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Wireless sensor networks are evolving from dedicated application-specific platforms to integrated infrastructure shared by multiple applications. Shared sensor networks offer inherent advantages in terms of flexibility and cost since they allow dynamic resource sharing and allocation among multiple applications. Such shared systems face the critical need for allocation of nodes to contending applications...
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Prior work has shown that the global earliest-deadline-first (GEDF) scheduling algorithm ensures bounded deadline tardiness on multiprocessors with no utilization loss; therefore, GEDF may be a good candidate scheduling algorithm for soft real-time workloads. However, such workloads are often implemented assuming an average-case provisioning, and in prior tardiness-bound derivations for GEDF, worst-case...
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This paper presents the design and analyzes the performance of a reliable communication scheme for the traffic control system built upon a wireless process control protocol, aiming at enhancing the robustness and timeliness of the safety-critical control applications. By exploiting the slot-based predictable access and the grid topology of urban area road networks, the proposed scheme establishes...
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Dynamic Voltage Scaling (DVS) and Dynamic Power Management (DPM) techniques form the basis of numerous energy management schemes proposed for real-time embedded systems. DVS targets reducing the dynamic CPU energy consumption, while DPM attempts to reduce theenergy consumption of idle devices by putting them to low-power states over sufficiently long intervals. It is imperative that the system-wide...
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Some real-time kernels (such as a recent real-time version of Linux) permit to execute interrupt handlers in dedicated threads, to control their interference on real-time applications. However, from the stand-point of real-time analysis, such threads are challenging and cannot be dealt with in the traditional ways. Furthermore, the application of traditional scheduling solutions (such as fixed priorities)...
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We propose two complementary methods to account for scheduler overhead in the schedulability analysis of Variable Bandwidth Servers (VBS), which control process execution speed by allocating variable CPU bandwidth to processes. Scheduler overhead in VBS may be accounted for either by decreasing process execution speed to maintain CPU utilization (called response accounting), or by increasing CPU utilization...
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A combination of a scratchpad and scratchpad memory management unit (SMMU) has been proposed as a way to implement fast and time-predictable memory access operations in programs that use dynamic data structures. A memory access operation is time-predictable if its execution time is known or bounded-this is important within a hard real-time task so that the worst-case execution time (WCET) can be determined...
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Application of runtime monitoring to maintain the health of an embedded real-time software system requires that anomalous behavior be detected within a bounded time while preserving the temporal guarantees of the underlying system. Existing results can compute bounds on the detection latency of runtime monitors that are realized as a deferrable server running at the highest priority. In this paper,...
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This paper describes the design and implementation of a pervasive computing framework, named Physicalnet. Essentially, Physicalnet is a generic paradigm for managing and programming world-wide distributed heterogeneous sensor and actuator resources in a multi-user and multi-network environment. Using a four-tier light-weight service oriented architecture, Physicalnet enables global uniform access...
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The global EDF scheduling of sporadic task systems upon uniform multiprocessor platforms is studied. A new sufficient schedulability test is presented and proved correct. Some interesting issues are discussed, that arise regarding the choice of an appropriate metric for evaluating the test quantitatively. Metrics based on processor speedup factor are proposed, and the test is quantitatively evaluated...
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This article studies the scheduling of critical embedded systems, which consist of a set of communicating periodic tasks with constrained deadlines. Currently, tasks are usually sequenced manually, partly because available scheduling policies do not ensure the determinism of task communications. Ensuring this determinism requires scheduling policies supporting task precedence constraints (which we...
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The following topics are discussed: real-time applications; embedded technology; scheduling; operating systems; robust and fault-tolerant systems, thermal and energy aware systems; hardware-software codesign; systems modeling and design; and wireless sensor networks.
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Many mission-critical applications such as military surveillance, human health monitoring, and obstacle detection in autonomous vehicles impose stringent requirements for event detection accuracy and demand long system lifetimes. Through quantitative study, we show that traditional approaches to event detection have difficulty meeting such requirements. Specifically, they cannot explore the detection...
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Hardware-managed caches introduce large amounts of timing variability, complicating real-time system design. One alternative is a memory system with scratchpad memories which improve system performance while eliminating such timing variability. Prior work introduced the DARTS approach, which combines static allocation of data into scratchpad memories, with task scheduling for preemptive multi-threaded,...
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The specification of the sporadic server real-time scheduling policy in the IEEE POSIX standard is defective, and needs to be corrected. Via experiments using a POSIX sporadic server implementation under Linux, as well as simulations, we have shown and confirmed previously unreported defects. We propose and demonstrate a corrected sporadic server formulation that eliminates these defects without changes...
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Thermal control is crucial to real-time systems as excessive processor temperature can cause system failure or unacceptable performance degradation due to hardware throttling. Real-time systems face significant challenges in thermal management as they must avoid processor overheating while still delivering desired real-time performance. Furthermore, many real-time systems must handle a broad range...
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In this paper we are interested in mixed hard/soft real-time fault-tolerant applications mapped on distributed heterogeneous architectures. We use the Earliest Deadline First (EDF) scheduling for the hard real-time tasks and the Constant Bandwidth Server (CBS) for the soft tasks. The bandwidth reserved for the servers determines the quality of service (QoS) for soft tasks. CBS enforces temporal isolation,...
