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As the increasing of system performance and computing power, embedded systems are more complicated and interactive. Therefore, operating system (OS) plays a more important role in embedded systems to utilize various hardware and software resources. However, no OS can meet all requirements of various embedded systems. Due to the advance of reconfigurable processors, system requirements can be more...
In this paper we consider data freshness and overload handling in embedded systems. The requirements on data management and overload handling are derived from an engine control software. Data items need to be up-to-date, and to achieve this data dependencies must be considered, i.e., updating a data item requires other data items are up-to-date. We also note that a correct result of a calculation...
This paper presents a performance study on various broadcast algorithms in a real-time information dispatch system. The objective of the study is to design an efficient broadcast algorithm for providing data in a timely manner for real-time transaction processing applications in broadcast environments. We construct and conduct a series of simulation experiments to look at the performance of our proposed...
The deferrable scheduling algorithm for fixed priority transactions (DS-FP) is demonstrated to be a very effective approach for minimizing real-time update transaction workload while maintaining temporal validity of real-time data. This paper examines the schedulability of deferrable scheduling and presents a sufficient condition. While its online scheduling overhead is a concern, we propose a hyperperiod...
From a real-time perspective, the garbage collector (GC) introduces unpredictable pauses that are not tolerated by real-time tasks. Real-time collectors eliminate this problem but introduce a high overhead. Another approach is to use memory regions (MR) within which allocation and deallocation are customized. This facility is supported by the memory model of the real-time specification for Java (RTSJ)...
Applying classical dynamic voltage scaling (DVS) techniques to real-time systems running on processors with discrete voltage/frequency modes causes a waste of computational resources. In fact, whenever the ideal speed level computed by the DVS algorithm is not available in the system, to guarantee the feasibility of the task set, the processor speed must be set to the nearest level greater than the...
In some real-time applications, it is desirable to trade off precision for timeliness. For such systems, considered typically under the imprecise computation model, a function assigns reward to the application depending on the amount of computation allotted to it. Also, many such applications run on battery-powered devices where the energy consumption is of utmost importance. We address in this paper...
The real-time implementation of a controller typically introduces artefacts like delay and jitters that have not been considered at the design stage. As a consequence, the system behaves in a non-periodic manner, and the real performance is degraded with respect to the expected response. This paper proposes a hybrid task model to reduce the impact of the scheduling on the control performance. For...
This paper extends U-Link scheduling to increase the average execution efficiency of the system. We first define the execution efficiency. Then we propose a new algorithm that establishes the co-scheduled sets where the execution efficiency can be increased. Also we present the static estimation of the execution time and provide the schedulability analysis for the extended U-Link scheduling. In the...
In this paper, we present a model-driven approach to RTOS-based embedded software development and an automated tool that can produce RTOS-specific code. Our contributions are two fold. First, we defined generic RTOS APIs (application programming interfaces) that can capture most of typical RTOS services but are not bound to any specific RTOS. The generic RTOS APIs can be used as a means for describing...
The number of computer-controlled functions in an automobile is increasing at a rapid rate and so is the number of microprocessors implementing and controlling these functionalities. Therefore, there is a need to minimize the computing power provided without affecting the performance and safety of the applications. The latter is especially important since intelligent automotive applications deal with...
A key issue in wireless real-time communications is to meet the real-time constraint with low energy consumption. In this paper, we propose an energy-efficient error correcting scheme for weakly hard real-time communications in wireless networks. A weakly hard read-time communication should send at least m messages during any window of k periods. The proposed scheme adaptively selects an error correcting...
This article introduces the concept of monotonic transactions. A monotonic transaction is a particular case of transactions for which the load arrival pattern is (or can be by rotation) localized at the beginning of the transaction. In the general context of tasks with offsets (general transactions) only exponential methods are known to calculate the worst-case response time. The pseudo-polynomial...
Dynamic voltage scaling (DVS) is a frequently used technique in mobile and embedded systems, aimed at reducing the energy consumption of mobile processors. In systems with a discrete number of frequency levels, existing dual-speed DVS approaches compute an optimal theoretical CPU speed and approximate it by choosing the two neighboring discrete speed levels. By comparing experimentally the energy...
This paper addresses the problem of processing event-timing queries over event streams where the uncertainty in the values of the timestamps is characterizable by histograms. We describe a stream-partitioning technique for checking the satisfaction of a probabilistic timing constraint upon event arrivals in a systematic way in order to delimit the "probing range" in event streams. This technique...
We propose a novel tool, called objSampler, with which users can record and recall "encounters" with objects in ubiquitous computing environments. We encounter various things, individuals, and places in the real world either consciously, meaning encounters that we are aware of, or unconsciously, meaning those we are unaware of but physically close to them. While some of those encounters...
A QoS adaptation to dynamically changing system conditions that takes into consideration the user's constraints on the stability of service provisioning is presented. The goal is to allow the system to make QoS adaptation decisions in response to fluctuations in task traffic flow, under the control of the user. We pay special attention to the case where monitoring the stability period and resource...
Mobile location estimation is becoming an important value-added service for mobile phone operators. Many mobile location estimation algorithms based on the cellular radio networks have been proposed but there exists no general solution since each algorithm has its own advantage depending on specific terrain and environmental factors. In this paper, we propose and investigate three algorithm selectors,...
Real-time logic (RTL) is useful for the verification of a safety assertion SA with respect to the specification SP of a real-time system. Since the satisfiability problem for RTL is undecidable, there were many efforts to find proper heuristics for proving that SPrarrSA holds. However, none of such heuristics necessarily finds an "optimal implication". After verifying SPrarrSA, and the system...
ILP (instruction level parallelism) processors are being increasingly used in embedded systems. In embedded systems, instructions may be subject to timing constraints. An optimising compiler for ILP processors needs to find a feasible schedule for a set of time-constrained instructions. In this paper, we present a fast algorithm for scheduling instructions with precedence-latency constraints, individual...
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