This paper presents an asynchronous cascading wake-up MAC protocol for heterogeneous traffic gathering in low-power wireless sensor networks. It jointly considers energy/delay optimization and switches between two modes, according to the traffic type and delay requirements. The first mode is high duty cycle, where energy is traded-off for a reduced latency in presence of realtime traffic (RT). The second mode is low duty cycle, which is used for non-realtime traffic and gives more priority to energy saving. The proposed protocol, DuoMAC, has many features. First, it quietly adjusts the wake-up of a node according to (1) its parent’s wake-up time and, (2) its estimated load. Second, it incorporates a service differentiation through an improved contention window adaptation to meet delay requirements. A comprehensive analysis is provided in the paper to investigate the effectiveness of the proposed protocol in comparison with some state-of-the-art energy-delay efficient duty-cycled MAC protocols, namely DMAC, LL-MAC, and Diff-MAC. The network lifetime and the maximum end-to-end packet latency are adequately modeled, and numerically analyzed. The results show that LL-MAC has the best performance in terms of energy saving, while DuoMAC outperforms all the protocols in terms of delay reduction. To balance the delay/energy objectives, a runtime parameter adaptation mechanism has been integrated to DuoMAC. The mechanism relies on a constrained optimization problem with energy minimization in the objective function, constrained by the delay required for RT. The proposed protocol has been implemented on real motes using MicaZ and TinyOS. Experimental results show that the protocol clearly outperforms LL-MAC in terms of latency reduction, and more importantly, that the runtime parameter adaptation provides additional reduction of the latency while further decreasing the energy cost.
Connected vehicles promise to enable a wide range of new automotive services that will improve road safety, ease traffic management, and make the overall travel experience more enjoyable. However, they also open significant new surfaces for attacks on the electronics that control most of modern vehicle operations. In particular, the emergence of vehicle-to-vehicle (V2V) communication risks to lay fertile ground for self-propagating mobile malware that targets automobile environments. In this work, we perform a first study on the dynamics of vehicular malware epidemics in a large-scale road network, and unveil how a reasonably fast worm can easily infect thousands of vehicles in minutes. We determine how such dynamics are affected by a number of parameters, including the diffusion of the vulnerability, the penetration ratio and range of the V2V communication technology, or the worm self-propagation mechanism. We also propose a simple yet very effective numerical model of the worm spreading process, and prove it to be able to mimic the results of computationally expensive network simulations. Finally, we leverage the model to characterize the dangerousness of the geographical location where the worm is first injected, as well as for efficient containment of the epidemics through the cellular network.
Contextual privacy in Wireless Sensor Networks (WSNs) is concerned with protecting contextual information such as whether, when, and where the data is collected. In this context, hiding the existence of a WSN from adversaries is a desirable feature. One way to mitigate the sensor nodes’ detectability is by limiting the transmission power of the nodes (i.e., the network is operating in the stealth mode) so that adversaries cannot detect the existence of the WSN unless they are within the sensing range of the WSN. Position dependent transmission power adjustment enables the network to maintain its level of stealth while allowing nodes farther from the network boundary to use higher transmission power levels. To mitigate the uneven energy dissipation characteristic, nodes that cannot dissipate their energies on communications reduce the amount of data they generate through computation so that the relay nodes convey less data. Dynamic data compression/decompression strategies reduce the amount of data to be communicated, thus, they achieve better energy savings when compared to static compression/decompression of data in which the data is always compressed independently of the power transmission strategy. In this study, we investigate various data compression strategies to maximize the lifetime of WSNs employing contextual privacy measures through a novel Mathematical Programming framework.
Esta tesis propone (i) algunas soluciones para reducir, mediante el uso de redes inalámbricas Wi-Fi y aprovechando la cooperación entre los nodos, el consumo de datos en redes celulares, (ii) estudia cómo hacer un buen despliegue de puntos deacceso para optimizar la difusión de contenidos, (iii) analiza el impacto de mecanismos usados para disminuir el consumo de energía en los nodos, (iv) así como explora algunos de las riesgos que surgen en estas redes.Entre las aplicaciones a tener en cuenta para la reducción de la carga que soportan las redes celulares, podemos encontrar la Diseminación de Información en Redes Móviles Ad-Hoc.En esta tesis, las redes móviles en que nos vamos a centrar, consistirán principalmente en Redes Vehiculares Ad-hoc y Redes Peatonales Ad-hoc.En ambos escenarios trataremos con aplicaciones que tienen el fin de diseminar contenidos vehículo a vehículo o peatón a peatón, así como de vehículo a infraestructura o de peatón a infraestructura.Veremos cómo ambos escenarios (vehículos y peatones) comparten varias características, mientras que por otro lado, existen diferencias importantes que los hacen únicos y que por lo tanto, requieren de soluciones específicas. Por ejemplo, las baterías de los vehículos relegan técnicas de ahorro de energía en el funcionamiento de la red a un segundo lugar, mientras que en las redes peatonales las técnicas de ahorro de energía y sus efectos en el rendimiento de la red son un tema muy relevante.Mientras que las redes celulares ofrecen cobertura geográfica total, en soluciones de redes Wi-Fi oportunistas el paradigma del corto alcance sin cobertura permanente, así como la alta movilidad de los nodos de la red, requiere de diferentes abstracciones o paradigmas de red, como son las redes oportunistas, Redes tolerantes al retardo o disrupciones y el Network Coding para poder analizarlos.Y como ejemplo concreto de aplicación de Difusión en redes móviles, estudiaremos también, la propagación de malware en las redes móviles. A pesar de que se basa en los mismos mecanismos de propagación ya estudiados en otros escenarios, veremoscómo esta aplicación supone una nueva perspectiva en cuanto a la Diseminación de información.
This thesis proposes some solutions to relieve, using Wi-Fi wireless networks, the data consumption of cellular networks using cooperation between nodes, studies how to make a good deployment of access points to optimize the dissemination of contents, analyzes some mechanisms to reduce the nodes' power consumption during data dissemination in opportunistic networks, as well as explores some of the risks that arise in these networks.
Among the applications that are being discussed for data off-loading from cellular networks, we can find Information Dissemination in Mobile Networks.
In particular, for this thesis, the Mobile Networks will consist of Vehicular Ad-hoc Networks and Pedestrian Ad-Hoc Networks. In both scenarios we will find applications with the purpose of vehicle-to-vehicle or pedestrian-to-pedestrian Information
dissemination, as well as vehicle-to-infrastructure or pedestrian-to-infrastructure Information dissemination. We will see how both
scenarios (vehicular and pedestrian) share many characteristics, while on the other hand some differences make them unique, and therefore requiring of specific solutions. For example, large car batteries relegate power saving techniques to a second place, while power-saving techniques and its effects to network performance is a really relevant issue in Pedestrian networks.
While Cellular Networks offer geographically full-coverage, in opportunistic Wi-Fi wireless solutions the short-range non-fullcoverage paradigm as well as the high mobility of the nodes requires different network abstractions like opportunistic networking,
Disruptive/Delay Tolerant Networks (DTN) and Network Coding to analyze them.
And as a particular application of Dissemination in Mobile Networks, we will study the malware spread in Mobile Networks.
Even though it relies on similar spreading mechanisms, we will see how it entails a different perspective on Dissemination.
Doudou, M.; Barcelo, J.; Djenouri, D.; Garcia, J.; Badache, N. ACM Symposium on Principles of Distributed Computing p. 147-149 DOI: 10.1145/2611462.2611509 Data de presentació: 2014-07 Presentació treball a congrés
Optimizing energy consumption and end-to-end (e2e) packet delay in energy constrained distributed wireless networks is a conflicting multi-objective optimization problem. This paper investigates this trade-off from a game-theoretic perspective, where the two optimization objectives are considered as virtual game players that attempt to optimize their utility values. The cost model of each player is mapped through a generalized optimization framework onto protocol specific MAC parameters. A cooperative game is then defined, in which the Nash Bargaining solution assures the balance between energy consumption and e2e packet delay. For illustration, this formulation is applied to three state-of-the-art wireless sensor network MAC protocols; X-MAC, DMAC, and LMAC as representatives of preamble sampling, slotted contention-based, and frame-based MAC categories, respectively. The paper shows the effectiveness of such framework in optimizing protocol parameters for achieving a fair energy-delay performance trade-off, under the application requirements in terms of initial energy budget and maximum e2e packet delay. The proposed framework is scalable with the increase in the number of nodes, as the players represent the optimization metrics instead of nodes.
The surge in vehicular network research has led, over the last few years, to the proposal of countless network solutions specifically designed for vehicular environments. A vast majority of such solutions has been evaluated by means of simulation, since experimental and analytical approaches are often impractical and intractable, respectively. The reliability of the simulative evaluation is thus paramount to the performance analysis of vehicular networks, and the first distinctive feature that has to be properly accounted for is the mobility of vehicles, i.e., network nodes. Notwithstanding the improvements that vehicular mobility modeling has undergone over the last decade, no vehicular mobility dataset is publicly available today that captures both the macroscopic and microscopic dynamics of road traffic over a large urban region. In this paper, we present a realistic synthetic dataset, covering 24 hours of car traffic in a 400-km2 region around the city of Köln, in Germany. We describe the generation process and outline how the dataset improves the traces currently employed for the simulative evaluation of vehicular networks. We also show the potential impact that such a comprehensive mobility dataset has on the network protocol performance analysis, demonstrating how incomplete representations of vehicular mobility may result in over-optimistic network connectivity and protocol performance.
Doudou, M.; Djenouri, D.; Barcelo, J.; Badache, N. IEEE Wireless Communications and Networking Conference p. 2868-2873 DOI: 10.1109/WCNC.2014.6952904 Data de presentació: 2014-04 Presentació treball a congrés
The real-world node deployment aspect is investigated, while considering cost minimization for resolving the energy hole around the sink, which represents a serious problem in typical sensor networks with uniform distribution. A novel strategy is proposed that is based on the use of two sinks and a few extra relay nodes close to the sinks' areas. The traffic is then alternatively sent to the sinks in every other cycle. As a second contribution, an efficient data collection mechanism has been developed to determine the optimal data rate that meets delay requirements of individual sensor reports and improves the network lifetime. The comparison of the proposed node deployment strategy with uniform, non-uniform geometric and linear increase node distributions demonstrates that the cost of the proposed solution is very close to that of the uniform distribution and much lower than all the others, while achieving a load balancing at the same order of the state-of-the-art solutions.
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.
Trullols-Cruces, O.; Fiore, M.; Barcelo, J. IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks p. 6583402-1-6583402-9 DOI: 10.1109/WoWMoM.2013.6583402 Data de presentació: 2013-07 Presentació treball a congrés
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.
Doudou, M.; Alaei, M.; Djenouri, D.; Barcelo, J.; Badache, N. International Wireless Communications and Mobile Computing Conference p. 424-430 DOI: 10.1109/IWCMC.2013.6583596 Data de presentació: 2013-07 Presentació treball a congrés
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.
En esta tesis, el objetivo es diseñar esquemas para la gestión de nodos en redes de sensores inalámbricos multimedia (WMSN) que permitan cooperación en la zona de cobertura, que permitan la monitorización de objetos y procesamiento dentro de la red, y que permitan aumentar la capacidad de conservación de la energía en los nodos.1. AGRUPACIONES NODO MULTIMEDIALa primera contribución de la tesis es la agrupación de nodos multimedia. Se propone un método para la agrupación de nodos multimedia que satisface las limitaciones del campo de visión (FoV) de las cámaras. El criterio para unirse a un grupo es el porcentaje de área intersectada del campo de visión (FoV) de los nodos del grupo, en contraste con el radio de cobertura o la cantidad de vecinos, es decir, los nodos que intersectan un área predefinida de sus FOV participan del mismo grupo. Los grupos se establecen con la posibilidad de tener nodos comunes entre ellos o para ser totalmente disjuntos. Se definen dos modos de agrupación: SCM (Single Cluster Membership) y MCM (Multiple Cluster Membership). En SCM, cada nodo pertenece exactamente a un grupo y por lo tanto las agrupaciones son disjuntas sin ningún nodo común entre ellos. En MCM, los grupos pueden tener nodos comunes siempre que el nodo común cumpla los criterios de agrupación con los grupos a los que pertenece. Por lo tanto, en este tipo de pertenencia, no sólo podemos establecer la cooperación dentro de los grupos, sino también entre los grupos que tienen intersecciones. Los métodos propuestos son los primeros esquemas de agrupación en la literatura definidos para WMSN teniendo en cuenta las características específicas FoV.2. GESTIÓN DE NODOS COLABORATIVOS CON EFICIENCIA ENERGÉTICALa segunda contribución es la planificación de mecanismos eficientes de gestión de nodos colaborativos, dentro y entre los grupos establecidos, para la monitorización de objetos. La monitorización colaborativa evita que los grupos de nodos adquieran datos de forma redundante y correlada y por lo tanto permita al subsistema de detección de los nodos ahorrar energía, además de permitir a los subsistemas de transmisión y de procesamiento de la información optimizar la cantidad de datos a transmitir/procesar. Los esquemas para planificar los nodos que monitorizan simultáneamente el entorno son ¿Intra Cluster Cooperation¿ (ICC) asociado al método de agrupación SCM y el ¿Intra-Inter Cluster Cooperation¿ (IICC) asociado al método de agrupación MCM. De acuerdo con la aplicación deseada en la red de sensores inalámbricos multimedia, los grupos de nodos disjuntos serán planificados para monitoriza el entorno simultáneamente dependiendo del esquema usado.Finalmente, también, se calcula un período de tiempo para el grupo y otro para cada nodo de acuerdo al tamaño del grupo y al número de miembros del grupo que permite que cada miembro de cada grupo se active y se desactive de forma óptima para monitorizar el entorno. 3. ARQUITECTURA ACÚSTICO-VISUAL HYBRID PARA WMSNLa última contribución es una arquitectura de colaboración híbrida, entre sensores acústicos y visuales. Los nodos acústicos realizan la detección y localización del objeto mientras que los sensores visuales tienen la responsabilidad de la monitorización de los objetos. Ambos sensores, acústicos y visuales, están agrupados y planificados con los esquemas propuestos previamente. Los sensores visuales son programados para ser despertados sólo para monitorizar los objetos detectados en su dominio, de forma que se ahorra energía. De hecho, los sensores acústicos juegan el papel de asistentes para los sensores visuales para detectar y localizar los objetos/eventos ya que consumen mucha menos energía que la que se requiere para dichas tareas mediante sensores visuales. En el esquema propuesto, la transmisión de datos usa métodos de procesamiento en el nodo a priori siempre que es posible.
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.
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.
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).
Cesana, M.; Redondi, A.; Tiglao, N.; Grilo, A.; Barcelo, J.; Alaei, M.; Todorova, P. Conference on Next Generation Internet Networks p. 79-86 DOI: 10.1109/NGI.2012.6252168 Data de presentació: 2012 Presentació treball a congrés
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.
Rivas, D.; Barcelo, J.; Guerrero, M.; Morillo, J. Journal of network and computer applications Vol. 34, num. 6, p. 1942-1955 DOI: 10.1016/j.jnca.2011.07.006 Data de publicació: 2011-11 Article en revista
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.
Trullols-Cruces, O.; Morillo, J.; Barcelo, J. International Symposium on Applied Sciences in Biomedical and Communication Technologies p. 1-564 DOI: 10.1145/2093698.2093828 Data de presentació: 2011 Presentació treball a congrés
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.
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.
Trullols-Cruces, O.; Morillo, J.; Barcelo, J.; Garcia, J. IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks p. 1-9 DOI: 10.1109/WoWMoM.2011.5986464 Presentació treball a congrés
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.
Alaei, M.; Barcelo, J. IEEE International Conference on Wireless and Mobile Computing, Networking and Communications p. 151-158 DOI: 10.1109/WIMOB.2010.5644981 Data de presentació: 2010-10-11 Presentació treball a congrés
A critical aspect of applications with wireless sensor networks is network lifetime. Sensing and communications consume energy particularly in wireless multimedia sensor networks (WMSN) due to huge amount of data generated by the multimedia sensors. Therefore, judicious power management and sensor scheduling can effectively extend network lifetime. In this paper we consider the problem of scheduling multimedia sensor activities to maximize network lifetime. The environment is divided in domains monitored by clusters of multimedia sensor nodes. Network lifetime increment is achieved by cooperation between multimedia sensors in two priority-based ways: Intra-cluster cooperation and Inter-cluster cooperation. We will see that the lifetime of cluster nodes is considerably increased under the proposed node selection and scheduling procedures. As for big clusters, the lifetime even is prolonged to 5.5 times with respect to the ordinary un-cooperative node awakening.
Trullols-Cruces, O.; Fiore, M.; Casetti, C.; Chiasserini, C-F.; Barcelo, J. Computer communications Vol. 33, num. 1, p. 432-442 DOI: 10.1016/j.comcom.2009.11.021 Data de publicació: 2010-06-01 Article en revista
Wireless multimedia sensor nodes sense areas that are uncorrelated to the areas covered by radio neighbouring 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 (WMSNs) based on overlapped Field of View (FoV) areas. Overlapping FoVs in dense networks cause the wasting of power due to redundant area sensing. The main aim of the proposed clustering method is energy conservation and network lifetime prolongation. This objective is achieved through coordination of nodes belonging to the same cluster to perform assigned tasks in a cooperative manner avoiding redundant sensing or processing. A paradigm in this concept, a cooperative scheduling scheme for object detection, is presented based on the proposed clustering method.
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.
Trullols-Cruces, O.; Barcelo, J.; Fiore, M.; Casetti, C.; Chiasserini, C-F. IEEE International Conference on Wireless and Mobile Computing, Networking and Communications p. 154-160 DOI: 10.1109/WiMob.2009.35 Data de presentació: 2009-10-14 Presentació treball a congrés
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.
We target urban scenarios where vehicular users can download large files from road-side Access Points (APs), and define a framework to exploit opportunistic encounters between mobile nodes to increase their transfer rate. We first devise a
technique for APs deployment, based on vehicular traffic flows analysis, which fosters cooperative download. Then, we propose and evaluate different algorithms for carriers selection and chunk scheduling in carry&forward data transfers. Results obtained under realistic road topology and vehicular mobility conditions show that coupling our APs deployment scheme with probabilistic carriers selection and redundant chunk scheduling yields a worstcase
2x gain in the average download rate with respect to direct download, as well as a lOx reduction in the rate of undelivered chunks with respect to a blind carry&forward.
Content distribution networks are nowadays becoming a mature technology. Nevertheless, content delivery research in ad hoc networks has dealt with overlay applications, information querying and data broadcasting techniques. The aim of this paper is to explore and discuss content delivery in
wireless ad hoc networks and to state challenges and reference models for this kind of networks. The concept of Information
Mobility is introduced to point out that the contents are being stored in mobile nodes and that the contents move and replicate
before being accessed. The network considered is a wireless ad hoc network with sparse connectivity and limited infrastructure support.
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.
Trullols-Cruces, O.; Morillo, J.; Barcelo, J.; Garcia, J. IEEE International Conference on Communications p. 1-6 DOI: 10.1109/ICC.2009.5198586 Data de presentació: 2009-06-17 Presentació treball a congrés
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.
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.
Morillo, J.; Trullols-Cruces, O.; Barcelo, J.; Garcia, J. International Conference on Distributed Computing Systems p. 192-197 DOI: 10.1109/ICDCS.Workshops.2008.58 Data de presentació: 2008-06-20 Presentació treball a congrés
This paper proposes a Cooperative ARQ protocol to be used in delay-tolerant vehicular networks. The proposed scheme has been implemented and evaluated through an experimental testbed, showing that packet
losses in transmissions from an access point to cars can be reduced to the half without any cost as long as cooperation takes place on areas where connectivity with access points is not present. In these areas, cars
in a platoon recover from other cars packets that they have failed to receive from the access point.