Proceedings - 8th IEEE International Conference on Mobile Ad-hoc and Sensor Systems, MASS 2011, 2011
given to me. Additionally, I'd like to thank to all members of the VDTN team, but especially to m... more given to me. Additionally, I'd like to thank to all members of the VDTN team, but especially to my colleagues Bruno Silva, João Alfredo, and Vasco Soares for all the daily support and help. My highest gratitude to all my family, especially to my parents and sister, for being a constant source of support, love, and inspiration. I am forever indebted to them.
Eurasip Journal on Wireless Communications and Networking, 2014
In the last decade, both scientific community and automotive industry enabled communications amon... more In the last decade, both scientific community and automotive industry enabled communications among vehicles in different kinds of scenarios proposing different vehicular architectures. Vehicular delay-tolerant networks (VDTNs) were proposed as a solution to overcome some of the issues found in other vehicular architectures, namely, in dispersed regions and emergency scenarios. Most of these issues arise from the unique characteristics of vehicular networks. Contrary to delay-tolerant networks (DTNs), VDTNs place the bundle layer under the network layer in order to simplify the layered architecture and enable communications in sparse regions characterized by long propagation delays, high error rates, and short contact durations. However, such characteristics turn contacts very important in order to exchange as much information as possible between nodes at every contact opportunity. One way to accomplish this goal is to enforce cooperation between network nodes. To promote cooperation among nodes, it is important that nodes share their own resources to deliver messages from others. This can be a very difficult task, if selfish nodes affect the performance of cooperative nodes. This paper studies the performance of a cooperative reputation system that detects, identify, and avoid communications with selfish nodes. Two scenarios were considered across all the experiments enforcing three different routing protocols (First Contact, Spray and Wait, and GeoSpray). For both scenarios, it was shown that reputation mechanisms that punish aggressively selfish nodes contribute to increase the overall network performance.
Resumo alargado em Português Introdução Esta secção resume, de forma alargada, os 4 anos de traba... more Resumo alargado em Português Introdução Esta secção resume, de forma alargada, os 4 anos de trabalho de investigação no âmbito da tese de doutoramento intitulada "Performance of Management Solutions and Cooperation Approaches for Vehicular Delay-Tolerant Networks". Esta tese foca-se no estudo e proposta de estratégias e metodologias de cooperação, monitorização e gestão de rede para ambientes veiculares. Numa primeira fase é descrito o enquadramento da tese, definido o problema abordado e os principais objetivos do estudo. De seguida, a hipótese de investigação é descrita e são apresentadas as principais contribuições deste trabalho para o avanço do estado da arte. Enquadramento da Tese Uma rede veicular pode ser definida como uma rede que se auto-organiza, onde os veículos se deslocam ao longo das estradas, comunicando uns com os outros ou com algum tipo de infraestrutura rodoviária. Este tipo de rede permite que as mensagens/informações possam circular pela rede sem necessidade de uma infraestrutura de rede tradicional. Para comunicarem entre si, os veículos estão equipados com dispositivos sem fios de curto alcance. Dada a grande mobilidade dos veículos, a topologia das redes veiculares está em constante mutação, o que se traduz numa rede em que os nós podem estar localizados dentro ou fora do alcance do raio de comunicação uns dos outros [1-3]. Nos últimos anos, este tipo de redes tem vindo a atrair muita atenção, não só da comunidade científica, mas também dos governos e da indústria automóvel. Algumas empresas ou consórcios do ramo automóvel têm no mercado, ou estão a desenvolver, protótipos de automóveis equipados com sensores, computadores de bordo, e dispositivos de comunicação sem fios [4-6]. Com base nesta tendência, é esperado que nos próximos anos as redes veiculares comecem a ter bastante utilidade e a serem usadas em diversos cenários. Uma das principais razões para o interesse exponencial neste tipo de redes é o elevado número de ambientes, serviços e aplicações que suportam. Alguns destes serviços e aplicações têm um impacto direto na vida diária das pessoas [7]. Por exemplo, as redes veiculares podem ser usadas para melhorar a segurança nas estradas, para otimizar o tráfego rodoviário e a capacidade das vias automóveis, ou ainda para recolher dados de sensores em redes de monitorização. Podem também ser usadas para permitir àqueles que viajam dentro dos veículos possam usufruir de serviços comerciais (ex., publicidade) ou usar aplicações de entretenimento (ex., partilha de conteúdo multimédia). As redes veiculares não se limitam a ser implementadas em cenários urbanos ou em áreas desenvolvidas. Estas também podem ser usadas em ambientes rurais ou em cenários de catástrofe, permitindo a existência de comunicações onde não é possível ter uma infraestrutura convencional de rede/comunicação. Apesar dos inúmeros cenários em que podem ser aplicadas, as redes veiculares têm ainda de ultrapassar alguns desafios/problemas de cariz tecnológico. Alguns destes desafios são partilhados pelas redes ad hoc e sem fios, enquanto outros advêm das propriedades únicas deste tipo xvii [33] Maicke C. G.
2016 Eighth International Conference on Ubiquitous and Future Networks (ICUFN), 2016
Vehicular Delay Tolerant Networks (VDTNs) appears as an innovative approach to deal with several ... more Vehicular Delay Tolerant Networks (VDTNs) appears as an innovative approach to deal with several issues faced by vehicular communications. By exploiting vehicles and deploying a DTN store-carry-and-forward paradigm with an Internet protocol over VDTN it is possible to enable asynchronous communications in the absence of end-to-end links. VDTNs also combine a bundle-oriented communication with an out-of-band signaling approach. To ensure that network nodes follow the protocol contributing to the welfare of the network, network monitoring and management functions play a key role. This paper proposes and describes a monitoring and management tool for VDTNs, called MoM, which collects realtime information from the network in order to improve the overall network performance. Conducted studies shown that MoM contributes to increase the bundle delivery probability and decreases the amount of wasted resources.
Vehicular Delay-Tolerant Network (VDTN) is a new disruptive network architecture where vehicles a... more Vehicular Delay-Tolerant Network (VDTN) is a new disruptive network architecture where vehicles act as the communication infrastructure. VDTN follows a layered architecture based on control and data planes separation, and positioning the bundle layer under the network layer. VDTN furnishes low-cost asynchronous communications coping with intermittent and sparse connectivity, variable delays and even no endto-end connection. This paper presents a VDTN prototype (testbed) proposal, which implements and validates the VDTN layered architecture considering the proposed outof-band signaling. The main goals of the prototype are emulation, demonstration, performance evaluation, and diagnose of protocol stacks and services, proving the applicability of VDTNs over a wide range of environments.
2011 7th EURO-NGI Conference on Next Generation Internet Networks, NGI 2011 - Proceedings, 2011
Vehicular Delay-Tolerant Networks use the delaytolerant architecture and protocols to overcome th... more Vehicular Delay-Tolerant Networks use the delaytolerant architecture and protocols to overcome the disruptions in network connectivity. These concepts help in cases where the network is sparse or with large variations in density or there is no end-to-end connectivity, by providing a communications solution for non real-time applications. This paper presents data fragmentation techniques to optimize the efficiency of data delivery for the case of the short node contacts that characterize vehicle networks. The techniques were tested in a laboratory environment with portable digital assistants and Lego Mindstorm NXT robotic cars. If no fragmentation is used, only small messages are successfully transferred. Proactive fragmentation fragments messages to a predefined size in the source node. Reactive fragmentation adjusts the fragment sizes to the real duration of the contact when it is broken. Reactive fragmentation showed a good efficiency in adapting the fragmentation in real time to the contact duration. Proactive fragmentation can perform slightly better if the fragment sizes are carefully chosen as it requires less processing. As this choice is difficult, reactive fragmentation is more practical to use.
2011 7th EURO-NGI Conference on Next Generation Internet Networks, 2011
The Vehicular Delay-Tolerant Networks (VTDN) project proposed a novel architecture for VDTN. Besi... more The Vehicular Delay-Tolerant Networks (VTDN) project proposed a novel architecture for VDTN. Besides positioning the bundle layer below the network layer, it employs out-of-band signaling and devises the separation of the control plane and data plane. A laboratory prototype was created to demonstrate this approach. The project also developed new applications, fragmentation mechanisms, content storage and retrieval mechanisms, dropping and scheduling policies, and routing protocols for VDTNs.
Vehicular networks experience a number of unique challenges due to the high mobility of vehicles ... more Vehicular networks experience a number of unique challenges due to the high mobility of vehicles and highly dynamic network topology, short contact durations, disruption intermittent connectivity, significant loss rates, node density, and frequent network fragmentation. All these issues have a profound impact on routing strategies in these networks. This paper gives an insight about available solutions on related literature for vehicular communications. It overviews and compares the most relevant approaches for data communication in these networks, discussing their influence on routing strategies. It intends to stimulate research and contribute to further advances in this rapidly evolving area where many key open issues that still remain to be addressed are identified.
Eurasip Journal on Wireless Communications and Networking, 2012
Vehicular delay-tolerant network (VDTN) is a network architecture based on the delay-tolerant net... more Vehicular delay-tolerant network (VDTN) is a network architecture based on the delay-tolerant network paradigm, which was designed to provide low-cost asynchronous vehicular communications in environments with disruptions, intermittency, variable delays, and network partition. This article proposes a laboratory testbed for VDTNs, called VDTN@Lab. It aims to support research studies related with the design, emulation, performance evaluation, and diagnose of new VDTN protocols, services, and applications. It intends to demonstrate the applicability of VDTNs over multiple application environments. VDTN@Lab features an emulation capability, allowing live experiments with prototyped hardware and software embedded into robotic cards, desktop, and netbooks computers. The proposed prototype is demonstrated and evaluated with Epidemic, and Spray, and Wait routing protocols, using different combinations of scheduling and dropping policies, in scenarios with different vehicular mobility models (bus movement and random movement across roads).
João A. Dias1, João N. Isento1, Bruno M. Silva1,2, Vasco NGJ Soares1,2, Paulo S. Ferreira3, Antón... more João A. Dias1, João N. Isento1, Bruno M. Silva1,2, Vasco NGJ Soares1,2, Paulo S. Ferreira3, António MD Nogueira3, and Joel JPC Rodrigues1,2 ... 1Department of Informatics, University of Beira Interior 2Instituto de Telecomunicações, NetGNA Group
Proceedings - 8th IEEE International Conference on Mobile Ad-hoc and Sensor Systems, MASS 2011, 2011
given to me. Additionally, I'd like to thank to all members of the VDTN team, but especially to m... more given to me. Additionally, I'd like to thank to all members of the VDTN team, but especially to my colleagues Bruno Silva, João Alfredo, and Vasco Soares for all the daily support and help. My highest gratitude to all my family, especially to my parents and sister, for being a constant source of support, love, and inspiration. I am forever indebted to them.
Eurasip Journal on Wireless Communications and Networking, 2014
In the last decade, both scientific community and automotive industry enabled communications amon... more In the last decade, both scientific community and automotive industry enabled communications among vehicles in different kinds of scenarios proposing different vehicular architectures. Vehicular delay-tolerant networks (VDTNs) were proposed as a solution to overcome some of the issues found in other vehicular architectures, namely, in dispersed regions and emergency scenarios. Most of these issues arise from the unique characteristics of vehicular networks. Contrary to delay-tolerant networks (DTNs), VDTNs place the bundle layer under the network layer in order to simplify the layered architecture and enable communications in sparse regions characterized by long propagation delays, high error rates, and short contact durations. However, such characteristics turn contacts very important in order to exchange as much information as possible between nodes at every contact opportunity. One way to accomplish this goal is to enforce cooperation between network nodes. To promote cooperation among nodes, it is important that nodes share their own resources to deliver messages from others. This can be a very difficult task, if selfish nodes affect the performance of cooperative nodes. This paper studies the performance of a cooperative reputation system that detects, identify, and avoid communications with selfish nodes. Two scenarios were considered across all the experiments enforcing three different routing protocols (First Contact, Spray and Wait, and GeoSpray). For both scenarios, it was shown that reputation mechanisms that punish aggressively selfish nodes contribute to increase the overall network performance.
Resumo alargado em Português Introdução Esta secção resume, de forma alargada, os 4 anos de traba... more Resumo alargado em Português Introdução Esta secção resume, de forma alargada, os 4 anos de trabalho de investigação no âmbito da tese de doutoramento intitulada "Performance of Management Solutions and Cooperation Approaches for Vehicular Delay-Tolerant Networks". Esta tese foca-se no estudo e proposta de estratégias e metodologias de cooperação, monitorização e gestão de rede para ambientes veiculares. Numa primeira fase é descrito o enquadramento da tese, definido o problema abordado e os principais objetivos do estudo. De seguida, a hipótese de investigação é descrita e são apresentadas as principais contribuições deste trabalho para o avanço do estado da arte. Enquadramento da Tese Uma rede veicular pode ser definida como uma rede que se auto-organiza, onde os veículos se deslocam ao longo das estradas, comunicando uns com os outros ou com algum tipo de infraestrutura rodoviária. Este tipo de rede permite que as mensagens/informações possam circular pela rede sem necessidade de uma infraestrutura de rede tradicional. Para comunicarem entre si, os veículos estão equipados com dispositivos sem fios de curto alcance. Dada a grande mobilidade dos veículos, a topologia das redes veiculares está em constante mutação, o que se traduz numa rede em que os nós podem estar localizados dentro ou fora do alcance do raio de comunicação uns dos outros [1-3]. Nos últimos anos, este tipo de redes tem vindo a atrair muita atenção, não só da comunidade científica, mas também dos governos e da indústria automóvel. Algumas empresas ou consórcios do ramo automóvel têm no mercado, ou estão a desenvolver, protótipos de automóveis equipados com sensores, computadores de bordo, e dispositivos de comunicação sem fios [4-6]. Com base nesta tendência, é esperado que nos próximos anos as redes veiculares comecem a ter bastante utilidade e a serem usadas em diversos cenários. Uma das principais razões para o interesse exponencial neste tipo de redes é o elevado número de ambientes, serviços e aplicações que suportam. Alguns destes serviços e aplicações têm um impacto direto na vida diária das pessoas [7]. Por exemplo, as redes veiculares podem ser usadas para melhorar a segurança nas estradas, para otimizar o tráfego rodoviário e a capacidade das vias automóveis, ou ainda para recolher dados de sensores em redes de monitorização. Podem também ser usadas para permitir àqueles que viajam dentro dos veículos possam usufruir de serviços comerciais (ex., publicidade) ou usar aplicações de entretenimento (ex., partilha de conteúdo multimédia). As redes veiculares não se limitam a ser implementadas em cenários urbanos ou em áreas desenvolvidas. Estas também podem ser usadas em ambientes rurais ou em cenários de catástrofe, permitindo a existência de comunicações onde não é possível ter uma infraestrutura convencional de rede/comunicação. Apesar dos inúmeros cenários em que podem ser aplicadas, as redes veiculares têm ainda de ultrapassar alguns desafios/problemas de cariz tecnológico. Alguns destes desafios são partilhados pelas redes ad hoc e sem fios, enquanto outros advêm das propriedades únicas deste tipo xvii [33] Maicke C. G.
2016 Eighth International Conference on Ubiquitous and Future Networks (ICUFN), 2016
Vehicular Delay Tolerant Networks (VDTNs) appears as an innovative approach to deal with several ... more Vehicular Delay Tolerant Networks (VDTNs) appears as an innovative approach to deal with several issues faced by vehicular communications. By exploiting vehicles and deploying a DTN store-carry-and-forward paradigm with an Internet protocol over VDTN it is possible to enable asynchronous communications in the absence of end-to-end links. VDTNs also combine a bundle-oriented communication with an out-of-band signaling approach. To ensure that network nodes follow the protocol contributing to the welfare of the network, network monitoring and management functions play a key role. This paper proposes and describes a monitoring and management tool for VDTNs, called MoM, which collects realtime information from the network in order to improve the overall network performance. Conducted studies shown that MoM contributes to increase the bundle delivery probability and decreases the amount of wasted resources.
Vehicular Delay-Tolerant Network (VDTN) is a new disruptive network architecture where vehicles a... more Vehicular Delay-Tolerant Network (VDTN) is a new disruptive network architecture where vehicles act as the communication infrastructure. VDTN follows a layered architecture based on control and data planes separation, and positioning the bundle layer under the network layer. VDTN furnishes low-cost asynchronous communications coping with intermittent and sparse connectivity, variable delays and even no endto-end connection. This paper presents a VDTN prototype (testbed) proposal, which implements and validates the VDTN layered architecture considering the proposed outof-band signaling. The main goals of the prototype are emulation, demonstration, performance evaluation, and diagnose of protocol stacks and services, proving the applicability of VDTNs over a wide range of environments.
2011 7th EURO-NGI Conference on Next Generation Internet Networks, NGI 2011 - Proceedings, 2011
Vehicular Delay-Tolerant Networks use the delaytolerant architecture and protocols to overcome th... more Vehicular Delay-Tolerant Networks use the delaytolerant architecture and protocols to overcome the disruptions in network connectivity. These concepts help in cases where the network is sparse or with large variations in density or there is no end-to-end connectivity, by providing a communications solution for non real-time applications. This paper presents data fragmentation techniques to optimize the efficiency of data delivery for the case of the short node contacts that characterize vehicle networks. The techniques were tested in a laboratory environment with portable digital assistants and Lego Mindstorm NXT robotic cars. If no fragmentation is used, only small messages are successfully transferred. Proactive fragmentation fragments messages to a predefined size in the source node. Reactive fragmentation adjusts the fragment sizes to the real duration of the contact when it is broken. Reactive fragmentation showed a good efficiency in adapting the fragmentation in real time to the contact duration. Proactive fragmentation can perform slightly better if the fragment sizes are carefully chosen as it requires less processing. As this choice is difficult, reactive fragmentation is more practical to use.
2011 7th EURO-NGI Conference on Next Generation Internet Networks, 2011
The Vehicular Delay-Tolerant Networks (VTDN) project proposed a novel architecture for VDTN. Besi... more The Vehicular Delay-Tolerant Networks (VTDN) project proposed a novel architecture for VDTN. Besides positioning the bundle layer below the network layer, it employs out-of-band signaling and devises the separation of the control plane and data plane. A laboratory prototype was created to demonstrate this approach. The project also developed new applications, fragmentation mechanisms, content storage and retrieval mechanisms, dropping and scheduling policies, and routing protocols for VDTNs.
Vehicular networks experience a number of unique challenges due to the high mobility of vehicles ... more Vehicular networks experience a number of unique challenges due to the high mobility of vehicles and highly dynamic network topology, short contact durations, disruption intermittent connectivity, significant loss rates, node density, and frequent network fragmentation. All these issues have a profound impact on routing strategies in these networks. This paper gives an insight about available solutions on related literature for vehicular communications. It overviews and compares the most relevant approaches for data communication in these networks, discussing their influence on routing strategies. It intends to stimulate research and contribute to further advances in this rapidly evolving area where many key open issues that still remain to be addressed are identified.
Eurasip Journal on Wireless Communications and Networking, 2012
Vehicular delay-tolerant network (VDTN) is a network architecture based on the delay-tolerant net... more Vehicular delay-tolerant network (VDTN) is a network architecture based on the delay-tolerant network paradigm, which was designed to provide low-cost asynchronous vehicular communications in environments with disruptions, intermittency, variable delays, and network partition. This article proposes a laboratory testbed for VDTNs, called VDTN@Lab. It aims to support research studies related with the design, emulation, performance evaluation, and diagnose of new VDTN protocols, services, and applications. It intends to demonstrate the applicability of VDTNs over multiple application environments. VDTN@Lab features an emulation capability, allowing live experiments with prototyped hardware and software embedded into robotic cards, desktop, and netbooks computers. The proposed prototype is demonstrated and evaluated with Epidemic, and Spray, and Wait routing protocols, using different combinations of scheduling and dropping policies, in scenarios with different vehicular mobility models (bus movement and random movement across roads).
João A. Dias1, João N. Isento1, Bruno M. Silva1,2, Vasco NGJ Soares1,2, Paulo S. Ferreira3, Antón... more João A. Dias1, João N. Isento1, Bruno M. Silva1,2, Vasco NGJ Soares1,2, Paulo S. Ferreira3, António MD Nogueira3, and Joel JPC Rodrigues1,2 ... 1Department of Informatics, University of Beira Interior 2Instituto de Telecomunicações, NetGNA Group
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