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Embedded wireless networks have largely focused on open-loop sensing and monitoring. To address actuation in closed-loop wireless control systems there is a strong need to re-think the communication architectures and protocols for reliability, coordination and control. As the links, nodes and topology of wireless systems are inherently unreliable, such time-critical and safety-critical applications...
Providing integrity, efficiency, and performance guarantees is a key challenge in the development of next-generation cyberphysical systems. Rather than mandating complete system verification, the Simplex Architecture provides robust designs by incorporating a supervisory controller that takes corrective action only when the system is in danger of violating a desired invariant property such as safety...
Open soft real-time systems, such as mobile robots, must respond adaptively to varying operating conditions, while balancing the need to perform multiple mission specific tasks against the requirement that those tasks complete in a timely manner. Setting and enforcing a utilization target for shared resources is a key mechanism for achieving this behavior. However, because of the uncertainty and non-preempt...
In this paper, we jointly optimize computation and communication task scheduling for streaming applications on MPSoC. The objective is to minimize schedule length by totally removing inter-core communication overhead. By minimizing schedule length, the system performance can be improved by adopting a smaller period or exploring the slacks generated for energy reduction with DVS. To guarantee the schedulability...
The problem of scheduling a set of tasks on a multiprocessor architecture is addressed. Tasks are assumed to be sporadic with arbitrary deadlines and may migrate between processors. The execution of migrating tasks is controlled by a bandwidth reservation scheme so that schedulability is guaranteed by EDF. Task migration costs are taken into consideration. Results from experiments indicate that the...
Recent research in compositional real-time systems has focused on determination of a component's real-time interface parameters. An important objective in interface-parameter determination is minimizing the bandwidth allocated to each component of the system while simultaneously guaranteeing component schedulability. With this goal in mind, in this paper we develop a fully-polynomial-time approximation...
Dynamic RAM (DRAM) has been the best technology for main memory for over thirty years. In embedded space applications, radiation hardened DRAM is needed because gamma rays cause transient errors; such rad-hard memories are extremely expensive and power hungry, leading to lower life (or increased battery weight) for satellite and other devices operating in space. Despite these problems, DRAM has been...
Modern computing systems have adopted multicore architectures and multiprocessor systems on chip (MPSoCs) for accommodating the increasing demand on computation power. However, performance boosting is constrained by shared resources, such as buses, main memory, DMA, etc.This paper analyzes the worst-case completion (response) time for real-time tasks when time division multiple access (TDMA) policies...
While most prior work on multiprocessor real-time scheduling focuses on independent tasks, dependencies due to non-preemptive sections, suspensions, and pipeline-based precedence constraints are common in practice. In this paper, such complexities are considered in the context of the global earliest-deadline-first scheduling algorithm. It is shown that any periodic task system with such dependencies...
Recent results have shown that the feasibility problem of scheduling periodic tasks with self-suspensions is NP-hard in the strong sense. We observe that a variation of the problem statement that includes sporadic tasks instead of periodic tasks results in a simple characterization of the critical scheduling instant. This in turn leads to an exact characterization of the critical instant for self-suspending...
The management of tasks is an essential requirement in most real-time and embedded systems, but invariably leads to unwanted CPU overheads. This paper is concerned with task management in real-time and embedded systems employing the Earliest Deadline First (EDF) scheduling algorithm. Currently, the best known techniques to manage EDF scheduling lead to overheads with complexity O(log n), where n is...
Many safety-critical embedded systems are subject to certification requirements; some systems may be required to meet multiple sets of certification requirements, from different certification authorities. Certification requirements in such "mixed-criticality" systems give rise to some interesting scheduling problems, that cannot be satisfactorily addressed using techniques from conventional...
This paper derives energy-optimal batching periods for asynchronous multistage data processing on sensor nodes in the sense of minimizing energy consumption while meeting end-to-end deadlines. Batching the processing of (sensor) data maximizes processor sleep periods, hence minimizing the wakeup frequency and the corresponding overhead. The algorithm is evaluated on mPlatform, a next-generation heterogeneous...
Liu and Layland discovered the famous utilization bound for fixed-priority scheduling on single processor systems in the 1970's. Since then, it has been a long standing open problem to find fixed-priority scheduling algorithms with the same bound for multiprocessor systems. In this paper, we present a partitioning-based fixed-priority multiprocessor scheduling algorithm with Liu and Layland's utilization...
Real-time systems used in media processing and transmission produce bursty workloads with highly variable execution and transmission times. To avoid the drawbacks of using the worst-case approach with these workloads, this paper uses a variation of the usual real-time task model where the WCET is replaced by a discrete statistical distribution. Using this approach, tasks are characterized by their...
Providing QoS and performance guarantees to arbitrarily divisible loads has become a significant problem for many cluster-based research computing facilities. While progress is being made in scheduling arbitrarily divisible loads, current approaches are not efficient and do not scale well. In this paper, we propose a linear algorithm for real-time divisible load scheduling. Unlike existing approaches,...
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