Distributed Data Management in Vehicular Networks Using Mobile Agents

En los últimos años, las tecnologías de la información y las comunicaciones se han incorporado al mundo de la automoción gracias a sus avances, y han permitido la creación de dispositivos cada vez más pequeños y potentes. De esta forma, los vehículos pueden ahora incorporar por un precio asequible equipos informáticos y de comunicaciones.En este escenario, los vehículos que circulan por una determinada zona (como una ciudad o una autopista) pueden comunicarse entre ellos usando dispositivos inalámbricos que les permiten intercambiar información con otros vehículos cercanos, formando así una red vehicular ad hoc, o VANET (Vehicular Ad hoc Network). En este tipo de redes, las comunicaciones se establecen con conexiones punto a punto por medio de dispositivos tipo Wi-Fi, que permiten la comunicación con otros del mismo tipo dentro de su alcance, sin que sea necesaria la existencia previa de una infraestructura de comunicaciones como ocurre con las tecnologías de telefonía móvil (como 3G/4G), que además requieren de una suscripción y el pago de una tarifa para poder usarlas.Cada vehículo puede enviar información y recibirla de diversos orígenes, como el propio vehículo (por medio de los sensores que lleva incorporados), otros vehículos que se encuentran cerca, así como de la infraestructura de tráfico presente en las carreteras (como semáforos, señales, paneles electrónicos de información, cámaras de vigilancia, etc.). Todos estas fuentes pueden transmitir datos de diversa índole, como información de interés para los conductores (por ejemplo, atascos de tráfico o accidentes en la vía), o de cualquier otro tipo, mientras sea posible digitalizarla y enviarla a través de una red.Todos esos datos pueden ser almacenados localmente en los ordenadores que llevan los vehículos a medida que son recibidos, y sería muy interesante poder sacarles partido por medio de alguna aplicación que los explotara. Por ejemplo, podrían utilizarse los vehículos como plataformas móviles de sensores que obtengan datos de los lugares por los que viajan. Otro ejemplo de aplicación sería la de ayudar a encontrar plazas de aparcamiento libres en una zona de una ciudad, usando la información que suministrarían los vehículos que dejan una plaza libre.Con este fin, en esta tesis se ha desarrollado una propuesta de la gestión de datos basada en el uso de agentes móviles para poder hacer uso de la información presente en una VANET de forma eficiente y flexible. Esta no es una tarea trivial, ya que los datos se encuentran dispersos entre los vehículos que forman la red, y dichos vehículos están constantemente moviéndose y cambiando de posición. Esto hace que las conexiones de red establecidas entre ellos sean inestables y de corta duración, ya que están constantemente creándose y destruyéndose a medida que los vehículos entran y salen del alcance de sus comunicaciones debido a sus movimientos.En un escenario tan complicado, la aproximación que proponemos permite que los datos sean localizados, y que se puedan hacer consultas sobre ellos y transmitirlos de un sitio cualquiera de la VANET a otro, usando estrategias multi-salto que se adaptan a las siempre cambiantes posiciones de los vehículos. Esto es posible gracias a la utilización de agentes móviles para el procesamiento de datos, ya que cuentan con una serie de propiedades (como su movilidad, autonomía, adaptabilidad, o inteligencia), que hace que sean una elección muy apropiada para este tipo de entorno móvil y con un elevado grado de incertidumbre.La solución propuesta ha sido extensamente evaluada y probada por medio de simulaciones, que demuestran su buen rendimiento y fiabilidad en redes vehiculares con diferentes condiciones y en diversos escenarios.<br /

Design and evaluation of two geocast protocols for vehicular ad-hoc networks

Vehicular ad-hoc networks (VANETs) offer a large number of new potential applications. One of the envisioned applications is of course Internet access, which can be provided with the help of some roadside basestations. Many of the applications benefit from multi-hop relaying of information, thus requiring a routing protocol. Characteristics unique to VANETs (such as high mobility and the need for geographical addressing) make many conventional ad hoc routing protocols unsuitable. In this paper we design and evaluate two different, so called, geocast protocols for VANETs. One protocol is designed for fast communication across a large area. The purpose of the other protocol is to provide a routing service for a future reliable transport protocol (enabling Internet applications). We evaluate the performance of the protocols using realistic network and traffic models

Dissemination of contextual information for assisted driving

Mestrado em Engenharia Electrónica e TelecomunicaçõesDriver assistance systems can be used to improve road and car safety, reduce driving fatigue and provide a more e cient driving experience. An important part of these systems is the communication between vehicles, and vehicle-to-infrastructure communication. This work presents mechanisms enabling driving support, exploring the vehicular network to provide information about the drivers neighborhood. The network is composed by vehicles, tra c signals and xed stations along the road. Each car is equipped with a recording camera, a GPS receiver, as well as communication modules such as WiFi, WAVE and 3G/4G, allowing the exchange of data between the various nodes. The data exchanged is composed by positional data of neighboring vehicles, sensor information from tra c signals and video images incoming from other vehicles. This data is used to facilitate the driver in decision making, but can also provide an overview of the tra c density in the neighborhood. The tra c signals broadcast their position and if they are dynamic (such as tra c lights), their status is also transmitted. The xed stations are equipped with numerous sensors and are used to provide environmental data. The driver can access all the collected data via visual information, on a display screen that contains a map of the neighborhood along with the information available of the nearby nodes. The proposed system is evaluated through real vehicular experiments in two distinct scenarios: urban and highway. The results show that the communication delay is higher in the highway scenario, mainly due to the distance between vehicles and travelling speeds. However, promising results regarding the maximum delay and the average number of retransmissions foresee important inputs for future services of assisted-driving, in general, and carovertaking assistance, in particular.Os sistemas de condução assistida podem ser utilizados para melhorar a segurança rodoviária e automóvel, reduzir a fadiga da condução e proporcionar uma experiência de condução mais e ciente. Uma parte importante desses sistemas e a comunicação entre veículos e comunicação veiculo infraestrutura. Este trabalho propõe mecanismos que permitem o suporte a condução, explorando a rede de veicular para fornecer informações sobre a vizinhança do condutor. A rede e composta por veículos, sinais de transito e estações fixas ao longo da estrada. Cada carro esta equipado com uma camera de gravação, um receptor GPS, bem como módulos de comunicação, como WiFi, WAVE e 3G/4G, permitindo a troca de dados entre os vários nos. Os dados trocados são compostos por dados posicionais de veículos vizinhos, informações sensoriais de sinais de trânsito e imagens de vídeo provenientes de outros veículos. Esses dados s~ao usados para facilitar a tomada de decisões, mas também podem fornecer uma vis~ao geral da densidade de tráfego na vizinhança. Os sinais de transito transmitem a sua posição e, no caso de serem dinâmicos (como semáforos), o seu estado actual também e transmitido. As estações fixas estão equipadas com vários sensores e sao usadas para fornecer dados ambientais. O condutor pode aceder a todos os dados recolhidos através de informações visuais, num ecrã que contém um mapa da sua redondeza junto com a informação disponível dos nos vizinhos. O sistema proposto e avaliado através de testes reais em dois cenários distintos: urbano e auto-estrada. Os resultados mostram que o atraso da comunicação e maior no cenário da auto-estrada, principalmente devido as maiores distancias entre os veículos e as velocidades mais elevadas. No entanto, resultados promissores em relação ao atraso máximo e ao numero médio de retransmissões prevêem contribuições importantes para serviços futuros de condução assistida em geral, e assistência de ultrapassagem de veículos, em particular

Fixed Cluster Based Cluster Head Selection Algorithm in Vehicular Adhoc Network

The emergence of Vehicular Adhoc Networks (VANETs) is expected support variety of applications for driver assistance, traffic efficiency and road safety. For proper transmission of messages in VANET, one of the proposed solutions is dividing the network into clusters and then selecting a cluster head (CH) in each cluster. This can decrease the communication overhead between road side units (RSUs) and other components of VANETs, because instead of every node communicating with RSU, only CH communicates with RSU and relays relevant messages. In clustering, an important step is the selection of CH. In this thesis, we implemented vehicle to vehicle (V2V), cluster head to road side unit and road side unit to trusted authority authentication for the clustered network. We also presented a heuristic algorithm for selecting a suitable vehicle as the cluster head in a cluster. For the selection of head vehicle, we used weighted fitness values based on three parameters; trust value, position from the cluster boundary and absolute relative average speed. Simulation results indicate that the proposed approach can lead to improvements in terms of QoS metrics like delay, throughput and packet delivery ratio

A holistic framework to improve message delivery in vehicular ad-hoc networks

Vehicular Ad-hoc Networks (VANETs) are wireless communication networks for vehicles that do not require any fixed or central infrastructure. It forms an important part of the intelligent transport system (ITS) which is the convergence of telecommunications, computing and wireless systems with the aim of improving transportation regarding efficiency, safety and management. In addition to the uses of ITS, VANETs will contribute in service access, cooperative driving, entertainment and navigation for cars of the future. Due to the varied use of VANETs, it becomes slightly cumbersome having a "one-fits-all" solution to challenges facing message dissemination in VANETs. While some applications might require a fast and reliable way of disseminating messages amongst members of the network, other applications might be more delay-tolerant without adding extra risks to the dependents of such application. Data dissemination methods are therefore important aspects of VANET that ensure messages are delivered to areas beyond the scope of the originating node. However, several types of research have shown that message propagation for each geographical route is unique to that route, owing to the number of network participants, their speed, and distribution of objects on that route. Many research designs do not consider the vehicles and their traffic characteristics and as such vehicular ad-hoc networks are under-utilised. One of the problems present in the emerging field of vehicular communications is that of optimally disseminating messages within the network to support services such as collision warnings, traffic management, and driverless vehicles amongst others. This problem is a unique research area which involves the entire network and its ability to support the efficient propagation of data. Message dissemination in VANETs could be viewed as routing on much higher macroscopic level, however, the techniques usually applied to data routing on a microscopic level does not utilise available data to efficiently disseminate messages within a vehicular ad-hoc network. Some work done in literature addresses a few constraints at a time; for example a focus on junctions, thereby ignoring vast areas of the wireless network which could have been otherwise used to improve the overall ability to efficiently deliver messages within the road network. For this reason, this thesis investigates the effects of several vehicular factors, how these factors affect the quality of the wireless network on each road, and how this knowledge is advantageous in improving the delivery of messages from a source to its destination within a vehicular ad-hoc network. In proposing a solution that uses otherwise largely ignored road traffic data to improving efficient message delivery, a holistic framework that utilises road traffic information in a unique way is presented. The quality of a wireless network for each road in terms of packets delivered is seen to be influenced by the number of vehicles and their speed which is seen to be unique for each road segment; therefore, allowing the generation of a wireless packet delivery map offline (wireless network map) based on varying number of vehicles and speeds. Current road traffic data can then be compared against the wireless map in order to determine which routes have good network quality and hence the ability to support better message dissemination. This framework is also aimed at helping to fully utilise the VANET bandwidth available by reducing network noise caused by multiple retransmissions of nodes in the network by picking the right path and using only the furthest node on each path. It aims to reduce messages delivery failure, reduce delays in the message delivery where possible and improve the utilisation of vehicles as communication nodes and relays. The Framework for Improving Message Delivery in VANETs (FIMDEV) proposed in this thesis shows the benefit of using the wireless communication database information processed by each vehicle to support message delivery from source to destination within the VANET. Experiments show improved overall packet delivery ratio when compared to standalone routing protocols as FIMDEV uses the wireless network database along with a set of rules for propagating messages within the network

Improving Vehicular ad hoc Network Protocols to Support Safety Applications in Realistic Scenarios

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/10251/9195Palanci

FRIEND: A Cyber-Physical System for Traffic Flow Related Information Aggregation and Dissemination

The major contribution of this thesis is to lay the theoretical foundations of FRIEND — A cyber-physical system for traffic Flow-Related Information aggrEgatioN and Dissemination. By integrating resources and capabilities at the nexus between the cyber and physical worlds, FRIEND will contribute to aggregating traffic flow data collected by the huge fleet of vehicles on our roads into a comprehensive, near real-time synopsis of traffic flow conditions. We anticipate providing drivers with a meaningful, color-coded, at-a-glance view of flow conditions ahead, alerting them to congested traffic. FRIEND can be used to provide accurate information about traffic flow and can be used to propagate this information. The workhorse of FRIEND is the ubiquitous lane delimiters (a.k.a. cat\u27s eyes) on our roadways that, at the moment, are used simply as dumb reflectors. Our main vision is that by endowing cat\u27s eyes with a modest power source, detection and communication capabilities they will play an important role in collecting, aggregating and disseminating traffic flow conditions to the driving public. We envision the cat\u27s eyes system to be supplemented by road-side units (RSU) deployed at regular intervals (e.g. every kilometer or so). The RSUs placed on opposite sides of the roadway constitute a logical unit and are connected by optical fiber under the median. Unlike inductive loop detectors, adjacent RSUs along the roadway are not connected with each other, thus avoiding the huge cost of optical fiber. Each RSU contains a GPS device (for time synchronization), an active Radio Frequency Identification (RFID) tag for communication with passing cars, a radio transceiver for RSU to RSU communication and a laptop-class computing device. The physical components of FRIEND collect traffic flow-related data from passing vehicles. The collected data is used by FRIEND\u27s inference engine to build beliefs about the state of the traffic, to detect traffic trends, and to disseminate relevant traffic flow-related information along the roadway. The second contribution of this thesis is the development of an incident classification and detection algorithm that can be used to classify different types of traffic incident Then, it can notify the necessary target of the incident. We also compare our incident detection technique with other VANET techniques. Our third contribution is a novel strategy for information dissemination on highways. First, we aim to prevent secondary accidents. Second, we notify drivers far away from the accident of an expected delay that gives them the option to continue or exit before reaching the incident location. A new mechanism tracks the source of the incident while notifying drivers away from the accident. The more time the incident stays, the further the information needs to be propagated. Furthermore, the denser the traffic, the faster it will backup. In high density highways, an incident may form a backup of vehicles faster than low density highways. In order to satisfy this point, we need to propagate information as a function of density and time

Design and Evaluation of a Traffic Safety System based on Vehicular Networks for the Next Generation of Intelligent Vehicles

La integración de las tecnologías de las telecomunicaciones en el sector del automóvil permitirá a los vehículos intercambiar información mediante Redes Vehiculares, ofreciendo numerosas posibilidades. Esta tesis se centra en la mejora de la seguridad vial y la reducción de la siniestralidad mediante Sistemas Inteligentes de Transporte (ITS). El primer paso consiste en obtener una difusión eficiente de los mensajes de advertencia sobre situaciones potencialmente peligrosas. Hemos desarrollado un marco para simular el intercambio de mensajes entre vehículos, utilizado para proponer esquemas eficientes de difusión. También demostramos que la disposición de las calles tiene gran influencia sobre la eficiencia del proceso. Nuestros algoritmos de difusión son parte de una arquitectura más amplia (e-NOTIFY) capaz de detectar accidentes de tráfico e informar a los servicios de emergencia. El desarrollo y evaluación de un prototipo demostró la viabilidad del sistema y cómo podría ayudar a reducir el número de víctimas en carretera

Adaptive Transmission Power Level with Vehicle Speed Approximation of Density for VANET Congestion Control

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

Schemes for multi-hop dissemination of non-safety information in VANETs

Vehicular Ad Hoc Networks (VANETs) are a special case of Mobile Ad Hoc Network (MANET), whose nodes are vehicles and occasional fixed devices with communication capabilities. What makes them special is the limited range of possible movements of the mobile nodes (they can only travel on the existing roads or rails) and their high speed. The potential applications in this new type of network are almost endless. Researchers have typically classified them in four groups: active safety, public service support, improved driving and business/entertainment. The communication patterns that they require are varied, being information dissemination one of them. It is aimed at reaching a group of vehicles in an area that is larger than the reception range of a single node, so that a multi-hop broadcast is necessary. It can take multiple forms depending on the type of message. For example, a warning caused by a sudden brake requires a fast and reliable dissemination, whereas a blocked route announcement is tolerant to delays up to a few seconds and may miss some target without risking safety. The work in this PhD thesis is focused on this last type of use. The objective is to create schemes that would allow for the multi-hop dissemination of messages that do not have hard delay and delivery requirements (typically, any non-safety information). Our goals for this solution are four. First, we want it to be useful in roadways as well as inside cities. Vehicles movements and the occurrence of obstacles to the signal propagation are very different in both scenarios and so we need to adapt it to both. Second, we want it to be independent of infrastructure. The cost of deploying fixed units along every road and street is high and it may take a long time until there is global coverage. Our intention is that this solution can be used regardlessly of the deployment point. In addition, it must avoid the broadcast storm problem by reducing as much as possible the number of generated duplicates. Lastly, the scheme needs to cope with intermittent partitions in the vehicular network. Implementing a store-carry-forward mechanism that allows a message reach disconnected groups of vehicles inside the destination area rises the number of necessary duplicates. In order to achieve the aforementioned goals, we first study how typical infrastructure-less dissemination schemes from the state of the art in MANETs, plus a new specific one, apply to VANETs. According to their results in relation to a series of metrics, we learn that the distance-based scheme is the one that best meets our requirements. We select it to create an optimized scheme for the two existing scenarios-roadways and urban areas. Regarding the adaptation for roadways, we begin by optimizing the scheme so that its forwarding ratio is as close to the minimum as possible, and analyzing its average per-hop delay in a connected network (i.e., there is at least one feasible route between any two nodes in the network). Next, we study how to add a custom store-carry-forward mechanism that, with minimal additions, manages to overcome short-lived network partitions. We validate the addition and the complete scheme under different channel loads and in contrast with a well-known protocol aimed at the same type of traffic, DV-CAST. Our work on the version for urban scenarios parts from the assumption that we need to detect junctions and react accordingly in order to spread the dissemination in new directions and reach as many vehicles as possible. We create two different modifications of the basic distance-based scheme, each using a different method to detect intersections, and test them along with the basic one. This first step leads us to discovering that it is not necessary to detect intersections in order to achieve good results. Then, similarly to the process for the roadway scenario, we work on optimizing the scheme and creating a suitable store-carry-forward mechanism. We follow the same reasoning but this time we consider three different options for subsequent retransmissions. We test each version of the scheme throughly via simulations using real city maps and compare the results to those of the urban counterpart of DV-CAST, named UV-CAST. We use validated simulators as ns-2 and the Veins framework for testing realistically the different stages of our work. The performance of the resulting schemes meet our requirements to a high degree and so we consider that we have fulfilled our goals. In addition, the work done so far opens the door to new lines of research that are either the natural consequence or an application of our achievements.La expresión inglesa Vehicular Ad Hoc Networks (VANETs) nombra a un tipo especial de Mobile Ad Hoc Network (MANET), cuyos nodos son vehículos y, ocasionalmente, dispositivos fijos con capacidad de comunicación. Lo que las hace especiales es el rango limitado de movimientos posibles para los nodos móviles (ya que sólo pueden viajar por las vías existentes) y su alta velocidad. Las aplicaciones potenciales de este nuevo tipo de red son casi infinitas. La comunidad investigadora las ha clasificado típicamente en cuatro grupos: seguridad activa, apoyo a servicios públicos, asistencia a la conducción y negocios/entretenimiento. Los patrones de comunicación que precisan son variados, siendo la diseminación de información uno de ellos. Su objetivo es alcanzar a un grupo de vehículos en un área mayor que el de la cobertura alcanzada por un nodo, de modo que es necesaria una difusión multisalto. Esta puede tomar múltiples formas dependiendo del tipo de mensaje. Por ejemplo, una alarma provocada por un frenazo brusco requiere una diseminación rápida y confiable, mientras que un aviso de calle cortada es tolerante a retardos de hasta algunos segundos y si no alcanza a algún destinatario no supone un riesgo para la seguridad. El trabajo contenido en esta tesis se enfoca en este último caso de uso. La meta es crear esquemas que permitan la diseminación multisalto de mensajes que no tienen requisitos fuertes en cuanto a retardo y entrega (típicamente, cualquier información no relacionada con la seguridad). Nuestros objetivos para esta solución son cuatro. Primero, queremos que sea útil en carretera así como en ciudad. Los movimientos de los vehículos y la existencia de obstáculos para la propagación de la señal son muy diferentes en ambos escenarios y por tanto necesitamos adaptarla a ambos. Segundo, queremos que no dependa de infraestructura. El coste de desplegar unidades fijas a lo largo de cada calle y carretera es alto, y puede llevar un largo tiempo hasta que haya cobertura global. Nuestra intención es que esta solución pueda ser usada en cualquier punto del proceso de despliegue. Además, debe evitar el problema conocido como “tormenta broadcast”, reduciendo en la medida de lo posible el número de duplicados generados. Por último, el esquema necesita hacer frente a particiones intermitentes de la red vehicular. Implementar un mecanismo de los llamados “store-carry-forward” (guardar-llevar-reenviar), que permita a un mensaje llegar a grupos desconectados de vehículos dentro de la zona de destino, aumenta el número de duplicados necesarios. Para conseguir estos objetivos, primero estudiamos cómo esquemas típicos de diseminación sin apoyo de infraestructura, tomados del estado del arte en MANETs, más uno nuevo y específico, se pueden aplicar en VANETs. De acuerdo con los resultados en relación con una serie de métricas, hemos aprendido que el esquema basado en distancia es el que mejor cubre nuestros requisitos. Seleccionamos este para crear un esquema optimizado para los dos tipos de escenarios existentes: carretera (entorno interurbano) y ciudad (entorno urbano). En cuanto a la adaptación al entorno interurbano, comenzamos optimizando el esquema de modo que su tasa de reenvío esté tan cerca del mínimo como sea posible, y analizando su retardo medio por salto en una red conectada (es decir, que hay al menos una ruta posible entre dos nodos cualesquiera de la red). A continuación, estudiamos cómo añadir un mecanismo “store-carry-forward" específico para nuestra solución que, con cambios mínimos, consiga superar particiones de red breves. Validamos este añadido y el esquema completo bajo diferentes cargas de canal y en contraste con un conocido protocolo para este mismo tipo de tráfico, DV-CAST. Nuestro trabajo en la versión para escenarios urbanos parte del supuesto de que necesitamos detectar intersecciones y reaccionar en consecuencia para poder extender la diseminación en nuevas direcciones y alcanzar tantos vehículos como sea posible. Creamos dos modificaciones del esquema basado en distancia, cada una en base a un método distinto para detectar cruces, y las probamos junto con el esquema básico. Este primer paso nos lleva a descubrir que no es necesaria dicha detección para poder conseguir buenos resultados. Después, de forma similar al proceso que seguimos para el escenario de carretera, trabajamos en optimizar el esquema y crear un mecanismo “store-carry-forward" apropiado. Seguimos el mismo razonamiento pero en esta ocasión consideramos tres opciones diferentes para las repetidas retransmisiones. Probamos cada versión del esquema concienzudamente con simulaciones, utilizando mapas reales de ciudades, y comparamos los resultados con los del equivalente urbano de DV-CAST, llamado UV-CAST. Usamos simuladores validados como ns-2 y Veins para probar de forma realista las diferentes etapas de nuestro trabajo. Las prestaciones de los esquemas resultantes cumplen con nuestros requisitos en un alto grado, por lo que consideramos que hemos conseguido alcanzar nuestros objetivos. Además, el trabajo realizado hasta el momento abre la puerta a nuevas líneas de investigación que son, bien consecuencia natural, bien aplicación de nuestros logros.Programa Oficial de Doctorado en Ingeniería TelemáticaPresidente: Juan Carlos Cano Escriba.- Secretario: Florina Almenares Mendoza.- Vocal: José Marta Barcelo Ordina