35 research outputs found

    LVMM: The Localized Vehicular Multicast Middleware - a Framework for Ad Hoc Inter-Vehicles Multicast Communications

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    This thesis defines a novel semantic for multicast in vehicular ad hoc networks (VANETs) and it defines a middleware, the Localized Vehicular Multicast Middleware (LVMM) that enables minimum cost, source-based multicast communications in VANETs. The middleware provides support to find vehicles suitable to sustain multicast communications, to maintain multicast groups, and to execute a multicast routing protocol, the Vehicular Multicast Routing Protocol (VMRP), that delivers messages of multicast applications to all the recipients utilizing a loop-free, minimum cost path from each source to all the recipients. LVMM does not require a vehicle to know all other members: only knowledge of directly reachable nodes is required to perform the source-based routing

    Geographical Forwarding Methods in Vehicular Ad hoc Networks

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    Vehicular ad hoc networks are new and emerging technology and special class of mobile ad hoc networks that provide wireless communication between vehicles without any fixed infrastructure. Geographical routing has appeared as one of the most scalable and competent routing schemes for vehicular networks. A number of strategies have been proposed for forwarding the packets in geographical direction of the destination, where information of direct neighbors is gained through navigational services. Due to dynamically changing topologies and high mobility neighbor information become outdated. To address these common issues in network different types of forwarding strategies have been proposed. In this review paper, we concentrate on beaconless forwarding methods and their forwarding methods in detail

    Advanced Transport Protocols for Wireless and Mobile Ad Hoc Networks

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    This thesis comprises transport protocols in the following different areas of research: Fast Handover allows mobile IP end-devices to roam between wireless access routers without interruptions while communicating to devices in an infrastructure (e.g., in the Internet). This work optimizes the Fast Handover algorithm and evaluates the performance of the transport protocols UDP and TCP during fast handovers via measurements. The following part of the thesis focuses on vehicular ad hoc networks. The thesis designs and evaluates through simulations a point-to-point transport protocol for vehicular ad hoc networks and an algorithm to facilitate the reliable and efficient distribution of information in a geographically scoped target area. Finally, the thesis evaluates the impact of wireless radio fluctuations on the performance of an Ad Hoc Network. Measurements quantify the wireless radio fluctuations. Based on these results, the thesis develops a simple but realistic radio model that evaluates by means of simulations the impact on the performance of an ad hoc network. As a result, the work provides guidelines for future ad hoc protocol design

    GEM : um protocolo eficiente de difusão de mensagens geocast em redes veiculares

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    Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, 2019.A Rede Ad hoc Veicular (do Inglês, Vehicular Ad hoc Network - VANET), tecnologia desenvolvida para melhorar o ambiente de trânsito, utiliza protocolos de difusão de mensagens geocast para alertar os motoristas em situações de risco. Este trabalho apresenta uma análise sobre a eficiência de protocolos encontrados na literatura e busca propor uma alternativa que traga melhorias em seu desempenho. Através do levantamento do estado da arte, descobriu-se que o processo de difusão geocast em redes VANET pode ser realizado utilizando-se várias abordagens distintas, e que, mesmo trazendo diversas vantagens, cada uma possui características que podem ser melhoradas. Seguindo estas observações, foi desenvolvido o Protocolo de Encaminhamento de Mensagens Geocast (GEM), de abordagem reativa, que utiliza o envio periódico de beacons para auxiliar o processo de escolha de encaminhadores. O desempenho do protocolo proposto foi avaliado através de simulação computacional em um cenário de rodovia e comparado com outras duas propostas semelhantes, já consolidadas na literatura: o protocolo Inundação e o Protocolo Reativo Baseado em Distância (DR). Em todos os aspectos avaliados, a nova proposta apresentou resultados satisfatórios, obtendo desempenho superior aos protocolos comparados, com destaque para a quantidade de transmissões 13 vezes menor e a quantidade de colisões 43 vezes menor que as quantidades apresentadas pelas outras propostas no cenário mais denso. O protocolo GEM também se mostrou ser aplicável em cenários com alta ou baixa densidade de trânsito, pois seu comportamento permaneceu estável mesmo com a mudança da densidade de veículos no trânsito.Vehicular Ad hoc Network (VANET), technology developed to improve the traffic environment, uses geocast message dissemination protocols to alert drivers in risky situations. This paper presents an analyses about the efficiency of protocols found in the literature and seeks to propose an alternative that brings improvements in its performance. By surveying the state of the art, it was found that the geocast dissemination process in VANET networks can be accomplished using several different approaches, and that, while having several advantages, each has characteristics that can be improved. Following these observations, the reactive approach Geocast Message Forwarding Protocol (from Portuguese, Protocolo de Encaminhamento de Mensagens Geocast - GEM) was developed, which uses the periodic sending of beacons to assist the process of choosing forwarders. The performance of the proposed protocol was evaluated by computer simulation in a highway scenario and compared with two other similar proposals, already consolidated in literature: the Flooding protocol and the Distance-based Reactive Protocol (DR). In all evaluated aspects, the new proposal presented satisfactory results, outperforming the compared protocols, with emphasis on the number of transmissions 13 times lower and the number of collisions 43 times lower than the amounts presented by the other proposals in the denser scenario. The GEM protocol also proved to be applicable in both high or low density traffic, as its behavior has remained stable even with the change in traffic density

    A content dissemination framework for vehicular networking

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    Vehicular Networks are a peculiar class of wireless mobile networks in which vehicles are equipped with radio interfaces and are, therefore, able to communicate with fixed infrastructure (if available) or other vehicles. Content dissemination has a potential number of applications in vehicular networking, including advertising, traffic warnings, parking notifications and emergency announcements. This thesis addresses two possible dissemination strategies: i) Push-based that is aiming to proactively deliver information to a group of vehicles based on their interests and the level of matching content, and ii) Pull-based that is allowing vehicles to explicitly request custom information. Our dissemination framework is taking into consideration very specific information only available in vehicular networks: the geographical data produced by the navigation system. With its aid, a vehicle's mobility patterns become predictable. This information is exploited to efficiently deliver the content where it is needed. Furthermore, we use the navigation system to automatically filter information which might be relevant to the vehicles. Our framework has been designed and implemented in .NET C# and Microsoft MapPoint. It was tested using a small number of vehicles in the area of Cambridge, UK. Moreover, to prove the correctness of our protocols, we further evaluated it in a large-scale network simulation over a number of realistic vehicular trace-based scenarios. Finally, we built a test-case application aiming to prove that vehicles can gain from such a framework. In this application every vehicle collects and disseminates road traffic information. Vehicles that receive this information can individually evaluate the traffic conditions and take an alternative route, if needed. To evaluate this approach, we collaborated with UCLA's Network Research Lab (NRL), to build a simulator that combines network and dynamic mobility emulation simultaneously. When our dissemination framework is used, the drivers can considerably reduce their trip-times

    Melhoria de protocolos de encaminhamento em VANETs de alta densidade

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    Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia Electrotécnica e de ComputadoresA elevada mobilidade das redes ad-hoc veiculares infuencia signi cativamente o comportamento dos protocolos utilizados. Muitos dos protocolos de rede desenvolvidos para redes ad-hoc móveis exibem fraco desempenho em redes veiculares, dadas as suas características de alta mobilidade e restrição de movimentos. Como tal, este trabalho apresenta um método de controlo de topologia para redes ad-hoc veiculares. O controlo de topologia pretende caracterizar as relações de comunicação entre dois nós, identi cando as ligações que apresentam uma duração mais prolongada. Este tipo de ligaçõess entre nós oferece maior estabilidade aos protocolos de encaminhamento, diminuindo simultaneamente o tráfego de controlo. As ligações de maior duração são identi cadas por um algoritmo de baixa complexidade, sendo um critério para realizar o agrupamento de n os de forma a diminuir o tráfego de controlo associado às operaçõess de inundação da rede. A utilidade da criação de grupos com base na duração das ligações é demonstrada através da integração do algoritmo no protocolo de encaminhamento OLSR. Comparam-se as estatatísticas da taxa de sucesso de encaminhamento e do tempo necessário a visitar o nó de destino (atraso do caminho), caso exista caminho para esse nó. Os resultados obtidos com as propostas descritas nesta dissertação exibem uma melhoria de desempenho, quando comparados ao protocolo de encaminhamento OLSR. Este facto traduz-se num aumento da taxa de sucesso de encaminhamento e na redução do atraso do caminho, sendo mais signi cativo em cenários onde a densidade de nós é mais elevada
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