116 research outputs found
Performance of management solutions and cooperation approaches for vehicular delay-tolerant networks
A wide range of daily-life applications supported by vehicular networks attracted the interest,
not only from the research community, but also from governments and the automotive
industry. For example, they can be used to enable services that assist drivers on the roads (e.g.,
road safety, traffic monitoring), to spread commercial and entertainment contents (e.g., publicity),
or to enable communications on remote or rural regions where it is not possible to have
a common network infrastructure. Nonetheless, the unique properties of vehicular networks
raise several challenges that greatly impact the deployment of these networks.
Most of the challenges faced by vehicular networks arise from the highly dynamic network
topology, which leads to short and sporadic contact opportunities, disruption, variable
node density, and intermittent connectivity. This situation makes data dissemination an interesting
research topic within the vehicular networking area, which is addressed by this study.
The work described along this thesis is motivated by the need to propose new solutions to deal
with data dissemination problems in vehicular networking focusing on vehicular delay-tolerant
networks (VDTNs).
To guarantee the success of data dissemination in vehicular networks scenarios it is important
to ensure that network nodes cooperate with each other. However, it is not possible
to ensure a fully cooperative scenario. This situation makes vehicular networks suitable to the
presence of selfish and misbehavior nodes, which may result in a significant decrease of the
overall network performance. Thus, cooperative nodes may suffer from the overwhelming load
of services from other nodes, which comprises their performance.
Trying to solve some of these problems, this thesis presents several proposals and studies
on the impact of cooperation, monitoring, and management strategies on the network performance
of the VDTN architecture. The main goal of these proposals is to enhance the network
performance. In particular, cooperation and management approaches are exploited to improve
and optimize the use of network resources. It is demonstrated the performance gains attainable
in a VDTN through both types of approaches, not only in terms of bundle delivery probability,
but also in terms of wasted resources.
The results and achievements observed on this research work are intended to contribute
to the advance of the state-of-the-art on methods and strategies for overcome the challenges
that arise from the unique characteristics and conceptual design of vehicular networks.O vasto número de aplicações e cenários suportados pelas redes veiculares faz com que
estas atraiam o interesse não só da comunidade científica, mas também dos governos e da indústria
automóvel. A título de exemplo, estas podem ser usadas para a implementação de serviços
e aplicações que podem ajudar os condutores dos veículos a tomar decisões nas estradas, para
a disseminação de conteúdos publicitários, ou ainda, para permitir que existam comunicações
em zonas rurais ou remotas onde não é possível ter uma infraestrutura de rede convencional.
Contudo, as propriedades únicas das redes veiculares fazem com que seja necessário ultrapassar
um conjunto de desafios que têm grande impacto na sua aplicabilidade.
A maioria dos desafios que as redes veiculares enfrentam advêm da grande mobilidade dos
veículos e da topologia de rede que está em constante mutação. Esta situação faz com que este
tipo de rede seja suscetível de disrupção, que as oportunidades de contacto sejam escassas e de
curta duração, e que a ligação seja intermitente. Fruto destas adversidades, a disseminação dos
dados torna-se um tópico de investigação bastante promissor na área das redes veiculares e por
esta mesma razão é abordada neste trabalho de investigação. O trabalho descrito nesta tese é
motivado pela necessidade de propor novas abordagens para lidar com os problemas inerentes
à disseminação dos dados em ambientes veiculares.
Para garantir o sucesso da disseminação dos dados em ambientes veiculares é importante
que este tipo de redes garanta a cooperação entre os nós da rede. Contudo, neste tipo de ambientes
não é possível garantir um cenário totalmente cooperativo. Este cenário faz com que
as redes veiculares sejam suscetíveis à presença de nós não cooperativos que comprometem
seriamente o desempenho global da rede. Por outro lado, os nós cooperativos podem ver o seu
desempenho comprometido por causa da sobrecarga de serviços que poderão suportar.
Para tentar resolver alguns destes problemas, esta tese apresenta várias propostas e estudos
sobre o impacto de estratégias de cooperação, monitorização e gestão de rede no desempenho
das redes veiculares com ligações intermitentes (Vehicular Delay-Tolerant Networks
- VDTNs). O objetivo das propostas apresentadas nesta tese é melhorar o desempenho global
da rede. Em particular, as estratégias de cooperação e gestão de rede são exploradas para
melhorar e optimizar o uso dos recursos da rede. Ficou demonstrado que o uso deste tipo de
estratégias e metodologias contribui para um aumento significativo do desempenho da rede,
não só em termos de agregados de pacotes (“bundles”) entregues, mas também na diminuição
do volume de recursos desperdiçados.
Os resultados observados neste trabalho procuram contribuir para o avanço do estado
da arte em métodos e estratégias que visam ultrapassar alguns dos desafios que advêm das
propriedades e desenho conceptual das redes veiculares
Recommended from our members
REPSYS: A robust and distributed incentive scheme for collaborative caching and dissemination in content-centric cellular-based vehicular delay-tolerant networks
In this article, a robust and distributed incentive scheme for collaborative caching and dissemination in content-centric cellular-based vehicular delay-tolerant networks (REPSYS) is proposed. REPSYS is robust because despite taking into account first- and second-hand information, it is resilient against false accusations and praise, and distributed, as the decision to interact with another node depends entirely on each node. The performance evaluation shows that REPSYS is capable, while evaluating each node's participation in the network, of correctly classifying nodes in most cases. In addition, it reveals that there are trade-offs in REPSYS, for example, to reduce detection time of nodes that neither cache nor disseminate other nodes' data, one may sacrifice the system's resilience against false accusations and praise, or even, by penalizing nodes that do not disseminate data, one may temporarily isolate nodes that could contribute to data dissemination
Performance evaluation of cooperation strategies for m-health services and applications
Health telematics are becoming a major improvement for patients’ lives, especially for
disabled, elderly, and chronically ill people. Information and communication technologies have
rapidly grown along with the mobile Internet concept of anywhere and anytime connection.
In this context, Mobile Health (m-Health) proposes healthcare services delivering, overcoming
geographical, temporal and even organizational barriers. Pervasive and m-Health services aim
to respond several emerging problems in health services, including the increasing number of
chronic diseases related to lifestyle, high costs in existing national health services, the need
to empower patients and families to self-care and manage their own healthcare, and the need
to provide direct access to health services, regardless the time and place. Mobile Health (m-
Health) systems include the use of mobile devices and applications that interact with patients
and caretakers. However, mobile devices have several constraints (such as, processor, energy,
and storage resource limitations), affecting the quality of service and user experience. Architectures
based on mobile devices and wireless communications presents several challenged issues
and constraints, such as, battery and storage capacity, broadcast constraints, interferences, disconnections,
noises, limited bandwidths, and network delays. In this sense, cooperation-based
approaches are presented as a solution to solve such limitations, focusing on increasing network
connectivity, communication rates, and reliability. Cooperation is an important research topic
that has been growing in recent years. With the advent of wireless networks, several recent
studies present cooperation mechanisms and algorithms as a solution to improve wireless networks
performance. In the absence of a stable network infrastructure, mobile nodes cooperate
with each other performing all networking functionalities. For example, it can support intermediate
nodes forwarding packets between two distant nodes.
This Thesis proposes a novel cooperation strategy for m-Health services and applications.
This reputation-based scheme uses a Web-service to handle all the nodes reputation and networking
permissions. Its main goal is to provide Internet services to mobile devices without
network connectivity through cooperation with neighbor devices. Therefore resolving the above
mentioned network problems and resulting in a major improvement for m-Health network architectures
performances. A performance evaluation of this proposal through a real network
scenario demonstrating and validating this cooperative scheme using a real m-Health application
is presented. A cryptography solution for m-Health applications under cooperative environments,
called DE4MHA, is also proposed and evaluated using the same real network scenario and
the same m-Health application. Finally, this work proposes, a generalized cooperative application
framework, called MobiCoop, that extends the incentive-based cooperative scheme for
m-Health applications for all mobile applications. Its performance evaluation is also presented
through a real network scenario demonstrating and validating MobiCoop using different mobile
applications
A novel approach for the fast detection of black holes in mobile ad hoc networks
Mobile ad hoc networks are infrastructure-less wireless networks that rely on node cooperation to properly work. In this kind of networks, attack detection and reaction is a key issue to the whole network. The most common threat in mobile ad hoc network scenarios consists in the presence of a certain percentage of selfish nodes, which try to reduce the consumption of their own resources to prolong their battery lifetime. Those nodes do not collaborate on forwarding activities, therefore affecting the overall network performance. Watchdogs are well-known mechanisms to detect threats and attacks from misbehaved and selfish nodes in computer networks. The problem behind the use of watchdogs is that while they can be quite effective in detecting selfishness by using their traffic overhearing behaviour, they can also cause a relatively high level of false negatives, thereby reducing their accuracy. This article proposes a collaborative approach for detecting selfish nodes in mobile ad hoc networks. It is based on using a set of collaborative watchdogs, which collaborate to enhance their individual and collective performance. By using both an analytical study and simulation, we demonstrate that our approach is able to improve accuracy and detection speed, while reducing the impact of false-negative eventsThis work was partially supported by the Ministerio de Ciencia e Innovacion, Spain, under grant TIN2011-27543-C03-01.Serrat Olmos, MD.; Hernández Orallo, E.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2013). A novel approach for the fast detection of black holes in mobile ad hoc networks. Concurrent Engineering: Research and Applications. 21(3):177-185. https://doi.org/10.1177/1063293X13493448S177185213Buchegger, S., & Le Boudec, J.-Y. (2005). Self-policing mobile ad hoc networks by reputation systems. IEEE Communications Magazine, 43(7), 101-107. doi:10.1109/mcom.2005.1470831Buttyán, L., & Hubaux, J.-P. (2003). Mobile Networks and Applications, 8(5), 579-592. doi:10.1023/a:1025146013151Groenevelt, R., Nain, P., & Koole, G. (2005). The message delay in mobile ad hoc networks. Performance Evaluation, 62(1-4), 210-228. doi:10.1016/j.peva.2005.07.018Hortelano, J., Calafate, C. T., Cano, J. C., de Leoni, M., Manzoni, P., & Mecella, M. (2010). Black-Hole Attacks in P2P Mobile Networks Discovered through Bayesian Filters. Lecture Notes in Computer Science, 543-552. doi:10.1007/978-3-642-16961-8_77Li, Y., Su, G., Wu, D. O., Jin, D., Su, L., & Zeng, L. (2011). The Impact of Node Selfishness on Multicasting in Delay Tolerant Networks. IEEE Transactions on Vehicular Technology, 60(5), 2224-2238. doi:10.1109/tvt.2011.2149552Marti, S., Giuli, T. J., Lai, K., & Baker, M. (2000). Mitigating routing misbehavior in mobile ad hoc networks. Proceedings of the 6th annual international conference on Mobile computing and networking - MobiCom ’00. doi:10.1145/345910.345955T.V.P, S., & A, S. (2010). Modeling the Behavior of Selfish Forwarding Nodes to Stimulate Cooperation in MANET. International journal of Network Security & Its Applications, 2(2), 147-160. doi:10.5121/ijnsa.2010.2212Xu, L., Lin, Z., & Ye, A. (2006). Analysis and Countermeasure of Selfish Node Problem in Mobile Ad Hoc Network. 2006 10th International Conference on Computer Supported Cooperative Work in Design. doi:10.1109/cscwd.2006.253072Zhong, S., Chen, J., & Yang, Y. R. (s. f.). Sprite: a simple, cheat-proof, credit-based system for mobile ad-hoc networks. IEEE INFOCOM 2003. Twenty-second Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE Cat. No.03CH37428). doi:10.1109/infcom.2003.1209220Zhu, H., Fu, L., Xue, G., Zhu, Y., Li, M., & Ni, L. M. (2010). Recognizing Exponential Inter-Contact Time in VANETs. 2010 Proceedings IEEE INFOCOM. doi:10.1109/infcom.2010.546226
Erkennung und Vermeidung von Fehlverhalten in fahrzeugbasierten DTNs
Delay- and Disruption-Tolerant Networks (DTNs) are a suitable technology for many applications when the network suffers from intermittent connections and significant delays. In current vehicular networks, due to the high mobility of vehicles, the connectivity in vehicular networks can be highly unstable, links may change or break soon after they have been established and the network topology varies significantly depending on time and location. When the density of networked vehicles is low, connectivity is intermittent and with only a few transmission opportunities. This makes forwarding packets very difficult. For the next years, until a high penetration of networked vehicles is realized, delay-tolerant methods are a necessity in vehicular networks, leading to Vehicular DTNs (VDTNs). By implementing a store-carry-forward paradigm, VDTNs can make sure that even under difficult conditions, the network can be used by applications. However, we cannot assume that all vehicles are altruistic in VDTNs. Attackers can penetrate the communication systems of vehicles trying their best to destroy the network. Especially if multiple attackers collude to disrupt the network, the characteristics of VDTNs, without continuous connectivity, make most traditional strategies of detecting attackers infeasible. Additionally, selfish nodes may be reluctant to cooperate considering their profit, and due to hard- or software errors some vehicles cannot send or forward data. Hence, efficient mechanisms to detect malicious nodes in VDTNs are imperative. In this thesis, two classes of Misbehavior Detection Systems (MDSs) are proposed to defend VDTNs against malicious nodes. Both MDSs use encounter records (ERs) as proof to document nodes' behavior during previous contacts. By collecting and securely exchanging ERs, depending on different strategies in different classes of MDSs, a reputation system is built in order to punish bad behavior while encouraging cooperative behavior in the network. With independently operating nodes and asynchronous exchange of observations through ERs, both systems are very well suited for VDTNs, where there will be no continuous, ubiquitous network in the foreseeable future. By evaluating our methods through extensive simulations using different DTN routing protocols and different realistic scenarios, we find that both MDS classes are able to efficiently protect the system with low overhead and prevent malicious nodes from further disrupting the network.In Netzwerken mit zeitweisen Unterbrechungen oder langen Verzögerungen sind Delay- and Disruption-Tolerant Networks (DTNs) eine geeignete Technologie für viele Anwendungen. Die Konnektivität in Fahrzeugnetzen ist bedingt durch die hohe Mobilität und die geringe Verbreitung von netzwerkfähigen Fahrzeugen oft instabil. Bis zur flächendeckenden Verbreitung von netzwerkfähigen Fahrzeugen ist es daher zwingend notwendig auf Methoden des Delay Tolerant Networking zurückzugreifen um die bestmögliche Kommunikation zu gewährleisten. In diesem Zusammenhang wird von Vehicular Delay Tolerant Networks (VDTNs) gesprochen. Durch das Store-Carry-Forward-Prinzip kann ein VDTN Kommunikation für Anwendungen ermöglichen. Allerdings ist davon auszugehen, dass sich nicht alle Fahrzeuge altruistisch verhalten: Angreifer können Fahrzeuge übernehmen und das Netzwerk attackieren oder Knoten sind aus egoistischen Motiven oder auf Grund von Defekten unkooperativ. Verfahren, die Fehlverhalten in stabilen Netzen durch direkte Beobachtung erkennen können, sind in VDTNs nicht anwendbar. Daher sind Methoden, die Fehlverhalten in VDTNs nachweisen können, zwingend erforderlich. In dieser Arbeit werden zwei Klassen von Misbehavior Detection Systems (MDSs) vorgestellt. Beide Systeme basieren auf Encounter Records (ERs): Nach einem Kontakt tauschen zwei Knoten kryptografisch signierte Meta-Informationen zu den erfolgten Datentransfers aus. Diese ERs dienen bei darauffolgenden Kontakten mit anderen Netzwerkteilnehmern als vertrauenswürdiger Nachweis für das Verhalten eines Knotens in der Vergangenheit. Basierend auf der Auswertung gesammelter ERs wird ein Reputationssystem entwickelt, das kooperatives Verhalten belohnt und unkooperatives Verhalten bestraft. Dauerhaft unkooperative Knoten werden aus dem Netzwerk ausgeschlossen. Durch den asynchronen Austausch von Informationen kann jeder Knoten das Verhalten seiner Nachbarn selbstständig und unabhängig evaluieren. Dadurch sind die vorgestellten MDS-Varianten sehr gut für den Einsatz in einem VDTN geeignet. Durch umfangreiche Evaluationen wird gezeigt, dass sich die entwickelten MDS-Verfahren für verschiedene Routingprotokolle und in unterschiedlichen Szenarien anwenden lassen. In allen Fällen ist das MDS in der Lage das System mit geringem Overhead gegen Angreifer zu verteidigen und eine hohe Servicequalität im Netzwerk zu gewährleisten
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