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  • A collaborative node management scheme for energy-efficient monitoring in wireless multimedia sensor networks

     Alaei, Mohammad; Barcelò Ordinas, José María
    Wireless networks
    Date of publication: 2013-07-01
    Journal article

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    Clustering in sensor networks provides energy conservation, network scalability, topology stability, reducing overhead and also allows data aggregation and cooperation in data sensing and processing. Wireless Multimedia Sensor Networks are characterized for directional sensing, the Field of View (FoV), in contrast to scalar sensors in which the sensing area usually is more uniform. In this paper, we first group multimedia sensor nodes in clusters with a novel cluster formation approach that associates nodes based on their common sensing area. The proposed cluster formation algorithm, called Multi-Cluster Membership (MCM), establishes clusters with nodes that their FoVs overlap at least in a minimum threshold area. The name of Multi-Cluster Membership comes from the fact that a node may belong to multiple clusters, if its FoV intersects more than one cluster-head and satisfies the threshold area. Comparing with Single-Cluster Membership (SCM) schemes, in which each node belongs to exactly one cluster, because of the capability of coordination between intersected clusters, MCM is more efficient in terms of energy conservation in sensing and processing subsystems at the cost of adding complexity in the node/cluster coordination. The main imposed difficulty by MCM, is the coordination of nodes and clusters for collaborative monitoring; SCMs usually assign tasks in a round-robin manner. Then, as second contribution, we define a node selection and scheduling algorithm for monitoring the environment that introduces intra and inter-cluster coordination and collaboration, showing how the network lifetime is prolonged with high lifetime prolongation factors particularly in dense deployments.

  • Understanding, modeling and taming mobile malware epidemics in a large-scale vehicular network

     Trullols Cruces, Oscar; Fiore, Marco; Barcelò Ordinas, José María
    IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks
    Presentation's date: 2013-07
    Presentation of work at congresses

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    The large-scale adoption of vehicle-to-vehicle (V2V) communication technologies risks to significantly widen the attack surface available to mobile malware targeting critical automobile operations. Given that outbreaks of vehicular computer worms self-propagating through V2V links could pose a significant threat to road traffic safety, it is important to understand the dynamics of such epidemics and to prepare adequate countermeasures. In this paper we perform a comprehensive characterization of the infection process of variously behaving vehicular worms on a road traffic scenario of unprecedented scale and heterogeneity. We then propose a simple yet effective data-driven model of the worm epidemics, and we show how it can be leveraged for smart patching infected vehicles through the cellular network in presence of a vehicular worm outbreak.

    The large-scale adoption of vehicle-to-vehicle (V2V) communication technologies risks to significantly widen the attack surface available to mobile malware targeting critical automobile operations. Given that outbreaks of vehicular computer worms self-propagating through V2V links could pose a significant threat to road traffic safety, it is important to understand the dynamics of such epidemics and to prepare adequate countermeasures. In this paper we perform a comprehensive characterization of the infection process of variously behaving vehicular worms on a road traffic scenario of unprecedented scale and heterogeneity. We then propose a simple yet effective data-driven model of the worm epidemics, and we show how it can be leveraged for smart patching infected vehicles through the cellular network in presence of a vehicular worm outbreak.

  • Duo-MAC: Energy and time constrained data delivery MAC protocol in wireless sensor networks

     Doudou, Messaoud; Alaei, Mohammad; Djenouri, Diamel; Barcelò Ordinas, José María; Badache, Nadjib
    International Wireless Communications and Mobile Computing Conference
    Presentation's date: 2013-07
    Presentation of work at congresses

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    We present Duo-MAC, an asynchronous cascading wake-up scheduled MAC protocol for heterogeneous traffic forwarding in low-power wireless networks. Duo-MAC deals with energy-delay minimization problem and copes with transmission latency encountered by Today's duty-cycled protocols when forwarding heterogeneous traffic types. It switches, according to the energy and delay requirements, between Low Duty cycle (LDC) and High Duty Cycle (HDC) operating modes, and it quietly adjusts the wake-up schedule of a node according to (i) its parent's wake-up time and (ii) its estimated load, using an effective real-time signal processing linear traffic estimator. As a second contribution, Duo-MAC, proposes a service differentiation through an improved contention window adaptation algorithm to meet delay requirements of heterogeneous traffic classes. Duo-MAC's efficiency stems from balancing between the two traffic award operation modes. Implementation and experimentation of Duo-MAC on a MicaZ mote platform reveals that the protocol outperforms other state-of-the-art MAC protocols from the energy-delay minimization perspective.

  • Channel Assignment protocols for Multi-Radio Multi-Channel Wireless Mesh Netwworks  Open access

     Amiri Nezhad, Maryam
    Defense's date: 2013-01-30
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    The increasing demand for large and low cost wireless coverage, ranging from campus to city wide areas, has motivated a high interest in multi-hop communications with Wireless Mesh Networks (WMN) based on IEEE 802.11s as the most recent and significant standard. Channel Assignment (CA) is mechanism which selects the best channels for an individual wireless node or the entire network aiming to increase the capacity of the network. Channel assignment has been extensively researched for multi-radio WMNs, but it is still very challenging when it comes to its implementation. Although IEEE 802.11s introduces new inter-working, routing and wireless frame forwarding at the link layer, the multi channel architecture receives less attention due to many unsolved challenges that arises while mesh service set works over multiple frequencies. This research work tries to give a solution to the needs of designing an efficient channel assignment mechanism. As a result we have proposed a new static channel assignment based on the fact that not all wireless links are practically useful. Our mechanism prunes the network topology by removing weak wireless links and improves the network performance by reaching a more diverse channel-radio assignation solution. Toward designing a distributed channel assignment we propose a new game theory based formulation of channel assignment which is applicable to a realistic scenario with imperfect information at each router. We have proposed a distributed and hybrid channel assignment protocol based on the game formulation. The proposed channel assignment makes wireless router to be able to follow the unpredictable changes in the wireless environment. We also investigated the types of channel assignment protocols which can be adapted to the IEEE 802.11s based mesh network and improve the network good-put in terms of data delivery ratio and end-to-end delay.

  • Energy Efficient Cooperative Node Management for Wireless Multimedia Sensor Networks  Open access

     Alaei, Mohammad
    Defense's date: 2013-06-27
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    In Wireless Multimedia Sensor Networks (WMSNs) the lifetime of battery operated visual nodes is limited by their energy consumption, which is proportional to the energy required for sensing, processing, and transmitting the data. The energy consumed in multimedia sensor nodes is much more than in the scalar sensors; a multimedia sensor captures images or acoustic signals containing a huge amount of data while in the scalar sensors a scalar value is measured (e.g., temperature). On the other hand, given the large amount of data generated by the visual nodes, both processing and transmitting image data are quite costly in terms of energy in comparison with other types of sensor networks. Accordingly, energy efficiency and prolongation of the network lifetime has become a key challenge in design and implementation of WMSNs. Clustering in sensor networks provides energy conservation, network scalability, topology stability, reducing overhead and also allows data aggregation and cooperation in data sensing and processing. Wireless Multimedia Sensor Networks (WMSNs) are characterized for directional sensing, the Field of View (FoV), in contrast to scalar sensors in which the sensing area usually is uniform and non-directional. Therefore, clustering and the other coverage-based techniques designed for WSNs, do not satisfy WMSNs. In WMSNs, sensor management policies are needed to assure balance between the opposite requirements imposed by the wireless networking and vision processing tasks. While reducing energy consumption by limiting data transmissions is the primary challenge of energy-constrained visual sensor networks, the quality of the image data and application, QoS, improve as the network provides more data. In such an environment, the optimization methods for sensor management developed for wireless sensor networks are hard to apply to multimedia sensor networks. Such sensor management policies usually employ the clustering methods which form clusters based on sensor neighbourhood or radiocoverage. But, as it was mentioned, because of the main difference between directional sensing region of multimedia sensors and the sensing range of scalar sensors, these schemes designed for WSNs, do not have efficiency for WMSNs. Moreover, sensor management strategies of WSNs do not consider the eventdriven nature of multimedia sensor networks, nor do they consider the unpredictability of data traffic caused by a monitoring procedure. This thesis, first, present a novel clustering mechanism based on the overlapping of the FoV of multimedia nodes. The proposed clustering method establishes clusters with grouping nodes that their FoVs overlap at least in a minimum threshold area. Two styles of cluster membership are offered by the mechanism depending on the desired network application; Single Cluster Membership (SCM) and Multi Cluster Membership (MCM). The name of MCM comes from the fact that a node may belong to multiple clusters, if its FoV intersects more than one cluster-head (CH) and satisfies the threshold area while in SCM each node belongs to exactly one cluster. Then, the proposed node management schemes designed for WMSNs are presented; the node selection and scheduling schemes manage the acts of the multimedia sensor nodes in a collaborative manner in clusters with employing the mentioned clustering method. Intra-Cluster Cooperation (ICC) and Intra&Inter-Cluster Cooperation (IICC) use the SCM and MCM clusters respectively. The monitoring period is optimized and the sensing region is divided among clusters and multimedia tasks are performed applying cooperation within and between clusters. The objective is conserving the residual energy of nodes to prolong the network lifetime. Finally, a hybrid architecture for WMSNs in order to energy efficient collaborative surveillance is proposed. The proposed mechanism employs a mixed random deployment of acoustic and visual sensor nodes. Acoustic sensors detect and localize the occurred event/object(s) in a duty-cycled manner by sampling the received signals and then trigger the visual sensor nodes covering the objects to monitor them. Hence, visual sensors are warily scheduled to be awakened just for monitoring the object(s) detected in their domain, otherwise they save their energy. Section B. 4 of Chapter I introduces the contributions of this thesis.

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    Power management in sensing subsystem of wireless multimedia sensor networks  Open access

     Alaei, Mohammad; Barcelò Ordinas, José María
    Date of publication: 2012-03-14
    Book chapter

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    A wireless sensor network consists of sensor nodes deployed over a geographical area for monitoring physical phenomena like temperature, humidity, vibrations, seismic events, and so on. Typically, a sensor node is a tiny device that includes three basic components: a sensing subsystem for data acquisition from the physical surrounding environment, a processing subsystem for local data processing and storage, and a wireless communication subsystem for data transmission. In addition, a power source supplies the energy needed by the device to perform the programmed task. This power source often consists of a battery with a limited energy budget. In addition, it is usually impossible or inconvenient to recharge the battery, because nodes are deployed in a hostile or unpractical environment. On the other hand, the sensor network should have a lifetime long enough to fulfill the application requirements. Accordingly, energy conservation in nodes and maximization of network lifetime are commonly recognized as a key challenge in the design and implementation of WSNs. Experimental measurements have shown that generally data transmission is very expensive in terms of energy consumption, while data processing consumes significantly less (Raghunathan et al., 2002). The energy cost of transmitting a single bit of information is approximately the same as that needed for processing a thousand operations in a typical sensor node (Pottie & Kaiser, 2000). The energy consumption of the sensing subsystem depends on the specific sensor type. In some cases of scalar sensors, it is negligible with respect to the energy consumed by the processing and, above all, the communication subsystems. In other cases, the energy expenditure for data sensing may be comparable to, or even greater (in the case of multimedia sensing) than the energy needed for data transmission. In general, energy-saving techniques focus on two subsystems: the communication subsystem (i.e., energy management is taken into account in the operations of each single node, as well as in the design of networking protocols), and the sensing subsystem (i.e., techniques are used to reduce the amount or frequency of energy-expensive samples).

  • RSU deployment for content dissemination and downloading in intelligent transportation systems

     Reineri, Massimo; Casetti, Claudio; Chiasserini, Carla-Fabiana; Fiore, Marco; Trullols Cruces, Oscar; Barcelò Ordinas, José María
    Date of publication: 2012-10-01
    Book chapter

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  • A hybrid cooperative design for energy-efficient surveillance in wireless multimedia sensor networks

     Alaei, Mohammad; Barcelò Ordinas, José María
    European Wireless Conference
    Presentation's date: 2012-04-19
    Presentation of work at congresses

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    In Wireless Multimedia Sensor Networks (WMSNs) the lifetime of battery-operated visual nodes is limited by their energy consumption, which is proportional to the energy required for sensing, processing, and transmitting the data. Given the large amount of data generated by the visual nodes, both processing and transmitting image data are quite costly in terms of energy in comparison with other types of sensor networks. Therefore, energy efficiency is a main concern in WMSNs. In this paper an energy efficient collaborative mechanism for environment surveillance is proposed. The proposed scheme employs a mixed random deployment of acoustic and visual sensor nodes. Acoustic sensors detect and localize the occurred event/object(s) in a duty-cycled manner by sampling the received signals and then trigger the visual sensor nodes covering the objects to monitor them. Hence, visual sensors are warily scheduled to be awakened just for monitoring the object(s) detected in their domain, otherwise they save their energy.

  • Real-time multimedia monitoring in large-scale wireless multimedia sensor networks: research challenges

     Cesana, Matteo; Redondi, Alessandro; Tiglao, Nestor; Grilo, Antonio; Barcelò Ordinas, José María; Alaei, Mohammad; Todorova, Petia
    Conference on Next Generation Internet Networks
    Presentation's date: 2012
    Presentation of work at congresses

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    Wireless Sensor Networks (WSNs) have enjoyed dramatic developments over the last decade. The availability of CMOS cameras and microphones enlarged the scope of WSNs paving the way to the development of Wireless Multimedia Sensor Networks (WMSN). Among the envisaged WMSN applications, Real-time Multimedia Monitoring constitutes one of the most promising. However, the resource requirements of these applica- tions place difficult challenges in terms of network lifetime and scalability. This paper starts by identifying the main charac- teristics and requirements of Real-time Multimedia Monitoring applications and then highlights key research directions that may help to overcome those challenges

    Wireless Sensor Networks (WSNs) have enjoyed dramatic developments over the last decade. The availability of CMOS cameras and microphones enlarged the scope of WSNs paving the way to the development of Wireless Multimedia Sensor Networks (WMSN). Among the envisaged WMSN applications, Real-time Multimedia Monitoring constitutes one of the most promising. However, the resource requirements of these applications place difficult challenges in terms of network lifetime and scalability. This paper starts by identifying the main characteristics and requirements of Real-time Multimedia Monitoring applications and then highlights key research directions that may help to overcome those challenges.

  • Cooperative download in vehicular environments

     Trullols Cruces, Oscar; Fiore, Marco; Barcelò Ordinas, José María
    IEEE transactions on mobile computing
    Date of publication: 2012-04
    Journal article

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  • A survey of visual sensor network platforms

     Tavli, Bülent; Bicakci, Kemal; Zilan, Ruken; Barcelò Ordinas, José María
    Multimedia tools and applications
    Date of publication: 2012-09
    Journal article

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  • Power saving trade-offs in delay/disruptive tolerant networks

     Trullols Cruces, Oscar; Morillo Pozo, Julian David; Barcelò Ordinas, José María; Garcia Vidal, Jorge
    IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks
    Presentation of work at congresses

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    Wireless nodes such as smart-phones in which the WiFi wireless card is continuously on, consume battery energy in just a few hours. Moreover, in many scenarios, an always-on wireless card is useless because there is often no need for transmission and/or reception. This fact is exacerbated in Delay/Disruptive Tolerant Network (DTN) environments, in which nodes exchange Delay Tolerant Objects (DTO) when they meet. Power Saving Management (PSM) techniques enable the lifetime of the nodes to be extended. This paper analyses the trade-offs that appear when wireless nodes periodically turn off the wireless card in order to save battery in DTN environments. The paper shows the conditions in which a node can switch off the battery without impacting the peer-to-peer contact probability, and those in which this contact probability is decreased. For example, it is shown that node lifetime can be doubled while keeping the peer-to-peer contact probability equal to one. But, further increase of the node lifetime quickly decreases peer-to-peer contact probability. Finally, the impact of power savings in DTO dissemination time is also analyzed.

  • VANET mobility modeling challenged by feedback loops

     Meyer, Harald; Trullols Cruces, Oscar; Hess, Andrea; Hummel, Karin Anna; Barcelò Ordinas, José María; Casetti, Claudio; Karlsson, Gunnar
    IEEE IFIP Annual Mediterranean Ad Hoc Networking Workshop
    Presentation of work at congresses

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    VANET applications are often providing street traffic information to vehicles and drivers, regarding, for instance, traffic conditions and parking space availability. This information influences in turn the driving behavior in real-world settings. Mobility models used in current VANET simulations are mostly ignoring this feedback entirely. In cases the feedback is included, it is mainly based on ad-hoc approaches with lack of generality. With this paper, we contribute to the investigation of such feedback loops within VANETs by describing the levels at which feedback loops can be introduced, i.e., on strategic, tactical, and operational levels of mobility. We further describe how feedback loops can be introduced in arbitrary mobility models and in particular in elementary mobility models. We exemplify our approach by introducing two types of feedback loops for the Manhattan Mobility model, the Random Trip model, and the Constrained Random Trip model. One feedback loop represents points of interest attracting vehicles, such as free parking spaces attracting vehicles searching for parking. The other feedback loop focuses on repelling vehicles, such as a traffic jam. We discuss the impacts of the feedback in terms of the mobility metrics: vehicle density per area, number of direction changes, and intensity of direction changes. Furthermore, we discuss the effects in terms of information availability and delays of transmission in an opportunistic vehicular network.

  • Impact of the infrastructure in mobile opportunistic networks

     Trullols Cruces, Oscar; Morillo Pozo, Julian David; Barcelò Ordinas, José María
    International Symposium on Applied Sciences in Biomedical and Communication Technologies
    Presentation's date: 2011
    Presentation of work at congresses

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    Epidemic modeling has been used to analyze many disciplines such as biology, ecology and medicine. In the last years, it also has been applied to networking paradigms such as social networks, virus spreading in Internet and lastly to opportunistic networking in mobile networks. In this paper we revise some of the facts of epidemic modeling in mobile networks and use these models to analyze the impact of adding infrastructure to sparse opportunistic mobile networks. We show how the position in which infrastructure is placed takes an important impact in the dissemination delay.

  • Security on VANETs: Privacy, misbehaving nodes, false information and secure data aggregation

     Antolino Rivas, David; Barcelò Ordinas, José María; Guerrero Zapata, Manel; Morillo Pozo, Julian David
    Journal of network and computer applications
    Date of publication: 2011-11
    Journal article

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  • Trade-off Among Timeliness, Messages and Accuracy For Large-Scale Information Management  Open access

     Brunner, René
    Defense's date: 2011-11-18
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    The increasing amount of data and the number of nodes in large-scale environments require new techniques for information management. Examples of such environments are the decentralized infrastructures of Computational Grid and Computational Cloud applications. These large-scale applications need different kinds of aggregated information such as resource monitoring, resource discovery or economic information. The challenge of providing timely and accurate information in large scale environments arise from the distribution of the information. Reasons for delays in distributed information system are a long information transmission time due to the distribution, churn and failures. A problem of large applications such as peer-to-peer (P2P) systems is the increasing retrieval time of the information due to the decentralization of the data and the failure proneness. However, many applications need a timely information provision. Another problem is an increasing network consumption when the application scales to millions of users and data. Using approximation techniques allows reducing the retrieval time and the network consumption. However, the usage of approximation techniques decreases the accuracy of the results. Thus, the remaining problem is to offer a trade-off in order to solve the conflicting requirements of fast information retrieval, accurate results and low messaging cost. Our goal is to reach a self-adaptive decision mechanism to offer a trade-off among the retrieval time, the network consumption and the accuracy of the result. Self-adaption enables distributed software to modify its behavior based on changes in the operating environment. In large-scale information systems that use hierarchical data aggregation, we apply self-adaptation to control the approximation used for the information retrieval and reduces the network consumption and the retrieval time. The hypothesis of the thesis is that approximation techniquescan reduce the retrieval time and the network consumption while guaranteeing an accuracy of the results, while considering user’s defined priorities. First, this presented research addresses the problem of a trade-off among a timely information retrieval, accurate results and low messaging cost by proposing a summarization algorithm for resource discovery in P2P-content networks. After identifying how summarization can improve the discovery process, we propose an algorithm which uses a precision-recall metric to compare the accuracy and to offer a user-driven trade-off. Second, we propose an algorithm that applies a self-adaptive decision making on each node. The decision is about the pruning of the query and returning the result instead of continuing the query. The pruning reduces the retrieval time and the network consumption at the cost of a lower accuracy in contrast to continuing the query. The algorithm uses an analytic hierarchy process to assess the user’s priorities and to propose a trade-off in order to satisfy the accuracy requirements with a low message cost and a short delay. A quantitative analysis evaluates our presented algorithms with a simulator, which is fed with real data of a network topology and the nodes’ attributes. The usage of a simulator instead of the prototype allows the evaluation in a large scale of several thousands of nodes. The algorithm for content summarization is evaluated with half a million of resources and with different query types. The selfadaptive algorithm is evaluated with a simulator of several thousands of nodes that are created from real data. A qualitative analysis addresses the integration of the simulator’s components in existing market frameworks for Computational Grid and Cloud applications. The proposed content summarization algorithm reduces the information retrieval time from a logarithmic increase to a constant factor. Furthermore, the message size is reduced significantly by applying the summarization technique. For the user, a precision-recall metric allows defining the relation between the retrieval time and the accuracy. The self-adaptive algorithm reduces the number of messages needed from an exponential increase to a constant factor. At the same time, the retrieval time is reduced to a constant factor under an increasing number of nodes. Finally, the algorithm delivers the data with the required accuracy adjusting the depth of the query according to the network conditions.

    La gestió de la informació exigeix noves tècniques que tractin amb la creixent quantitat de dades i nodes en entorns a gran escala. Alguns exemples d’aquests entorns són les infraestructures descentralitzades de Computacional Grid i Cloud. Les aplicacions a gran escala necessiten diferents classes d’informació agregada com monitorització de recursos i informació econòmica. El desafiament de proporcionar una provisió ràpida i acurada d’informació en ambients de grans escala sorgeix de la distribució de la informació. Una raó és que el sistema d’informació ha de tractar amb l’adaptabilitat i fracassos d’aquests ambients. Un problema amb aplicacions molt grans com en sistemes peer-to-peer (P2P) és el creixent temps de recuperació de l’informació a causa de la descentralització de les dades i la facilitat al fracàs. No obstant això, moltes aplicacions necessiten una provisió d’informació puntual. A més, alguns usuaris i aplicacions accepten inexactituds dels resultats si la informació es reparteix a temps. A més i més, el consum de xarxa creixent fa que sorgeixi un altre problema per l’escalabilitat del sistema. La utilització de tècniques d’aproximació permet reduir el temps de recuperació i el consum de xarxa. No obstant això, l’ús de tècniques d’aproximació disminueix la precisió dels resultats. Així, el problema restant és oferir un compromís per resoldre els requisits en conflicte d’extracció de la informació ràpida, resultats acurats i cost d’enviament baix. El nostre objectiu és obtenir un mecanisme de decisió completament autoadaptatiu per tal d’oferir el compromís entre temps de recuperació, consum de xarxa i precisió del resultat. Autoadaptacío permet al programari distribuït modificar el seu comportament en funció dels canvis a l’entorn d’operació. En sistemes d’informació de gran escala que utilitzen agregació de dades jeràrquica, l’auto-adaptació permet controlar l’aproximació utilitzada per a l’extracció de la informació i redueixen el consum de xarxa i el temps de recuperació. La hipòtesi principal d’aquesta tesi és que els tècniques d’aproximació permeten reduir el temps de recuperació i el consum de xarxa mentre es garanteix una precisió adequada definida per l’usari. La recerca que es presenta, introdueix un algoritme de sumarització de continguts per a la descoberta de recursos a xarxes de contingut P2P. Després d’identificar com sumarització pot millorar el procés de descoberta, proposem una mètrica que s’utilitza per comparar la precisió i oferir un compromís definit per l’usuari. Després, introduïm un algoritme nou que aplica l’auto-adaptació a un ordre per satisfer els requisits de precisió amb un cost de missatge baix i un retard curt. Basat en les prioritats d’usuari, l’algoritme troba automàticament un compromís. L’anàlisi quantitativa avalua els algoritmes presentats amb un simulador per permetre l’evacuació d’uns quants milers de nodes. El simulador s’alimenta amb dades d’una topologia de xarxa i uns atributs dels nodes reals. L’algoritme de sumarització de contingut s’avalua amb mig milió de recursos i amb diferents tipus de sol·licituds. L’anàlisi qualitativa avalua la integració del components del simulador en estructures de mercat existents per a aplicacions de Computacional Grid i Cloud. Així, la funcionalitat implementada del simulador (com el procés d’agregació i la query language) és comprovada per la integració de prototips. L’algoritme de sumarització de contingut proposat redueix el temps d’extracció de l’informació d’un augment logarítmic a un factor constant. A més, també permet que la mida del missatge es redueix significativament. Per a l’usuari, una precision-recall mètric permet definir la relació entre el nivell de precisió i el temps d’extracció de la informació. Alhora, el temps de recuperació es redueix a un factor constant sota un nombre creixent de nodes. Finalment, l’algoritme reparteix les dades amb la precisió exigida i ajusta la profunditat de la sol·licitud segons les condicions de xarxa. Els algoritmes introduïts són prometedors per ser utilitzats per l’agregació d’informació en nous sistemes de gestió de la informació de gran escala en el futur.

  • MSTACK: A COMMUNICATIONS STACK FOR MOBILE AD-HOC NETWORKS  Open access

     Fusté Vilella, David
    Defense's date: 2011-10-21
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    Les xarxes mòbils ad-hoc, també conegues com a MANETs, han estat des de fa ja molt temps objectiu d'estudi per part de la comunitat científica. No obstant això, la seva importància dins el món de la indústria és encara molt baix. Aquests tipus de xarxes, formades per dispositius mòbils tals com smartphones o portàtils, poden ser usades per exemple en entorns mòbils com els campus universitaris, els centres de conferència, o en les indústries militars, de seguretat ciutadana, etc. Per poder establir comunicacions fiables entre els diferents dispositius d'una MANET fa falta un stack de comunicacions. Des de sempre, la comunitat científica ha basat els seus esforços en optimitzar l'stack de comunicacions TCP/IP, l'stack per excel·lència en la majoria de les xarxes actuals. Enlloc de dissenyar un nou stack de comunicacions, els científics han intentat adaptar i millorar les solucions ja existents provinents del món de les xarxes cablejades. Nosaltres, en canvi, creiem que un nou stack de comunicacions específicament dissenyat per a les MANETs és indispensable si el que volem és aconseguir comunicacions fiables en aquest tipus de xarxes, les quals tenen propietats molt diferents a les de les xarxes cablejades. En aquesta tesi presentem el que avui en dia encara no existeix: un nou stack de comunicacions específicament dissenyat per MANETs. Aquest stack és un exemple de com molts dels mecanismes usats en el món de les xarxes cablejades han de ser redissenyats des de la seva base si del que es tracta és de dissenyar protocols per a xarxes mòbils ad-hoc. En definitiva, nosaltres creiem que els resultats presentats en aquesta tesi demostren el potencial d'aquest nou stack de comunicacions per a les MANETs.

    Mobile ad-hoc networks have received considerable attention in the wireless communications research community. Nevertheless, its importance in industry is still low. Self-organized MANETs of smartphones or laptops can be used, for example, in military, public safety and disaster relief, conference, or campus environments. In order to enable communications between nodes inside a MANET, a communications stack is needed in each node of the network. Research in this area was always focused on optimizing the TCP/IP stack, the stack par excellence in the majority of our current networks. Instead of designing a complete new communications stack, researchers focused their work mainly on improving already existing solutions coming from the wired networks. However, we think that a complete and new communications stack specifically designed for MANETs is needed if we want to achieve robust communications in this type of networks, which have properties very different from what wired networks have. In this thesis we present what nowadays is still missing: a novel communications stack specifically designed for mobile ad-hoc networks. The MStack is an example of how some of the basic assumptions and mechanisms used in wired or wireless infrastructure networks must be fundamentally modified when dealing with MANETs. All in all, we believe that the results presented in this thesis provide interesting insights into the potential of the MStack in MANETs.

  • COOPERACIÓN Y OPORTUNISMO EN REDES DE ACCESO INALÁMBRICAS Y HETEROGÉNEAS

     Cerdà Alabern, Llorenç; Guerrero Zapata, Manel; Morillo Pozo, Julian David; Garcia Vidal, Jorge; Barcelò Ordinas, José María
    Participation in a competitive project

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    Exact decoding probability under random linear network coding  Open access

     Trullols Cruces, Oscar; Barcelò Ordinas, José María; Fiore, Marco
    IEEE communications letters
    Date of publication: 2011-01
    Journal article

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    In this letter, we compute the exact probability that a receiver obtains N linearly independent packets among K ≥ N received packets, when the sender/s use/s random linear network coding over a Galois Field of size q. Such condition maps to the receiver's capability to decode the original information, and its mathematical characterization helps to design the coding so to guarantee the correctness of the transmission. Our formulation represents an improvement over the current upper bound for the decoding probability, and provides theoretical grounding to simulative results in the literature.

  • MCM: multi-cluster-membership approach for FoV-based cluster formation in wireless multimedia sensor networks

     Alaei, Mohammad; Barcelò Ordinas, José María
    International Wireless Communications and Mobile Computing Conference
    Presentation's date: 2010-07
    Presentation of work at congresses

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    Node clustering based on overlapping FoVs for wireless multimedia sensor networks  Open access

     Alaei, Mohammad; Barcelò Ordinas, José María
    IEEE Wireless Communications and Networking Conference
    Presentation's date: 2010
    Presentation of work at congresses

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    Wireless Multimedia Sensor nodes sense areas that are uncorrelated to the areas covered by radio neighbor sensors. Thus, node clustering for coordinating multimedia sensing and processing cannot be based on classical sensor clustering algorithms. This paper presents a clustering mechanism for Wireless Multimedia Sensor Networks based on overlapped Field of View (FoV) areas. Today, for random deployments, dense networks of low cost, low resolution and low power multimedia nodes are preferred than sparse cases of high cost, high resolution and high power nodes. Overlapping FoVs in dense networks causes wasting power of system because of redundant sensing of area. The main aim of the proposed clustering method is energy conservation and prolonging network lifetime. This aim is achieved through coordination of nodes belonging to the same cluster in assigned tasks, avoiding redundant sensing or processing.

  • Priority-based node selection and scheduling for wireless multimedia sensor networks

     Alaei, Mohammad; Barcelò Ordinas, José María
    IEEE International Conference on Wireless and Mobile Computing, Networking and Communications
    Presentation's date: 2010-10-11
    Presentation of work at congresses

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  • Planning Roadside Infrastructure for Information Dissemination in Intelligent Transportation Systems

     Trullols Cruces, Oscar; Fiore, Marco; Casetti, Claudio; Chiasserini, Carla-Fabiana; Barcelò Ordinas, José María
    Computer communications
    Date of publication: 2010-06-01
    Journal article

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  • A method for clustering and cooperation in wireless multimedia sensor networks

     Alaei, Mohammad; Barcelò Ordinas, José María
    Sensors
    Date of publication: 2010-04
    Journal article

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  • The future of security in Wireless Multimedia Sensor Networks: a position paper

     Guerrero Zapata, Manel; Zilan, Ruken; Barcelò Ordinas, José María; Bicakci, Kemal; Tavli, Bülent
    Telecommunication systems
    Date of publication: 2010-09
    Journal article

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  • A cluster-based scheduling for object detection in wireless sensor networks

     Alaei, Mohammad; Barcelò Ordinas, José María
    ACM Symposium on QoS and Security for Wireless and Mobile Network
    Presentation's date: 2009-10-28
    Presentation of work at congresses

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  • Quality of service through bandwidth reservation on multirate ad hoc wireless networks

     Paoliello Guimarães, Rafael; Cerdà Alabern, Llorenç; Barcelò Ordinas, José María; Garcia Vidal, Jorge; Voorhaen, Michael; Blondia, Chris
    Ad hoc networks
    Date of publication: 2009-03
    Journal article

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  • Cooperative download in urban vehicular networks

     Fiore, Marco; Barcelò Ordinas, José María
    International Conference on Mobile Ad Hoc and Sensor Systems
    Presentation's date: 2009-10-12
    Presentation of work at congresses

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    A Max coverage formulation for information dissemination in vehicular networks  Open access

     Trullols Cruces, Oscar; Barcelò Ordinas, José María; Fiore, Marco; Casetti, Claudio; Chiasserini, Carla-Fabiana
    IEEE International Conference on Wireless and Mobile Computing, Networking and Communications
    Presentation's date: 2009-10-14
    Presentation of work at congresses

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    We consider that a given number of Dissemination Points (DPs) have to be deployed for disseminating information to vehicles travelling in an urban area. We formulate our problem as a Maximum Coverage Problem (MCP) so as to maximize the number of vehicles that get in contact with the DPs and as a second step with a sufficient amount of time. Since the MCP is NP-hard, we solve it though heuristic algorithms. Evaluation of the proposed solutions in a realistic urban environment shows how knowledge of vehicular mobility plays a major role in achieving an optimal coverage of mobile users, and that simple heuristics provide near-optimal results even in large-scale scenarios.

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    A cooperative vehicular network framework  Open access

     Trullols Cruces, Oscar; Morillo Pozo, Julian David; Barcelò Ordinas, José María; Garcia Vidal, Jorge
    IEEE International Conference on Communications
    Presentation's date: 2009-06-17
    Presentation of work at congresses

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    Vehicular Ad Hoc Networks are networks characterized by intermittent connectivity and rapid changes in their topology. This paper addresses car-to-road communications in which vehicles use Access Points (AP) in a Delay Tolerant Network architecture. Results show how the combination of a Delay-Cooperative ARQ mechanism reduces packet losses and in conjunction with a Carry-and-Forward cooperative mechanism improves performance parameters in terms of total file transfer delay and number of AP needed to download files.

  • XARXES DE COMPUTADORS I SISTEMES DISTRIBUÏTS

     Navarro Moldes, Leandro; Guerrero Zapata, Manel; Barcelò Ordinas, José María; Morillo Pozo, Julian David; Cerdà Alabern, Llorenç; Trullols Cruces, Oscar; Garcia Vidal, Jorge
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  • Estructura de redes de computadores

     Iñigo Griera, Jordi; Barcelò Ordinas, José María; Cerdà Alabern, Llorenç; Peig Olive, Enric; Abella Fuentes, Jaume; Corral Torruella, Guiomar
    Date of publication: 2009-01-01
    Book

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    Information dissemination in VANETs: deployment strategies for maximizing coverage  Open access

     Trullols Cruces, Oscar; Barcelò Ordinas, José María; Fiore, Marco; Casetti, Claudio; Chiasserini, Carla-Fabiana
    Euro-NF Workshop on Wireless and Mobility
    Presentation's date: 2009-09-22
    Presentation of work at congresses

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    We consider that a given number of Dissemination Points (DPs) have to be deployed for disseminating information to vehicles travelling in an urban area. We formulate our problem as a Maximum Coverage Problem (MCP) so as to maximize the number of vehicles that get in contact with the DPs. Since the MCP is NP-hard, we solve it though heuristic algorithms. Evaluation of the proposed solutions in a realistic urban environment shows how knowledge of vehicular mobility plays a major role in achieving an optimal coverage of mobile users, and that simple heuristics provide near-optimal results even in large-scale scenarios.

  • Information mobility: a new paradigm for wireless content dissemination

     Barcelò Ordinas, José María; Casetti, Claudio; Karlsson, Gunnar; Sargento, Susana
    2nd European Wireless Technology Conference
    Presentation's date: 2009-09-28
    Presentation of work at congresses

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  • Evaluation of a Cooperative ARQ Protocol for Delay-Tolerant Vehicular Networks

     Morillo Pozo, Julian David; Trullols-Cruces, O; Barcelò Ordinas, José María; Garcia Vidal, Jorge
    Lecture notes in computer science
    Date of publication: 2008-01
    Journal article

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    Evaluation of a cooperative ARQ protocol for delay-tolerant vehicular networks  Open access

     Morillo Pozo, Julian David; Trullols Cruces, Oscar; Barcelò Ordinas, José María; Garcia Vidal, Jorge
    Date of publication: 2008-10-16
    Book chapter

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    This paper evaluates a Cooperative ARQ protocol to be used in delay-tolerant vehicular networks. The scenario consists in cars downloading information from Access Points along a road. The key difference between proposed Cooperative ARQ protocols is when the cooperation takes place. Simply C-ARQ cooperation occurs in a packet-by-packet basis. In this proposal, that we call DC-ARQ (Delayed Cooperative ARQ), the cooperation is delayed until cars are out of the coverage area of the Access Point. The scheme has been evaluated through simulations. A comparison of DC-ARQ with a baseline case in which no cooperation is used has been performed under different vehicle densities scenarios.

    Postprint (author’s final draft)

  • TSI2007-66869-C02-01 "Integración de Redes Ad Hoc, Mesh y Celulares"

     Garcia Vidal, Jorge; Guerrero Zapata, Manel; Barcelò Ordinas, José María; Morillo Pozo, Julian David; Cerdà Alabern, Llorenç; Alaei, Mohammad; Fusté Vilella, David; Trullols Cruces, Oscar
    Participation in a competitive project

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  • Object Recognition Basics and Visual Surveillance

     Ruken, Zilan; Barcelò Ordinas, José María
    Date: 2008-07
    Report

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  • Image Recognition Traffic Patterns for Wireless

     Ruken, Zilan; Barcelò Ordinas, José María; Bulent, Tavli
    Date: 2008-02
    Report

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  • Available Mote Platforms for Wireless Image Sensors

     Ruken, Zilan; Barcelò Ordinas, José María; Bulent, Tavli
    Date: 2008-03
    Report

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  • A Cooperative ARQ for Delay-Tolerant Vehicular Networks

     Morillo, Julián David; Trullols, Oscar; Barcelò Ordinas, José María; Garcia Vidal, Jorge
    Date: 2008-03
    Report

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  • Routing Protocols and Wireless Multimedia Sensor Networks

     Ruken, Zilan; Barcelò Ordinas, José María; Bulent, Tavli
    Date: 2008-06
    Report

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  • A Survey of Wireless Multimedia Sensor Network Platforms

     Ruken, Zilan; Barcelò Ordinas, José María; Bulent, Tavli
    Date: 2008-09
    Report

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  • New networking paradigms applied to vehicular ad hoc networks

     Trullols Cruces, Oscar; Morillo Pozo, Julian David; Barcelò Ordinas, José María; Garcia Vidal, Jorge
    EuroNF Workshop on Wireless and Mobility
    Presentation's date: 2008-10-24
    Presentation of work at congresses

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  • Recognition Traffic Patterns for Wireless Multimedia Sensor Networks

     Barcelò Ordinas, José María
    Fourth EuroFGI Workshop on "Wireless and Mobility"
    Presentation's date: 2008-01-16
    Presentation of work at congresses

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  • A Cooperative ARQ for Delay Tolerant Delay Networks

     Morillo-Pozo, J; Morillo Pozo, Julian David; Barcelò Ordinas, José María; Trullols, O; Garcia-Vidal, J
    IEEE International Workshop on Delay/Disruption-Tolerant Mobile Networks (DTMN'08)
    Presentation of work at congresses

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  • Applying cooperation for delay tolerant vehicular networks

     Morillo Pozo, Julian David; Barcelò Ordinas, José María; Trullols Cruces, Oscar; Garcia Vidal, Jorge
    EuroFGI Workshop on Wireless and Mobility
    Presentation's date: 2008-01-16
    Presentation of work at congresses

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  • A cooperative ARQ for delay-tolerant vehicular networks

     Morillo Pozo, Julian David; Trullols Cruces, Oscar; Barcelò Ordinas, José María; Garcia Vidal, Jorge
    International Conference on Distributed Computing Systems
    Presentation's date: 2008-06-20
    Presentation of work at congresses

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  • Applying cooperation for Delay Tolerant Vehicular Networks

     Barcelò Ordinas, José María
    Fourth EuroFGI Workshop on "Wireless and Mobility"
    Presentation's date: 2008-01-16
    Presentation of work at congresses

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  • Image Recognition Traffic Patterns for Wireless Multimedia Sensor Networks

     Zilan, R; Barcelò Ordinas, José María; Tavli, B
    Lecture notes in computer science
    Date of publication: 2008-01
    Journal article

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