6 Search Results for "Alçada-Almeida, Luis"

Document
DOI: 10.4230/OASIcs.NG-RES.2023.5
Response Time Analysis for RT-MQTT Protocol Grounded on SDN

Authors: Ehsan Shahri, Paulo Pedreiras, and Luis Almeida

Published in: OASIcs, Volume 108, Fourth Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2023)

Abstract
The current industry trend is to replace the use of custom components with standards-based Commercially available Off-The-Shelf (COTS) based hardware and protocols. Furthermore, the emergence of new industrial paradigms, such as Industry 4.0 and the Industrial Internet of Things, sets additional requirements regarding e.g. scale, transparency, agility, flexibility and efficiency. Therefore, in these domains, application layer protocols such as Message Queuing Telemetry Transport protocol (MQTT) are gaining popularity, in result of their simplicity, scalability, low resource-usage and decoupling between end nodes. However, such protocols were not designed for real-time applications, missing key features such as determinism and latency bounds. A recent work proposed extending MQTT with real-time services, taking advantage of Software Defined Networking (SDN) to manage the network resource. These extensions allow applications to specify real-time requirements that are then captured by a resource manager and used to reserve the necessary resources at the network layer. This paper shows that such MQTT extended architecture is analyzable from a worst-case timing perspective. We derive a system model that captures the real-time features and we present a response-time analysis to assess the schedulability of the real-time traffic. Finally, we validate the analysis with a set of experimental results.
Cite as

Ehsan Shahri, Paulo Pedreiras, and Luis Almeida. Response Time Analysis for RT-MQTT Protocol Grounded on SDN. In Fourth Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2023). Open Access Series in Informatics (OASIcs), Volume 108, pp. 5:1-5:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{shahri_et_al:OASIcs.NG-RES.2023.5,
  author =	{Shahri, Ehsan and Pedreiras, Paulo and Almeida, Luis},
  title =	{{Response Time Analysis for RT-MQTT Protocol Grounded on SDN}},
  booktitle =	{Fourth Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2023)},
  pages =	{5:1--5:15},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-268-6},
  ISSN =	{2190-6807},
  year =	{2023},
  volume =	{108},
  editor =	{Terraneo, Federico and Cattaneo, Daniele},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.NG-RES.2023.5},
  URN =		{urn:nbn:de:0030-drops-177364},
  doi =		{10.4230/OASIcs.NG-RES.2023.5},
  annote =	{Keywords: Real-time systems, OpenFlow, fixed-priority non-preemptive scheduling, response time analysis, MQTT}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.17
Reasoning with Portuguese Word Embeddings

Authors: Luís Filipe Cunha, J. João Almeida, and Alberto Simões

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
Representing words with semantic distributions to create ML models is a widely used technique to perform Natural Language processing tasks. In this paper, we trained word embedding models with different types of Portuguese corpora, analyzing the influence of the models' parameterization, the corpora size, and domain. Then we validated each model with the classical evaluation methods available: four words analogies and measurement of the similarity of pairs of words. In addition to these methods, we proposed new alternative techniques to validate word embedding models, presenting new resources for this purpose. Finally, we discussed the obtained results and argued about some limitations of the word embedding models' evaluation methods.
Cite as

Luís Filipe Cunha, J. João Almeida, and Alberto Simões. Reasoning with Portuguese Word Embeddings. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 17:1-17:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{cunha_et_al:OASIcs.SLATE.2022.17,
  author =	{Cunha, Lu{\'\i}s Filipe and Almeida, J. Jo\~{a}o and Sim\~{o}es, Alberto},
  title =	{{Reasoning with Portuguese Word Embeddings}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{17:1--17:14},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.17},
  URN =		{urn:nbn:de:0030-drops-167636},
  doi =		{10.4230/OASIcs.SLATE.2022.17},
  annote =	{Keywords: Word Embeddings, Word2Vec, Evaluation Methods}
}
Document
DOI: 10.4230/OASIcs.NG-RES.2021.2
EDF Scheduling and Minimal-Overlap Shortest-Path Routing for Real-Time TSCH Networks

Authors: Miguel Gutiérrez Gaitán, Luís Almeida, Pedro Miguel Santos, and Patrick Meumeu Yomsi

Published in: OASIcs, Volume 87, Second Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2021)

Abstract
With the scope of Industry 4.0 and the Industrial Internet of Things (IIoT), wireless technologies have gained momentum in the industrial realm. Wireless standards such as WirelessHART, ISA100.11a, IEEE 802.15.4e and 6TiSCH are among the most popular, given their suitability to support real-time data traffic in wireless sensor and actuator networks (WSAN). Theoretical and empirical studies have covered prioritized packet scheduling in extenso, but only little has been done concerning methods that enhance and/or guarantee real-time performance based on routing decisions. In this work, we propose a greedy heuristic to reduce overlap in shortest-path routing for WSANs with packet transmissions scheduled under the earliest-deadline-first (EDF) policy. We evaluated our approach under varying network configurations and observed remarkable dominance in terms of the number of overlaps, transmission conflicts, and schedulability, regardless of the network workload and connectivity. We further observe that well-known graph network parameters, e.g., vertex degree, density, betweenness centrality, etc., have a special influence on the path overlaps, and thus provide useful insights to improve the real-time performance of the network.
Cite as

Miguel Gutiérrez Gaitán, Luís Almeida, Pedro Miguel Santos, and Patrick Meumeu Yomsi. EDF Scheduling and Minimal-Overlap Shortest-Path Routing for Real-Time TSCH Networks. In Second Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2021). Open Access Series in Informatics (OASIcs), Volume 87, pp. 2:1-2:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{gaitan_et_al:OASIcs.NG-RES.2021.2,
  author =	{Gait\'{a}n, Miguel Guti\'{e}rrez and Almeida, Lu{\'\i}s and Santos, Pedro Miguel and Yomsi, Patrick Meumeu},
  title =	{{EDF Scheduling and Minimal-Overlap Shortest-Path Routing for Real-Time TSCH Networks}},
  booktitle =	{Second Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2021)},
  pages =	{2:1--2:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-178-8},
  ISSN =	{2190-6807},
  year =	{2021},
  volume =	{87},
  editor =	{Bertogna, Marko and Terraneo, Federico},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.NG-RES.2021.2},
  URN =		{urn:nbn:de:0030-drops-134786},
  doi =		{10.4230/OASIcs.NG-RES.2021.2},
  annote =	{Keywords: Real-time communication, Routing, Scheduling, TDMA, Wireless networks}
}
Document
DOI: 10.4230/OASIcs.ICPEC.2020.1
EasyCoding - Methodology to Support Programming Learning

Authors: Marcela Viana P. Almeida, Luís M. Alves, Maria João Varanda Pereira, and Glívia Angélica R. Barbosa

Published in: OASIcs, Volume 81, First International Computer Programming Education Conference (ICPEC 2020)

Abstract
Knowing that the programming curricular units in the first year of engineering courses have a high failure rate and, assuming that this failure is due, in large part, to the lack of motivation and the lack of autonomy of the student to program in context outside the classroom, a methodology based on activity guides using attractive web platforms is proposed. The proposed methodology aims to facilitate both the planning of activities by the teachers and the autonomy and motivation by students. In order to receive a first feedback about this work, the methodology is being used by programming professors from Polytechnic Institute of Bragança, but in the near future it will be also evaluated by professors from the Federal Center of Technological Education of Minas Gerais and from the Federal Technological University of Paraná, both from Brazil. Following this work, a system is being developed that allows the automatic construction of guides based on exercises available from the web and systems that facilitate the collection of solutions and analysis of results.
Cite as

Marcela Viana P. Almeida, Luís M. Alves, Maria João Varanda Pereira, and Glívia Angélica R. Barbosa. EasyCoding - Methodology to Support Programming Learning. In First International Computer Programming Education Conference (ICPEC 2020). Open Access Series in Informatics (OASIcs), Volume 81, pp. 1:1-1:8, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{almeida_et_al:OASIcs.ICPEC.2020.1,
  author =	{Almeida, Marcela Viana P. and Alves, Lu{\'\i}s M. and Pereira, Maria Jo\~{a}o Varanda and Barbosa, Gl{\'\i}via Ang\'{e}lica R.},
  title =	{{EasyCoding - Methodology to Support Programming Learning}},
  booktitle =	{First International Computer Programming Education Conference (ICPEC 2020)},
  pages =	{1:1--1:8},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-153-5},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{81},
  editor =	{Queir\'{o}s, Ricardo and Portela, Filipe and Pinto, M\'{a}rio and Sim\~{o}es, Alberto},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ICPEC.2020.1},
  URN =		{urn:nbn:de:0030-drops-122887},
  doi =		{10.4230/OASIcs.ICPEC.2020.1},
  annote =	{Keywords: learning programming, teaching programming, automatic activity guides, programming motivation}
}
Document
Invited Talk
DOI: 10.4230/OASIcs.NG-RES.2020.1
SDN for Dynamic Reservations on Real-Time Networks (Invited Talk)

Authors: Luis Almeida

Published in: OASIcs, Volume 77, Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2020)

Abstract
Recent growing frameworks such as the IoT, IIot, Cloud/Fog/Edge computing, CPS, etc, bring the networking platforms on which they rely to the spotlight, as first class citizens of an increasingly software-dependent landscape. As a result, networks play an increasingly central role in supporting the needed system-wide properties. In particular, we have been working to provide openness and adaptivity together with timeliness guarantees. This combination seems fundamental to support inherently dynamic applications in a resource efficient way, covering not only the cases of systems of systems, systems with variable number of users, components or resources but also systems that undergo frequent live maintenance and even reconfiguration during their lifetime. Examples range from autonomous vehicles to collaborative robotics, remote interactions, fog/edge computing, flexible manufacturing, etc. We postulate that combining openess and adaptivity with guaranteed timeliness can only be achieved with an adequate communication abstraction supported on adequate protocols. To this end, we have been proposing channel reservation-based communication as a means to provide scalable and open latency-constrained communication and thus enable a more efficient system design. In this talk we will show our recent work in using Software-Defined Networking (SDN) to provide standard interfaces for traffic flexibility. We proposed extending the SDN OpenFlow protocol with adequate services to take advantage of flexible real-time communication protocols and thus provide standard interfaces for flexible real-time reservations, too. We call it the Real-Time OpenFlow framework (RTOF). We end describing and assessing a prototype implementation based on the HaRTES Ethernet switches.
Cite as

Luis Almeida. SDN for Dynamic Reservations on Real-Time Networks (Invited Talk). In Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2020). Open Access Series in Informatics (OASIcs), Volume 77, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{almeida:OASIcs.NG-RES.2020.1,
  author =	{Almeida, Luis},
  title =	{{SDN for Dynamic Reservations on Real-Time Networks}},
  booktitle =	{Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2020)},
  pages =	{1:1--1:1},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-136-8},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{77},
  editor =	{Bertogna, Marko and Terraneo, Federico},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.NG-RES.2020.1},
  URN =		{urn:nbn:de:0030-drops-117774},
  doi =		{10.4230/OASIcs.NG-RES.2020.1},
  annote =	{Keywords: Latency-constrained networks, Real-time communication, Software-defined networking}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2018.2
Large Scale Railway Renewal Planning with a Multiobjective Modeling Approach

Authors: Nuno Sousa, Luis Alçada-Almeida, and João Coutinho-Rodrigues

Published in: OASIcs, Volume 65, 18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)

Abstract
A multiobjective modeling approach for managing large scale railway infrastructure asset renewal is presented. An optimized intervention project schedule is obtained considering operational constraints in a three objectives model: evenly spreading investment throughout multiple years, minimizing total cost, minimizing work start postponements on higher priority railway sections. The MILP model was based on a real world case study; the objectives and constraints specified by an infrastructure management company. Results show that investment spreading greatly influences the other objectives and that total cost fluctuations depend on the overall condition of the railway infrastructure. The model can produce exact efficient solutions in reasonable time, even for very large-sized instances (a test network of similar size to the USA railway network, the largest in the world). The modeling approach is therefore a very useful, practical methodology, for generating optimized solutions and analyzing trade-offs among objectives, easing the task of ultimately selecting a solution and produce the works schedule for field implementation.
Cite as

Nuno Sousa, Luis Alçada-Almeida, and João Coutinho-Rodrigues. Large Scale Railway Renewal Planning with a Multiobjective Modeling Approach. In 18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018). Open Access Series in Informatics (OASIcs), Volume 65, pp. 2:1-2:9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{sousa_et_al:OASIcs.ATMOS.2018.2,
  author =	{Sousa, Nuno and Al\c{c}ada-Almeida, Luis and Coutinho-Rodrigues, Jo\~{a}o},
  title =	{{Large Scale Railway Renewal Planning with a Multiobjective Modeling Approach}},
  booktitle =	{18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)},
  pages =	{2:1--2:9},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-096-5},
  ISSN =	{2190-6807},
  year =	{2018},
  volume =	{65},
  editor =	{Bornd\"{o}rfer, Ralf and Storandt, Sabine},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2018.2},
  URN =		{urn:nbn:de:0030-drops-97071},
  doi =		{10.4230/OASIcs.ATMOS.2018.2},
  annote =	{Keywords: Rail infrastructure, Renewal maintenance, Multiobjective modeling}
}
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