Browsing by Author "Meumeu Yomsi, Patrick"
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- A Configuration Framework for Multi-level Preemption Schemes in Time Sensitive NetworkingPublication . Ojewale, Mubarak; Meumeu Yomsi, Patrick; Almeida, LuísTo reduce the latency of time-sensitive flows in Ethernet networks, the IEEE TSN Task Group introduced the IEEE 802.1Qbu Standard, which specifies a 1-level preemption scheme for IEEE 802.1 networks. Recently, serious limitations of this scheme w.r.t. flows responsiveness were exposed and the so-called multi-level preemption approach was proposed to address these drawbacks. As is the case with most, if not all, real-time and/or time-sensitive preemptive systems, an appropriate priority-to-flow assignment policy plays a central role in the resulting performance of both 1-level and multi-level preemption schemes to avoid the over-provisioning and/or the sub-optimal use of hardware resources. Yet on another front, the multi-level preemption scheme raises new configuration challenges. Specifically, the right number of preemption level(s) to enable for swift transmission of flows; and the flow-to-preemption-class assignment synthesis remain open problems. To the best of our knowledge, there is no prior work in the literature addressing these important challenges. In this work, we address these three challenges. We demonstrate the applicability of our proposed solution by using both synthetic and real-life use-cases. Our experimental results show that multi-level preemption schemes improve the schedulability of flows by over 12% as compared to a 1-level preemption scheme, and at a higher abstraction level, the proposed configuration framework improves the schedulability of flows by up to 6% as compared to the dominant Deadline Monotonic Priority Ordering.
- EDF Scheduling and Minimal-Overlap Shortest-Path Routing for Real-Time TSCH NetworksPublication . Gutiérrez Gaitán, Miguel; Almeida, Luis; Santos, Pedro M.; Meumeu Yomsi, PatrickWith 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.
- FF-DBF-WIN: On the Forced-Forward Demand-Bound Function Analysis for Wireless Industrial NetworksPublication . Gutiérrez, Miguel; Meumeu Yomsi, PatrickWireless Industrial Networks (WINs) have brought to the forefront the need for real-time strategies to ensure network schedulability. The Demand Bound Function (DBF) has recently been borrowed from the multicore scheduling theory and adapted to the wireless industrial domain to compute the network demand. However, a more precise estimation can be obtained by using alternative supply/demand analyses. This paper proposes the forced-forward demand bound function to estimate the network demand and better determine the schedulability of WINs.
- Implementation Cost Comparison of TSN Traffic Control MechanismsPublication . Pruski, Aleksander; Meumeu Yomsi, Patrick; Berger, Michael Stübert; Almeida, Luis; Ojewale, MubarakThe IEEE Time-Sensitive Networking (TSN) Task Group specifies a set of standards that enables real-time communication with predictable and bounded delays over the Ethernet. Specifically, TSN introduces a new set of so-called shapers, which regulate traffic arrival and transmission in the networks. Prominent among those are the IEEE 802.1 Qbv Time Aware Shaper (TAS) and IEEE 802.1Qav Credit-Based Shaper (CBS).Another traffic control mechanism is the IEEE 802.1Qbu Frame Preemption. Most works in the literature have focused on the quantitative performance comparison between these mechanisms. However, the discussion on how they compare in terms of implementation cost has received less attention. In this paper,we provide a comprehensive comparison of the implementation cost of the aforementioned TSN traffic control mechanisms. This comparison can help system designers in choosing which of the mechanism(s) to deploy for their applications.
- Manycore PlatformsPublication . Marongiu, Andrea; Nélis, Vincent; Meumeu Yomsi, PatrickThis chapter surveys state-of-the-art manycore platforms. It discusses the historical evolution of computing platforms over the past decades and the technical hurdles that led to the manycore revolution, then presents in details several manycore platforms, outlining (i) the key architectural traits that enable scalability to several tens or hundreds of processing cores and (ii) the shared resources that are responsible for unpredictable timing.
- Multi-Factor Authentication and Fingerprint-based Debit Card SystemPublication . Ojewale, Mubarak; Meumeu Yomsi, PatrickOne thing can be said to be common to all forms of debit card fraud –authentication bypass. This implies that a secure debit card transaction system can only be guaranteed by a safe and reliable authentication system. Many approaches have been adopted to ensure a secure authentication system, but often, these approaches are either focused on the Automated Teller Machines (ATM)/Point of Sales (POS) terminals or Online/e-commerce transactions, thus not providing full security on both fronts. In this work, we address this problem by adopting a multi-factor debit card system that uses a combination of the traditional Personal Identification Number code (PIN) and the mobile-phone delivered One-Time Password (OTP) with a biometric authentication option(fingerprint). We demonstrate that this approach ensures the security of both online and terminal transactions. The fingerprint option makes it easy to use by people who find memorizing PINs difficult.
- Multi-Level Preemption in TSN: Feasibility and Requirements AnalysisPublication . Ojewale, Mubarak; Meumeu Yomsi, Patrick; Nikolić, BorislavTo overcome the limitation of strictly non-preemptive frame transmission in Ethernet networks, the IEEE 802.1Qbu standard was introduced. This standard specifies a one-level frame preemption paradigm wherein, depending on their priority levels, frames are grouped into two categories: namely, the “express frames” and the “preemptable frames”. These two categories are given with the interpretation that (1) only express frames can preempt preemptable frames; and (2) two frames belonging to the same category cannot preempt each other. While this approach partially solves the problem, some preemptable frames can still suffer long blocking periods, irrespective of their individual priority levels. Indeed, there are frames that do not fall into the express frames category, but nevertheless have firm timing requirements that can only be met if they can benefit from preempting lower priority frames. To ameliorate the condition of such frames, we propose a multi-level preemption paradigm. Specifically, we expose the limitations of the one-level preemption approach experimentally; and we present the feasibility and implementation requirements of the multi-level preemption scheme in details.
- Non-preemptive and SRP-based fullypreemptive scheduling of real-time Software Transactional MemoryPublication . Barros, António; Pinho, Luís Miguel; Meumeu Yomsi, PatrickRecent embedded processor architectures containing multiple heterogeneous cores and non-coherent caches renewed attention to the use of Software Transactional Memory (STM) as a building block for developing parallel applications. STM promises to ease concurrent and parallel software development, but relies on the possibility of abort conflicting transactions to maintain data consistency, which in turns affects the execution time of tasks carrying transactions. Because of this fact the timing behaviour of the task set may not be predictable, thus it is crucial to limit the execution time overheads resulting from aborts. In this paper we formalise a FIFO-based algorithm to order the sequence of commits of concurrent transactions. Then, we propose and evaluate two non-preemptive and one SRP-based fully-preemptive scheduling strategies, in order to avoid transaction starvation.
- On Multi-Level Preemption in EthernetPublication . Ojewale, Mubarak; Meumeu Yomsi, Patrick; Nelissen, GeoffreyEthernet is increasingly being considered as the solution to high bandwidth requirements in the next generation of timing critical applications that make their way in cars, planes or smart factories to mention a few examples. Until recently, ethernet frames used to be transmitted exclusively in a nonpreemptive manner. That is, once a frame starts transmitting on a switch output port, its transmission cannot be interrupted by any other frame until completion. This constraint may cause time critical frames to be blocked for long periods of time because of the transmission of non-critical frames. The IEEE 802.3br standard addressed this issue by introducing a one-level ethernet frame preemption paradigm. In this approach, frames transmitted through a switch output port are classified as express frames or preemptable frames, depending on their priority levels. Express frames can preempt preemptable frames and two frames belonging to the same class cannot preempt each other. While this partially solves the problem for express frames, all preemptable frames can still suffer blocking irrespective of their priority level. In this work, we investigate the feasibility and advantages of multi-level preemptions in time-sensitive ethernet networks.
- P-SOCRATES: A parallel software framework for time-critical many-core systemsPublication . Pinho, Luís Miguel; Nélis, Vincent; Meumeu Yomsi, Patrick; Quiñones, Eduardo; Bertogna, Marko; Burgio, Paolo; Marongiu, Andrea; Scordino, Claudio; Gai, Paolo; Ramponi, Michele; Mardiak, Michal MCurrent generation of computing platforms is embracing multi-core and many-core processors to improve the overall performance of the system, meeting at the same time the stringent energy budgets requested by the market. Parallel programming languages are nowadays paramount to extracting the tremendous potential offered by these platforms: parallel computing is no longer a niche in the high performance computing (HPC) field, but an essential ingredient in all domains of computer science. The advent of next-generation many-core embedded platforms has the chance of intercepting a converging need for predictable high-performance coming from both the High-Performance Computing (HPC) and Embedded Computing (EC) domains. On one side, new kinds of HPC applications are being required by markets needing huge amounts of information to be processed within a bounded amount of time. On the other side, EC systems are increasingly concerned with providing higher performance in real-time, challenging the performance capabilities of current architectures. This converging demand raises the problem about how to guarantee timing requirements in presence of parallel execution. The paper presents how the time-criticality and parallelisation challenges are addressed by merging techniques coming from both HPC and EC domains, and provides an overview of the proposed framework to achieve these objectives
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