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1. Reliable and Energy-Aware Fixed-Priority (m,k)-Deadlines Enforcement with Standby-Sparing

   Niu, Linwei ; Zhu, Dakai. ( March 2020 , Proceedings of 2020 IEEE/ACM Design, Automation & Test in Europe Conference (DATE’20))

   For real-time computing systems, energy efficiency, Quality of Service, and fault tolerance are among the major design concerns. In this work, we study the problem of reliable and energy-aware fixed-priority (m,k)-deadlines enforcement with standby-sparing. The standby-sparing systems adopt a primary processor and a spare processor to provide fault tolerance for both permanent and transient faults. In order to reduce energy consumption for such kind of systems, we proposed a novel scheduling scheme under the QoS constraint of (m,k)- deadlines. The evaluation results demonstrate that our proposed approach significantly outperformed the previous research in energy conservation while assuring (m,k)-deadlines and fault tolerance for real-time systems. 

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2. Fault-Tolerant Energy Management for Real-Time Systems with Weakly Hard QoS Assurance

   Linwei Niu ( May 2021 , 2021 IEEE International Conference on Computer Communications)

   While energy consumption is the primary concern for the design of real-time embedded systems, fault-tolerance and quality of service (QoS) are becoming increasingly important in the development of today’s pervasive computing systems. In this work, we study the problem of energy-aware standby-sparing for weakly hard real-time embedded systems. The standby-sparing systems adopt a primary processor and a spare processor to provide fault tolerance for both permanent and transient faults. In order to reduce energy consumption for such kind of systems, we proposed two novel scheduling schemes: one for (1,1)-hard tasks and one for general (m,k)-hard tasks which require that at least m out of any k consecutive jobs of a task meet their deadlines. Through extensive evaluations, our results demonstrate that the proposed techniques significantly outperform the previous research in reducing energy consumption for both (1,1)-hard task sets and general (m,k)-hard task sets while assuring fault tolerance through standby-sparing. 

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3. Work-In-Progress: Enhanced Energy-Aware Standby-Sparing Techniques for Fixed-Priority Hard Real-Time Systems

   Niu, Linwei ; Musselwhite, Jonathan ; Li, Wei ( December 2018 , Proceedings - Real-Time Systems Symposium)

   For real-time computing systems, energy efficiency and reliability are two primary design concerns. In this research work, we study the problem of enhanced energy-aware standbysparing for fixed-priority (FP) hard real-time systems under reliability requirement. The standby-sparing system adopts a primary processor and a spare processor to provide fault tolerance for both permanent and transient faults. In order to keep the energy consumption for such kind of systems under control, we explore enhanced fixed-priority scheduling schemes to minimize the overlapped concurrent executions of the workloads on the primary processor and on the spare processor, enabling energy savings. Moreover, efficient online scheduling techniques are under development to boost the energy savings during runtime while preserving the system reliability. 

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4. EASYR: E nergy-Efficient A daptive Sy stem R econfiguration for Dynamic Deadlines in Autonomous Driving on Multicore Processors

   https://doi.org/10.1145/3570503  

   Yi, Saehanseul ; Kim, Tae-Wook ; Kim, Jong-Chan ; Dutt, Nikil ( May 2023 , ACM Transactions on Embedded Computing Systems)

   The increasing computing demands of autonomous driving applications have driven the adoption of multicore processors in real-time systems, which in turn renders energy optimizations critical for reducing battery capacity and vehicle weight. A typical energy optimization method targeting traditional real-time systems finds a critical speed under a static deadline, resulting in conservative energy savings that are unable to exploit dynamic changes in the system and environment. We capture emerging dynamic deadlines arising from the vehicle’s change in velocity and driving context for an additional energy optimization opportunity. In this article, we extend the preliminary work for uniprocessors [66] to multicore processors, which introduces several challenges. We use the state-of-the-art real-time gang scheduling [5] to mitigate some of the challenges. However, it entails an NP-hard combinatorial problem in that tasks need to be grouped into gangs of tasks, gang formation, which could significantly affect the energy saving result. As such, we present EASYR, an adaptive system optimization and reconfiguration approach that generates gangs of tasks from a given directed acyclic graph for multicore processors and dynamically adapts the scheduling parameters and processor speeds to satisfy dynamic deadlines while consuming as little energy as possible. The timing constraints are also satisfied between system reconfigurations through our proposed safe mode change protocol. Our extensive experiments with randomly generated task graphs show that our gang formation heuristic performs 32% better than the state-of-the-art one. Using an autonomous driving task set from Bosch and real-world driving data, our experiments show that EASYR achieves energy reductions of up to 30.3% on average in typical driving scenarios compared with a conventional energy optimization method with the current state-of-the-art gang formation heuristic in real-time systems, demonstrating great potential for dynamic energy optimization gains by exploiting dynamic deadlines.

    

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5. A test bed study of network determinism for heterogeneous traffic using time-triggered ethernet

   https://doi.org/10.1109/MILCOM.2017.8170786  

   Starke, A. ; Kumar, D. ; Ford, M. ; McNair, J. ; Bell, A. ( October 2017 , 2017 IEEE Military Communications Conference, MILCOM 2017)

   Future tactical communications involves high data rate best effort traffic working alongside real-time traffic for time-critical applications with hard deadlines. Unavailable bandwidth and/or untimely responses may lead to undesired or even catastrophic outcomes. Ethernet-based communication systems are one of the major tactical network standards due to the higher bandwidth, better utilization, and ability to handle heterogeneous traffic. However, Ethernet suffers from inconsistent performance for jitter, latency and bandwidth under heavy loads. The emerging Time-Triggered Ethernet (TTE) solutions promise deterministic Ethernet performance, fault-tolerant topologies and real-time guarantees for critical traffic. In this paper we study the TTE protocol and build a TTTech TTE test bed to evaluate its performance. Through experimental study, the TTE protocol was observed to provide consistent high data rates for best effort messages, determinism with very low jitter for time-triggered messages, and fault-tolerance for minimal packet loss using redundant networking topologies. In addition, challenges were observed that presented a trade-off between the integration cycle and the synchronization overhead. It is concluded that TTE is a capable solution to support heterogeneous traffic in time-critical applications, such as aerospace systems (eg. airplanes, spacecraft, etc.), ground-based vehicles (eg. trains, buses, cars, etc), and cyber-physical systems (eg. smart-grids, IoT, etc.). 

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