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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.
- 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.
- Towards Robust and Cost-Effective Critical Real-Time Systems under Thermal-Aware DesignPublication . Meumeu Yomsi, Patrick; Perez Rodriguez, JavierThe advent of multi-core platforms in critical realtime domains such as the avionics, automotive and railways to achieve higher and higher computing performances has turned the view on thermal concerns of the underlying chip die while it is still mandatory to meet all the temporal constraints. As a matter of fact, high chip temperature may not only degrade system performance and reliability, but it may also damage the chip permanently. We propose a methodology to address this problem, based on fixed task-to-core mapping and per-core analysis to derive a sound system model without feedback loops. To this end, it is important to have a better and deeper understanding of the existing thermal models in the literature. This is the main contribution of this research.
- Work-in-Progress: Towards a fine-grain thermal model for uniform multi-core processorsPublication . Pérez Rodríguez, Javier; Meumeu Yomsi, PatrickOn-chip power dissipation is recognized as one of the primary limiters, if not a show stopper, of performance for high-end safety-critical uniform multi-core processors. This paper proposes an efficient and simple thermal model for such a platform to be coupled with the large variety of schedulers designed to control the processor activity and the triggering of the cooling mechanism with as little impact on performance as possible.
- 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.
- Thermal-Aware Schedulability Analysis for Fixed-Priority Non-preemptive Real-Time SystemsPublication . Perez Rodriguez, Javier; Meumeu Yomsi, PatrickTechnology advances in microprocessor design have resulted in high device density and performance during the last decades. More components are fabricated on the chip die and millions, if not billions, of instructions can now be executed within microseconds. A consequence of this advancement is heat dissipation by the microprocessors. In this context, elevated on-chip temperature issues have become an important subject for the design of future generations of microprocessors, especially in avionics and automotive industries. In this paper, we address the scheduling problem of non-preemptive periodic tasks on a single processor platform under thermal-aware design. We assume that the tasks are scheduled by following any Fixed-Task-Priority (FTP) scheduler (e.g., Rate Monotonic (RM) or Deadline Monotonic (DM)) and we propose a unique framework wherein we capture both the temporal and thermal behavior of the system. Then, we present two new thermal-aware scheduling strategies, referred to as NP-HBC and NP-CBH, to keep the system temperature within specified parameters and we derive their respective schedulability analysis. Finally, we evaluate the performance of the proposed theoretical results through intensive simulations.
- 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.
- 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.
- Work-In-Progress: Assessing Supply/Demand-Bound Based Schedulability Tests For Wireless Sensor-Actuator NetworksPublication . Gutiérrez Gaitán, Miguel; Meumeu Yomsi, Patrick; Santos, Pedro Miguel; Almeida, LuisThe rising adoption of wireless technologies in the Industrial Internet of Things has stressed the need for traffic schedulability validation at system design-time to support safety and time critical streams (e.g., process control and emergency response). In this context, the demand-based schedulability tests have recently been proposed in the literature. This work revisits two well-established techniques borrowed from the multi-processor scheduling theory, namely the demand-bound-function (DBF) and the forced-forward-demand-bound-function (FFDBF), and evaluates their performances when adapted to the field of wireless sensor-actuator networks. Simulation experiments when varying network configurations confirm the equal or better accuracy of FFDBF over DBF to estimate both network demand and schedulability. In future work, we aim at building upon these promising results in order to design novel admission control and adaptation strategies that improve network schedulability under varying workload conditions.