159 research outputs found

    Analysis and design of efficient techniques for video transmission in IEEE 802.11 wireless ad hoc networks

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    [EN] Wireless mobile ad ho networks, also known as MANETs, are omposed by independent mobile stations that ommuni ate without requiring any sort of infrastru ture for support. These networks are hara terized by variable bandwidth values and frequent path breaks, whi h are due to hannel noise, interferen e between stations and mobility. Su h fa tors require significant adaptation apabilites at different levels of the proto ol suites employed, enabling stations to qui kly respond to fast- hanging network onditions. Resear h on the most adequate proto- ols for the physi al, MAC and routing layers is still on-going, though some basi onsensus has already been rea hed and several testbeds have been setup around the world. To deploy real-time multimedia servi es, namely voi e and video, on top of su h an unreliable network environment is a very hallenging task. In this thesis we propose to a hieve that goal starting from urrently available Wi-Fi te hnology, and gradually finding the most adequate enhan ements to ea h proto ol layer of interest; we then ombine these enhan ements until we a hieve a omplete QoS framework for ad ho networks. By using urrently available te hnology we assure that the proposal of this thesis has an inherent high-level of appli ability on real life environments. Sin e our working field fo uses on video transmission over wireless ad ho networks, we will show how it is possible to support several QoS- onstrained video streams in MANET environments hara terized by moderate to high mobility levels, and by a significant amount of best efort traffic[ES] Las redes inalámbricas ad hoc, también conocidas como redes MANET, están compuestas por un conjunto de estaciones móviles independientes capaces de omunicarse entre sí sin necesidad de ningún tipo de infraestructura común de comunicaciones. Estas redes se caracterizan por tener un ancho de banda variable y pérdidas frecuentes de ruta que se pueden atribuir al ruido del anal inalámbrico, a la interferencia entre las estaciones móviles o bien a la movilidad de las estaciones. Dichos factores requieren una gran capacidad de adaptación en las diferentes capas de la arquitectura de protocolos, permitiendo a una estación responder rápidamente a posibles cambios bruscos en las condiciones de la red. A pesar de que aún se están realizando trabajos de investigación en bus a de los protocolos más adecuados para las capas físicas, a eso al medio (MAC) y encaminamiento, ha sido posible llegar a un nivel básico de consenso, lo cual ha permitido el despliegue de plataformas y entornos aplicados que utilizan tecnología de red MANET. Ofrecer servicios multimedia, como voz y vídeo, en redes con tan poca habilidad es un desafío importante. En esta tesis nos proponemos alcanzar este objetivo partiendo de la tecnología Wi-Fi actualmente disponible, encontrando de forma paulatina las mejoras más importantes en las diferentes capas de la arquitectura de red, para llegar, finalmente, a una solución integrada capaz de ofrecer calidad de servicio (QoS) en las redes MANET. Al utilizar la tecnología que disponemos actualmente nos aseguramos que las propuestas de esta tesis tengan un alto grado de aplicabilidad en entornos reales. Ya que la línea de trabajo de la tesis está aplicada a la transmisión de vídeo en redes MANET, demostraremos que es posible ofrecer calidad de servicio a varios flujos de vídeo en una red MANET caracterizada por altos grados de movilidad en sus nodos y un nivel significativo de tráfico o de tipo best effortTavares De Araujo Cesariny Calafate, CM. (2006). Analysis and design of efficient techniques for video transmission in IEEE 802.11 wireless ad hoc networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/135282TESI

    On the Use of Mobile Sensors for Estimating City-Wide Pollution Levels

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    ©2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Obtaining detailed pollution maps for urban environments is an effort that is gathering much interest by allowing to better regulate traffic and protect citizens from hazardous conditions. However, the scarcity of pollution sensors prevents obtaining the desired degree of detail, requiring alternative solutions to be deployed. In this paper we explore the concept of mobile pollution sensing by studying the feasibility of equipping buses with ozone measurement hardware to estimate ozone patterns for the city of Compiègne. Overall, we achieve accurate estimations, with error values typically ranging from 2% to 10%. Compared to solutions based on deploying static sensors on the different bus stops available, we find that the proposed mobile sensing approach is able to provide a degree of accuracy comparable to deploying tens of static sensors, substantially reducing costs and management.This work was carried out and funded in the framework of the Labex MSZT. It was supported by the French Government, through the program "Investments for the future” managed by the National Agency for Research (Reference ANR-11-IDEX-0004-02). This work was partially funded by the Celtic Plus CoMoSeF project "Cooperative mobility for the services of the future". The authors thank the Agglomération de la Région de Compiégne (ARC).Tavares De Araujo Cesariny Calafate, CM.; Ducourthial, B. (2015). On the Use of Mobile Sensors for Estimating City-Wide Pollution Levels. IEEE. doi:10.1109/IWCMC.2015.7289093

    Unmanned Aerial Vehicles-Platforms, Applications, Security and Services

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    Tavares De Araujo Cesariny Calafate, CM.; Tropea, M. (2020). Unmanned Aerial Vehicles-Platforms, Applications, Security and Services. Electronics. 9(6):1-3. https://doi.org/10.3390/electronics9060975S1396Stellin, M., Sabino, S., & Grilo, A. (2020). LoRaWAN Networking in Mobile Scenarios Using a WiFi Mesh of UAV Gateways. Electronics, 9(4), 630. doi:10.3390/electronics9040630Hiba, A., Sántha, L. M., Zsedrovits, T., Hajder, L., & Zarandy, A. (2020). Onboard Visual Horizon Detection for Unmanned Aerial Systems with Programmable Logic. Electronics, 9(4), 614. doi:10.3390/electronics9040614Tropea, M., Fazio, P., De Rango, F., & Cordeschi, N. (2020). A New FANET Simulator for Managing Drone Networks and Providing Dynamic Connectivity. Electronics, 9(4), 543. doi:10.3390/electronics9040543Chen, C.-L., Deng, Y.-Y., Weng, W., Chen, C.-H., Chiu, Y.-J., & Wu, C.-M. (2020). A Traceable and Privacy-Preserving Authentication for UAV Communication Control System. Electronics, 9(1), 62. doi:10.3390/electronics9010062Khan, M. A., Qureshi, I. M., Ullah, I., Khan, S., Khanzada, F., & Noor, F. (2019). An Efficient and Provably Secure Certificateless Blind Signature Scheme for Flying Ad-Hoc Network Based on Multi-Access Edge Computing. Electronics, 9(1), 30. doi:10.3390/electronics9010030Wubben, J., Fabra, F., Calafate, C. T., Krzeszowski, T., Marquez-Barja, J. M., Cano, J.-C., & Manzoni, P. (2019). Accurate Landing of Unmanned Aerial Vehicles Using Ground Pattern Recognition. Electronics, 8(12), 1532. doi:10.3390/electronics8121532Zhou, Y., Wu, C., Wu, Q., Eli, Z. M., Xiong, N., & Zhang, S. (2019). Design and Analysis of Refined Inspection of Field Conditions of Oilfield Pumping Wells Based on Rotorcraft UAV Technology. Electronics, 8(12), 1504. doi:10.3390/electronics812150

    Breaking persistent working group partnerships: a social experiment

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    Facing multidisciplinary projects is becoming quite common in companies worldwide, meaning that experts from a specific area must team up with experts from other areas in a dynamic, ad hoc manner. For a professional to meet such requirements successfully, it is important that teamwork skills are developed during college. However, such issue is usually not addressed thoroughly, and most students end up teaming with the same partners over and over again, thereby failing to achieve the critical adaptability skills expected from them. To address this drawback, in this paper we present the results of a study where students were forced to team up with other partners based on the results of a computer networking skills-ranking exam. Experimental results confirm the repeating pattern in terms of past partnerships, and student resistance to partner changes. On the positive side, results show that having new partners indeed help at achieving a more even task distribution, and that students are moderately aware of the upcoming challenges in their future professional activity, recognizing the benefits of teaming up with new people.This work was partially supported by the School of Informatics (ETSINF) and the Department of Computer Engineering (DISCA) at the Universitat Politècnica de València.Tavares De Araujo Cesariny Calafate, CM.; Arlandis, J.; Torres Cortes, A. (2015). Breaking persistent working group partnerships: a social experiment. En INTED2015 Proceedings. IATED. 1329-1337. http://hdl.handle.net/10251/70447S1329133

    Detection of glaucoma using three-stage training with EfficientNet

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    [EN] This paper sets forth a methodology that is based on three-stage-training of a state-of-the-art network architecture previously trained on Imagenet, and iteratively finetuned in three steps; freezing first all layers, then re-training a specific number of them and finally training all the architecture from scratch, to achieve a system with high accuracy and reliability. To determine the performance of our technique a dataset consisting of 17.070 color cropped samples of fundus images, and that includes two classes, normal and abnormal, is used. Extensive evaluations using baselines models (VGG16, InceptionV3 and Resnet50) are carried out, in addition to thorough experimentation with the proposed pipeline using variants of EfficientNet and EfficientNetV2. The training procedure is described accurately, putting emphasis on the number of parameters trained, the confusion matrices (with analysis of false positives and false negatives), accuracy, and F1-score obtained at each stage of the proposed methodology. The results achieved show that the intelligent system presented for the task at hand is reliable, presents high precision, its predictions are consistent and the number of parameters needed to train are low compared to other alternatives.This work is supported by the HK Innovation and Technology Commission (InnoHK Project CIMDA), the HK Research Grants Council (Project CityU 11204821) and City University of Hong Kong (Project 9610034). We acknowledge the support of Universitat Politècnica de València; R&D project PID2021-122580NB-I00, funded by MCIN/AEI/ 10.13039/501100011033 and ERDF.De Zarzà, I.; De Curtò, J.; Tavares De Araujo Cesariny Calafate, CM. (2022). Detection of glaucoma using three-stage training with EfficientNet. Intelligent Systems with Applications. 16:1-10. https://doi.org/10.1016/j.iswa.2022.2001401101

    A comparative study of two automated workgroup composition strategies

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    [EN] Nowadays, the professional environment of leading companies requires multidisciplinary teams to be created, including both internal and external experts, to adequately face the challenges of a fast-evolving and complex market. For newcomers, this situation can be difficult to handle if no previous experiences allowed preparing them for those situations. This is where college education finds its place, and in fact the curricula of different university careers are being updated to include more transversal competences like leadership and cooperation skills within groups. However, such efforts still remain at an amateur level in most cases due to lack of specific expertise by the majority of instructors, due to limitations in terms of creating actual multidisciplinary groups, and due to the little resources available to maximize the benefits of such experiences. Students also show little involvement in this issue, typically opting for approaches that minimize their efforts. Thus, simple and yet effective strategies that can be helpful for instructors to make a meaningful change to the current status quo are necessary. To address this need, in this paper we present the results of a 2-year study where students were forced to team up with other partners based on the results of a computer networking skills-ranking exam. In the first experiment, groups where formed by students achieving a similar performance (homogeneous), while in the second experiment groups were formed so that the average score of group members was the same (mostly heterogeneous). Through detailed survey results taken by students at the end of both courses, we find that, compared to an alternative group assignment strategy promoting group heterogeneity, having partners with similar skills does not help at improving the coordination between group members nor students perception about the usefulness of the experience towards future jobs. In fact, their rating of the overall experience was mostly the same, and, to our surprise, the partner expertise on the course topics was not a motivating factor, being that students complaints were always about not being able to decide about their partner. Thus, we consider that a simple strategy to define groups (e.g. randomly) suffices, but it should be adopted on all courses since the first year of the degree.Tavares De Araujo Cesariny Calafate, CM.; Tornell, SM.; Arlandis, J. (2016). A comparative study of two automated workgroup composition strategies. En INTED2016 Proceedings. IATED Digital Library. 5890-5899. doi:10.21125/inted.2016.0409S5890589

    A density-based contention window control scheme for unicast communications in vehicular ad hoc networks

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    [EN] Achieving a well-designed medium access control (MAC) protocol is a challenging issue to improve communications efficiency due to the dynamic nature of vehicular ad hoc networks (VANETs). IEEE 802.11p standard was selected as the best choice for vehicular environments considering its availability, maturity, and cost. The common problem in all IEEE 802.11 based protocols is scalability, exhibiting performance degradation in highly variable network scenarios. Experimental results for the IEEE 802.11-based MAC protocol show the importance of contention window adjustment on communications performance; However the vehicular communications community has not yet addressed this issue in unicast communication environments. This paper proposes a novel contention window control scheme for VANET environments based on estimating the network density, which is then used to dynamically adapt the CW size. Analysis and simulation results showthat our proposal provides better overall performance compared with previous proposals, even in high network density scenarios.This work was supported by the Ministerio de Economía y Competitividad, Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, Proyectos I+D+I 2014, Spain, under Grant TEC2014-52690-R.Balador, A.; Tavares De Araujo Cesariny Calafate, CM.; Cano, J.; Manzoni, P. (2017). A density-based contention window control scheme for unicast communications in vehicular ad hoc networks. International Journal of Ad Hoc and Ubiquitous Computing. 24(1-2):65-75. doi:10.1504/IJAHUC.2017.080913S6575241-

    Supporting Beacon and Event-Driven Messages in Vehicular Platoons through Token-Based Strategies

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    [EN] Timely and reliable inter-vehicle communications is a critical requirement to support traffic safety applications, such as vehicle platooning. Furthermore, low-delay communications allow the platoon to react quickly to unexpected events. In this scope, having a predictable and highly effective medium access control (MAC) method is of utmost importance. However, the currently available IEEE 802.11p technology is unable to adequately address these challenges. In this paper, we propose a MAC method especially adapted to platoons, able to transmit beacons within the required time constraints, but with a higher reliability level than IEEE 802.11p, while concurrently enabling efficient dissemination of event-driven messages. The protocol circulates the token within the platoon not in a round-robin fashion, but based on beacon data age, i.e., the time that has passed since the previous collection of status information, thereby automatically offering repeated beacon transmission opportunities for increased reliability. In addition, we propose three different methods for supporting event-driven messages co-existing with beacons. Analysis and simulation results in single and multi-hop scenarios showed that, by providing non-competitive channel access and frequent retransmission opportunities, our protocol can offer beacon delivery within one beacon generation interval while fulfilling the requirements on low-delay dissemination of event-driven messages for traffic safety applications.This work was partially supported by the Knowledge Foundation (KKS) via the ELECTRA project, the SafeCOP project, which is funded from the ECSEL Joint Undertaking under grant agreement n0 692529, and from national funding.Balador, A.; Uhlemann, E.; Tavares De Araujo Cesariny Calafate, CM.; Cano, J. (2018). Supporting Beacon and Event-Driven Messages in Vehicular Platoons through Token-Based Strategies. Sensors. 18(4):1-17. https://doi.org/10.3390/s18040955S117184Omar, H. A., Zhuang, W., & Li, L. (2013). VeMAC: A TDMA-Based MAC Protocol for Reliable Broadcast in VANETs. IEEE Transactions on Mobile Computing, 12(9), 1724-1736. doi:10.1109/tmc.2012.142Bergenhem, C., Hedin, E., & Skarin, D. (2012). Vehicle-to-Vehicle Communication for a Platooning System. Procedia - Social and Behavioral Sciences, 48, 1222-1233. doi:10.1016/j.sbspro.2012.06.1098Hadded, M., Muhlethaler, P., Laouiti, A., Zagrouba, R., & Saidane, L. A. (2015). TDMA-Based MAC Protocols for Vehicular Ad Hoc Networks: A Survey, Qualitative Analysis, and Open Research Issues. IEEE Communications Surveys & Tutorials, 17(4), 2461-2492. doi:10.1109/comst.2015.2440374Fernandes, P., & Nunes, U. (2012). Platooning With IVC-Enabled Autonomous Vehicles: Strategies to Mitigate Communication Delays, Improve Safety and Traffic Flow. IEEE Transactions on Intelligent Transportation Systems, 13(1), 91-106. doi:10.1109/tits.2011.2179936Hassanabadi, B., & Valaee, S. (2014). Reliable Periodic Safety Message Broadcasting in VANETs Using Network Coding. IEEE Transactions on Wireless Communications, 13(3), 1284-1297. doi:10.1109/twc.2014.010214.122008OMNeT++http://www.omnetpp.orgSommer, C., German, R., & Dressler, F. (2011). Bidirectionally Coupled Network and Road Traffic Simulation for Improved IVC Analysis. IEEE Transactions on Mobile Computing, 10(1), 3-15. doi:10.1109/tmc.2010.133Akhtar, N., Ergen, S. C., & Ozkasap, O. (2015). Vehicle Mobility and Communication Channel Models for Realistic and Efficient Highway VANET Simulation. IEEE Transactions on Vehicular Technology, 64(1), 248-262. doi:10.1109/tvt.2014.231910

    UWB and MB-OFDM for Lunar Rover Navigation and Communication

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    [EN] This paper presents a comprehensive study of ultra-wideband (UWB) and multi-band orthogonal frequency-division multiplexing (MB-OFDM) technologies for lunar rover navigation and communication in challenging terrains. Lunar missions pose unique challenges, such as signal propagation in the lunar environment, terrain elevation, and rover movement constraints. To address these challenges, we propose a hybrid communication and navigation system that leverages UWB technology for high-precision positioning and MB-OFDM for robust and high-throughput communication. We develop a realistic simulation framework that incorporates terrain elevation, obstacles, and rover movement constraints, along with a simple fading model for communication. Simulation results demonstrate the effectiveness of the proposed system in navigating lunar rovers to their target locations while maintaining reliable communication links with a lunar lander. A novel approach based on game theory for rover navigation is also presented. The study provides valuable insights into the design and optimization of communication and navigation systems for future lunar missions, paving the way for seamless integration of advanced terrestrial technologies in extraterrestrial environments.We thank the following funding sources from GOETHE-University Frankfurt am Main;"DePP-Dezentrale Plannung von Platoons im Stra beta engueterverkehr mit Hilfe einer KI auf Basiseinzelner LKW", "Center for Data Science & AI", and "xAIBiology". We acknowledge the support of R & D project PID2021-122580NB-I00, funded by MCIN/AEI/10.13039/501100011033 and ERDF.De Curtò, J.; De Zarzà, I.; Tavares De Araujo Cesariny Calafate, CM. (2023). UWB and MB-OFDM for Lunar Rover Navigation and Communication. Mathematics. 11(18). https://doi.org/10.3390/math11183835111

    FFP: A Force Field Protocol for the tactical management of UAV conflicts

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    [EN] In recent years, we have seen a tremendous growth in the adoption of Unmanned Aerial Vehicles (UAVs). Nowadays, UAVs are used in many different industries such as agriculture, inspection (bridges, pipelines, etc.), parcel delivery, etc. In the near future, this will lead to a substantial increase of aircraft in our airspace, especially in urban areas. Many existing collision avoidance approaches rely on heavy and/or expensive sensors, which limits its use for real UAVs due to increased costs, weight and complexity. Hence, to address this problem, in this paper we present a solution for the tactical management (i.e. in-flight) of UAV conflicts outdoors that introduces minimal requirements: a wireless interface and a GPS module. Specifically, we provide a collision avoidance algorithm based on artificial potential fields to provide flight safety. Our solution, called Force Field Protocol (FFP), allows the UAVs to autonomously detect each other using wireless communications, and to maintain a safe distance between them without the intervention of any central service. Experiments performed in our multi-UAV simulator ArduSim show that, with our approach, collisions between two UAVs are completely avoided in a wide set of scenarios, while introducing low disturbances to the original flight plans. Specifically, in the scenarios that we tested, the additional flight time introduced will be only 7 s longer in the worst case; in addition, it is able to improve upon previous approaches by reducing flight time by up to 54 s. We have shown experimentally that our approach can be scaled easily up to 100 UAVs, and that the probability of a collision is very low (< 0.06) despite flying in a small area (2.5 km × 2.5 km).This work is derived from R&D project PID2021-122580NB-I00, funded by MCIN/AEI/10.13039/501100011033 and ERDF A way of making Europe.Wubben, J.; Tavares De Araujo Cesariny Calafate, CM.; Cano, J.; Manzoni, P. (2023). FFP: A Force Field Protocol for the tactical management of UAV conflicts. Ad Hoc Networks. 140. https://doi.org/10.1016/j.adhoc.2022.10307814
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