may still be able to lie about the data it transmits in CAMs. In current Vehicular ad hoc Network (VANET) models, each vehicle is responsible for determining and informing its own position, generally using a Global Navigation Satellite System (GNSS) such as the Global Positioning System (GPS). This allows malicious actors to lie about their position and therefore cause unwanted effects in vehicular applications. The dependence of VANET applications on correct node localization introduces the need for position assurance mechanisms. In this dissertation, we first identify the risks associated with falsifying the position in vehicular platooning. Through simulations using the Veins framework, we show that collisions at high speed on a platoon may be caused by nodes that collude in falsification attacks. Given that truthful positioning is essential to proper behavior of VANET applications, we investigate proof-of-location schemes proposed in the literature. Then, a proof-of-location mechanism tailored for VANETs is designed using roadside units, with the capability of using different proof frequencies according to detection accuracy and overhead requirements. Through simulations using the studied attacks in this work, we show that the mechanism can counteract Sybil and message falsification attacks.

Actuellement les communications véhiculaires sont devenues une réalité guidée par diverses applications. Notamment, la diffusion de vidéo de qualité élevée avec des contraintes de faible latence requises par les applications temps réel. Grâce au niveau de compression jamais atteint auparavant, l’encodeur H.265/HEVC est très prometteur pour la diffusion de vidéos en temps réel dans les réseaux ad hoc véhiculaire (VANET). Néanmoins, la qualité de la vidéo reçue est pénalisée par les mauvaises caractéristiques du canal de transmission (disponibilité, non stationnarité, rapport signal à bruit, etc.). Afin d’améliorer et d’assurer une qualité vidéo minimale à la réception nous proposons dans ce travail une optimisation conjointe source-canal-protocole de la transmission en tenant compte à la fois des paramètres de transmission et d’encodage vidéo. Dans un premier temps, nous montrons l’intérêt et le gain apporté par les solutions dites inter-couches « cross-layer ». Par la suite, nous développons deux approches l’une exploitant un « cross-layer » entre la couche application et la couche MAC et une seconde exploitant les protocoles de transports dans l’adaptation du flux vidéo. En ce qui concerne la première approche nous proposons une solution utilisant une gestion hiérarchique des trames au niveau des files d’attentes de la couche MAC, basée sur l’importance des images du flux vidéo. Dans une seconde solution, nous retenons le codage par descriptions multiples comme solution de protection à la source. Les résultats de simulations obtenus pour plusieurs types de scénarios véhiculaires réalistes montrent que les différents schémas de transmission véhiculaire proposés offrent des améliorations significatives en termes de qualité vidéo à la réception et de retard de bout en bout par rapport aux schémas classiques. / At present, vehicular communications have become a reality guided by various applications. In particular, high-quality video delivery with low latency constraints is required for real-time applications. The new state-of-the-art high-effciency video coding (HEVC) standard is very promising for real-time video streaming in vehicular ad hoc networks (VANET). Nevertheless, these networks have variable channel quality and a limited bandwidth that penalizes the overall performances of end-to-end video transmission. In order to meet these constraints, we proposed in this work to consider both transmission and video encoding parameters through a joint source-channel-protocol coding approach to provide an improvement in video transmission. First, we have shown the interest and the gain brought by the "cross-layer" solutions. Then, we developed two approaches. The first one exploits a "crosslayer" solution between the application layer and the Medium Access Control (MAC) layer while the second exploits the transport layer protocols in the adaptation of the video stream. Regarding the first approach, we have proposed solutions to allocate the frames to the most appropriate Access Category (AC) queue on the MAC layer based on the image importance in the video stream. In another solution, we chose multiple descriptions source coding as an error resilient solution. Thus, the simluation results obtained for different realistic vehicular scenarios demonstrate that the proposed transmission schemes offer significant video quality improvements and end-to-end delay reduction compared to conventional transmission schemes.

車載網路受到各方廣泛討論，激發出許多新的議題，由於車載網路的通訊品質不穩定，速度快、節點多，封包傳送不易，因此許多人都採用分群式架構增進效能，以集中式管理群組，避免封包被重複傳送，降低封包碰撞的機會。然而，現有的分群機制只能用在即時方面的應用，在檔案傳輸方面效能不足。本篇論文擬改善C. Shea等人[1]所提出的分群機制File-based Affinity Propagation Cluster, FAPC，建立兼具動態性和檔案相關性的叢集架構，並且提出改善失去叢集管理員的重建機制，以提升分群的穩定性及吞吐量（throughput）。最後，我們以模擬證明所提出的方法優於C. Shea [1]的方法，以query hit ratio、retrieve file ratio、average number of clusters及average cluster head duration為效能指標，觀察在不同時間、車輛數目及車輛速度時效能表現。 / Vehicular Ad-hoc Network (VANET) has been widely discussed and many issues have been proposed. Due to VANET’s unstable quality, varying speed, lots of mobility nodes, it’s not easy to deliver packets. Thus many researchers suggested using cluster architecture to enhance performance. Because of the central management, we can avoid duplication of packets in the same cluster and decrease the probability of packet collision. However, we find most of the cluster architectures are suitable for real-time applications, but not for file transfer. In this research, we improve C. Shea’s [1] method by adding file-similarity by classifying into groups and reselecting cluster head, when the group of nodes have not cluster head. This cluster architecture can enhance stability and throughput. Finally, we use simulation to prove that our method outperforms Chen’s [1] cluster method in terms of query hit ratio, retrieve file ratio, average number of clusters and average cluster head duration.

Current geocasting algorithms for VANETs are being designed to enable either private or reliable communications, but not both. Existing algorithms preserve privacy by minimizing the information used for routing, and sacrifice message delivery success. On the other hand, reliable protocols often store node information that can be used to compromise a vehicle's privacy. We have designed two private and reliable geocasting protocols for VANETs that ensure confidentiality. One is a probabilistic algorithm that uses direction-based dissemination, while the other is a deterministic algorithm that uses transmission-coverage dissemination. To preserve privacy, we create unlinkable and pseudonymous channels of communication with geocasting. For encryption and authentication, we use a public key technique. Our probabilistic forwarding model depends on message rate and cumulative payload, as well as the value of the angle of spreading of the direction-based scheme. To reduce message duplication, we apply dynamic traffic restriction and probabilistic forwarding techniques. The deterministic forwarding algorithm delays forwarding messages based on its uncovered transmission area after neighbouring nodes have broadcast the message. We prove that both algorithms ensure node privacy with appropriate message encryption security, and we ran simulations to demonstrate that both meet the message delivery requirements. From the gathered data, we observe that both algorithms behave differently depending on the scenario, with node density affecting the deterministic algorithm, while the angle of spreading does have a significant impact on the probabilistic protocol.