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Recent and Emerging Topics in Wireless Industrial Communications: A Selection
, 2007
"... In this paper we discuss a selection of promising and interesting research areas in the design of protocols and systemsforwirelessindustrialcommunications.Wehaveselected topicsthathaveeitheremergedashottopicsintheindustrial communicationscommunityinthelastfewyears(likewireless sensornetworks),orwhi ..."
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Cited by 93 (1 self)
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In this paper we discuss a selection of promising and interesting research areas in the design of protocols and systemsforwirelessindustrialcommunications.Wehaveselected topicsthathaveeitheremergedashottopicsintheindustrial communicationscommunityinthelastfewyears(likewireless sensornetworks),orwhichcouldbeworthwhileresearchtopicsin thenextfewyears(forexamplecooperativediversitytechniques for error control, cognitive radio/opportunistic spectrum access for mitigation of external interferences).
Optimal Reward-Based Scheduling of Periodic Real-Time Tasks
, 1999
"... Reward-based scheduling refers to the problem in which there is a reward associated with the execution of a task. In our framework, each real-time task comprises a mandatory and an optional part, with which a nondecreasing reward function is associated. Imprecise computation and Increased-Reward-wit ..."
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Cited by 78 (16 self)
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Reward-based scheduling refers to the problem in which there is a reward associated with the execution of a task. In our framework, each real-time task comprises a mandatory and an optional part, with which a nondecreasing reward function is associated. Imprecise computation and Increased-Reward-with-Increased-Service models fall within the scope of this framework. In this paper, we address the reward-based scheduling problem for periodic tasks. For linear and concave reward functions we show: (a) the existence of an optimal schedule where the optional service time of a task is constant at every instance and (b) how to efficiently compute this service time. We also prove that RMS (with harmonic periods), EDF and LLF policies are optimal when used with the optimal service times we computed, and that the problem becomes NP-Hard, when the reward functions are convex. Further, our solution eliminates runtime overhead, and makes possible the use of existing scheduling disciplines.
Overload management in real-time control applications using (m,k)-firm guarantee
- IEEE Transactions on Parallel and Distributed Systems
, 1999
"... AbstractÐTasks in a real-time control application are usually periodic and they have deadline constraints by which each instance of a taskis expected to complete its computation, even in the adverse circumstances caused by component failures. Techniques to recover from processor failures often invol ..."
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Cited by 75 (0 self)
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AbstractÐTasks in a real-time control application are usually periodic and they have deadline constraints by which each instance of a taskis expected to complete its computation, even in the adverse circumstances caused by component failures. Techniques to recover from processor failures often involve a reconfiguration in which all tasks are assigned to fault-free processors. This reconfiguration may result in processor overload where it is no longer possible to meet the deadlines of all tasks. In this paper, we discuss an overload management technique which discards selected taskinstances in such a way that the performance of the control loops in the system remain satisfactory even after a failure. The technique is based on the rationale that real-time control applications can tolerate occasional misses of the control law updates, especially if the control law is modified to account for these missed updates. The paper devises a scheduling policy which deterministically guarantees when and where the misses will occur. The paper also proposes a methodology for modifying the control law to minimize the deterioration in the control system behavior as a result of these missed control law updates. Index TermsÐReal-time systems, fault-tolerant controllers, real-time scheduling, overload management, optimal feedbackcontrol. 1
Analysis of a Window-Constrained Scheduler for Real-Time and Best-Effort Packet Streams
- In Proceedings of the 21st IEEE Real-Time Systems Symposium
, 2000
"... This paper describes how Dynamic WindowConstrained Scheduling (DWCS) can guarantee real-time service to packets from multiple streams with different performance objectives. We show that: (1) DWCS can guarantee that no more than x packets miss their deadlines for every y consecutive packets requiring ..."
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Cited by 69 (16 self)
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This paper describes how Dynamic WindowConstrained Scheduling (DWCS) can guarantee real-time service to packets from multiple streams with different performance objectives. We show that: (1) DWCS can guarantee that no more than x packets miss their deadlines for every y consecutive packets requiring service, as long as the minimum aggregate bandwidth requirement of all real-time packet streams does not exceed the available bandwidth, (2) using DWCS, the delay of service to realtime packet streams is bounded even when the scheduler is overloaded, (3) DWCS can ensure that the delay bound of any given stream is independent of other streams, and (4) a fast response time for best-effort packet streams, in the presence of real-time packet streams, is possible. Furthermore, if a feasible schedule exists, each stream is guaranteed a minimum fraction of available bandwidth over a finite window of time. 1. Introduction Many real-time, distributed applications, such as telemedicine, virtual env...
Tardiness bounds under global edf scheduling on a multiprocessor
- In RTSS ’05: Proceedings of the 26th IEEE International Real-Time Systems Symposium
, 2005
"... This paper considers the scheduling of soft real-time sporadic task systems under global EDF on an iden-tical multiprocessor. Though Pfair scheduling is theoretically optimal for hard real-time task systems on multiprocessors, it can incur signicant run-time overhead. Hence, other scheduling algorit ..."
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Cited by 62 (36 self)
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This paper considers the scheduling of soft real-time sporadic task systems under global EDF on an iden-tical multiprocessor. Though Pfair scheduling is theoretically optimal for hard real-time task systems on multiprocessors, it can incur signicant run-time overhead. Hence, other scheduling algorithms that are not optimal, including EDF, have continued to receive considerable attention. However, prior research on such algorithms has focussed mostly on hard real-time systems, where, to ensure that all deadlines are met, ap-proximately 50 % of the available processing capacity will have to be sacriced in the worst case. This may be overkill for soft real-time systems that can tolerate deadline misses by bounded amounts (i.e., bounded tardiness). In this paper, we derive tardiness bounds under preemptive and non-preemptive global EDF on multiprocessors when the total utilization of a task system is not restricted and may equal the number of pro-cessors. Our tardiness bounds depend on per-task utilizations and execution costs the lower these values, the lower the tardiness bounds. As a nal remark, we note that global EDF may be superior to partitioned EDF for multiprocessor-based soft real-time systems in that the latter does not offer any scope to improve system utilization even if bounded tardiness can be tolerated. ¤Work supported by NSF grants CCR 0204312, CCR 0309825, and CCR 0408996. The rst author was also supported by an IBM Ph.D. fellowship.
Dynamic window-constrained scheduling for multimedia applications
- In ICMCS
, 1999
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QoS Guarantee Using Probabilistic Deadlines
- IN PROCEEDINGS OF THE 11TH EUROMICRO CONFERENCE OF REAL-TIME SYSTEMS
, 1999
"... This paper presents a probabilistic approach to guarantee the performance of a real-time system. While traditional real-time system analysis tends to guarantee that each task instance will complete its execution before its absolute deadline (hard guarantee), our approach permits to estimate the prob ..."
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Cited by 48 (3 self)
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This paper presents a probabilistic approach to guarantee the performance of a real-time system. While traditional real-time system analysis tends to guarantee that each task instance will complete its execution before its absolute deadline (hard guarantee), our approach permits to estimate the probability that it will happen. Such a statistical guarantee is performed based on interarrival and execution times probability distributions, rather than their worst case values. The advantage of a probabilistic approach is a more efficient usage of system resources, allowing to give a certain level of deadline guarantee to task sets that the classical schedulability analysis would reject.
