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Documents authored by Almeida, Luis

Found 2 Possible Name Variants:

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.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.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.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
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)

Copy BibTex To Clipboard

@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.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}
}

Almeida, Luís

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)

Copy BibTex To Clipboard

@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.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.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)

Copy BibTex To Clipboard

@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.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
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)

Copy BibTex To Clipboard

@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.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}
}
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