Road traffic safety has been a subject of worldwide concern. Dedicated short range communications (DSRC) is widely regarded as a promising enabling technology for collaborative safety applications (CSA), which can provide robust communication and affordable performance to build large scale CSA system. The main focus of this thesis is to develop solutions for DSRC QoS control in order to provide robust QoS support for CSA. The first design objective is to ensure robust and reliable message delivery services for safety applications from the DSRC networks. As the spectrum resources allocated to DSRC network are expected to be shared by both safety and non-safety applications, the second design objective is to make QoS control schemes bandwidth-efficient in order to leave as much as possible bandwidth for non-safety applications. The first part of the thesis investigates QoS control in infrastructure based DSRC networks, where roadside access points (AP) are available to control QoS control at road intersections. After analyse DSRC network capabilities on QoS provisioning without congestion control, we propose a two-phases adaptive QoS control method for DSRC vehicle networks. In the first phase an offline simulation based approach is used to and out the best possible system configurations (e.g. message rate and transmit power) with given numbers of vehicles and QoS requirements. It is noted that with different utility functions the values of optimal parameters proposed by the two phases centralized QoS control scheme will be different. The conclusions obtained with the proposed scheme are dependent on the chosen utility functions. But the proposed two phases centralized QoS control scheme is general and is applicable to different utility functions. In the second phase, these configurations are used online by roadside AP adaptively according to dynamic traffic loads. The second part of the thesis is focused on distributed QoS control for DSRC networks. A framework of collaborative QoS control is proposed, following which we utilize the local channel busy time as the indicator of network congestion and adaptively adjust safety message rate by a modified additive increase and multiplicative decrease (AIMD) method in a distributed way. Numerical results demonstrate the effectiveness of the proposed QoS control schemes.

Ad-Hoc mesh networks offer great promise. Low-cost ad-hoc mesh networks can be built using popular IEEE 802.11 equipment, but such networks are unable to guarantee each node a fair share of bandwidth. Furthermore, hidden node problems cause collisions which can cripple the throughput of a network. This research proposes a novel mechanism which is able to overcome hidden node problems and provide fair bandwidth sharing among nodes on ad-hoc 802.11 networks, and can be implemented on existing network devices. The scheme uses TDM (time division multiplexing) with slot reservation. A distributed beacon packet latency measurement mechanism is used to achieve node synchronisation. The distributed nature of the mechanism makes it applicable to ad-hoc 802.11 networks, which can either grow or fragment dynamically.

Made available in DSpace on 2015-04-11T14:03:12Z (GMT). No. of bitstreams: 1 DISSERTACAO ANDERSON.pdf: 945892 bytes, checksum: 13a676735f1c713ef1251e829d5e41bb (MD5) Previous issue date: 2006-09-13 / Fundação de Amparo à Pesquisa do Estado do Amazonas / More and more the demanding for mobility has been wanted by the users who want to have everything no matter where they are. The applications have been modified in order to attend this needs demanded by the new environment without any predictable infrastructure or topology. The adhoc networks are very popular when concerning about non-infrastructures environment and many studies have been started looking for solutions and strategies to understand and adapt the applications originally created to work over client/server architecture. Voice over IP applications also have to be adapted to work properly over this environment and this study try to identify the factors which can impact on application performance. It is made looking at the look up algorithms used by them to find other nodes around the net. / A medida que a mobilidade se torna uma exigência cada vez maior dos usuários de redes de computadores, as aplicações precisam adaptarem-se ao novo ambiente descentralizado, que por vezes, é totalmente imprevisível e mutável. As redes adhoc estão muito difundidas em cenários totalmente descentralizados e desprovidos de infra-estrutura fixa e por isso diversos estudos estão sendo realizados visando a adaptação de aplicações originalmente construídas sobre a luz da arquitetura cliente/servidor. As aplicações de voz sobre IP (VoIP) também precisam se adaptar a nova realidade, e para isso foram adotadas diversas estratégias de descentralização, sendo uma delas a utilização de algoritmos de busca P2P para prover a independência de pontos centralizadores. Este trabalho realiza um estudo do comportamento desse tipo de algoritmo sobre redes adhoc visando identificar os fatores que podem influênciar direta ou indiretamente a performance de uma aplicação VoIP que os utilize como m´método de localização de seus nós.

Internet and mobile communications have had a profound effect on today’s society. New services are constantly being deployed, in which an increasing amount of personal data is being processed in return for personally tailored services. Further, the use of electronic surveillance is increasing. There is the risk that honest citizens will have their privacy invaded for “the greater good”. We argue that it is of uttermost importance to retain the individuals’ control over their personal spheres. One approach for enhancing the users’ privacy is to deploy technical measures for safeguarding privacy, so-called Privacy-Enhancing Technologies (PETs). This thesis examines a set of PETs for enabling anonymous communication, so-called anonymous overlay networks,which eliminate the processing of personal data altogether by allowing the users act anonymously when communicating in a networked environment. This thesis focuses mainly on mobile networks. These are of great interest because on the one hand they lay the groundwork for new innovative applications, but on the other hand they pose numerous novel challenges to privacy. This thesis describes the implementation and performance evaluation of mCrowds – an anonymous overlay network for mobile Internet that enables anonymous browsing. It also describes the ongoing investigation on how to design anonymous overlay networks in order to make them suitable for mobile ad hoc networks, a required building block for ambient intelligence.

Dans les réseaux sans fil ad hoc, les liens de communication sont sujets à un taux d'erreurimportant. Dans ce contexte, le routage joue un rôle stratégique pour augmenter les performancesdans les transmissions. Dans nos études, par une approche cross-layer, nous prenons en compte lafiabilité des liens dans le choix des routes. Pour cela, dans un premier temps, nous construisonsdeux nouvelles métriques, l'une basée sur le taux d'erreur binaire (au niveau couche physique) etl'autre, plus adaptée à la mesure, sur le nombre de retransmissions (au niveau couche MAC).Ensuite, pour exploiter ces métriques lors du calcul de routes, nous adaptons les algorithmes à labase des protocoles de routage.Les trois familles de protocoles de routage ont été traitées : les protocoles pro-actifs où chaquenoeud a une vision globale du réseau grâce aux échanges périodiques de messages de contrôle detopologie ; les protocoles réactifs où, avant de commencer ses transmissions de données, chaquenoeud doit initier un processus de recherche de route ; les protocoles hybrides qui mixent les deuxapproches.Pour tester l'effectivité de nos améliorations, nous utilisons le simulateur NS2 enrichi par unmodèle de propagation et un modèle de mobilité réalistes. Les paramètres de performance tels quele délai, le taux de livraison de paquets et la charge de routage sont mesurés dans plusieursscénarios représentatifs des conditions d'utilisation. Les résultats obtenus montrent une améliorationsignificative des protocoles standards dans un contexte de qualité de service. / In ad hoc wireless networks, links are error-prone. In this context, routing plays a decisive role inimproving transmission performances. In our studies, by a cross-layer approach, we take intoaccount the reliability of links in route choice. For this, first, we concept two new metrics, onebased on bit error rate (at physical layer) and the other, more suitable for the measurement, onnumber of retransmissions (at MAC layer). Then, to exploit these metrics when determining routes,we adapt the algorithms based routing protocols.The three families of routing protocols have been addressed: proactive protocols where eachnode has a global view of the network through periodic exchanges of topology control messages;reactive protocols where, before starting data transmission, each node must initiate a routediscovery process; hybrid protocols which mix the two approaches.To test the effectiveness of our enhancements, we use the simulator NS.2 enhanced by arealistic propagation model and a realistic mobility model. Performance parameters such as delay,packets delivery ratio and routing load are measured in several scenarios including mobility andmulti-communication. The results show a significant improvement of standard protocols in thequality of service context.

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Vehicular networks are an emerging technology that offer potential for providing a variety of new services. However, extending vehicular networks to include IP connections is still problematic, due in part to the incompatibility of mobile IP handovers with the increased mobility of vehicles. The handover process, consisting of discovery, registration, and packet forwarding, has a large overhead and disrupts connectivity. With increased handover frequency and smaller access point dwell times in vehicular networks, the handover causes a large degradation in performance. This thesis proposes a predictive handover solution, using a combination of a Kalman filter and an online hidden Markov model, to minimize the effects of prediction errors and to capitalize on advanced handover registration. Extensive simulated experiments were carried out in NS-2 to study the performance of the proposed solution within a variety of traffic and network topology scenarios. Results show a significant improvement to both prediction accuracy and network performance when compared to recent proposed approaches.

Data transmission has become a need in various fields, like in social networks with the diverse interaction applications, or in the scientific and engineering areas where for example the use of sensors to capture data is growing, or in emergency situations where there is the imperative need to have a communication system to coordinate rescue operations. Wireless networks have been able to solve these issues to a great extent, but what can we do when a fixed supporting infrastructure is not available or becomes inoperative because of saturation? Opportunistic wireless networks are an alternative to consider in these situations, since their operation does not depend on the existence of a telecommunications infrastructure but they provide connectivity through the organized cooperation of users. This research thesis focuses on these types of networks and is aimed at improving the dissemination of information in opportunistic networks analyzing the main causes that influence the performance of data transmission. Opportunistic networks do not depend on a fixed topology but depend on the number and mobility of users, the type and quantity of information generated and sent, as well as the physical characteristics of the mobile devices that users have to transmit the data. The combination of these elements impacts on the duration of the contact time between mobile users, directly affecting the information delivery probability. This thesis starts by presenting a thorough "state of the art" study where we present the most important contributions related to this area and the solutions offered for the evaluation of the opportunistic networks, such as simulation models, routing protocols, simulation tools, among others. After offering this broad background, we evaluate the consumption of the resources of the mobile devices that affect the performance of the the applications of opportunistic networks, both from the energetic and the memory point of view. Next, we analyze the performance of opportunistic networks considering either pedestrian and vehicular environments. The studied approaches include the use of additional fixed nodes and different data transmission technologies, to improve the duration of the contact between mobile devices. Finally, we propose a diffusion scheme to improve the performance of data transmission based on extending the duration of the contact time and the likelihood that users will collaborate in this process. This approach is complemented by the efficient management of the resources of the mobile devices. / La transmisión de datos se ha convertido en una necesidad en diversos ámbitos, como en las redes sociales con sus diversas aplicaciones, o en las áreas científicas y de ingeniería donde, por ejemplo, el uso de sensores para capturar datos está creciendo, o en situaciones de emergencia donde impera la necesidad de tener un sistema de comunicación para coordinar las operaciones de rescate. Las redes inalámbricas actuales han sido capaces de resolver estos problemas en gran medida, pero ¿qué podemos hacer cuando una infraestructura de soporte fija no está disponible o estas se vuelven inoperantes debido a la saturación de peticiones de red? Las redes inalámbricas oportunísticas son una alternativa a considerar en estas situaciones, ya que su funcionamiento no depende de la existencia de una infraestructura de telecomunicaciones sino que la conectividad es a través de la cooperación organizada de los usuarios. Esta tesis de investigación se centra en estos tipos de redes oportunísticas y tiene como objetivo mejorar la difusión de información analizando las principales causas que influyen en el rendimiento de la transmisión de datos. Las redes oportunísticas no dependen de una topología fija, sino que dependen del número y la movilidad de los usuarios, del tipo y cantidad de información generada y enviada, así como de las características físicas de los dispositivos móviles que los usuarios tienen para transmitir los datos. La combinación de estos elementos influye en la duración del tiempo de contacto entre usuarios móviles, afectando directamente a la probabilidad de entrega de información. Esta tesis comienza presentando un exhaustivo estudio del ``estado del arte", donde presentamos las contribuciones más importantes relacionadas con esta área y las soluciones existentes para la evaluación de las redes oportunísticas, tales como modelos de simulación, protocolos de enrutamiento, herramientas de simulación, entre otros. Tras ofrecer esta amplia compilación de investigaciones, se evalúa el consumo de recursos de los dispositivos móviles que afectan al rendimiento de las aplicaciones de redes oportunísticas, desde el punto de vista energético así como de la memoria. A continuación, analizamos el rendimiento de las redes oportunísticas considerando tanto los entornos peatonales como vehiculares. Los enfoques estudiados incluyen el uso de nodos fijos adicionales y diferentes tecnologías de transmisión de datos, para mejorar la duración del contacto entre dispositivos móviles. Finalmente, proponemos un esquema de difusión para mejorar el rendimiento de la transmisión de datos basado en la extensión de la duración del tiempo de contacto, y de la probabilidad de que los usuarios colaboren en este proceso. Este enfoque se complementa con la gestión eficiente de los recursos de los dispositivos móviles. / La transmissió de dades s'ha convertit en una necessitat en diversos àmbits, com ara en les xarxes socials amb les diverses aplicacions d'interacció, o en les àrees científiques i d'enginyeria, en les quals, per exemple, l'ús de sensors per a capturar dades creix en l'actualitat, o en situacions d'emergència en què impera la necessitat de tenir un sistema de comunicació per a coordinar les operacions de rescat. Les xarxes sense fil han sigut capaces de resoldre aquests problemes en gran manera, però què podem fer quan una infraestructura de suport fixa no està disponible, o bé aquestes es tornen inoperants a causa de la saturació de peticions de xarxa? Les xarxes sense fil oportunistes són una alternativa que cal considerar en aquestes situacions, ja que el funcionament d'aquestes xarxes no depèn de l'existència d'una infraestructura de telecomunicacions, sinó que la connectivitat s'hi aconsegueix a través de la cooperació organitzada dels usuaris. Aquesta tesi de recerca se centra en aquest tipus de xarxes, i té com a objectiu millorar la difusió d'informació en xarxes oportunistes tot analitzant les principals causes que influeixen en el rendiment de la transmissió de dades. Les xarxes oportunistes no depenen d'una topologia fixa, sinó del nombre i la mobilitat dels usuaris, del tipus i la quantitat d'informació generada i enviada, i de les característiques físiques dels dispositius mòbils que els usuaris tenen per a transmetre les dades. La combinació d'aquests elements influeix en la durada del temps de contacte entre usuaris mòbils, i afecta directament la probabilitat de lliurament d'informació. Aquesta tesi comença amb un estudi exhaustiu de l'estat de la qüestió, en què presentem les contribucions més importants relacionades amb aquesta àrea i les solucions oferides per a l'avaluació de les xarxes oportunistes, com ara models de simulació, protocols d'encaminament o eines de simulació, entre d'altres. Després de mostrar aquest ampli panorama, s'avalua el consum dels recursos dels dispositius mòbils que afecten l'acompliment de les aplicacions de xarxes oportunistes, tant des del punt de vista energètic com de la memòria. A continuació, analitzem l'acompliment de xarxes oportunistes considerant tant els entorns de vianants com els vehiculars. Els enfocaments estudiats inclouen l'ús de nodes fixos addicionals i diferents tecnologies de transmissió de dades per a millorar la durada del contacte entre dispositius mòbils. Finalment, proposem un esquema de difusió per a millorar el rendiment de la transmissió de dades basat en l'extensió de la durada del temps de contacte, i de la probabilitat que els usuaris col·laboren en aquest procés. Aquest enfocament es complementa amb la gestió eficient dels recursos dels dispositius mòbils. / Herrera Tapia, J. (2017). Improving Message Dissemination in Opportunistic Networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86129 / TESIS

A mobile ad hoc network (MANET) is an infrastructure-less multi-hop network where each node communicates with other nodes directly or indirectly through intermediate nodes. Thus, all nodes in a MANET basically function as mobile routers participating in some routing protocol required for deciding and maintaining the routes. Since MANETs are infrastructure-less, self-organizing, rapidly deployable wireless networks, they are highly suitable for applications such as military tactical operations, search and rescue missions, disaster relief operations, and target tracking. Building such ad-hoc networks poses a significant technical challenge because of energy constraints and specifically in relation to the application of wireless network protocols. As a result of its highly dynamic and distributed nature, the routing layer within the wireless network protocol stack, presents one of the key technical challenges in MANETs. In particular, energy efficient routing may be the most important design criterion for MANETs since mobile nodes are powered by batteries with limited capacity and variable recharge frequency, according to application demand. In order to conserve power it is essential that a routing protocol be designed to guarantee data delivery even should most of the nodes be asleep and not forwarding packets to other nodes. Load distribution constitutes another important approach to the optimisation of active communication energy. Load distribution enables the maximisation of the network lifetime by facilitating the avoidance of over-utilised nodes when a route is in the process of being selected. Routing algorithms for mobile networks that attempt to optimise routes while at- tempting to retain a small message overhead and maximise the network lifetime has been put forward. However certain of these routing protocols have proved to have a negative impact on node and network lives by inadvertently over-utilising the energy resources of a small set of nodes in favour of others. The conservation of power and careful sharing of the cost of routing packets would ensure an increase in both node and network lifetimes. This thesis proposes simultaneously, by using an ant colony optimisation (ACO) approach, to optimise five power-aware metrics that do result in energy-efficient routes and also to maximise the MANET's lifetime while taking into consideration a realistic mobility model. By using ACO algorithms a set of optimal solutions - the Pareto-optimal set - is found. This thesis proposes five algorithms to solve the multi-objective problem in the routing domain. The first two algorithms, namely, the energy e±ciency for a mobile network using a multi-objective, ant colony optimisation, multi-pheromone (EEMACOMP) algorithm and the energy efficiency for a mobile network using a multi-objective, ant colony optimisation, multi-heuristic (EEMACOMH) algorithm are both adaptations of multi-objective, ant colony optimisation algorithms (MOACO) which are based on the ant colony system (ACS) algorithm. The new algorithms are constructive which means that in every iteration, every ant builds a complete solution. In order to guide the transition from one state to another, the algorithms use pheromone and heuristic information. The next two algorithms, namely, the energy efficiency for a mobile network using a multi-objective, MAX-MIN ant system optimisation, multi-pheromone (EEMMASMP) algorithm and the energy efficiency for a mobile network using a multi-objective, MAX- MIN ant system optimisation, multi-heuristic (EEMMASMH) algorithm, both solve the above multi-objective problem by using an adaptation of the MAX-MIN ant system optimisation algorithm. The last algorithm implemented, namely, the energy efficiency for a mobile network using a multi-objective, ant colony optimisation, multi-colony (EEMACOMC) algorithm uses a multiple colony ACO algorithm. From the experimental results the final conclusions may be summarised as follows:<ul><li> Ant colony, multi-objective optimisation algorithms are suitable for mobile ad hoc networks. These algorithms allow for high adaptation to frequent changes in the topology of the network. </li><li> All five algorithms yielded substantially better results than the non-dominated sorting genetic algorithm (NSGA-II) in terms of the quality of the solution. </li><li> All the results prove that the EEMACOMP outperforms the other four ACO algorithms as well as the NSGA-II algorithm in terms of the number of solutions, closeness to the true Pareto front and diversity. </li></ul> / Thesis (PhD)--University of Pretoria, 2010. / Computer Science / unrestricted