Дисертації з теми "Vehicular Application"

A wide range of vehicular applications require packet routing mechanisms and protocols for efficient, reliable and robust delivery of data packets over vehicles, from a single source or from multiple sources to either a specific destination or multiple destinations in a specific region. All vehicular applications, e.g., non-safety applications and safety applications, have their own specific challenges, considerations and Quality of Service (QoS) requirements which are different from those of other vehicular applications. Hence, we believe that the design of packet routing mechanisms and protocols for each vehicular application should be application-specific. In non-safety applications, to access the backhaul network through the infrastructure on the roadside, so-called Road-side Units (RSUs), since many parts of the network may not be directly covered by RSUs, appropriate routing protocols need to be designed and employed. In this thesis, we developed a single-technology routing protocol for Vehicular Ad hoc Networks (VANETs), Connectivity-aware Minimum-delay Geographic Routing (CMGR), which adapts well to continuously changing network status in such networks. As the next step we studied how packet routing mechanisms and protocols should be adapted to heterogeneous environments. In this regard, we developed optimal Vertical Hand-Off (VHO) strategies for vehicular heterogeneous networks when RSUs directly cover all parts of the vehicular network under study. Next, we turned our attention to the case where some parts of the network are not directly covered by any RSU and proposed a Hybrid Multi-Technology Routing (HMTR) protocol to consider different combinations of wireless technologies in intermediate hops when establishing routes from vehicular end-users to RSUs. In safety applications the notification of hazardous situations needs to be sent from the hazard-detecting vehicle to every other vehicle in the neighborhood, so-called data dissemination. Fully ad hoc data dissemination mechanisms have gained more acceptance due to their robustness and avoiding the excessive costs of infrastructure deployment and maintenance. In this regard, one of the main challenges is to overcome the packet delivery failures at intersections in the ad hoc manner. In this regard, we developed a fully ad hoc data dissemination mechanism, Enhanced Intersection-mode Data Dissemination (EIDD), which provides reliable packet delivery at intersections.

Mestrado em Engenharia de Computadores e Telemática
As redes veiculares têm sido alvo de grandes avanços tecnológicos, e a comunicação entre veículos é hoje uma realidade que tem despertado o interesse tanto ao nível da investigação como de alguns dos principais fabricantes de automóveis com o intuito de criar um conjunto de serviços para melhorar a experiência dos utilizadores deste tipo de redes. Por outro lado, os dispositivos móveirs como smartphones, tablets ou PDA’s também são uma área emergente no mundo das tecnologias devido ao enorme aumento de capacidade computacional que sofreram nos últimos anos. Embora as redes veiculares tenham sido alvo de grandes avanços tecnológicos continuam a encontrar obstáculos para a sua afirmação devido à indisponibilidade de dispositivos nos veículos que permitam usufruir das suas potencialidades. Esta falta de dispositivos pode ser ultrapassada aliando o mundo dos dispositivos móveis com as redes veiculares. Utilizando o potencial das redes veiculares e a capacidade computacional dos novos dispositivos móveis pode-se explorar um cenário de criação de serviços e aplicações de segurança, controlo e eficiência de tráfego e entretenimento. O presente trabalho propõe-se a estudar, criar e testar uma solução para a integração das duas áreas tecnológicas referidas anteriormente. Neste documento é descrita uma arquitectura de alto nível que permite a integração de aplicações móveis com as redes veiculares, abstraindo as camadas de transporte e de rede com um módulo de software que fornece os métodos necessários para as aplicações usufruírem dos serviços das redes veiculares. O resultado final deste trabalho é uma arquitectura de software para integração em aplicações Android que permite utilizar a rede veicular para comunicação entre as aplicações. Ao longo deste documento é descrito todo o processo de implementação desta arquitectura, e posteriormente é apresentada a implementação de aplicações exemplo para experimentação da arquitectura e avaliação do seu desempenho. No âmbito da Dissertação foram criados cenários para realização de testes de desempenho das aplicações em ambientes reais e simulados. Estes testes serviram para identificar a viabilidade da utilização do REINVENT em dispositivos com diferentes características de hardware, e também para identificar potenciais pontos de atraso na estrutura da arquitectura criada. Os resultados obtidos permitiram constatar que a utilização desta arquitectura não induz qualquer tipo de interferência nem atraso no normal funcionamento das aplicações, e que o REINVENT pode ser utilizado na criação de novas aplicações móveis no âmbito das redes veiculares.
Vehicular networks have been the subject of major technological progress, and the communication between vehicles is a reality that has been the subject of interest both in terms of research and of some of the major car manufacturers in order to create a set of services to enhance the user experience of such networks. On the other hand, mobile devices such as smartphones, tablets and PDA's are also an emerging technology in the world due to the enormous increase of computing power they got in recent years. Although vehicular networks have been the subject of great technological advances, they continue to encounter obstacles to their raising due to unavailability of devices in vehicles that allow the use of its potential. This lack of devices can be overcome by combining the world of mobile devices with vehicular networks. Using the potential of vehicular networks and computational capabilities of new mobile devices, a set of scenarios can be explored in order to create services and applications for security, control and efficiency of traffic and entertainment. This work proposes to study, create and test a solution for the integration of the two technology areas mentioned above, applications and vehicular networks. In this Dissertation we describe a high-level architecture that allows the integration of mobile applications with vehicular networks by abstracting transport and network layers with a software architecture that provides the methods needed for the applications to take advantage of vehicular networks services. The end result of this work is a software architecture for integration into Android applications that allows the use of vehicular network for relaying communication between applications. Throughout this document, the whole process of the architecture implementation is described as well as two example applications for proof of concept, testing purpose and performance evaluation. In order to test the performance of the REINVENT module in the applications, two test scenario environments were created, a simulated environment, integrating a VANET simulation framework with mobile devices, and a real environment using an on board unit for vehicle communication purposes. These tests served to identify the feasibility of using REINVENT in devices with different hardware characteristics, and also to identify potential sources of delay in the structure of the architecture created. The results revealed that the use of this module does not induce any interference or delay on the normal operation of applications, and REINVENT can be used in creating new mobile applications in the context of vehicular networks.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
As redes veiculares surgiram como um caso particular de redes mÃveis e passaram a formar um campo especÃfico de pesquisa na Ãrea de redes de computadores. Elas tÃm sido alvo de inÃmeras pesquisas cientÃficas nos Ãltimos anos, cujo principal foco à o desenvolvimento do Sistema Inteligente de Transporte. AlÃm disso, dado que os automÃveis sÃo cada vez mais importantes na vida das pessoas, embarcar softwares inteligentes em seus carros pode melhorar substancialmente a qualidade de vida dos usuÃrios. Esse fato, somado à significante demanda do mercado por mais confiabilidade, seguranÃa e entretenimento nos veÃculos, levou ao desenvolvimento e suporte significantes para as redes veiculares e suas aplicaÃÃes. Dentre estas aplicaÃÃes pode-se citar a utilizaÃÃo do VoIP. Entretanto, os aplicativos VoIP sofrem com problemas de atraso, perda de pacotes e jitter. Estes desafios tÃcnicos se agravam ainda mais quando utilizado em redes sem fio. Um fator que influencia diretamente a utilizaÃÃo de uma aplicaÃÃo em redes em fio à o protocolo de roteamento. O roteamento à uma tarefa desafiadora devido à alta mobilidade dos nÃs, à instabilidade dos enlaces sem-fio e a diversidade de cenÃrios. Por essa razÃo, diversos protocolos de roteamento foram projetados com o objetivo de solucionar um ou mais problemas especÃficos de cada cenÃrio. Entretanto, apesar de existirem vÃrias soluÃÃes propostas para o problema do roteamento em redes veiculares, nenhuma soluÃÃo geral foi encontrada, ou seja, nenhum protocolo proposto obteve desempenho considerÃvel nos diversos cenÃrios existentes nas redes veiculares. Sendo assim, nesta dissertaÃÃo, analisamos atravÃs de simulaÃÃes o impacto da densidade, do alcance de transmissÃo, da mobilidade e do tipo de protocolo de roteamento no desempenho de uma aplicaÃÃo VoIP nos cenÃrios urbano e de rodovia em redes veiculares.
Vehicular networks have emerged as a particular case of mobile networks and then became a specific field of research in computer networks. They have been the subject of numerous scientific research in recent years, whose main focus is the development of Intelligent Transport System. Furthermore, given that cars are increasingly important in people's lives, smart board software in their cars can substantially improve the quality of life of users. This fact and the significant market demand for more reliability, security and entertainment in vehicles, has led to significant development and support for vehicular networks and their applications. Among these applications we can mention the use of VoIP, however, VoIP applications suffer from problems of delay, packet loss and jitter. These technical challenges are further aggravated when used in wireless networks. One factor that directly influences the use of an application in wireless networks is the routing protocol. Routing is a challenging task due to the high node mobility, the instability of wireless links and the diversity of scenarios. For this reason, several routing protocols have been designed with the goal of solving one or more specific problems of each scenario. However, although there are several proposed solutions to the problem routing in vehicular networks, no general solution was found, in other words, any proposed protocol obtained considerable performance in the various scenarios that exist in vehicular networks. Thus, in this paper, we analyze through simulations the impact of density, of the reach of transmission, the mobility and the type of routing protocol on the performance of a VoIP application in urban and highway scenarios of vehicular networks.

The primary goal of this thesis is to implement peer to peer technology in vehicular communication. The emerging concept of Vehicular Communication including road side infrastructure is a promising solution to avoid accidents and providing live traffic data. There is a high demand for the technologies which ensure low latency communication. Modern vehicles equipped with computing, communication and storage and sensing capabilities eased the transmission of data. To achieve deterministic bounds on data delivery, ability to be established anywhere quickly, and efficiency of data query we have chosen to implement a structured peer to peer overlay model in a cluster of vehicles. The vehicles in the cluster exchange information with the cluster head. The cluster head acts as a leader of the cluster, it fetches the data from the Road-side unit and other cluster heads. We have implemented Pyramid Tree Model in structured peer to peer models. A pyramid tree is group of clusters organized in a structured format with the data links between the clusters. The core concepts behind the pyramid tree model is clustering the nodes based on interest.

Vehicle to vehicle communication (V2VC) is one of the modern approaches for exchanging and generating traffic information with (yet to be realized) potential to improve road safety, driving comfort and traffic control. In this research, we present a novel algorithm which is based on V2V communication, uses in-vehicle sensor information and in collaboration with the other vehicles' sensor information can detect road conditions and determine the geographical area where this road condition exists – e.g. geographical area where there is traffic density, unusual traffic behaviour, a range of weather conditions (raining), etc. The algorithms' built-in automatic geographical restriction of the data collection, aggregation and dissemination mechanisms allows warning messages to be received by any car, not necessarily sharing the identified road condition, which may then be used to identify the optimum route taken by the vehicle e.g. avoid bottlenecks or dangerous areas including accidents or congestions on their current routes. This research covers the middle ground between MANET [1] and collaborative data generation based on knowledge granularity (aggregation). It investigates the possibility of designing, implementing and modelling of the functionality of an algorithm (as part of the design of an intelligent node in an Intelligent Transportation System - ITS) that ensures active participation in the formation, routing and general network support of MANETs and also helps in-car traffic information and real-time control generation and distribution. The work is natural extension of the efforts of several large EU projects like DRIVE [2], GST [3] and SAFESPOT [4]. The main difference between this research work and the research efforts outlined in these projects and related work is that they focus on V2I (Vehicle to Infrastructure) algorithms and node design, while all work related to ad-hoc wireless communication is mentioned, but not developed fully. In that respect this specific research domain is increasingly under active research consideration – utilizing ad-hoc networks algorithms for creating ad-hoc based wireless architectures and algorithms for building future intelligent information systems. The research challenge is to design, implement and investigate novel algorithms as part of an intelligent wireless information systems node design so that the functionality of the node has all the characteristics of the network node in parallel with all the characteristics of in-car data processing device. The project redefines the base line connectivity of the device and describes to what extend the functionality of the node will depend on external factors: e.g. connectivity based on the underlying wireless technology, support of the ad-hoc networks based on the speed and the type of mobility of the mobile node etc. The big difference between MANET as described so-far in the literature and the one which will be underlined by the functionality of the intelligent node described in this project is in the functionality of the active component of the MANET described here. The MANET designed in the project will be able to more effectively generate data (not network data – but user traffic data) and also will be able to take part in the on street control of the traffic lights. Although much research work worldwide is dedicated to the subject, the fact is that there are none implemented on the road traffic information systems based on ad-hoc networking, which shows that the principles of building such effective networks are yet to be discovered. The achievements of this research include introducing a novel algorithm based on the “Single Ripple” algorithm approach [5], investigating and reporting in papers the parameters transmission delay and number of hops for optimum working mode of the algorithm. The work includes also developing a simulation tool and tool for analyses of the data.

The performance of many protocols and applications of Vehicular Ad hoc Networks (VANETs), depends on vehicles obtaining enough fresh information on the status of their neighbouring vehicles. This should be fulfilled by exchanging Basic Safety Messages (BSMs) also called beacons using a shared channel. In dense vehicular conditions, many of the beacons are lost due to channel congestion. Therefore, in such conditions, it is necessary to control channel load at a level that maximizes BSM dissemination. To address the problem, in this thesis algorithms for adaptation of beaconing to control channel load are proposed. First, a position-based routing protocol for VANETs is proposed and the requirement of adaptive beaconing to increase the performance of the protocol is indicated. The routing protocol is traffic-aware and suitable for city environments and obtains real-time traffic information in a completely ad hoc manner without any central or dedicated control, such as traffic sensors, roadside units, or information obtained from outside the network. The protocol uses an ant-based algorithm to find a route that has optimum network connectivity. Using information included in small control packets called ants, vehicles calculate a weight for every street segment that is proportional to the network connectivity of that segment. Ant packets are launched by vehicles in junction areas. To find the optimal route between a source and destination, a source vehicle determines the path on a street map with the minimum total weight for the complete route. The correct functionality of the protocol design has been verified and its performance has been evaluated in a simulation environment. Moreover, the performance of the protocol in different vehicular densities has been studied and indicated that in dense vehicular conditions the performance of the protocol degrades due to channel load created by uncontrolled periodic beaconing. Then, the problem of beaconing congestion control has been formulated as non-cooperative games, and algorithms for finding the equilibrium point of the games have been presented. Vehicles as players of the games adjust their beacon rate or power or both, based on the proposed algorithms so that channel load is controlled at a desired level. The algorithms are overhead free and fairness in rate or power or both rate and power allocation are achieved without exchanging excess information in beacons. Every vehicle just needs local information on channel load while good fairness is achieved globally. In addition, the protocols have per-vehicle parameters, which makes them capable of meeting application requirements. Every vehicle can control its share of bandwidth individually based on its dynamics or requirements, while the whole usage of the bandwidth is controlled at an acceptable level. The algorithms are stable, computationally inexpensive and converge in a short time, which makes them suitable for the dynamic environment of VANETs. The correct functionality of the algorithms has been validated in several high density scenarios using simulations.

The emerging concept of vehicle cloudification is a promising solution to deal with ever-growing computational and communication demands of connected vehicles. A key idea is to have connected vehicles in the vicinity form a cluster which is called vehicular micro cloud. Vehicles in this micro cloud collaborate with other cluster members over vehicle-to-vehicle (V2V) networks for collective data processing, shared data storage, collaborative sensing and communication services. A typical use case of vehicular micro cloud is creation of a regional distributed data storage service, where member vehicles of the cloud collaboratively keep data contents in their on-board data storage devices. This allows vehicles in and around the vehicular micro cloud to request the contents from the micro cloud member(s) over vehicle-to-vehicle networks, or even update the data on the spot. In this thesis, we will discuss the need for vehicular micro clouds, followed by the architecture, formation of the micro clouds, and feasibility of micro clouds. Furthermore, we will cover aspects of efficient data transmission between vehicles, how to increase the scalability and to make it time efficient and cost efficient on practical road conditions for moving vehicles by encouraging coordination between neighboring micro cloud to help transfer data .

As important components of intelligent transportation system, lane detection and tracking (LDT) and lane departure warning (LDW) systems have attracted great interest from the computer vision community over the past few years. Conversely, lane markings recognition (LMR) systems received surprisingly little attention. This thesis proposed a real-time lane assisting framework for intelligent vehicles, which consists of a comprehensive module and simplified module. To the best of our knowledge, this is the first parallel architecture that considers not only lane detection and tracking, but also lane marking recognition and departure warning. A lightweight version of the Hough transform, PPHT is used for both modules to detect lines. After detection stage, for the comprehensive module, a novel refinement scheme consisting of angle threshold and segment linking (ATSL) and trapezoidal refinement method (TRM) takes shape and texture information into account, which significantly improves the LDT performance. Also based on TRM, colour and edge informations are used to recognize lane marking colors (white and yellow) and shapes (solid and dashed). In the simplified module, refined MSER blobs dramatically simplifies the preprocessing and refinement stage, and enables the simplified module performs well on lane detection and tracking. Several experiments are conducted in highway and urban roads in Ottawa. The detection rate of the LDT system in comprehensive module average 95.9% and exceed 89.3% in poor conditions, while the recognition rate depends on the quality of lane paint and achieves an average accuracy of 93.1%. The simplified module has an average detection rate of 92.7% and exceeds 84.9% in poor conditions. Except the conventional experimental methods, a novel point cluster evaluation and pdf analysis method have been proposed to evaluate the performance of LDT systems, in terms of the stability, accuracy and similarity to Gaussian distribution.

There are still many challenges in the field of VANETs that encouraged researchers to conduct further investigation in this field to meet these challenges. The issue pertaining to routing protocols such as delivering the warning messages to the vehicles facing Non-Line of Sight (NLOS) situations without causing the storm problem and channel contention, is regarded as a serious dilemma which is required to be tackled in VANET, especially in congested environments. This requires the designing of an efficient mechanism of routing protocol that can broadcast the warning messages from the emergency vehicles to the vehicles under NLOS, reducing the overhead and increasing the packet delivery ratio with a reduced time delay and channel utilisation. The main aim of this work is to develop the novel routing protocol for a high-density environment in VANET through utilisation of its high mobility features, aid of the sensors such as Global Positioning System (GPS) and Navigation System (NS). In this work, the cooperative approach has been used to develop the routing protocol called the Co-operative Volunteer Protocol (CVP), which uses volunteer vehicles to disseminate the warning message from the source to the target vehicle under NLOS issue; this also increases the packet delivery ratio, detection of NLOS and resolution of NLOS by delivering the warning message successfully to the vehicle under NLOS, thereby causing a direct impact on the reduction of collisions between vehicles in normal mode and emergency mode on the road near intersections or on highways. The cooperative approach adopted for warning message dissemination reduced the rebroadcast rate of messages, thereby decreasing significantly the storm issue and the channel contention. A novel architecture has been developed by utilising the concept of a Context-Aware System (CAS), which clarifies the OBU components and their interaction with each other in order to collect data and take the decisions based on the sensed circumstances. The proposed architecture has been divided into three main phases: sensing, processing and acting. The results obtained from the validation of the proposed CVP protocol using the simulator EstiNet under specific conditions and parameters showed that performance of the proposed protocol is better than that of the GRANT protocol with regard to several metrics such as packet delivery ratio, neighbourhood awareness, channel utilisation, overhead and latency. It is also successfully shown that the proposed CVP could detect the NLOS situation and solves it effectively and efficiently for both the intersection scenario in urban areas and the highway scenario.

El presente trabajo corresponde al curso de Desarrollo de Negocios 2, a lo largo del desarrollo aplicaremos conceptos y herramientas aprendidas a lo largo de la carrera de la Universidad Peruana de Ciencias Aplicadas. Actualmente el Perú presenta un crecimiento paulatino en el parque automotor, con mayor concentración en Lima Metropolitana y Callao. Muestra de ello se puede apreciar a simple vista en la cotidianidad, siendo específicos el tráfico. Service Car Express, plantea la idea de negocios que apunta al sector automotriz, al cuidado de los vehículos y asesoramiento vehicular. Nuestra idea está dirigida al NSE B y C y a personas o empresas que cuenten con vehículos considerados de segunda mano o a aquellos que estén planeando adquirir un vehículo dentro de distritos como Miraflores, Surco, Chorrillos, Barranco, San Miguel, Surquillo y Jesús María. Service Car Express, llega con una propuesta de valor diferente a la que está acostumbrado el cliente, servicios netamente a domicilio buscando reducir el tiempo perdido de nuestros clientes y volviendo esa parte de sus vidas tan tediosa de ir al taller en algo simplemente práctico e innovador, disponible en el momento. Con la finalidad de cumplir esta propuesta de valor, ScarX ha creado un modelo de negocios que a través de la tecnología por aplicativos busca optimizar los tiempos de servicios que pueda brindar a sus clientes, de este modo buscara alcanzar la máxima calidad y perfeccionar sus procesos operacionales identificando y aprovechando todos sus recursos disponibles.
The present work corresponds to the course of Business Development 2, throughout the development we will apply concepts and tools learned throughout the career of the UPC University. Currently, Peru presents a gradual growth in the automotive fleet, with a greater concentration in Lima Metropolitana and Callao. Sample of this can be seen in everyday life, when see traffic everywhere. Service Car Xpress, raises the business idea that points to the automotive sector, car care and vehicle advice. Our idea is directed to B and C socioeconomic status and to people or companies that have vehicles considered second-hand or to those who are planning to acquire a vehicle within districts such as Miraflores, Surco, Chorrillos, Barranco, San Miguel, Surquillo and Jesús María. Service Car Xpress, arrives with a different value proposition, services purely at home trying to reduce the lost time of our customers while they are in workshops, we are going to make it be something simply practical and innovative, available at the time. In order to fulfill this value proposition, ScarX has created a business model that, through technology is going to optimize the time a car service can take. We offer our clients the highest quality in all processes taking advantage of all available resources.
Trabajo de investigación

Ingeniero Civil Eléctrico
Las redes vehiculares ad-hoc (VANets) son un nuevo paradigma en comunicación móvil que se plantea que podría permitir el despliegue de sistemas de transporte inteligente (ITS), más seguros, eficientes y amigables con el medioambiente. Se cuenta con el estándar DSRC de comunicaciones vehiculares pero no está comprobado que sea capaz de ofrecer la robustez y seguridad que necesitan los ITS. Las comunicaciones por luz visible (VLCs), son tecnologías de comunicación inalámbricas basadas en la modulación de intensidad de luz. Se realizan con dispositivos opto-electrónicos como diodos LED y foto-diodos. Se plantea que éstas podrían complementar a las radio-frecuencias (RF), como las del protocolo DSRC, por ejemplo, y permitir a las VANets entregar un mejor servicio, sobre todo en ambientes congestionados. En el presente trabajo, se realizó el desarrollo de una plataforma con herramientas para prototipado de enlaces VLC con aplicación en VANets bajo la hipótesis que las tecnologías existentes de illuminación en automóviles y señales de tránsito son una infraestructura que permite implementar VLCs en ambientes vehiculares. Primero se consultó el estado del arte de VANets y de VLCs, enfocado en entender el origen del interés por la implementación de redes vehiculares, así como sus desafíos y cómo las VLCs pueden mejorar el desempeño de dichos sistemas. Se estudiaron tecnologías aplicables a los sistemas de información y comunicaciones de las redes vehiculares con enfoque en las VLC. Un grupo fueron las plataformas de hardware programable como radios definidas por software (SDRs) y las placas Arduino. Otro tema fue la red de control interna de los vehículos y cómo existen interfaces para acceder a ella y obtener mediciones de los sensores e incluso dar instrucciones a los actuadores del auto. También, se revisaron los transductores de una red VLC: los diodos LED y fotodiodos, incluyendo la electrónica necesaria para su funcionamiento. Finalmente, se implementó un sistema de comunicaciones por VLC, basado en SDRs y optoelectrónica, y también un sistema adquisición de datos para la red de control del vehículo, basado en Arduino y un circuito integrado ELM327. Ambos sistemas se diseñaron modulares y se construyeron robustos. Se logró con ellos la transmisión de datos por luz y la lectura de datos del area de control del vehículo. Actualmente, el sistema desarrollado está en manos de un grupo de investigación que se dedica a estudiar las tecnologías de comunicación vehicular. También se está trabajando en una publicación con la evaluación de los sistemas implementados.
Este trabajo ha sido parcialmente financiado por ERANet-LAC Proyecto "RETRACT" Código ELAC2015/T10-0761, FONDECYT iniciación N° 11160517, FONDECYT Posdoctorado N° 3170021

This study focuses on the older person with chronic diseases, something that yields them vulnerable to a decline in self–care and medication adherence. South Africa has the highest percentage of older persons in Africa, and the North–West Province where the study was conducted presents with 7.34% persons older than 60 years. The growing population of older persons not only poses challenges to the primary health care (PHC) facilities, but also to the older persons themselves, their family members and the community where they live. Health services to the older persons have become overshadowed by an emphasis on child– and maternal care, as well as communicable diseases such as HIV/AIDS and TB. The reality however is that the older population is subjected to an ageing process that predisposes them to a number of chronic diseases, such as hypertension, cardiac diseases, diabetes mellitus and arthritis. This often requires that the older person be put on multiple chronic medications and therefore be made aware of the importance of self–care and medication adherence to deal effectively with their chronic diseases and in turn improving quality of life. Non–experimental, quantitative research design was used to reach the aim of the study, namely to explore and identify possibilities for the enhancement of self–care and medication adherence of older persons in a rural area. This was done through objectives to explore and describe the factors of self–care and medication adherence in relation to age, gender, relationship status, behaviour and medication use amongst older persons in a rural area of the North–West Province. A literature review was first conducted by the researcher for a clear understanding of self–care and medication adherence of older persons. Thereafter a structured questionnaire consisting of a demographic–, self–care– and medication adherence section was employed. Trained field workers assisted with data collection. The questionnaires were distributed to 150 participants and 143 were completed in the homes of the older persons, resulting in a participation rate of 95%. Data collected was analysed in a sequential order; demographic data was first analysed with results shown in a frequency table; the exploratory factor analyses were done for data reduction on the self–care and the medication adherence questionnaire. Descriptive statistics and Cohen’s effect sizes for the factors of self–care and medication adherence in relation to age, gender, relationship status, behaviour and medication use amongst the older persons in a rural area. v The results revealed that the oldest participants, those older than 80 years, will seek help when they are unable to care for themselves, thus gender, relationship status and whether they smoke or not, showed no practical effect on self–care and medication adherence. There was however results that showed that different aspects of medication use can have a medium and/or large practical effect on factors of self–care and/or medication adherence. The results gave direction to the researcher to make recommendation to the nurses working in PHC facilities, future nursing research and nursing education.
Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.

Platooning has the potential to be a breakthrough in increasing road capacity and reducing fuel consumption, as it allows a chain of vehicles to closely follow each other on the road. When the number of vehicles increases, platoons will follow one another in what is referred to as multiplatooning. Many Cooperative Intelligent Transportation Systems (C-ITS) applications rely on periodically exchanged beacons among vehicles to improve traffic safety. However, as the number of connected vehicles increases, the network may become congested due to periodically exchanged beacons. Therefore, without some congestion control method, safety critical messages such as Cooperative Awareness Messages (CAMs) may not be delivered on time in high vehicle density scenarios. Both the European Telecommunications Standards Institute (ETSI) and the Institute of Electrical and Electronics Engineers (IEEE) have been working on different standards to support vehicular communication. ETSI dened the Decentralized Congestion Control (DCC) mechanism which adapts transmission parameters (message rate, transmit data rate, and transmit power, etc.) to keep channel load under control. ETSI DCC utilizes a three-state machine with RELAXED, ACTIVE, and RESTRICTIVE states. In this thesis, we implemented this three-state machine by adapting the message rate based on the channel busy ratio (CBR). We name this message-rate based three-state machine DCC-3. DCC-3 has the ability to control channel load; however, it has unfairness and instability problems due to the dramatic parameter changes between states. Therefore, we divided the ACTIVE state of DCC-3 into ve sub-states, and refer to this as DCC-7. We benchmarked DCC-3 against static beaconing (STB), dynamic beaconing (DynB), LInear MEssage Rate Integrated Control (LIMERIC), and DCC-7 using different evaluation metrics with different numbers of platoons. Our results from the Plexe simulator demonstrate that DCC-7 has the best performance when considering all evaluation metrics, including CBR, Inter-reception time (IRT), collisions, safe time ratio, and fairness. Furthermore, we found using transmit power control could greatly improve the performance of CBR and collision rates.
Platooning (fordonskonvojer) har potential att bli ett genombrott i öka vägkapaciteten och minska bränsleförbrukning, eftersom det tillåter en kedja av fordon att noga följa varandra på vägen. När antalet fordon ökar, kommer att plutoner följa varandra i vad som benämns multiplatooning (konvoj av fordonskonvojer). Många kooperativ intelligenta transportsystem (C-ITS) tillämpningar förlitar sig på regelbundet utbytte beacons bland fordon att förbättra traffiksäkerheten. Dock som antalet uppkopplade fordon ökar, kan nätverket bli överbelastat på grund av regelbundet utbytte beacons. Utan någon trängsel kontrollmetod, får därför säkerhet kritiska meddelanden såsom kooperativ medvetenhet meddelanden (CAMs) inte levereras i tid i höga fordon densitet scenarier. Både Europeiska institutet för telekommunikationsstandarder (ETSI) och Institute el och elektroniska tekniker (IEEE) har arbetat på olika standarder för att stödja vehicular kommunikation. ETSI definieras den decentraliserade överbelastning kontroll (DCC) mekanism som anpassar överföring parametrar (meddelande hastighet, överföra datahastighet och sändningseffekt, etc.) för att hålla kanalen belastningen under kontroll. ETSI DCC använder en tre-state maskin med RELAXED, ACTIVE och RESTRICTIVE stater. I denna avhandling har genomfört vi denna tre-state maskin genom att anpassa meddelande hastighet baserat på kanal upptagen förhållandet (CBR). Vi nämna detta meddelande-hastighet baserat tre-state machine DCC-3. DCC-3 har förmågan att kontrollera kanal belastning; Det har dock otillbörlighet och instabilitet problem på grund av de dramatiska parameterändringar mellan stater. Därför vi indelat det ACTIVE tillståndet för DCC-3 i fem undertillstånd och hänvisar till detta som DCC-7. Vi benchmarkade DCC-3 mot statiska leda (STB), dynamisk leda (DynB), linjära MEssage Rate integrerad kontroll (LIMERIC) och DCC-7 med olika utvärdering statistik med olika antal plutoner. Våra resultat från Plexe simulator visar att DCC-7 har bästa prestanda när man överväger alla utvärdering statistik, inklusive CBR, mellan receptionen tid (IRT), kollisioner, säker tid baserat och rättvisa. Vi fann dessutom använda Sändareffektstyrning kan avsevärt förbättra prestanda för CBR och kollision priser.

[ES] Para proporcionar un entorno de tráfico vial más seguro y eficiente, los sistemas ITS o Sistemas Inteligentes de Transporte representan como una solución dotada de avances tecnológicos de vanguardia. La integración de elementos de transporte como automóviles junto con elementos de infraestructura como RoadSide Units (RSUs) ubicados a lo largo de la vía de comunicación permiten ofrecer un entorno de red conectado con múltiples servicios, incluida conectividad a Internet. Esta integración se conoce con el término C-ITS o Sistemas Inteligentes de Transporte Cooperativos. La conexión de automóviles con dispositivos de infraestructura permite crear redes vehiculares conectadas (V2X) vehículo a dispositivos, que ofrecen la posibilidad de nuevos despliegues en aplicaciones C-ITS como las relacionadas con la seguridad. Hoy en día, con el uso masivo de teléfonos inteligentes y debido a su flexibilidad y movilidad, existen varios esfuerzos para integrarlos con los automóviles. De hecho, con el soporte adecuado de unidad a bordo (OBU), los teléfonos inteligentes se pueden integrar perfectamente con las redes vehiculares, permitiendo a los conductores usar sus teléfonos inteligentes como dispositivos de bordo a que participan en los servicios C-ITS, con el objeto de mejorar la seguridad al volante entre otros. Tópico este, que hoy día representa un tema relevante de investigación. Un problema a solucionar surge cuando las comunicaciones vehiculares sufren inferencias y bloqueos de la señal debidos al escenario. De hecho, el impacto de la vegetación y los edificios, ya sea en áreas urbanas y rurales, puede afectar a la calidad de la señal. Algunas estrategias para mejorar la comunicación vehicular en este tipo de entorno consiste en desplegar UAVs o vehículo aéreo no tripulado (drones), los cuales actúan como enlaces de comunicación entre vehículos. De hecho, UAV ofrece importantes ventajas de implementación, ya que tienen una gran flexibilidad en términos de movilidad, además de un rango de comunicaciones mejorado. Para evaluar la calidad de las comunicaciones, debe realizarse un conjunto de mediciones. Sin embargo, debido al costo de las implementaciones reales de UAV y automóviles, los experimentos reales podrían no ser factibles para actividades de investigación con recursos limitados. Por lo tanto, los experimentos de simulación se convierten en la opción preferida para evaluar las comunicaciones entre UAV y vehículos terrestres. Lograr modelos de propagación de señal correctos y representativos que puedan importarse a los entornos de simulación se vuelve crucial para obtener un mayor grado de realismo, especialmente para simulaciones que involucran el movimiento de UAVs en cualquier lugar del espacio 3D. En particular, la información de elevación del terreno debe tenerse en cuenta al intentar caracterizar los efectos de propagación de la señal. En esta tesis doctoral, proponemos nuevos enfoques tanto teóricos como empíricos para estudiar la integración de redes vehiculares que combinan automóviles y UAVs, así mismo el impacto del entorno en la calidad de las comunicaciones. Esta tesis presenta una aplicación, una metodología de medición en escenarios reales y un nuevo modelo de simulación, los cuales contribuyen a modelar, desarrollar e implementar servicios C-ITS. Más específicamente, proponemos un modelo de simulación que tiene en cuenta las características del terreno en 3D, para lograr resultados confiables de comunicación entre UAV y vehículos terrestres.
[CAT] Per a proporcionar un entorn de trànsit viari més segur i eficient, els sistemes ITS o Sistemes Intel·ligents de Transport representen una solució dotada d'avanços tecnològics d'avantguarda. La integració d'elements de transport com auto móvils juntament amb elements d'infraestructura com Road Side Units (RSUs) situats al llarg de lav via de comunicació permeten oferir un entorn de xarxa connectat amb multiples serveis, inclusa connectivitat a Internet. Aquesta integració es connex amb el terme C-ITS o Sistemes Intel·ligents de Transport Cooperatius , com ara els automòbils, amb elements d'infraestructura, com ara les road side units (RSU) o pals situats al llarg de la carretera, per a aconseguir un entorn de xarxa que oferisca nous serveis a més de connectivitat a Internet. Aquesta integració s'expressa amb el terme C-ITS, o sistemes intel·ligents de transport cooperatius. La connexió d'automòbils amb dispositius d'infraestructura permet crear xarxes vehiculars connectades (V2X) vehicle a dispositiu, que ofreixen la possibilitat de nous desplegaments en aplicacions C-ITS, com ara les relacionades amb la seguretat. Avui dia, amb l'ús massiu dels telèfons intel·ligents, i a causa de la flexibilitat i mobilitat que presenten, es fan esforços per integrar-los amb els automòbils. De fet, amb el suport adequat d'unitat a bord (OBU), els telèfons intel·ligents es poden integrar perfectament amb les xarxes vehiculars, permetent als conductors usar els seus telèfons intel·ligents com a dispositius per a participar en els serveis de C-ITS, a fi de millorar la seguretat al volant entre altres. Tòpic est, que hui dia representa un tema rellevant d'investigació. Un problema a solucionar sorgeix quan les comunicacions vehiculars ateixen inferències i bloquejos del senyal deguts a l'escenari. De fet, l'impacte de la vegetació i els edificis, tant en àrees urbanes com rurals, pot afectar la qualitat del senyal. Algunes estratègies de millorar la comunicació vehicular en aquest tipus d'entorn consisteix a desplegar UAVs o vehicles aeris no tripulats (drones), els quals actuen com a enllaços de comunicació entre vehicles. De fet, l'ús d'UAVs ofereix importants avantatges d'implementació, ja que tenen una gran flexibilitat en termes de mobilitat, a més d'un rang de comunicacions millorat. Per a avaluar la qualitat de les comunicacions, s'han de realitzar mesures en escenaris reals. No obstant això, a causa del cost de les implementacions i desplegaments reals d'UAV i el seu ús combinat amb vehicles, aquests experiments reals podrien no ser factibles per a activitats d'investigació amb recursos limitats. Per tant, la metodologia basada en simulació es converteixen en l'opció preferida entre els investigadors per a avaluar les comunicacions entre UAV i vehicles terrestres. Aconseguir models de propagació de senyal correctes i representatius que puguen importar-se als entorns de simulació resulta crucial per a obtenir un major grau de realisme, especialment per a simulacions que involucren el moviment d'UAV en qualsevol lloc de l'espai 3D. En particular, cal tenir en compte la informació d'elevació del terreny per a intentar caracteritzar els efectes de propagació del senyal. En aquesta tesi doctoral proposem enfocaments tant teòrics com empírics per a estudiar la integració de xarxes vehiculars que combinen automòbils i UAV, així com l'impacte de l'entorn en la qualitat de les comunicacions. Aquesta tesi presenta una aplicació, una metodología de mesurament en escenaris reals i un nou model de simulació, els quals contribueixen a modelar, desenvolupar i implementar serveis C-ITS. Més específicament, proposem un model de simulació que té en compte les característiques del terreny en 3D, per a aconseguir resultats fiables de comunicació entre UAV i vehicles terrestres.
[EN] To provide a safer road traffic environment and make it more convenient, Intelligent Transport Systems (ITSs) are proposed as a solution endowed with cutting-edge technological advances. The integration of transportation elements like cars together with infrastructure elements like Road Side Units to achieve a networking environment offers new services in addition to Internet connectivity. This integration comes under the term Cooperative Intelligent Transport System (C-ITS). Connecting cars with surrounding devices forming vehicular networks in Vehicle-to-Everything (V2X) open new deployments in C-ITS applications like safety-related ones. With the massive use of smartphones nowadays, and due to their flexibility and mobility, several efforts exist to integrate them with cars. In fact, with the right support from the vehicle's On-Board Unit (OBU), smartphones can be seamlessly integrated with vehicular networks. Hence, drivers can use their smartphones as a device to participate in C-ITS services for safety purposes, among others, which is a quite interesting research topic. A significant problem arises when vehicular communications face signal obstructions caused by the environment. In fact, the impact of vegetation and buildings, whether in urban and rural areas, can result in a lower signal quality. One way to enhance vehicular communication networks is to deploy Unmanned Aerial Vehicles (UAVs) to act as relays for communication between cars, or ground vehicles. In fact, UAVs offer important deployment advantages, as they offer great flexibility in terms of mobility, in addition to an enhanced communications range. To assess the quality of the communications, a set of measurements must take place. However, due to the cost of real deployments of UAVs and cars, real experiments might not be feasible for research activities with limited resources. Hence, simulation experiments become the preferred option to assess UAV-to- car communications. Achieving correct and representative signal propagation models that can be imported to the simulation environments becomes crucial to obtain a higher degree of realism, especially for simulations involving UAVs moving anywhere throughout the 3D space. In particular, terrain elevation information must be taken into account when attempting to characterize signal propagation effects. In this research work, we propose both theoretical and empirical approaches to study the integration of vehicular networks combining cars and UAVs, and we study the impact of the surrounding environment on the communications quality. An application, a measurement framework, and a simulation model are presented in this thesis in an effort to model, develop, and deploy C-ITS services. More specifically, we propose a simulation model that takes into account 3D terrain features to achieve reliable UAV-to-car communication results.
I want to thank the Spanish government through the Ministry of Economy and Competitiveness (MINECO) and the European Union Commission through the European Social Fund (ESF) for co-financing and granting me the fellowship to fund my studies in Spain and my research stay in Russia. In addition, I would to thank the National Institute of Informatics for granting me the internship fund and the Japanese government through the Japan Society for the Promotion of Science (JSPS) for supporting my research work in Japan.
Hadiwardoyo, SA. (2019). Modelling and Real Deployment of C-ITS by Integrating Ground Vehicles and Unmanned Aerial Vehicles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/118796
TESIS

Mestrado em Engenharia Electrónica e Telecomunicações
Os acidentes rodoviários têm um enorme impacto na sociedade, quer devido às perdas humanas daí resultantes quer devido aos custos económicos a si associados. Por todo o mundo, esta situação levou ao estudo de mecanismos que permitem aumentar a segurança nas estradas. Por exemplo, na Europa estão a ser financiados vários projectos para desenvolver estes mecanismos e a maior parte das iniciativas em curso requerem a possibilidade dos veículos comunicarem entre si e/ou com estações que se encontram fixas junto à estrada. Devido aos requisitos de mobilidade dos veículos, as tecnologias de comunicação sem fios têm um papel crucial neste tipo de aplicações. Neste sentido, esta dissertação avalia a adequação da tecnologia de comunicação sem fios WiMAX para a transmissão de serviços de segurança rodoviária e/ou outros, entre os veículos e a infraestrutura, usando para isso os mecanismos integrados de diferenciação de tráfego desta mesma tecnologia de comunicação. Especificamente, o objectivo é avaliar se estes mecanismos são apropriados para fornecer os serviços atrás mencionados tendo em conta os seus requisitos tempo-real (largura de banda, latência, variação da latência, etc.).
Road accidents have a huge impact on the society, both because of the resulting human life losses and injuries as well as because of the associated economic costs. This situation fostered the study of mechanisms for increasing road safety all over the world. In Europe, several projects are being funded to develop such mechanisms. Many of the approaches that are being pursued require the ability of the vehicles to communicate with each other and/or with fixed roadside equipments. Due to the mobility constraints, wireless technologies have a crucial role in this kind of applications. This dissertation assesses the suitability of the WiMAX wireless technology for supplying vehicle to infrastructure road safety services and others, using this communication technology integrated quality of service mechanisms that provides traffic differentiation. Specifically, the purpose is to evaluate if these mechanisms are appropriate to provide the referred services taking in account their real-time requirements (bandwidth, latency, jitter, etc.).

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV
In this paper, we present our research on using computer-vision analysis for vehicular safety applications. Our research has potential applications for both autonomous vehicles and connected vehicles. In particular, for connected vehicles, we propose three image analysis algorithms that enhance the quality of a vehicle's on-board video before inter-vehicular information exchange takes place. For autonomous vehicles, we are investigating a visual analysis scheme for collision avoidance during back up and an algorithm for automated 3D map building. These algorithms are relevant to the telemetering domain as they involve determining the relative pose between a vehicle and other vehicles on the road, or between a vehicle and its 3D driving environment, or between a vehicle and obstacles surrounding the vehicle.

IEEE 802.11p, the known standard for Vehicular Adhoc NETworks (VANETs), suffers from scalability issues and unbounded delay. In addition, the desire to use networks already in existence has created motivation for using cellular networks for vehicular applications. LTE-Advanced is one of the most promising access technologies in the wireless field, providing high data rate, low latency, and a large coverage area. Thus, LTE/LTE-A can be potential access technologies for supporting vehicular applications. Vehicular safety applications are based on broadcasting messages to neighboring vehicles. The vehicle location precision is crucial for safety applications. Thus, the freshness of the information (i.e. vehicle location) at the neighboring vehicles is very important. As LTE is an infrastructure-based network, all transmissions should pass through it. When the load of the network is high compared to the available resources, large delays may occur. The focus of this thesis is to propose solutions to make LTE suitable for vehicular safety applications. The first solution is to adapt the vehicular safety application to be suitable in LTE network. For this purpose, we propose an adaptation of the safety message generation rate. This adaptation uses a queueing model to compute the freshness of the information of vehicles at the destination, based on their message generation rates. It then adjusts the generation periods to provide a similar accuracy for all vehicles. The second approach is to modify the LTE and make it suitable for these kinds of applications. Thus, we proposed a scheduler for LTE which is suitable for vehicular safety applications. It considers the speed and location of the vehicles to allocate the resources to them for the transmission of safety messages. We also studied the message dissemination in the downlink, and proposed an efficient way to deliver the safety messages to the neighboring vehicles. Finally, we propose a scheme that uses both LTE-D2D and LTE-cellular communication for the transmission of safety messages. The centralized location information is used for Device-to-Device (D2D) pair discovery and resource allocation. The proposed scheme provides resource efficiency by enabling the reuse of the resources by vehicles. We also study the effect of the awareness range and period of updating location information at the server on resource usage and accuracy of D2D pair detection.

Doutoramento em Engenharia Electrotécnica
In the last decades the number of vehicles travelling in European road has raised significantly. Unfortunately, this brought a very high number of road accidents and consequently various injuries and fatalities. Even after the introduction of passive safety systems, such as seat belts, airbags, and some active safety systems, such as electronic brake system (ABS) and electronic stabilization (ESP), the number of accidents is still too high. Approximately eight per cent of the fatal accidents occur in motorways, in the Portuguese case, the number of fatalities has remained constant in the first decade of the 21st century. The evolution of wireless communications, along with the north-American and European policies that reserve spectrum near the 5,9GHz band for safety applications in the vehicular environment, has lead to the development of several standards. Many of these applications are based on the possibility of using a wireless communication system to warn drivers and passengers of events occurring on the road that can put at risk their own safety. Some examples of safety applications are the hard-brake warning, the wrong-way warning and the accident warning. This work aims to contribute in defining a communication protocol that guarantees the timely dissemination of safety critical events, occurring in scenarios with a high number of vehicles or in the neighbourhood of so called motorway “blackspots”, to all vehicles in the zone of interest. To ensure information integrity and user trust, the proposed system is based on the motorway infrastructure, which will validate all events reported by the vehicles with the usage of several means, such as video surveillance or other sensors. The usage of motorway infrastructure that has full motorway coverage using fixed stations also known as road side units, allows to have a global vision of the interest zone, avoiding the problems associated to networks that depend solely on vehicle to vehicle communication, generally total ad-hoc networks. By using the infrastructure, it is possible to control medium access, avoiding possible badly intended intrusions and also avoiding the phenomenon known as alarm showers or broadcast storm that occur when all vehicles want to simultaneously access the medium to warn others of a safety event. The thesis presented in this document is that it is possible to guarantee in time information about safety events, using an architecture where the road side units are coordinated among themselves, and communicate with on board units (in vehicles) that dynamically register and deregister from the system. An exhaustive and systematic state of the art of safety applications and related research projects is done, followed by a study on the available wireless communications standards that are able to support them. The set of standards IEEE802.11p and ETSI-G5 was created for this purpose and is found to be the more adequate, but care is taken to define a scenario where WAVE enabled and non-enabled vehicles can coexist. The WAVE medium access control protocol suffers from collision problems that do not guarantee a bounded delay, therefore a new protocol (V-FTT) is proposed, based on the adaptation of the Flexible Time Triggered protocol to the vehicular field. A theoretical analysis of the V-FTT applied to WAVE and ETSI-G5 is done, including quantifying a real scenario based on the A5 motorway from Lisbon to Cascais, one of the busiest Portuguese motorways. We conclude the V-FTT protocol is feasible and guarantees a bounded delay.
Nas últimas décadas tem-se assistido a um aumento do número de veículos a circular nas vias rodoviárias europeias, trazendo consigo um elevado número de acidentes e como consequência muitos feridos e vítimas mortais. Apesar da introdução de sistemas de segurança passivos, tais como cintos de segurança, airbags e de alguns sistemas de segurança activos, tais como o sistema electrónico de travagem (ABS) e o sistema electrónico de estabilidade (ESP), o número de acidentes continua a ser demasiado elevado. Aproximadamente oito por cento dos acidentes fatais na Europa ocorrem em auto-estradas, no caso Português, o número de vítimas mortais tem-se mantido constante ao longo da primeira década do século XXI. A evolução das comunicações sem fios, acompanhada de políticas europeias e norte-americanas no sentido de reservar frequências próximas dos 5,9GHz para aplicações de segurança no ambiente veicular, levou à especificação de várias normas. A maior parte destas aplicações baseiam-se na possibilidade de usar um sistema confiável de comunicação sem fios para alertar os condutores e passageiros de veículos para eventos ocorridos nas estradas que possam colocar em risco a sua segurança. Exemplos de aplicações de segurança crítica são o aviso de travagem brusca, o aviso de veículo em contra mão e o aviso de acidente na estrada. Este trabalho contribui para a definição de protocolos de comunicação capazes de garantir que a informação sobre eventos relacionados com situações de segurança crítica, que ocorram em cenários com um elevado número de veículos em zonas urbanas ou na vizinhança dos chamados “pontos negros” das auto-estradas, é disseminada com pontualidade por todos os veículos localizados na zona de interesse Por uma questão da integridade das comunicações e confiança dos condutores, o sistema proposto baseia-se na infra-estrutura do concessionário da auto-estrada, que validará os eventos reportados pelos veículos usando vários meios à sua disposição, como por exemplo sistemas de videovigilância e outros sensores. O uso de uma infra-estrutura de comunicações, que dispõe de cobertura integral a partir de estações fixas, permite uma visão global da zona coberta, evitando os problemas associados a redes baseadas apenas na comunicação entre veículos, que são em geral totalmente ad-hoc. O uso da infra-estrutura permite, entre outras vantagens, controlar o acesso ao meio, evitando simultaneamente intrusões de estranhos ao sistema e o fenómeno conhecido como “chuva de alarmes” desencadeado quando todos os veículos querem aceder simultaneamente ao meio para avisar os restantes da existência dum evento de segurança crítica. A tese apresentada neste documento defende que é possível garantir informação atempada sobre eventos que põem em risco a segurança dos veículos a partir de uma arquitectura de interligação entre as estações de comunicações fixas, coordenadas entre si, e unidades móveis (veículos) que se registam e se desligam dinamicamente do sistema. Nesta tese faz-se um levantamento exaustivo e sistemático das aplicações de segurança abordando projectos de investigação relacionados, estudam-se as tecnologias de comunicação sem fios disponíveis e a sua possibilidade de suportar aplicações de segurança rodoviária. Desta análise, conclui-se que a norma norte americana WAVE/IEEE802.11p e a europeia ETSI-G5, criadas especificamente para o efeito são as que mais se adequam à finalidade desejada. Considera-se que o cenário de utilização é evolutivo, podendo coexistirem veículos que não dispõem de sistemas de comunicação com outros que suportam a norma WAVE. Dado que o protocolo de acesso ao meio proposto pela norma WAVE não garante um acesso determinístico ao meio partilhado, propõe-se um novo protocolo, o Vehicular Flexible Time-Triggered protocol (VFTT). Faz-se a análise teórica da viabilidade do protocolo proposto para a norma WAVE e respectiva norma europeia (ETSI-G5). Quantifica-se o protocolo VFTT para um cenário real: a auto-estrada A5 Lisboa-Cascais, uma das autoestradas portuguesas mais movimentadas. Conclui-se que o protocolo é viável e garante um atraso restringido temporalmente.

The DSRC/WAVE initiative is forecast to enable a plethora of applications, classified in two broad types of safety and non-safety applications. In the former type, the reliability performance is of tremendous prominence while, in the latter case, the efficiency of information dissemination is the key driving factor. For safety applications, we adopt a systematic approach to analytically investigate the reliability of the communication system in a symbiotic relationship with the host system comprising a vehicular traffic system and radio propagation environment. To this aim, the¬ interference factor is identified as the central element of the symbiotic relationship. Our approach to the investigation of interference and its impacts on the communication reliability departs from previous studies by the degree of realism incorporated in the host system model. In one dimension, realistic traffic models are developed to describe the vehicular traffic behaviour. In a second dimension, a realistic radio propagation model is employed to capture the unique signal propagation aspects of the host system. We address the case of non-safety applications by proposing a generic framework as a capstone architecture for the development of new applications and the efficiency evaluation of existing ones. This framework, while being independent from networking technology, enables accurate characterization of the various information dissemination tasks that a node performs in cooperation with others. As the central element of the framework, we propose a game theoretic model to describe the interaction of meeting nodes aiming to exchange information of mutual or social interests. An adaptive mechanism is designed to enable a mobile node to measure the social significance of various information topics, which is then used by the node to prioritize the forwarding of information objects.

The use of power electronics in the electrical propulsion systems leads to the optimal and efficient utilization of the traction motors and the energy sources (batteries and/or fuel cells) through the recourse to suitable power converters and their proper control. Power electronics is also used for implementing the multiple conversions of the energy delivered by the sources to feed the various loads, most of them requiring different waveforms of voltage (ac or dc) and/or different levels of voltage. This work focuses on the solutions aimed at improving the efficiency of power converters for vehicular applications, which is of great importance because of the limited amount of energy that can be stored in the electric vehicles. The study takes into consideration both the traction applications and the battery charging applications whether it is done by conductive means or by wireless power transfer (WPT) systems. The improvement in traction drive efficiency results in an increment of the drivetrain efficiency of the vehicle, leading to an extension in the driving range, while the employment of efficient power converters is required to charge batteries with increasingly large capacity. The losses of power devices are even more significant when they operate at high frequencies to compact the size of the filter elements and/or the transformers. The losses of power devices can be minimized by making the commutation soft or by replacing the conventional devices with the new generation devices based on wide bandgap (WBG) semiconductor materials. In this work, the properties of the WBG semiconductor materials are illustrated and the operation of the devices based on these materials are analyzed to grasp better their characteristics and performance. The losses of individual devices (i.e. diode, IGBT, MOSFET) as well as the operation of power converters for various applications are examined in detail. To evaluate the performance of the SiC devices in electric vehicle applications, an AC traction drive for the propulsion of a typical compact C-class electric car has been considered. Two versions of the inverter have been investigated, one built up with conventional Si IGBTs and the other one with SiC MOSFETs, and the losses in the semiconductor devices of the two versions have been found along the standard New European Driving Cycle (NEDC). By comparing the results, it is emerged that the usage of the SiC MOSFETs reduces the losses in the traction inverter of about 5%, yielding an equal increase in the car range. To complete the study, calculation of the efficiency has been extended to the whole traction drive, including the traction motor and the gear. Afterwards, a power factor correction (PFC) circuit, which is commonly used to mitigate the distortion in line current, has been studied. The study is started by considering the basic and the interleaved PFC configurations and by defining their circuit parameters. After selecting the interleaved configuration, the magnitude of voltages and currents in the PFC rectifier has been determined and the values obtained have been verified by a power circuit simulation software. The digital signal processing (DSP) has been also studied as it is used for the control operation of the PFC. At last, a prototype of PFC rectifier with interleaved configuration is designed. The design process and the specification of the components are described in brief. A prototype of synchronous rectifier (SR) is designed for the output stage of a WPT system. With respect to conventional rectifiers, in SRs the diodes are replaced by MOSFETs with their antiparallel diodes. MOSFETs are bidirectional devices that conduct with a low voltage drop. During the dead time, the diodes in antiparallel to the MOSFETs are conducting. At the end of dead-time, signals are applied at the MOSFET gates that make conducting all along the remaining period, thus reducing the conduction losses. The dead-time length is optimized by using fast switching devices based on SiC semiconductor materials. The prototype is designed and tested at the line frequency. The experimental results obtained from the prototype corroborate both the analytical results and the simulation results. As SR exhibits is working with high efficiency at the line frequency, it is expected that at the higher operating frequencies of the WPT systems, the performance of SR will be even better. A DC-DC isolated power converters used to setup the battery charger through wire system are studied. Two topologies of DC-DC converters, i.e. Dual Active Bridge (DAB) and Single Active Bridge (SAB) converters, are considered. For both the topologies operation are described at steady state. For SAB converter, two possible modes of operation are examined: discontinuous current conduction (DCM) and continuous current conduction (CCM). Soft-switching operation of both SAB and DAB converters, obtained by the insertion of auxiliary capacitors, is analyzed. Moreover, the soft-switching operating zone for the two converters are found as a function of the their output voltages and currents. Finally, the comparative analysis of soft-switching operation of SAB versus DAB converter is presented. The thesis work has been carried out at the Laboratory of “Electric Systems for Automation and Automotive” headed by Prof. Giuseppe Buja. The laboratory belongs to the Department of Industrial Engineering of the University of Padova, Italy.
L’utilizzo dell’elettronica di potenza nei sistemi di propulsione elettrica porta all'utilizzo ottimale ed efficiente dei motori di trazione e delle sorgenti di energia (batterie e/o celle a combustibile) attraverso il ricorso a convertitori statici e al loro controllo. L’elettronica di potenza è utilizzata anche per implementare più conversioni dell’energia fornita dalle sorgenti per alimentare i vari carichi, la maggior parte delle quali richiede forme d'onda di tensione diverse (AC o DC) e/o diversi livelli di tensione. Questo elaborato si concentra sulle soluzioni volte a migliorare l'efficienza dei convertitori di potenza per applicazioni veicolari, tema che è di grande interesse per la limitata quantità di energia accumulabile a bordo. Sono prese in considerazione sia le applicazioni di trazione che le applicazioni di ricarica degli accumulatori realizzate con mezzi conduttivi o con i sistemi di trasferimento di potenza senza fili (WPT). Il miglioramento dell’efficienza degli azionamenti di trazione produce un incremento dell'efficienza dell’intero powertrain del veicolo, che si traduce in un incremento dell’autonomia del veicolo, mentre l’impiego di convertitori di potenza efficienti si rende necessario per la ricarica di batterie con capacità sempre maggiori. Le perdite dei dispositivi di potenza sono ancora più significative quando operano ad alte frequenze di lavoro per compattare le dimensioni degli elementi filtranti e/o dei trasformatori. Le perdite nei dispositivi di potenza possono essere minimizzate rendendo la commutazione soft o sostituendo i dispositivi convenzionali con i dispositivi di nuova generazione basati su materiali semiconduttori con ampia banda proibita (WBG). Nell’elaborato, sono illustrate le proprietà dei materiali semiconduttori WBG e si analizza il funzionamento dei dispositivi basati su questi materiali per comprendere le loro caratteristiche e prestazioni. Le perdite di singoli dispositivi (come diodi, IGBT, MOSFET) nonché il funzionamento di convertitori di potenza per varie applicazioni sono esaminati in dettaglio. Per valutare le prestazioni dei dispositivi SiC quando vengano impiegati nei veicoli elettrici, è preso in esame un azionamento di trazione in AC impiegato per la propulsione di una tipica automobile elettrica di classe C. Due versioni di invertitore sono esaminate, una costruita con convenzionali Si IGBT e l'altra con MOSFET SiC, ed è calcolata la potenza persa nei dispositivi a semiconduttore delle due versioni di invertitore mentre l’automobile percorre il ciclo normalizzato di guida europeo (NEDC). Dal confronto dei risultati è emerso che l'utilizzo dei MOSFET SiC riduce le perdite nel convertitore di trazione di circa 5%, ottenendo un uguale incremento dell’autonomia dell’automobile. Per completare lo studio, si è successivamente esteso il calcolo dell’efficienza all’intero azionamento di trazione, comprendente il motore e il riduttore. Si è quindi studiato un raddrizzatore con circuito di correzione del fattore di potenza (PFC), utilizzato per ridurre la distorsione di corrente in linea. Lo studio è iniziato considerando sia la configurazione di base che quella interleaved e individuando i parametri circuitali. Dopo aver scelto la configurazione interleaved, sono determinate le ampiezze delle tensioni e delle correnti presenti nel raddrizzatore PFC e i valori ottenuti sono verificati mediante un software di simulazione di circuiti di potenza. E’ anche studiato un dispositivo per l'elaborazione digitale dei segnali (DSP) nel quale implementare il controllo del raddrizzatore PFC. Infine è progettato un prototipo di raddrizzatore PFC con configurazione interleaved. Il processo di progettazione e le specifiche dei componenti sono brevemente descritti. Un prototipo di rettificatore sincrono (SR) è stato sviluppato per lo stadio di uscita di un sistema WPT. In confronto con i raddrizzatori convenzionali, in un SR i diodi sono sostituiti da MOSFET con diodi in antiparallelo. I MOSFET sono dispositivi bidirezionali caratterizzati da una bassa caduta di tensione e dalla direzionalità nel condurre la corrente. Durante il tempo morto, entrano in conduzione i diodi in antiparallelo ai MOSFET. Al termine del tempo morto, ai MOSFET sono applicati segnali di comando che li portano in conduzione per tutta la restante parte del semiperiodo, riducendo così le perdite di conduzione. La durata del tempo morto è ottimizzata utilizzando dispositivi di commutazione veloci basati su materiali semiconduttori SiC. Il prototipo è stato progettato e sperimentato alla frequenza di rete. I risultati sperimentali ottenuti hanno confermato sia i risultati analitici che le simulazioni. L’elevato valore di efficienza ottenuto sul prototipo operante alla frequenza di rete fanno prevedere che il suo impiego alle alte frequenze operative dei sistemi WPT possa dare risultati ancora migliori. Si sono studiati i convertitori isolati di potenza DC-DC impiegati nei caricabatteria di tipo conduttivo per veicoli elettrici. Si sono prese in considerazione due topologie di convertitori DC-DC, il convertitore con doppio ponte attivo (DAB) e quello con un unico ponte attivo (SAB). Per entrambe le topologie è analizzato il funzionamento in condizioni di regime. Per il convertitore SAB sono esaminate due possibili modalità di funzionamento: conduzione discontinua di corrente (DCM) e conduzione di corrente continua (CCM). Si è analizzato il funzionamento in soft-switching, ottenuto con l’inserzione di condensatori ausiliari, sia del convertitore SAB che di quello DAB. E’ individuata la zona di funzionamento in soft-switching per i due convertitori in funzione delle tensioni e delle correnti di uscita. Infine, è stata eseguita un’analisi comparativa del funzionamento in soft-switching dei due convertitori. Il lavoro di tesi è stato realizzato presso il Laboratorio di "Sistemi Elettrici per l'Automazione e Automotive" diretto dal Prof. Giuseppe Buja. Il laboratorio fa parte del Dipartimento di Ingegneria Industriale dell'Università degli Studi di Padova, Italia.

Nowadays emissions and fuel efficiency are crucial performance indicators for any vehicle. The diminishing oil resources along with climate changes are pushing car makers towards more ecofriendly solutions. Hybrid electric vehicles seem to be a necessary step towards zero-emissions cars. The contribution of this dissertation focuses on the analysis and the energy management of hybrid energy storage systems, consisting of a battelY and a supercapacitor, for hybrid electric vehicles and electric vehicles. This PhD is funded as part of the European FP7 project AUTOSUPERCAP, which aims to develop high energy and high power density supercapacitors for vehicle applications. Therefore, the objective of this PhD is the assessment of the potential benefit deriving from the adoption of hybrid energy storage systems, rather than the conventional solution based on battery only. This target is achieved through a series of modelling, simulation and validation activities, based on different case study vehicle applications (e.g. micro-hybrid electric vehicle, through-the-road parallel hybrid electric vehicles, parallel hybrid electric vehicles and fully electric vehicles). In parallel, different novel algorithms for the power split within hybrid energy storage systems are investigated. The results of this work show that the adoption of a supen;:apacitor stack within a hybrid energy storage system is very promising in te1111S of reduction of battery CUlTent and extension of the battery life. In patticular, the simulated results, over a selection of driving cycles, indicate a reduction of the root mean square and peak value of the battery Current by respectively 77% and 93% for a parallel-through-the road hybrid electric vehicle when compared to the battery only case. These results are achieved with the adoption of a control strategy based on the optimal control theory. Moreover, the hybrid storage pack can be optimally designed, which means that the size (i.e. weight) of the system can be reduced. This, together with the higher power density of supercapacitors, can be beneficial in ten11S of energy efficiency. A 3% of fuel savings are achieved when the hybrid energy storage system is adopted within a novel parallel hybrid electric vehicle.

Vehicular communications systems may one day save lives, reduce fuel consumption, and advance connectivity, but they may also transmit information which could be deanonymized to obtain personal information. Vehicle location data are of special concern because they could be used maliciously. This dissertation presents a systematic study resulting in novel definitions, metrics and methods for evaluating and applying location privacy preserving protocols specifically in vehicular settings.

Previous work in vehicular network privacy has not thoroughly considered vehicular mobility patterns. Previous work in vehicular network privacy has not solved the problem of collusion between MAC layer and application layer attackers. As defenses against location privacy attacks, previous work has favored the privacy methods of anonymization and obfuscation, but these methods have weaknesses. Spatial-temporal cloaking, for example, requires overhead of trusted third parties, and provides little protection in low vehicle densities especially when applications require frequent precise location data. Little published work has addressed the "location" part of location privacy, the geographical distance of location privacy, focusing instead on the size of the anonymity set. The need for new metrics is indicated.

The present research addresses these issues. In addition to new definitions and metrics, this study develops privacy methods which would (1) accommodate vehicular mobility patterns, (2) defend against collusion by MAC and application layer attackers, (3) produce privacy solutions which depend on cooperation neither by large numbers of other motorists nor by trusted third parties, and (4) function in low vehicle densities, notably during the transition period between system initialization and full saturation, (5) provide protection even when applications require frequent and precise location queries, and (6) provide protection over a geographical range beyond a vehicle's wireless communications range and provide protection over measurable and lengthy spans of time. Finally, it presents a new metric for measuring privacy (KDT), an equation to estimate the safety impact of privacy protocols (SSTE), and three new privacy models, Endpoint Protection Zones (EPZ), Privacy by Decoy (PBD) and Random Rotation of Vehicular Trajectory (RRVT).

One of the main challenges in order to make electric cars competitive with gas-powered cars is in the improvement of the electric power system. Although many of the energy sources currently used in electric vehicles have sufficientlyhigh specific energy, their applicability is limited due to low specific power. It would therefore be advantageous to create a driveline with the main energy storage separated from a smaller energy buffer, designed to have high power capabilities and to withstand frequent and deep discharge cycles. It has been found that rotating kinetic energy storage in flywheels is very well suited for this type of application. A composite shell, comprising an inner part made of glassfiber and an outer part made of carbonfiber, was analyzed analytically and numerically, designed, and constructed. The shell was fitted onto a metallic rotor using shrinkfitting. The cost of the shell, and the complexity of assembly, was reduced by winding the glass- and carbonfiber consecutively on a mandrel, and curing the complete assembly simultaneously. Thereby, the shell obtained an internal segmentation, without the need for fitting several concentric parts onto each other. The radial stress inside the composite shell was kept compressive thanks to a novel approach of using the permanent magnets of the integrated electric machine to provide radial mechanical load during rotation. Two thrust bearing units (one upper and one lower) comprising one segmented unit with the permanent magnets in a cylindrical Halbach configuration and one non-segmented unit in a up/down configuration were optimized, constructed and tested. Each thrust bearing unit generated 1040 N of repelling force, and a positive axial stiffness of 169 N/mm at the nominal airgap of 5 mm.  Two radial active magnetic bearings (one upper and one lower) were optimized, constructed and tested. By parameterizing the shape of the actuators, a numerical optimization of force over resistive loss from the bias currentcould be performed. The optimized shape of the electromagnets was produced by watercutting sheets of laminated steel. A maximum current stiffness of120 N/A at a bias current of 1.5 A was achieved.

A web app was developed which allows any internet-connected device to remotely monitor a roadway intersection’s state over HTTP. A mapping simulation was enhanced to allow researchers to retroactively track the location and the ad-hoc connectivity of vehicle clusters. A performance analysis was conducted on the utilized network partitioning algorithm. This work was completed under and for the utility of ETSU’s Vehicular Networking Lab. It can serve as a basis for further development in the field of wireless automobile connectivity.

Les réseaux ad hoc de véhicules accueillent une multitude d’applications intéressantes. Parmi celles-ci, les applications d’info-divertissement visent à améliorer l’expérience des passagers. Ces applications ont des exigences rigides en termes de délai de livraison et de débit. De nombreuses approches ont été proposées pour assurer la qualité du service des dites applications. Elles sont réparties en deux couches : réseau et contrôle d’accès. Toutefois, ces méthodes présentent plusieurs lacunes. Cette thèse a trois volets. Le premier aborde la question du routage dans le milieu urbain. A cet égard, un nouveau protocole, appelé SCRP, a été proposé. Il exploite l’information sur la circulation des véhicules en temps réel pour créer des épines dorsales sur les routes et les connecter aux intersections à l’aide des nœuds de pont. Ces derniers collectent des informations concernant la connectivité et le délai, utilisées pour choisir les chemins de routage ayant un délai de bout-en-bout faible. Le deuxième s’attaque au problème d’affectation des canaux de services afin d’augmenter le débit. A cet effet, un nouveau mécanisme, appelé ASSCH, a été conçu. ASSCH collecte des informations sur les canaux en temps réel et les donne à un modèle stochastique afin de prédire leurs états dans l’avenir. Les canaux les moins encombrés sont sélectionnés pour être utilisés. Le dernier volet vise à proposer un modèle analytique pour examiner la performance du mécanisme EDCA de la norme IEEE 802.11p. Ce modèle tient en compte plusieurs facteurs, dont l’opportunité de transmission, non exploitée dans IEEE 802.11p.
The fact that vehicular ad hoc network accommodates two types of communications, Vehicle-to-Vehicle and Vehicle-to-Infrastructure, has opened the door for a plethora of interesting applications to thrive. Some of these applications, known as infotainment applications, focus on enhancing the passengers' experience. They have rigid requirements in terms of delivery delay and throughput. Numerous approaches have been proposed, at medium access control and routing layers, to enhance the quality of service of such applications. However, existing schemes have several shortcomings. Subsequently, the design of new and efficient approaches is vital for the proper functioning of infotainment applications. This work proposes three schemes. The first is a novel routing protocol, labeled SCRP. It leverages real-time vehicular traffic information to create backbones over road segments and connect them at intersections using bridge nodes. These nodes are responsible for collecting connectivity and delay information, which are used to select routing paths with low end-to-end delay. The second is an altruistic service channel selection scheme, labeled ASSCH. It first collects real-time service channels information and feeds it to a stochastic model that predicts the state of these channels in the near future. The least congested channels are then selected to be used. The third is an analytical model for the performance of the IEEE 802.11p Enhanced Distributed Channel Access mechanism that considers various factors, including the transmission opportunity (TXOP), unexploited by IEEE 802.11p.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 183-187).
This thesis presents an investigation of the effects of Ported Shroud (PS) self-recirculating casing treatment used in turbocharger centrifugal compressors for increasing the operable range. Computed results, assessed with experimental measurements on ported and non-ported variants of a representative turbocharger compressor, are used to determine the impact of the PS on the flow field and hence performance. It is shown that the main flow path perceives the PS flow as a combination of flow actuations that include injection and removal of mass flow, and injection of axial momentum and tangential momentum. A computational model in which the presence of the PS is replaced by imposed boundary conditions that reflect the individual flow actuations has thus been formulated and implemented. The removal of a fraction of the inducer mass flow was determined to be the dominant flow actuation in setting the performance of PS compressors. Mass flow removal reduces the flow blockage associated with the impeller tip leakage flow and increases the diffusion in the main flow path. Adding swirl to the injected flow in the direction opposite of the wheel rotation results in an increase of the stagnation pressure ratio and a decrease of the efficiency. The loss generation in the flow path has been defined to rationalize efficiency changes associated with PS operation.
by George Alexander Christou.
Ph. D.

[ES] Una de las áreas de investigación que está recibiendo más atención recientemente es la de vehículos autónomos. Los investigadores están en este momento centrados en el tercer de los cinco niveles de autonomía, los cuales son: asistencia en la conducción, automatización parcial, automatización condicional, alta automatización y automatización completa. A pesar de los rápidos progresos que están habiendo en este campo, la adopción de estas soluciones llevará tiempo no sólo debido a cuestiones legales, sino también por el hecho de que los avances tecnológicos se enfrentan a un lento respaldo por parte de los fabricantes. Además, la baja tasa de renovación de vehículos de carretera, dificulta el despliegue de tecnologías innovadoras, como es el caso de la red vehicular. Ocho años después de la introducción de la norma 802.11p para la comunicación vehicular del Instituto de Ingenieros Eléctricos y Electrónicos (IIEE), los vehículos que se usan a diario todavía carecen de la capacidad de comunicarse entre sí. Este hecho impide el uso de las muchas aplicaciones de seguridad del Sistema de Inteligencia de Transporte (SIT) que aprovecha la red vehicular para el intercambio de datos. La forma obvia de manejar este problema es poner las tecnologías disponibles a la disposición de los usuarios comunes para desarrollar soluciones que se puedan implementar fácilmente y, además, económicas. Por esta razón, trasladamos nuestra atención a los dispositivos inteligentes, especialmente a los teléfonos inteligentes, los cuales han recorrido un largo camino desde la primera introducción de teléfonos móviles a finales del siglo XX. Hoy en día casi todos llevan uno en su bolsillo a donde sea que vayan, permitiéndoles no sólo hacer llamadas, sino también medir y controlar diferentes parámetros con la ayuda de los muchos sensores integrados que están disponibles para estos dispositivos compactos pero potentes. Nuestro objetivo es estudiar los efectos de la integración de los teléfonos inteligentes a la red vehicular para desarrollar aplicaciones de seguridad del SIT. La elección de los teléfonos inteligentes aquí no solo está justificada por su amplia disponibilidad y uso, sino también porque están evolucionando hacia terminales de alto rendimiento con microprocesadores de múltiples núcleos cargados dotados de un grupo suficientemente diverso de sensores. En esta tesis proponemos tres diferentes aplicaciones de seguridad SIT para teléfonos inteligentes, diseñados para aprovechar el entorno de red vehicular: una aplicación de generación de advertencia llamada Messiah que alerta a los conductores de la presencia de vehículos de emergencia en las cercanías; una aplicación de Advertencia de Colisión Frontal (ACF) que advierte a los conductores si no se mantiene la distancia de seguridad mínima entre el vehículo que va delante y el que lo sigue; y, por último, una aplicación que tiene como objetivo ayudar a los conductores con asistencia visual durante el adelantamiento, llamada EYES. Todas estas aplicaciones han sido desarrolladas para la plataforma Android, y dependen de la transmisión de datos entre vehículos. Dado que los vehículos que utilizamos día a día no admiten la posibilidad de comunicarse entre sí, también diseñamos GRCBox, que es una unidad integrada de bajo coste que permite la comunicación del Vehículo a Todo (V2X). A partir de nuestro estudio de aplicaciones para dispositivos móviles diseñados para redes vehiculares, descubrimos que el uso de teléfonos inteligentes proporciona una nueva dirección para la investigación relacionada con SIT y redes vehiculares al permitir la adopción rápida de las soluciones existentes, donde los usuarios pueden descargar y usar las aplicaciones con sólo un clic a un botón. Al mismo tiempo, la portabilidad y compacidad de los dispositivos los hace limitados en términos de velocidad, potencia de procesamiento y precisi
[CAT] Una de les àrees d'investigació que està rebent més atenció recentment és la de vehicles autònoms. Els investigadores estan en este moment centrats en el tercer dels cinc nivells d'autonomia, els quals són: assistència en la conducció, automatització parcial, automatització condicional, alta automatització i automatització completa. Malgrat els ràpids progressos que s'estan donant en este camp, l'adopció d'estes solucions portarà temps no sols degut a qüestions legals, sinó també pel fet que els avanços tecnològics s'enfronten a un lent recolzament per part dels fabricants. A més a més, la baixa taxa de renovació de vehicles de carretera, dificulta el desplegament de tecnologies innovadores com és el cas de la xarxa vehicular. Huit anys després de la introducció de la norma 802.11p per a la comunicació vehicular de l'Institut d'Enginyers Elèctrics i Electrònics (IEEE), els vehicles que s'utilitzen a diari encara manquen de la capacitat de comunicar-se entre sí. Este fet impedeix l'ús de les moltes aplicacions de seguretat del Sistema d'Intel·ligència de Transport (SIT) que aprofita la xarxa vehicular per a l'intercanvi de dades. La forma òbvia de tractar aquest problema és posar les tecnologies disponibles a la disposició dels usuaris comuns per a desenvolupar solucions que es puguen implementar fàcilment, còmodes d'adoptar i, a més a més, econòmiques. Per aquesta raó, traslladem la nostra atenció als dispositius intel·ligents, especialment als telèfons intel·ligents, els quals han recorregut un llarg camí des de la primera introducció de telèfons mòbils a finals del segle XX. Hui en dia quasi tots porten un en la butxaca on siga que vagen, permetent-los no sols fer cridades, sinó també mesurar i controlar diferents paràmetres amb l'ajuda dels molts sensors integrats que estan disponibles per a estos dispositius compactes però potents. El nostre objectiu és estudiar els efectes de la integració dels telèfons intel·ligents a la xarxa vehicular per a desenvolupar aplicacions de seguretat del SIT. L'elecció dels telèfons intel·ligents ací no està sols justificada per la seua àmplia disponibilitat i ús, sinó també perquè estan evolucionant cap a terminals d'alt rendiment amb microprocessadors de múltiples nuclis dotats amb un grup suficientment divers de sensors. En esta tesi proposem tres diferents aplicacions de seguretat SIT per a telèfons intel·ligents, dissenyats per a aprofitar l'entorn de xarxa vehicular: una aplicació de generació d'advertència anomenada Messiah que alerta els conductors de la presència de vehicles d'emergència en les proximitats; una aplicació Advertència de Col·lisió Frontal (ACF) que adverteix els conductors si no mantenen la distància de seguretat mínima entre el vehicle que va davant i el que el segueix; i, per últim, una aplicació que té com objectiu ajudar els conductors amb assistència visual durant l'avançament, anomenat EYES. Totes aquestes aplicacions han sigut desenvolupades per a la plataforma Android, i depenen de la transmissió de dades entre vehicles. Donat que els vehicles que utilitzem a diari no admeten la possibilitat de comunicar-se entre sí, també dissenyem GRCBox, que és una unitat integrada de baix cost que permet la comunicació de Vechicle a Tot (V2X). A partir del nostre estudi d'aplicacions per a dispositius mòbils dissenyats per a xarxes vehiculars, descobrim que l'ús de telèfons intel·ligents proporciona una nova direcció per a la investigació relacionada amb SIT i xarxes vehiculars al permetre l'adopció ràpida de les solucions existents, on els usuaris poden descarregar i utilitzar les aplicacions amb un sol clic a un botó. Però al mateix temps, la portabilitat i la compacitat dels dispositius els fa limitats en termes de velocitat, potència de processament i precisió del sensor integrat, cosa que afecta al rendiment de les aplicacions.
[EN] One of the research areas that is receiving a lot of attention recently is autonomous vehicles. Researchers are currently focused on the third level of autonomy out of the five levels, which are: drive assistance, partial automation, conditional automation, high automation, and full automation. Even though rapid progress is being made in this field, the adoption of these solutions will take time not only due to legal issues, but also due to the fact that technological improvements face slow endorsement by manufacturers. Also, the slow renewal rate of vehicles on road hinders the deployment of novel technologies, as is the case of Vehicular Networks (VNs). Eight years after the introduction of the IEEE 802.11p standard for vehicular communication, vehicles used on a daily basis still lack the capability of communicating with one other. This fact impedes the use of the many ITS safety applications that take advantage of VNs for data exchange. The obvious way to handle this problem is to use the available technologies at the disposal of common users to develop solutions that are easily deployable, effortless to adopt, and moreover, cost effective. For this reason we shift our attention to smart devices, specially smartphones, which have come a long way since the first introduction of mobile phones in the late 20th century. Nowadays, nearly everyone carries one in their pocket anywhere they go, allowing them to not only make calls, but also to measure and monitor different parameters with the help of the many on-board sensors that are available to these compact yet powerful devices. Our objective is to study the effects of integrating smartphones to vehicular networks, to develop ITS safety applications. The choice of smartphones here is not only justified by their wide availability and use, but also because they are evolving towards high performance terminals with multi-core microprocessors packed with a sufficiently diverse group of sensors. In this thesis we propose three different ITS safety applications for smartphones, designed to take advantage of the vehicular network environment: a warning generation application called Messiah that alerts drivers of the presence of emergency vehicles in close proximity; a FCW application which warns drivers if a minimum safe distance is not maintained between the vehicle ahead and the one following it; and lastly an application that aims to aid drivers with visual assistance while overtaking, named EYES. All these applications have been developed for the Android platform, and are dependent on the data transmission among vehicles. Since vehicles we use on a day to day basis still do not accommodate the possibility to communicate with one another, we also designed the GRCBox, which is a low cost on-board unit that supports V2X communication. From our study of applications for mobile devices designed for VNs, we found that the use of smartphones provides a new direction to research related to ITS and VNs by allowing a quick adoption of the existing solutions, where users are able to download and use applications just by one click of a button. But at the same time, the portability and compactness of the devices makes them limited in terms of speed, processing power, and accuracy of the on-board sensor, thus affecting the performance of the applications. In our case, the simpler Messiah application performed very well, while the EYES application that is dependent on GPS data, and the FCW application which required heavy processing and use of the camera due to its dependence on plate recognition, were affected by the hardware limitations of the smartphones.
Patra, S. (2019). Development and evaluation of smartphone-based ITS applications for vehicular networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124058
TESIS

This thesis collects some of the work accomplished during the PhD research activity focused on the study of special electric machines for vehicle traction applications. The work is divided into due parts. The rst part is mainly technological and covers some studies and experimental activities concerning new technical solutions to solve some common issues in operation of electric motors for automotive use, namely ux weakening and cogging torque. The second part has a more theoretical nature and focuses on some methods for electric machine modeling and analysis which has been developed to facilitate the study and design optimizations carried out during the PhD research work. The chapters in the rst part address the following topics: 1. Development and testing of an interior-permanent-magnet motor prototype fully conceived, designed and manufactured at the University of Trieste to implement a new concept of flux weakening system at high speeds. The concept has been also protected through a pending patent. 2. Multi-objective design optimization of an interior permanent magnet reluctance-assisted synchronous motor for the automotive industry. The design optimization was meant to support an industrial development project which is still in progress so no prototype has been built yet. 3. Study of a new optimized magnetic wedge design capable of reducing cogging torque in automotive propulsion motors having open stator slots. The second part proposes some analytical and numerical results that have been worked out to approach the modeling and optimization of various kinds of permanent magnet synchronous motors. The main problem to which these chapters try to answer is to nd suciently fast but accurate methods for permanent magnet analysis without time-consuming finite-element transient analysis. The proposed methods have been successfully integrated into design optimization programs used in the industrial environment in the development of innovative electric machines not only for the automotive industry.
Questa tesi contiene alcuni dei temi riguardanti le macchine elettriche per trazione veicolare che si sono arontati durante i tre anni di dottorato di ricerca. Il lavoro è suddiviso in due parti. La prima parte si concentra su aspetti tecnologici e riguarda alcuni studi ed attività sperimentali che vanno a risolvere alcune problematiche comuni delle macchine elettriche per trazione, in particolare il deflussaggio e le pulsazioni di coppia. La seconda parte, invece risulta essere più teorica e si concentra su alcuni metodi matematici di modellizzazione ed analisi sviluppati per facilitare la progettazione e lo studio delle macchine elettriche che si è portato avanti durante il periodo di dottorato. I capitoli della prima parte sono così suddivisi: 1. Sviluppo e sperimentazione di un motore a magneti permanenti prototipale; interamente concepito, progettato e realizzato presso l'Università degli Studi di Trieste; in cui un nuovo metodo di deflussagio per alte velocità è stato implementato. Inoltre tale tecnologia è stata assoggettata a brevetto. 2. Ottimizzazione multi obiettivo di un motore sincrono a magneti permanenti a riluttanza assistita per applicazioni nell'industria automobilistica. L'ottimizzazione aveva lo scopo di supportare un progetto industrale portato avanti da un nostro partner ed ancora in atto, di conseguenza nessun prototipo è ancora stato realizzato. 3. Studio e ottimizzazione di una bietta magnetica per motori con statore a cave aperte, in grado di ridurre la pulsazione di coppia. La seconda parte propone dei metodi di analisi numerica delle macchine elettriche sviluppati per modellizzare ed analizzare diversi tipi di macchine a magneti permanenti. La principale criticità alla quale questi capitoli tentano di dare soluzione è quello di trovare dei metodi di analisi delle macchine a magneti permanenti accurati, senza dover ricorrere a simulazioni transitorie agli elementi niti, che come è noto sono molto dispendiose in termini di tempo.

Le parking intelligent, permettant aux conducteurs d'accéder aux informations de stationnement sur leurs appareils mobiles, réduit les difficultés des usagers. Tout d'abord, nous mettons en lumière la manière de recueillir les informations de parking en introduisant une architecture de réseaux de capteurs multi-saut, et les modèles d'intensité applicative en examinant la probabilité d'arrivées et de départs de véhicules. Puis nous étudions la stratégie de déploiement des réseaux de capteurs et définissons un problème multi-objectifs, puis nous le résolvons sur deux cartes de parking réelles. Ensuite, nous définissons un service Publish-Subscribe pour fournir aux conducteurs des informations pertinentes. Nous illustrons le système dans des réseaux véhiculaires et mobiles et soulignons l'importance du contenu et du contexte du message au conducteur. Afin d'évaluer la résilience du système, nous proposons un modèle Publish-Subscribe étendu et nous l'évaluons dans différentes circonstances imprévues. Notre travail est basé sur la prémisse que les capteurs de parking sont déployés à une grande échelle dans la ville. Nous considérons une vue d'ensemble des services urbains du point de vue de la municipalité. Ainsi, nous faisons la lumière sur deux thèmes principaux: la collecte d'informations sur le déploiement de capteurs et un modèle étendu de Publish-Subscribe. Notre travail donne un guide avant de démarrer un projet de parking intelligent ou tout service urbain similaire en temps réel. Il fournit également une plate-forme d'évaluation valable pour tester des jeux de données plus réalistes, comme des traces de véhicules ou de trafic réseau
Smart parking, allowing drivers to access parking information through their smart-phone, is proposed to ease drivers' pain. We first spotlight the manner to collect parking information by introducing the multi-hop sensor network architecture, and how the network is formed. We then introduce the traffic intensity models by looking at the vehicle's arrival and departure probabilities, following the heavy-tailed distribution. We study the deployment strategy of wireless on-street parking sensor layouts. We define a multiple-objective problem and solve it with two real street parking maps. In turn, we present a Publish-Subscribe service system to provide good parking information to drivers. We illustrate the system with a vehicular network and point out the importance of content and context of a driver’s message. To evaluate the resilience, we propose an extended Publish-Subscribe model, and evaluate it under different unforeseen circumstances. Our work is based on the premise that large-scale parking sensors are deployed in the city. We look at the whole picture of urban service from viewpoint of the municipality. As such, we shed light on two main topics: the information collection on sensor deployment and an extended version of Publish-Subscribe messaging paradigm. Our work gives a guideline from network-related perspectives for city before launching a smart parking or any similar real-time urban service. It also provides a meaningful evaluation platform for testing more realistic datasets, such as real vehicle traces or network traffic

Intelligent Transport Systems (ITS) are aiming to provide innovative services related to different modes of transport and traffic management, and enable various users to be better informed and make safer, more coordinated and smarter use of transport networks. Cooperative-ITS (C-ITS) support connectivity between vehicles, vehicles and roadside infrastructure, traffic signals as well as with other road users. In order to enable vehicular communications European Telecommunication Standards Institute (ETSI) delivered ITS-G5 – a of set of C-ITS standards. Considering the goals of C-ITS, inter-vehicle communications should be reliable and efficient. The subject of this thesis is evaluation of the performance, efficiency, and depend- ability of ITS-G5 communications for cooperative driving applications support. This thesis includes eight scientific papers and extends the research area in three directions: evaluation of the performance of ITS-G5 beaconing protocols; studying the performance of ITS-G5 congestion control mechanisms; and studying the radio jamming Denial-of- Service (DoS) attacks and their detection methods. First, an overview of currently available and ongoing standardization targeting communications in C-ACC/platooning cooperative driving application is provided. Then, as part of the first research direction, we demonstrate via number of studies, that adaptive beaconing approach where message generation is coupled to the speed variation of the originating ITS-s may lead to a similar message synchronization effect in the time domain when vehicles follow mobility scenarios that involve cooperative speed variation. We ex- plain in detail the cause of this phenomenon and test it for a wide range of parameters. In relation to the second problem, we, first, study the influence of different available ITS-G5 legitimate setups on the C-ACC/platooning fuel efficiency and demonstrate that proper communication setup may enhance fuel savings. Then we thoroughly study the standardization of the congestion control mechanism for ITS-G5, which will affect the operation of all cooperative driving C-ITS applications as a mandatory component. We study the influence of congestion control on application performance and give recommendations for improvement to make the congestion control to target at optimizing the applications performance metrics. In the scope of the last research direction, we propose two real-time jamming DoS detection methods. The main advantage of our detection techniques is their short learning phase that not exceed a few seconds and low detection delay of a few hundreds of milliseconds. Under some assumptions, the proposed algorithms demonstrates the ability to detect certain types of attacks with high detection probability.
Els Sistemes de Transport Intel·ligents (ITS) tenen com a objectiu proporcionar serveis innovadors relacionats amb diferents modes de transport i gestió del trànsit, i permetre que els usuaris en facin un ús més segur, més coordinat i més intel·ligent. Cooperative-ITS (C-ITS) fa possible la connectivitat entre vehicles, entre vehicles i la infraestructura de la carretera, entre senyals de trànsit, i amb altres usuaris de la carretera. Per tal de permetre la comunicació entre vehicles, l'Institut Europeu de les Telecomunicacions (ETSI) va crear el ITS-G5 - un conjunt de normes C-ITS. Tenint en compte els objectius de C-ITS, les comunicacions entre vehicles han de ser fiables i eficients.Lobjectiu d'aquesta tesi és l'avaluació del rendiment i l'eficiència de les comunicacions ITS-G5 per donar suport a les aplicacions de conducció cooperativa. La tesi inclou vuit articles científics al voltant de tres àrees de recerca: avaluació del rendiment dels protocols de baliseig ITS-G5; estudi del rendiment dels mecanismes de control de la congestió ITS-G5; i estudi de d’atacs de tipus Denial-of-Service (DoS) i els seus mètodes de detecció. En primer lloc, s’inclou una descripció general dels objectius d'estandardització actuals i futurs respecte a la conducció cooperativa C-ACC / platooning. Després, com a part de la primera àrea de recerca, es demostra a través de diversos estudis, que l'enfocament de balisa adaptativa on la generació de missatges està acoblada a la variació de velocitat dels ITS-s originadors, pot portar a un efecte de sincronització de missatges similar en el domini del temps quan els vehicles adapten de manera cooperativa la seva velocitat. Així, s’explica detalladament la causa d'aquest fenomen i s’estudia per a una àmplia gamma de paràmetres. En relació amb el segon problema, primer s’estudia la influència de diferents configuracions base del ITS-G5 en el consum de combustible, demostrant que amb una configuració adequada es pot millorar l'estalvi de combustible. Després, s’estudia el mecanisme de control de congestió definit per ITS-G5, que afectarà el funcionament de totes les aplicacions de C-ITS de conducció cooperativa ja que es un component obligatori, avaluant la seva influència en el rendiment de les aplicacions, i donant recomanacions de millora. Finalment, en l’àrea de l'última direcció d'investigació, es proposen dos mètodes de detecció de DoS en temps real. El principal avantatge de les tècniques de detecció presentades és la seva curta fase d'aprenentatge, que no excedeix d’uns pocs segons, i el seu baix retard de detecció d'uns pocs centenars de milisegons. Sota alguns supòsits, els algoritmes proposats demostren la capacitat de detectar certs tipus d'atacs amb alta probabilitat de detecció.
Los Sistemas de Transporte Inteligentes (ITS) tienen como objetivo proporcionar servicios innovadores relacionados con diferentes modos de transporte y gestión del tráfico, y permitir que los usuarios hagan un uso más seguro, más coordinado y más inteligente. Cooperative-ITS (C-ITS) hace posible la conectividad entre vehículos, entre vehículos y la infraestructura de la carretera, entre señales de tráfico, y con otros usuarios de la carretera. Para permitir la comunicación entre vehículos, el Instituto Europeo de las Telecomunicaciones (ETSI) creó el ITS-G5 - un conjunto de normas C-ITS. Teniendo en cuenta los objetivos de C-ITS, las comunicaciones entre vehículos deben ser fiables y eficientes. El objetivo de esta tesis es la evaluación del rendimiento y la eficiencia de las comunicaciones ITS-G5 para dar soporte a las aplicaciones de conducción cooperativa. La tesis incluye ocho artículos científicos en torno a tres áreas de investigación: evaluación del rendimiento de los protocolos de baliza ITS-G5; estudio del rendimiento de los mecanismos de control de la congestión ITS-G5; y estudio de de ataques de tipo Denial-of-Service (DoS) y sus métodos de detección. En primer lugar, se incluye una descripción general de los objetivos de estandarización actuales y futuros respecto a la conducción cooperativa C-ACC / platooning. Luego, como parte de la primera área de investigación, se demuestra a través de varios estudios, que el enfoque de baliza adaptativa donde la generación de mensajes está acoplada a la variación de velocidad de los ITS-s originadores, puede llevar a un efecto de sincronización de mensajes similar en el dominio del tiempo cuando los vehículos adaptan de manera cooperativa su velocidad. Así, se explica detalladamente la causa de este fenómeno y se estudia para una amplia gama de parámetros. En relación con el segundo problema, primero se estudia la influencia de diferentes configuraciones base del ITS-G5 en el consumo de combustible, demostrando que con una configuración adecuada se puede mejorar el ahorro de combustible. Después, se estudia el mecanismo de control de congestión definido por ITS-G5, que afectará el funcionamiento de todas las aplicaciones de C-ITS de conducción cooperativa ya que es un componente obligatorio, evaluando su influencia en el rendimiento de las aplicaciones, y dando recomendaciones de mejora. Finalmente, en el área de la última dirección de investigación, se proponen dos métodos de detección de DoS en tiempo real. La principal ventaja de las técnicas de detección presentadas es su corta fase de aprendizaje, que no excede de unos pocos segundos, y su bajo retraso de detección de unos pocos cientos de milisegundos. Bajo algunos supuestos, los algoritmos propuestos demuestran la capacidad de detectar ciertos tipos de ataques con alta probabilidad de detección.

Intrusion detection systems (IDSs) play a crucial role in the identification and mitigation for attacks on host systems. Of these systems, vehicular ad hoc networks (VANETs) are difficult to protect due to the dynamic nature of their clients and their necessity for constant interaction with their respective cyber-physical systems. Currently, there is a need for a VANET-specific IDS that meets this criterion. To this end, a spline-based intrusion detection system has been pioneered as a solution. By combining clustering with spline-based general linear model classification, this knot flow classification method (KFC) allows for robust intrusion detection to occur. Due its design and the manner it is constructed, KFC holds great potential for implementation across a distributed system. The purpose of this thesis was to explain and extrapolate the afore mentioned IDS, highlight its effectiveness, and discuss the conceptual design of the distributed system for use in future research.

The popularity of the wireless networks is so great that we will soon reach the point where most of the devices work based on that, but new challenges in wireless channel access will be created with these increasingly widespread wireless communications. Multi-channel CSMA protocols have been designed to enhance the throughput of the next generation wireless networks compared to single-channel protocols. However, their performance analysis still needs careful considerations. In this thesis, a set of techniques are proposed to model and analyse the CSMA protocols in terms of channel sensing and channel access. In that respect, the performance analysis of un-slotted multi-channel CSMA protocols is studied through considering the hidden terminals. In the modelling phase, important parameters such as shadowing and path loss impairments are being considered. Following that, due to the high importance of spectrum sensing in CSMA protocols, the Double-Threshold Energy Detector (DTED) is thoroughly investigated in this thesis. An iterative algorithm is also proposed to determine optimum values of detection parameters in a sensing-throughput problem formulation. Vehicle-to-Roadside (V2R) communication, as a part of Intelligent Transportation System (ITS), over multi-channel wireless networks is also modelled and analysed in this thesis. In this respect, through proposing a novel mathematical model, the connectivity level which an arbitrary vehicle experiences during its packet transmission with a RSU is also investigated.

Foggy and hazy weather conditions considerably effect visibility distance which impacts speed, flow of traffic, travel time delay and increases the risk accidents. Bad weather condition is considered a cause of road accidents, since it the poor conditions can effect drivers field of vision. In addition, fog, haze and mist can have negative influences on visual applications in the open air since they decrease visibility by lowering the contrast and whitening the visible color palette. The poor visibility in these images leads to some failures in recognition and detection of the outdoor object systems and also in Intelligent Transportation Systems (ITS). In this thesis, we propose an image visibility restoration algorithm under foggy weather in intelligent transportation systems. Various camera based Advanced Driver Assistant Systems (ADAS), which can be improved by applying the visibility restoration algorithm, have been applied in this field of study to enhance vehicle safety by displaying the image from a frontal camera to driver after visibility enhancement. To remove fog, automatic methods have been proposed which are categorized into two approaches based on the number of input images: 1) methods which are using polarizing filters, 2) methods which are using captured images from different fog densities. In both of these approaches multiple images are required which have to be taken from exactly the same point of view. While these applications can generate good results, their requirements make them impractical, particularly in real time applications, such as intelligent transportation systems. Therefore, in this thesis we introduce a high-performance visibility restoration algorithm only using a single foggy image which applies a recursive filtering to preserve the edge of images and videos in real time and also compute depth map of the scene to restore image. The applied edge preserving filtering is based on a domain transform in which 1-Dimensional edge-preserving filtering is performed by preserving the geodesic distance between points on the curves that is adaptable with wrapping the input signal. The proposed algorithm can be applied in intelligent transportation system applications, such as Advanced Driver Assistance Systems (ADAS). The main features of the proposed algorithm are its speed, which plays a main role in real time applications, since 1-Dimensional operations are used in the applied filtering leads to remarkable speedups in comparison with classical median filters and robust bilateral lfilters. Potential of memory saving is considered as another one advantage of the proposed model and also the parameters of applied edge-preserving filtering do not effect on its computational cost. It is the first edge-preserving filter for color images with arbitrary scales in real time. The proposed algorithm is also able to handle both color and gray-level images and achieves the restored image without the presence of artifacts in comparison with other state-of-the-art algorithms.

Les accidents routiers et leurs dommages représentent un problème croissant dans le monde entier. Dans ce contexte, les réseaux véhiculaires (VANETs) peuvent être déployés pour réduire les risques et pour améliorer le confort. Ils permettent aux véhicules d'échanger différents types de données qui vont des applications de sécurité et de gestion du trafic aux applications de confort. De nos jours, les applications de sécurité sont l’objet de beaucoup d'attention des chercheurs ainsi que des fabricants d'automobiles. Dans cette thèse, nous étudierons les applications critiques pour la sécurité routière visant à fournir une assistance dans des situations dangereuses ou difficiles. Notre objectif principal sera de proposer de nouveaux protocoles de contrôle d'accès au support de transmission (MAC) et de routage, qui peuvent s’adapter dynamiquement aux changements fréquents de topologies des VANETs. Après un aperçu des protocoles d’accès sans contention dans les VANETs, nous proposons des solutions basées sur la technique de division du temps: Time Division Multiple Access (TDMA). D’abord, nous nous concentrons sur le développement d’un nouveau protocole distribué (DTMAC), qui ne repose pas sur l’utilisation d’infrastructure. DTMAC utilise les informations de localisation et un mécanisme de réutilisation des slots pour assurer que les véhicules accèdent au canal efficacement et sans collision. Les résultats obtenus ont confirmé l’efficacité de notre protocole, DTMAC se comporte très significativement mieux que VeMAC (protocole MAC basé sur TDMA.) Ensuite nous proposons TRPM, un protocole de routage basé sur une approche cross-layer. Dans TRPM, l’ordonnancement des slots TDMA construit par DTMAC et la position de la destination sont utilisés pour choisir le meilleur relais. Les résultats montrent que TRPM offre de meilleures performances, du nombre moyen de relais et de la fiabilité de livraison des messages comparé à d’autres protocoles. Dans la deuxième partie de cette thèse, nous nous focaliserons sur les mécanismes centralisés d’allocation de slots qui utilisent des coordinateurs. D’abord, nous proposons CTMAC, un protocole basé sur TDMA centralisé utilisant les RSUs (RoadSide Units) pour créer et maintenir les ordonnancements. CTMAC met en œuvre un mécanisme qui permet d’empêcher les “Access Collisions” de se produire plus que deux fois entre les véhicules qui tentent d’acquérir un même slot disponible. Les résultats ont montré que CTMAC permet de mieux minimiser les collisions, ainsi que le surcoût généré pour créer et maintenir les ordonnancements par rapport aux protocoles MAC, basés sur TDMA distribué. Cependant, dans CTMAC, les véhicules roulant vite devront acquérir des nouveaux slots après une courte période de temps à chaque fois qu’ils quittent les zones de leurs RSUs courants. Cette situation rend les protocoles centralisés inefficaces et couteux dans les réseaux à grande vitesse. Afin de pallier à ce problème inhérent à l’utilisation des RSUs, nous adaptons un algorithme d’ordonnancement basé sur le clustering dans lequel certains véhicules sont élus pour gérer l'accès au canal. Ceci permet aux véhicules de rester attachés à leurs clusters plus longtemps. Pour ce faire, nous proposons 1- un protocole de clustering nommé AWCP afin de former des clusters stables avec une longue durée de vie. AWCP est basé sur l’algorithme de clustering pour les réseaux mobiles WCA dans lequel les têtes des clusters sont élues en se basant sur une fonction de poids. 2- Nous formulons le réglage des paramètres de protocole AWCP comme un problème d’optimisation multi-objective et nous proposons un outil d’optimisation qui combine la version multi-objective de l’algorithme génétique appelé NSGA-II avec le simulateur de réseau ns-2 pour trouver les meilleurs paramètres du protocole AWCP. 3- Nous proposons ASAS, une stratégie adaptative pour l’attribution des slots temporels basée sur une approche cross-layer entre TDMA et AWCP
Road crashes and their damages represent a serious issue and are one of the main causes of people death. In this context, Vehicular Ad hoc NETworks (VANETs) are deployed to reduce the risk of road accident as well as to improve passengers’ comfort by allowing vehicles to exchange different kinds of data which ranges widely from road safety and traffic management to infotainment. Nowadays, safety applications are receiving a great deal of attention from researchers as well as from automobile manufacturers. In this thesis, we particularly focus on safety-critical applications, designed to provide drivers assistance in dangerous situations and to avoid accidents in highway environments. Such applications must guarantee to the vehicles access to the medium and have strict requirements regarding end-to-end delay and packet loss ratio. Therefore, our main goal is to propose new medium access control and routing protocols, which can efficiently adapt to frequent changing VANET network topologies. After a comprehensive overview of free-contention MAC protocols, we propose several solutions, based on Time Division Multiple Access Technique (TDMA). We have designed DTMAC, a fully distributed TDMA-based MAC protocol, which does not rely on an expensive infrastructure. DTMAC uses vehicles’ locations and a slot reuse concept to ensure that vehicles in adjacent areas have collision-free schedule. Using simulations, we prove that DTMAC provides a lower rate of access and merging collisions than VeMAC, a well-known TDMA based MAC protocol in VANET. Then, in order to ensure that event-driven safety messages can be sent over a long distance, we propose TRPM, a TDMA aware Routing Protocol for Multi-hop communication. Our routing scheme is based on a cross layer approach between the MAC and the routing layers, in which the intermediate vehicles are selected using TDMA scheduling information. Simulation results show that TRPM provides better performances in terms of average end-to-end delay, average number of hops and average delivery ratio. In the second part, we focus on coordinator-based TDMA scheduling mechanisms. First, we propose the Centralized TDMA based MAC protocol (CTMAC) which uses Road Side Units (RSUs) as a central coordinator to create and maintain the TDMA schedules. CTMAC implements an Access Collision Avoidance mechanism that can prevent the access collision problem occurring more than twice between the same vehicles that are trying to access the channel at the same time. Using simulation we show an improvement in terms of access and merging collisions as well as the overhead required to create and maintain the TDMA schedules compared to distributed scheduling mechanisms. However, in the CTMAC protocol, fast moving vehicles will need to compete for new slots after a short period of time when they leave their current RSU area, which makes a centralized scheduling approach very expensive. In order to further improve the performance of coordinator-based TDMA scheduling mechanisms, we focus on cluster-based TDMA MAC protocols in which some vehicles in the network are elected to coordinate the channel access, allowing the vehicles to remain connected with their channel coordinator for a longer period of time. To this end, first we propose an adaptive weighted clustering protocol, named AWCP, which is road map dependent and uses road IDs and vehicle directions to make the clusters’ structure as stable as possible. Then, we formulate the AWCP parameter tuning as a multi-objective problem and we propose an optimization tool to find the optimal parameters of AWCP to ensure its QoS. Next, we propose ASAS, an adaptive slot assignment strategy for a cluster-based TDMA MAC protocol. This strategy is based on a cross layer approach involving TDMA and AWCP. The objective is to overcome the inter-cluster interference issue in overlapping areas by taking into account vehicles’ locations and directions when the cluster head assign slots

A pesar de que las medidas de seguridad en los sistemas de transporte cada vez son mayores, el aumento progresivo del número de vehículos que circulan por las ciudades y carreteras en todo el mundo aumenta, sin duda, la probabilidad de que ocurra un accidente. En este tipo de situaciones, el tiempo de respuesta de los servicios de emergencia es crucial, ya que está demostrado que cuanto menor sea el tiempo transcurrido entre el accidente y la atención hospitalaria de los heridos, mayores son sus probabilidades de supervivencia. Las redes vehiculares permiten la comunicación entre los vehículos, así como la comunicación entre los vehículos y la infraestructura [4], lo que da lugar a una plétora de nuevas aplicaciones y servicios en el entorno vehicular. Centrándonos en las aplicaciones relacionadas con la seguridad vial, mediante este tipo de comunicaciones, los vehículos podrían informar en caso de accidente al resto de vehículos (evitando así colisiones en cadena) y a los servicios de emergencia (dando información precisa y rápida, lo que sin duda facilitaría las tareas de rescate). Uno de los aspectos importantes a determinar sería saber qué información se debe enviar, quién será capaz de recibirla, y cómo actuar una vez recibida. Actualmente los vehículos disponen de una serie de sensores que les permiten obtener información sobre ellos mismos (velocidad, posición, estado de los sistemas de seguridad, número de ocupantes del vehículo, etc.), y sobre su entorno (información meteorológica, estado de la calzada, luminosidad, etc.). En caso de accidente, toda esa información puede ser estructurada y enviada a los servicios de emergencia para que éstos adecúen el rescate a las características específicas y la gravedad del accidente, actuando en consecuencia. Por otro lado, para que la información enviada por los vehículos accidentados pueda llegar correctamente a los servicios de emergencias, es necesario disponer de una infraestructura capaz de dar cobertura a todos los vehículos que circulan por una determinada área. Puesto que la instalación y el mantenimiento de dicha infraestructura conllevan un elevado coste, sería conveniente proponer, implementar y evaluar técnicas consistentes en dar cobertura a todos los vehículos, reduciendo el coste total de la infraestructura. Finalmente, una vez que la información ha sido recibida por las autoridades, es necesario elaborar un plan de actuación eficaz, que permita el rápido rescate de los heridos. Hay que tener en cuenta que, cuando ocurre un accidente de tráfico, el tiempo de personación de los servicios de emergencia en el lugar del accidente puede suponer la diferencia entre que los heridos sobrevivan o fallezcan. Además, es importante conocer si la calle o carretera por la que circulaban los vehículos accidentados ha dejado de ser transitable para el resto de vehículos, y en ese caso, activar los mecanismos necesarios que permitan evitar los atascos asociados. En esta Tesis, se pretende gestionar adecuadamente estas situaciones adversas, distribuyendo el tráfico de manera inteligente para reducir el tiempo de llegada de los servicios de emergencia al lugar del accidente, evitando además posibles atascos.
Barrachina Villalba, J. (2014). Using Ontologies and Intelligent Systems for Traffic Accident Assistance in Vehicular Environments [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/39004
TESIS

Each day, Humanity loses thousands of persons on roads when they were traveling to work, to study or even to distract. The financial cost of these injuries is also terrifying: Some statistics evaluate the financial cost of vehicle accidents at 160 billion Euro in Europe each year. These alarming figures have driven researchers, automotive companies and public governments to improve the safety of our transportation systems and communication technologies aiming at offering safer roads and smooth driving to human beings. In this context, Vehicular Adhoc Networks, where vehicles are able to communicate with each others and with existent road side units, emerge as a promising wireless technology able to enhance the vision of drivers and offer larger telematic horizon. VANETs promising applications are not only restricted to road safety but span from vehicle trafficoptimization like flow congestion control to commercial applications like file sharing and internet access. Safety applications require that their alert information is propagated to the concerned vehicles (located in the hazardous zone) with little delay and high reliability. For these reasons, this category of applications is considered as delay sensitive and broadcast-oriented nature. While classical blind flooding is rapid, its major drawback is its huge bandwidth utilization. In this thesis, we are interested on enhancing vehicular communications under different scenarios and optimizations: First, We focus on deriving a new solution (EBDR) to disseminate alert messages among moving vehicles while maintaining it efficient and rapid. Our proposal is based on directional antennas to broadcast messages and a route guidance algorithm to choose the best path for the packets. Findings confirmed the efficiency of our approach in terms of probability of success and end-to-end delays. Moreover, in spite of the broadcast nature of the proposed technique, all transmissions stop very soon after the arrival of a packet to its destination representing a strong feature in the conception of EBDR. Second, we propose a novel mathematical framework to evaluate the performance of EBDR analytically. Although most of the proposed techniques present in literature use experimental or simulation tools to defend their performance, we rely here on mathematical models to confirm our achieved results. Our proposed framework allows to derive meaningful performance metrics including the probability of transmission success and the required number of hops to reach thefinal destination. Third, we refine our proposed broadcast-based routing EBDR to provide more efficient broadcasting by adjusting the transmission range of each vehicle based on its distance to the destination and the local node density. This mechanism allows better minimization of interferences and bandwidth's saving. Furthermore, an analytical model is derived to calculate thetransmission area in the case of a simplified node distribution. Finally, we are interested on data collection mechanisms as they make inter-vehicle communications more efficient and reliable and minimize the bandwidth utilization. Our technique uses Q-learning to collect data among moving vehicles in VANETs. The aim behind using the learning technique is to make the collecting operation more reactive to nodes mobility and topology changes. For the simulation part, we compare it to a non-learning version to study the effect of the learning technique. Findings show that our technique far outperforms other propositions and achieves a good trade off between delay and collection ratio. In conclusion, we believe that the different contributions presented in this Thesis will improve the efficiency of inter-vehicle communications in both dissemination and data collection directions. In addition, our mathematical contributions will enrich the literature in terms of constructing suitable models to evaluate broadcasting techniques in urban zones

In the past few years, many research works have demonstrated that mobile crowdsensing could be effectively applied in vehicular social networks (VSNs) to serve many purposes and bring huge economic benefits in transportation. In this thesis, we provide a crowdsensing platform which addresses the research challenges in the overall workflow of crowdsensing in VSNs in terms of task allocation and task execution. This platform supports the creation of different context-aware mobile crowdsensing applications and facilitates their real-world deployments in VSNs. First, because of the inherent nature of crowdsensing, usually a crowdsensing task needs a group of different participants to finish it collaboratively. Thus, for task allocation in crowdsensing, we propose an application-oriented service collaboration model (ASCM). This ASCM automatically allocates multiple participants with multiple crowdsensing tasks across different mobile devices and cloud platform in an efficient and effective manner in VSNs. Second, for task exaction of mobile crowdsensing applications in VSNs, the dynamic network connectivity of the underlying vehicular ad-hoc networks (VANETs) may cause failures of such applications during their executions. We design S-Aframe, an agent-based multi-layer framework, which provides a programming model to support creation and deployment of robust and reliable crowdsensing applications that self-adapt to the dynamic nature of VANETs. Furthermore, due to the dynamism of VANETs and the opportunism of user connections in VSNs, the changing environments of the users involved in the VSNs may also result in users’ dynamic contexts. We propose a context-aware semantic service (CSS), and incorporate this service with S-Aframe to improve the self-adaptiveness of mobile crowdsensing applications to users’ dynamic contexts of VSNs. Finally, we design and develop SAfeDJ, a crowdsensing-based situation-aware music recommendation application for drivers. The development of SAfeDJ has further demonstrated how our platform supports the creation of a context-aware mobile crowdsensing application, and facilitates the realization of such an application in real-world deployment in VSNs.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

Vehicular ad-hoc networks (VANETs) that enable communication among vehicles and between vehicles and unmanned aerial vehicles (UAVs) and cellular base stations have recently attracted significant interest from the research community, due to the wide range of practical applications they can facilitate (e.g., road safety, traffic management and rescue missions). Despite this increased research activity, the high vehicle mobility in a VANET raises concerns regarding the robustness and adaptiveness of such networks to support time-critical applications and internetworking. In this thesis, as a first step toward the design of efficient MAC protocol to support time-critical applications and internetworking, we show that it is indeed possible to follow the dynamics of a network and consequently adapt the transmission probability of the Aloha protocol to reduce the interference and maximise the single-hop throughput between adjacent nodes. Extensive simulation validates the proposed analytical model, which thus can serve as a promising tool to improve VANETs performance. By exploiting the parallel between the CSMA/CA and Aloha performance models, the optimal transmission probability for the Aloha protocol as a function of estimated vehicular density is derived. This probability is then used to obtain the optimal maximum CW that can be integrated in an amended CSMA/CA protocol to maximise the single-hop throughput among adjacent vehicles. We show by means of simulation that the beneficial impact the proposed protocol is increased channel throughput and reduced transmission delay when compared with the standardised protocol CSMA/CA in IEEE 802.11p. These results reveal the applicability of the new, optimised protocol to safety applications and clustering techniques with stringent performance requirements. Lastly, we propose a Stable Clustering Algorithm for vehicular ad-hoc networks (SCalE) internetworking. The exchange of the necessary status information to support the efficient clusters formation can firmly relay on the support of our optimised CSMA/CA protocol. The SCalE algorithm makes use of the knowledge of the vehicles behaviour (explained in Chapter 5) for efficient selection of CHs, and selects a backup CH on top of the CH to maintain the stability of cluster structures. The increased stability and improved performance of the SCalE algorithm is studied and compared with existing clustering algorithms.

La convergencia de las telecomunicaciones, la informática, la tecnología inalámbrica y los sistemas de transporte, va a facilitar que nuestras carreteras y autopistas nos sirvan tanto como plataforma de transporte, como de comunicaciones. Estos cambios van a revolucionar completamente cómo y cuándo vamos a acceder a determinados servicios, comunicarnos, viajar, entretenernos, y navegar, en un futuro muy cercano. Las redes vehiculares ad hoc (vehicular ad hoc networks VANETs) son redes de comunicación inalámbricas que no requieren de ningún tipo de infraestructura, y que permiten la comunicación y conducción cooperativa entre los vehículos en la carretera. Los vehículos actúan como nodos de comunicación y transmisores, formando redes dinámicas junto a otros vehículos cercanos en entornos urbanos y autopistas. Las características especiales de las redes vehiculares favorecen el desarrollo de servicios y aplicaciones atractivas y desafiantes. En esta tesis nos centramos en las aplicaciones relacionadas con la seguridad. Específicamente, desarrollamos y evaluamos un novedoso protocol que mejora la seguridad en las carreteras. Nuestra propuesta combina el uso de información de la localización de los vehículos y las características del mapa del escenario, para mejorar la diseminación de los mensajes de alerta. En las aplicaciones de seguridad para redes vehiculares, nuestra propuesta permite reducir el problema de las tormentas de difusión, mientras que se mantiene una alta efectividad en la diseminación de los mensajes hacia los vehículos cercanos. Debido a que desplegar y evaluar redes VANET supone un gran coste y una tarea dura, la metodología basada en la simulación se muestra como una metodología alternativa a la implementación real. A diferencia de otros trabajos previos, con el fin de evaluar nuestra propuesta en un entorno realista, en nuestras simulaciones tenemos muy en cuenta tanto la movilidad de los vehículos, como la transmisión de radio en entornos urbanos, especialmente cuando los edificios interfieren en la propagación de la señal de radio. Con este propósito, desarrollamos herramientas para la simulación de VANETs más precisas y realistas, mejorando tanto la modelización de la propagación de radio, como la movilidad de los vehículos, obteniendo una solución que permite integrar mapas reales en el entorno de simulación. Finalmente, evaluamos las prestaciones de nuestro protocolo propuesto haciendo uso de nuestra plataforma de simulación mejorada, evidenciando la importancia del uso de un entorno de simulación adecuado para conseguir resultados más realistas y poder obtener conclusiones más significativas.
Martínez Domínguez, FJ. (2010). Improving Vehicular ad hoc Network Protocols to Support Safety Applications in Realistic Scenarios [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/9195
Palancia

Questa tesi affronta l’analisi circa il possibile utilizzo di un particolare set di sequenze, le cosiddette sequenze de Bruijn, in un sistema radar veicolare di tipo Direct Sequence Spread Spectrum (DSSS). Rispetto ad altri codici di espansione adottati nei sistemi DSSS, maggiore è la lunghezza delle sequenze del set, più la numerosità delle sequenze di de Bruijn aumenta in modo esponenziale e permette teoricamente di assegnare ad ogni radar una diversa sequenza generata, che funge da specifica chiave personale. In questo modo è possibile sviluppare un sistema radar autoconsistente in grado di lavorare senza alcuna infrastruttura necessaria all’assegnazione delle sequenze, come accade per i convenzionali codici di espansione tipo i codici Gold o i codici di Kasami. Grazie alle loro favorevoli proprietà di auto- e cross-correlazione, sono particolarmente indicati per sistemi automotive dove è molto importante rilevare con precisione un bersaglio in un contesto di radar multi-utente. Considerando le loro buone proprietà di correlazione e la loro elevata numerosità, le sequenze di de Bruijn possono essere utilizzate non solo nei sistemi radar veicolari ma anche in altri scenari di tipo Spread Spectrum, come il canale di downlink e uplink di sistemi DS-CDMA. Infatti, le sequenze di de Bruijn, nella versione standard, se selezionate accuratamente hanno proprietà di ortogonalità e quindi particolarmente vantaggioso è il loro utilizzo nel canale di downlink di un sistema DS-CDMA. Inoltre, dal set di sequenze di de Bruijn è possibile derivare un altro particolare insieme di sequenze, le cosiddette sequenze di de Bruijn modificate. Queste sequenze mostrano prestazioni migliori in termini di cross-correlazione e potrebbero essere utilizzate nel canale uplink di un sistema DS-CDMA. Al fine di verificare le prestazioni in un vero e proprio banco di prova, è stata sviluppata anche una preliminare implementazione di un radar DSSS su Software Defined Radio. Infine è stato sviluppato un simulatore per sistemi radar veicolari DSSS su scenari multi-utente. L’analisi effettuata ed i risultati sulle prestazioni ottenuti suggeriscono di evolvere questa soluzione verso le recenti tecniche di radar cognitivo tramite l’ausiliodi tecniche di visione computazionale.
This thesis deals with the analysis about a possible utilization of a particular set of sequences, the so-called de Bruijn sequences, in a Direct Sequence Spread Spectrum (DSSS) vehicular radar system. Compared with other spreading codes adopted in DSSS systems, the greater the span of the set is, the more the number of de Bruijn sequences exponentially increases and theoretically permits to assign each radar a different generated sequence, as a specific key. By this way it is possible to develop a self-consistent radar system, which is able to work without any infrastructure required to assign sequences, as it happens in the case conventional spreading codes, like Gold codes or Kasami codes, are adopted. Due to their both favourable auto- and cross-correlation properties they are particularly indicated for automotive systems in which there are the needs of detecting accurately a target and performing in a multi-user radar environment. Considering their good correlation properties and their huge number, de Bruijn sequences could be used not only in vehicular radar systems but also in other Spread Spectrum and so, they are evaluated in various scenarios like downlink and uplink channel of DS-CDMA systems. In fact, in standard version de Bruijn sequences, if accurately selected, have the property of orthogonality and so they are tested in a downlink channel of a DS-CDMA system. In addition, from de Bruijn sequences another particular set of sequences, the so-called modified de Bruijn sequences, can be derived. These sequences show better performance in terms of cross-correlation properties and could be used in uplink channel of DS-CDMA system. In order to verify the performance in a real test-bed, a preliminary implementation on Software Defined Radios is also developed. Finally they are adopted and compared in simulated multiuser DSSS radar scenarios. The analysis done and the performance results obtained suggest to evolve this radar solution to a cognitive radar approach using computer vision systems as external aid sensor which can outperform actual solutions.

[EN] In recent years, advances in wireless technologies and improved sensing and computational capabilities have led to a gradual transition towards Intelligent Transportation Systems (ITS) and related applications. These applications aim at improving road safety, provide smart navigation, and eco-friendly driving. Vehicular Ad hoc Networks (VANETs) provide a communication structure for ITS by equipping cars with advanced sensors and communication devices that enable a direct exchange of information between vehicles. Different types of ITS applications rely on two types of messages: periodic beacons and event-driven messages. Beacons include information such as geographical location, speed, and acceleration, and they are only disseminated to a close neighborhood. Differently from beacons, event-driven messages are only generated when a critical event of general interest occurs, and it is spread within a specific target area for the duration of the event. The reliability of information exchange is one of the main issues for vehicularcommunications since the safety of people on the road is directly related to the effectiveness of these transmissions. A Medium Access Control (MAC) protocol must guarantee reliable beacon broadcasting within deadline bounds to all vehicles in the neighbourhood, thereby providing them timely notifications about unsafe driving conditions or other hazardous events. Moreover, infotainment and comfort applications require reliable unicast transmissions that must be taken into account. However, high node mobility, highly dynamic topology, and lack of a central control unit, are issues that make the design of a reliable MAC protocol for vehicular environments a very difficult and challenging task, especially when efficient broadcasting strategies are required. The IEEE 802.11p MAC protocol, an approved amendment to the IEEE 802.11 standard, is a random access protocol that is unable to provide guaranteed delay bounds with sufficient reliability in vehicular scenarios, especially under high channel usage. This problem is particularly serious when implementing (semi-) automated driving applications such as platooning, where inter-vehicle spacing is drastically reduced, and the control loop that manages and maintains the platoon requires frequent, timely and reliable exchange of status information (beacons). In this thesis novel protocols compatible with the IEEE 802.11 and 802.11p standards are proposed in order to optimally adjust the contention window size for unicast applications in Mobile Ad hoc Networks (MANETs) and VANETs. Experimental tests comparing our proposals to existing solutions show that the former are able to improve the packet delivery ratio and the average end-to-end delay for unicast applications. Concerning efficient message diffusion (broadcast) in VANET environments, we proposed token-based MAC solutions to improve the performance achieved by existing 802.11p driving safety applications in different vehicular environments, including highway, urban, and platooning scenarios. Experimental results show that the proposed solutions clearly outperform 802.11p when delay-bounded beacons and event notifications must be delivered.
[ES] Recientemente, los avances en las tecnologías inalámbricas y las mejoras en términos de capacidades de sensorización y computación de los dispositivos electrónicos, han dado lugar a una transición gradual hacia servicios y aplicaciones de los Sistemas Inteligentes de Transporte (ITS). Estas aplicaciones tienen como objetivo mejorar la seguridad vial, proporcionar una navegación inteligente, y promover la conducción eco-eficiente. Las redes vehiculares ad hoc (VANETs) proporcionan una infraestructura de comunicaciones para ITS al equipar los coches con sensores avanzados y dispositivos de comunicación que permiten el intercambio directo de información entre vehículos. Los diferentes tipos de aplicaciones ITS se basan en dos tipos de mensajes: mensajes periódicos conocidos como beacons y mensajes asociados a eventos. Los mensajes periódicos incluyen información relativa a la ubicación geográfica, la velocidad y la aceleración, entre otros, y sólo son distribuidos entre los vehículos vecinos. A diferencia de estos beacons, los mensajes asociados a eventos sólo se generan cuando se produce un evento crítico de interés general, el cual se propaga dentro del área de interés de dicho evento y mientras éste siga activo. La fiabilidad del intercambio de información es uno de los principales problemas para las comunicaciones vehiculares, debido principalmente a que las aplicaciones de seguridad dependen directamente de la eficacia de estas transmisiones. Un protocolo de Control de Acceso al Medio (MAC) debe garantizar la difusión fiable de información a todos los vehículos vecinos dentro de unos límites máximos de retardo, proporcionándoles las notificaciones oportunas respecto a condiciones de conducción inseguras y otros eventos peligrosos. Por otra parte, las aplicaciones de información y entretenimiento, así como las aplicaciones orientadas al confort, también requieren transmisiones fiables extremoa-extremo. Sin embargo, la alta movilidad de los vehículos, la variabilidad de la topología, así como la falta de una unidad central de control, son factores que hacen que el diseño de un protocolo MAC fiable para entornos vehiculares sea una tarea especialmente compleja, especialmente cuando son necesarias estrategias de difusión eficientes. El protocolo MAC IEEE 802.11p, una modificación ya aprobada al estándar IEEE 802.11 original para entornos de comunicación vehiculares, es un protocolo de acceso que no es capaz de garantizar unos límites de retardo con la fiabilidad necesaria para estos entornos, especialmente en escenarios de alta utilización del canal inalámbrico. Este problema es particularmente importante a la hora de implementar aplicaciones de conducción (semi-)automática, como el caso de grupos de vehículos donde la separación entre vehículos se reduce drásticamente, y el sistema de control que gestiona y mantiene el grupo requiere de un intercambio frecuente de información fiable y acotado en retardo. En esta tesis se proponen nuevos protocolos MAC compatibles con los estándares IEEE 802.11 y 802.11p basados en el ajuste del tamaño de la ventana de contención para aplicaciones unicast en rede MANETs y VANETs. Los resultados experimentales obtenidos comparando nuestras propuestas con las soluciones existentes muestran que los protocolos propuestos son capaces de mejorar la tasa de entrega de paquetes y el retardo medio extremo-a-extremo para aplicaciones unicast. En lo que respecta a la difusión eficiente de mensajes broadcast en entornos VANET, se han propuesto soluciones MAC basadas en el uso de tokens que mejoran las prestaciones de aplicaciones de conducción segura basadas en el estándar 802.11p, tanto en autopistas, zonas urbanas, y escenarios con grupos de vehículos. Los resultados experimentales muestran que las soluciones propuestas superan claramente al protocolo 802.11p cuando es necesario entregar mensajes y notificaciones de eventos con restricc
[CAT] Recentment, els avan en les tecnologies sense fils i les millores en termes de capacitats de sensorització i computació dels dispositius electrònics, han donat lloc a una transició gradual cap a serveis i aplicacions dels sistemes intelligents de transport (ITS). Aquestes aplicacions tenen com a objectiu millorar la seguretat vial, proporcionar una navegació intelligent, i promoure la conducció ecoeficient. Les xarxes vehiculars ad hoc (VANET) proporcionen una infraestructura de comunicacions per a ITS, ja que equipen els cotxes amb sensors avançats i dispositius de comunicació que permeten l'intercanvi directe d'informació entre vehicles. Els diversos tipus d'aplicacions ITS es basen en dos classes de missatges: missatges periòdics coneguts com a beacons i missatges associats a esdeveniments. Els missatges periòdics inclouen informació relativa a la ubicació geogràfica, la velocitat i l'acceleració, entre uns altres, i només són distribuïts entre els vehicles veïns. A diferència d'aquests beacons, els missatges associats a esdeveniments només es generen quan es produeix un esdeveniment crític d'interès general, el qual es propaga dins de l àrea d'interès d'aquest esdeveniment i mentre aquest seguisca actiu. La fiabilitat de l'intercanvi d'informació és un dels principals problemes per a les comunicacions vehicular, principalment perquè les aplicacions de seguretat depenen directament de l'eficàcia d'aquestes transmissions. Un protocol de control d'accés al medi (MAC) ha de garantir la difusió fiable d'informació a tots els vehicles veïns dins d'uns límits màxims de retard, i proporcionar-los les notificacions oportunes respecte a condicions de conducció insegures i altres esdeveniments perillosos. D'altra banda, les aplicacions d'informació i entreteniment, com també les aplicacions orientades al confort, també requereixen transmissions fiables extrema-extrem. No obstant això, l'alta mobilitat dels vehicles, la variabilitat de la topologia, i la falta d'una unitat central de control, són factors que fan que el disseny d'un protocol MAC fiable per a entorns vehiculars siga una tasca especialment complexa, especialment quan són necessàries estratègies de difusió eficients. El protocol MAC IEEE 802.11p, una modificació ja aprovada a l'estàndard IEEE 802.11 original per a entorns de comunicació vehiculars, és un protocol d'accés que no és capa garantir uns límits de retard amb la fiabilitat necessària per a aquests entorns, especialment en escenaris d'alta utilització del canal sense fil. Aquest problema és particularment important a l'hora d'implementar aplicacions de conducció (semi)automàtica, com el cas de grups de vehicles en què la separació entre vehicles es redueix dràsticament, i el sistema de control que gestiona i manté el grup requereix un intercanvi freqüent d'informació fiable i delimitat en retard. En aquesta tesi es proposen nous protocols MAC compatibles amb els estàndards IEEE 802.11 i 802.11p basats en l'ajust de les dimensions de la finestra de contenció per a aplicacions unicast en xarxes MANET i VANET. Els resultats experimentals obtinguts comparant les nostres propostes amb les solucions existents mostren que els protocols proposats són capa de millorar la taxa de lliurament de paquets i el retard mitjà extrem-a-extrem per a aplicacions unicast. Pel que fa a la difusió eficient de missatges broadcast en entorns VANET, s'han proposat solucions MAC basades en l'ús de tokens que milloren les prestacions d'aplicacions de conducció segura basades en l'estàndard 802.11p, tant en autopistes, zones urbanes, i escenaris amb grups de vehicles. Els resultats experimentals mostren que les solucions proposades superen clarament el protocol 802.11p quan cal lliurar missatges i notificacions d'esdeveniments amb restriccions de latència.
Balador, A. (2016). Design and Evaluation of Efficient Medium Access Control Solutions for Vehicular Environments [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64073
TESIS

Le contrôle de congestion des canaux sans fil pour la communication véhiculaires (V2X) basée sur IEEE 802.11p ont été conçus pour un seul service de sécurité routière notamment ‘Cooperative Awareness’. Les futurs véhicules connectés seront basés sur plusieurs services V2X, avec un besoin de communication hétérogène, auxquels les mécanismes existants ne répondent pas. Dans cette thèse, on analyse plusieurs protocoles de contrôle de congestion et d’allocation de ressources de canaux, normalisés en Europe pour le déploiement V2X initial. Nous présentons des problèmes liés à l’approche existante, notamment l’utilisation inefficace de la capacité des canaux, la coordination dans la pile protocolaire, la gestion des ressources parmi plusieurs services et l’allocation des ressources pour un besoin asymétrique par les véhicules. On propose des améliorations en tenant compte des exigences des futurs scénarios V2X. Nous montrons les limites de la classification statique des services V2X pour la qualité de service et proposons une classification dynamique. Nous concevons un orchestrateur de ressources afin d'améliorer la coordination dans la pile protocolaire et de répartir dynamiquement la ressource de canal parmi plusieurs services d'un véhicule. En outre, on présente un mécanisme permettant d'orchestrer de manière décentralisée les ressources de canal parmi une distribution mixte de véhicules ayant des exigences d'utilisation de canal diverse, dans un canal de communication congestionné. Les résultats analytiques et résultats par simulations montrent la validité de notre approche qui améliore la performance des applications V2X, par rapport aux protocoles standardisés existants
Wireless channel congestion control and decentralized resource allocation for 802.11p based V2X communication have been widely investigated for a single Cooperative Awareness service, considering mostly homogenous communication requirement per vehicle. Future connected vehicles will be based on multiple V2X services, with heterogenous number of services and communication needs, which existing resource allocation mechanisms does not address. In this thesis, we analyze several decentralized congestion control and channel resource allocation protocols standardized in Europe for initial V2X deployment. We present issues with the existing approach, in particular the inefficient channel capacity utilization, problematic cross layer coordination, inability to balance resources among multiple V2X safety services and distributed resource allocation for asymmetric number of services per vehicle. We propose improvements to the shortcomings, considering the requirements of future V2X scenarios. We demonstrate the limitations of classifying V2X services using static priority for Quality of Service and propose dynamic prioritization. We design a resource orchestrator at the Service Layer to improve cross layer coordination and dynamically distribute the limited channel resource among multiple services of a vehicle. Furthermore, we present a mechanism to decentrally orchestrate channel resource among a mixed distribution of vehicles with diverse channel usage requirements under channel congestion. Analytical and simulation-based results show the validity of our proposed approach, and the V2X application performance improvement it renders, compared to existing standardized protocols