129 research outputs found

    TRULLO - local trust bootstrapping for ubiquitous devices

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    Handheld devices have become sufficiently powerful that it is easy to create, disseminate, and access digital content (e.g., photos, videos) using them. The volume of such content is growing rapidly and, from the perspective of each user, selecting relevant content is key. To this end, each user may run a trust model - a software agent that keeps track of who disseminates content that its user finds relevant. This agent does so by assigning an initial trust value to each producer for a specific category (context); then, whenever it receives new content, the agent rates the content and accordingly updates its trust value for the producer in the content category. However, a problem with such an approach is that, as the number of content categories increases, so does the number of trust values to be initially set. This paper focuses on how to effectively set initial trust values. The most sophisticated of the current solutions employ predefined context ontologies, using which initial trust in a given context is set based on that already held in similar contexts. However, universally accepted (and time invariant) ontologies are rarely found in practice. For this reason, we propose a mechanism called TRULLO (TRUst bootstrapping by Latently Lifting cOntext) that assigns initial trust values based only on local information (on the ratings of its user’s past experiences) and that, as such, does not rely on third-party recommendations. We evaluate the effectiveness of TRULLO by simulating its use in an informal antique market setting. We also evaluate the computational cost of a J2ME implementation of TRULLO on a mobile phone

    Quality-of-service in wireless sensor networks: state-of-the-art and future directions

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    Wireless sensor networks (WSNs) are one of today’s most prominent instantiations of the ubiquituous computing paradigm. In order to achieve high levels of integration, WSNs need to be conceived considering requirements beyond the mere system’s functionality. While Quality-of-Service (QoS) is traditionally associated with bit/data rate, network throughput, message delay and bit/packet error rate, we believe that this concept is too strict, in the sense that these properties alone do not reflect the overall quality-ofservice provided to the user/application. Other non-functional properties such as scalability, security or energy sustainability must also be considered in the system design. This paper identifies the most important non-functional properties that affect the overall quality of the service provided to the users, outlining their relevance, state-of-the-art and future research directions

    Delay-Tolerant, Low-Power Protocols for Large Security-Critical Wireless Sensor Networks

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    This paper reports the analysis, implementation, and experimental testing of a delay-tolerant and energy-aware protocol for a wireless sensor node, oriented to security applications. The solution proposed takes advantages from different domains considering as a guideline the low power consumption and facing the problems of seamless and lossy connectivity offered by the wireless medium along with very limited resources offered by a wireless network node. The paper is organized as follows: first we give an overview on delay-tolerant wireless sensor networking (DTN); then we perform a simulation-based comparative analysis of state-of-the-art DTN approaches and illustrate the improvement offered by the proposed protocol; finally we present experimental data gathered from the implementation of the proposed protocol on a proprietary hardware node

    A decentralized framework for multi-agent robotic systems

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    Over the past few years, decentralization of multi-agent robotic systems has become an important research area. These systems do not depend on a central control unit, which enables the control and assignment of distributed, asynchronous and robust tasks. However, in some cases, the network communication process between robotic agents is overlooked, and this creates a dependency for each agent to maintain a permanent link with nearby units to be able to fulfill its goals. This article describes a communication framework, where each agent in the system can leave the network or accept new connections, sending its information based on the transfer history of all nodes in the network. To this end, each agent needs to comply with four processes to participate in the system, plus a fifth process for data transfer to the nearest nodes that is based on Received Signal Strength Indicator (RSSI) and data history. To validate this framework, we use differential robotic agents and a monitoring agent to generate a topological map of an environment with the presence of obstacles

    Bandwidth and Energy Consumption Tradeoff for IEEE 802.15.4 in Multihop Topologies

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    IEEE 802.15.4, Multi-hop,ZigBee,WSNwe analyze IEEE 802.15.4 mechanisms including node organization, MAC mechanisms, energy conservation, topology construction and node association. We detail how we should modify IEEE 802.15.4 to cope efficiently with multihop topologies, scheduling the transmissions. We quantify the impact of the cluster-tree algorithm on the network performances. We expose how the overall throughput can be improved with a novel cluster-tree construction algorithm defined formally as a Mixed Integer Linear Programming formulation. We quantify the impact of each parameter on the performances of IEEE 802.15.4. In particular, we present a self-configuration algorithm to dynamically adjust the Backoff Exponent so that the protocol always operates in optimal conditions

    On Evaluating the Performance Impact of the IEEE 802.15.4 Security Sub-layer

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    Nowadays, wireless sensor networks (WSNs) are used in a wide range of application scenarios ranging from structural monitoring to health-care, from surveillance to industrial automation. Most of these applications require forms of secure communication. On the other hand, security has a cost in terms of reduced performance. In this paper we refer to the IEEE 802.15.4 standard and investigate the impact of the 802.15.4 security sub-layer on the WSN performance. Specifically, we analyze the impact that security mechanisms and options, as provided by the standard, have on the overall WSN performance, in terms of latency, goodput, and energy consumption. To this end, we develop an analytical model and a security enabled simulator. We also use a real testbed, based on a complete open-source implementation of the standard, to validate simulation and analytical results, as well as to better understand the limits of the current WSN technology

    Simulating Real-Time Aspects of Wireless Sensor Networks

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    Wireless Sensor Networks (WSNs) technology has been mainly used in the applications with low-frequency sampling and little computational complexity. Recently, new classes of WSN-based applications with different characteristics are being considered, including process control, industrial automation and visual surveillance. Such new applications usually involve relatively heavy computations and also present real-time requirements as bounded end-to- end delay and guaranteed Quality of Service. It becomes then necessary to employ proper resource management policies, not only for communication resources but also jointly for computing resources, in the design and development of such WSN-based applications. In this context, simulation can play a critical role, together with analytical models, for validating a system design against the parameters of Quality of Service demanded for. In this paper, we present RTNS, a publicly available free simulation tool which includes Operating System aspects in wireless distributed applications. RTNS extends the well-known NS-2 simulator with models of the CPU, the Real-Time Operating System and the application tasks, to take into account delays due to the computation in addition to the communication. We demonstrate the benefits of RTNS by presenting our simulation study for a complex WSN-based multi-view vision system for real-time event detection

    Security wireless sensor networks: prospects, challenges, and future

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    With the advancements of networking technologies and miniaturization of electronic devices, wireless sensor network (WSN) has become an emerging area of research in academic, industrial, and defense sectors. Different types of sensing technologies combined with processing power and wireless communication capability make sensor networks very lucrative for their abundant use in near future. However, many issues are yet to be solved before their full-scale practical implementations. Among all the research issues in WSN, security is one of the most challenging topics to deal with. The major hurdle of securing a WSN is imposed by the limited resources of the sensors participating in the network. Again, the reliance on wireless communication technology opens the door for various types of security threats and attacks. Considering the special features of this type of network, in this chapter we address the critical security issues in wireless sensor networks. We talk about cryptography, steganography, and other basics of network security and their applicability in WSN. We explore various types of threats and attacks against wireless sensor networks, possible countermeasures, mentionable works done so far, other research issues, etc. We also introduce the view of holistic security and future trends towards research in wireless sensor network security

    Identifying the key factors affecting warning message dissemination in VANET real urban scenarios

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    [EN] In recent years, new architectures and technologies have been proposed for Vehicular Ad Hoc networks (VANETs). Due to the cost and complexity of deploying such networks, most of these proposals rely on simulation. However, we find that most of the experiments made to validate these proposals tend to overlook the most important and representative factors. Moreover, the scenarios simulated tend to be very simplistic (highways or Manhattan-based layouts), which could seriously affect the validity of the obtained results. In this paper, we present a statistical analysis based on the 2 k factorial methodology to determine the most representative factors affecting traffic safety applications under real roadmaps. Our purpose is to determine which are the key factors affecting Warning Message Dissemination in order to concentrate research tests on such parameters, thus avoiding unnecessary simulations and reducing the amount of simulation time required. Simulation results show that the key factors affecting warning messages delivery are the density of vehicles and the roadmap used. Based on this statistical analysis, we consider that VANET researchers must evaluate the benefits of their proposals using different vehicle densities and city scenarios, to obtain a broad perspective on the effectiveness of their solution. Finally, since city maps can be quite heterogeneous, we propose a roadmap profile classification to further reduce the number of cities evaluatedThis work was partially supported by the Ministerio de Ciencia e Innovacion, Spain, under Grant TIN2011-27543-C03-01, and by the Diputacion General de Aragon, under Grant "subvenciones destinadas a la formacion y contratacion de personal investigador".Fogue, M.; Garrido, P.; Martínez, FJ.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2013). Identifying the key factors affecting warning message dissemination in VANET real urban scenarios. Sensors. 13(4):5220-5250. https://doi.org/10.3390/s130405220S52205250134Galaviz-Mosqueda, G., Aquino-Santos, R., Villarreal-Reyes, S., Rivera-Rodríguez, R., Villaseñor-González, L., & Edwards, A. (2012). Reliable Freestanding Position-Based Routing in Highway Scenarios. Sensors, 12(11), 14262-14291. doi:10.3390/s121114262Gramaglia, M., Bernardos, C., & Calderon, M. (2013). Virtual Induction Loops Based on Cooperative Vehicular Communications. Sensors, 13(2), 1467-1476. doi:10.3390/s130201467Rahim, A., Khan, Z. S., Muhaya, F. T. B., Sher, M., & Kim, T.-H. (2010). Sensor Based Framework for Secure Multimedia Communication in VANET. Sensors, 10(11), 10146-10154. doi:10.3390/s101110146Martinez, F. J., Fogue, M., Toh, C. K., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2012). Computer Simulations of VANETs Using Realistic City Topologies. Wireless Personal Communications, 69(2), 639-663. doi:10.1007/s11277-012-0594-6Cenerario, N., Delot, T., & Ilarri, S. (2011). A Content-Based Dissemination Protocol for VANETs: Exploiting the Encounter Probability. IEEE Transactions on Intelligent Transportation Systems, 12(3), 771-782. doi:10.1109/tits.2011.2158821Sahoo, J., Wu, E. H.-K., Sahu, P. K., & Gerla, M. (2011). Binary-Partition-Assisted MAC-Layer Broadcast for Emergency Message Dissemination in VANETs. IEEE Transactions on Intelligent Transportation Systems, 12(3), 757-770. doi:10.1109/tits.2011.2159003Liu, C., & Chigan, C. (2012). RPB-MD: Providing robust message dissemination for vehicular ad hoc networks. Ad Hoc Networks, 10(3), 497-511. doi:10.1016/j.adhoc.2011.09.003Perkins, D. D., & Hughes, H. (2002). Investigating the performance of TCP in mobile ad hoc networks. Computer Communications, 25(11-12), 1132-1139. doi:10.1016/s0140-3664(02)00024-5Fogue, M., Garrido, P., Martinez, F. J., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2012). Evaluating the impact of a novel message dissemination scheme for vehicular networks using real maps. Transportation Research Part C: Emerging Technologies, 25, 61-80. doi:10.1016/j.trc.2012.04.017Sanguesa, J., Fogue, M., Garrido, P., Martinez, F., Cano, J.-C., Calafate, C., & Manzoni, P. (2013). An Infrastructureless Approach to Estimate Vehicular Density in Urban Environments. Sensors, 13(2), 2399-2418. doi:10.3390/s130202399Tseng, Y.-C., Ni, S.-Y., Chen, Y.-S., & Sheu, J.-P. (2002). Wireless Networks, 8(2/3), 153-167. doi:10.1023/a:1013763825347Wisitpongphan, N., Tonguz, O. K., Parikh, J. S., Mudalige, P., Bai, F., & Sadekar, V. (2007). Broadcast storm mitigation techniques in vehicular ad hoc networks. IEEE Wireless Communications, 14(6), 84-94. doi:10.1109/mwc.2007.4407231Alasmary, W., & Zhuang, W. (2012). Mobility impact in IEEE 802.11p infrastructureless vehicular networks. Ad Hoc Networks, 10(2), 222-230. doi:10.1016/j.adhoc.2010.06.006Harri, J., Filali, F., & Bonnet, C. (2009). Mobility models for vehicular ad hoc networks: a survey and taxonomy. IEEE Communications Surveys & Tutorials, 11(4), 19-41. doi:10.1109/surv.2009.090403Simulation of Urban MObility (SUMO)http://sumo.sourceforge.nethttp://www.openstreetmap.orghttp://www.census.gov/geo/www/tigerKrauss, S., Wagner, P., & Gawron, C. (1997). Metastable states in a microscopic model of traffic flow. Physical Review E, 55(5), 5597-5602. doi:10.1103/physreve.55.5597Wagner, P. (2006). How human drivers control their vehicle. The European Physical Journal B, 52(3), 427-431. doi:10.1140/epjb/e2006-00300-1ns Notes and Documentshttp://www.isi.edu/nsnam/ns/ns-documentation.htm

    Interim research assessment 2003-2005 - Computer Science

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    This report primarily serves as a source of information for the 2007 Interim Research Assessment Committee for Computer Science at the three technical universities in the Netherlands. The report also provides information for others interested in our research activities
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