State-based Scheduling Research Articles

Energy-Efficient Dynamic and Adaptive State-Based Scheduling (EDASS) Scheme for Wireless Sensor Networks

Today is the era of super-connectivity, where real-world things connect, gather real-time data from their surroundings and disseminate the recorded data into the environment. The users can access services without understanding the basic composite structure of heterogeneous devices and hybrid IoT infrastructure. Data is collected, managed, and processed by minute and plug-able sensors for the IoT paradigm. Due to the resource-constrained nature of these sensors, massive and recurrent tasks create congestion in the network and drain the energy of sensors. Sending unnecessary and redundant data packets is life-threatening and affects the availability of other resources. This paper proposes a novel scheme, an “Energy-Efficient Dynamic and Adaptive State-based Scheduling” (EDASS) for Wireless Sensor Network. The suggested method switches nodes between states dynamically and adapts to new states based on the contents of sensed data packets. Four distinct states of energy are derived from a combination of internal modules of the sensor. The typical sequence of operation is abruptly changed, and all sensors become active when a new event occurs. EDASS decreases energy consumption by 29% in live nodes, 41% in message overhead and 33% in the cluster head selection process. At the same time, the average delay in EDASS increases from 1.26 ms to 1.39 ms due to control message overhead.

Programmable Controller with Flexible Redundancy for Safety Functions in a Nuclear Power Plant

This paper presents the redundancy architecture of the Programmable Logic Controller called the Safety PLC(SPLC) for the safety functions such as reactor protection in a nuclear power plant. The architecture of the SPLC is designed to switch flexibly redundancy model between the Dual Modular Redundancy(DMR) and Triple Modular Redundancy(TMR). Using this flexible redundancy architecture, the controller can be optimally configured to the application area, and the reliability and availability of the overall system can be increased because redundancy model varies as failures occur. The operating system of the SPLC is also specially designed to guarantee the strict real-time operation using the non-preemptive state-based scheduler and the supervisory task that manages timing violation of each task. The data communication of the SPLC uses the deterministic state-based protocol based on the Guaranteed Time Slot(GTS) protocol. The reliability analysis results show that MTTF of SPLC is 41,630 hours, which is about 15% and 50% more reliable than the TMR or DMR architecture, respectively.

Design of State-Based Schedulers for a Network of Control Loops

For a closed-loop system, which has a contention-based multiple access network on its sensor link, the Medium Access Controller (MAC) may discard some packets when the traffic on the link is high. We use a local state-based scheduler to select a few critical data packets to send to the MAC. In this paper, we analyze the impact of such a scheduler on the closed-loop system in the presence of traffic, and show that there is a dual effect with state-based scheduling. In general, this makes the optimal scheduler and controller hard to find. However, by removing past controls from the scheduling criterion, we find that certainty equivalence holds. This condition is related to the classical result of Bar-Shalom and Tse, and it leads to the design of a scheduler with a certainty equivalent controller. This design, however, does not result in an equivalent system to the original problem, in the sense of Witsenhausen. Computing the estimate is difficult, but can be simplified by introducing a symmetry constraint on the scheduler. Based on these findings, we propose a dual predictor architecture for the closed-loop system, which ensures separation between scheduler, observer and controller. We present an example of this architecture, which illustrates a network-aware event-triggering mechanism.

State-based scheduling with tree schedules: analysis and evaluation

Distributed real-time systems require bounded communication delays and achieve them by means of a predictable and verifiable control mechanism for the communication medium. Real-time bus arbitration mechanisms control access to the medium and guarantee bounded communication delays. These arbitration mechanisms can be static dispatch tables or dynamic, algorithmic approaches. In this work, we introduce a real-time bus arbitration mechanism called tree schedules that takes the best parts of both sides: It can be analyzed like static dispatch tables, and it provides a certain degree of flexibility similar to algorithmic approaches. We present tree schedules as a framework to specify real-time traffic and introduce mechanisms to analyze it. We discuss how tree schedules can capture application-specific behavior in a time-triggered state-based supply model by means of conditional branching built into the model. We present analysis results for this model specifically aiming at schedulability in fixed and dynamic priority schemes and waiting time analysis. Finally, we demonstrate the advantages of state-based supply over stateless supply by means of two case studies.