动态电压调整多处理器实时系统任务调度

动态电压调整DVS（Dynamic Voltage Scaling）是根据处理器电压（速度）降低之后，能量消耗平方级的减少这一原理提出的。文章通过DVS机制在多处理器实时系统中进行任务调度．通过对任务调度中的静态能量管理进行分析，在此基础上提出了一种新的基于DVS的适用于多处理器实时系统中的调度算法。这种新的调度算法是通过对贪婪法调度进行研究，发现其不足．并以此为基础进行改进。结合了动态电压调整的多处理器实时系统任务调度的能量消耗比普通的任务调度能量消耗有了很大的改善。     

Real-Time Dynamic Voltage Loop Scheduling for Multi-Core Embedded Systems

In this brief, we propose a novel real-time loop-scheduling technique to minimize energy consumption via dynamic voltage scaling (DVS) for applications with loops considering transition overhead. One algorithm, dynamic voltage loop scheduling (DVLS), is designed integrating with DVS. In DVLS, we repeatedly regroup a loop based on rotation scheduling and decrease the energy by DVS as much as possible within a timing constraint. We conduct the experiments on a set of digital signal processing benchmarks. The experimental results show that DVLS achieves big energy saving compared with the traditional time-performance-oriented scheduling algorithm     

基于DVS的多核实时系统节能调度

动态电压调节是一种有效的节能技术．本文提出了多核处理器平台上的一种近似最优的动态电压调节算法．算法将电压调节问题转化为松弛时间分配问题，由任务集结构找到存在的松弛时间，针对不同类型的松弛时间，使用了并行补偿等分配方法．实验结果表明本文的算法能够有效的降低能量消耗且具有较低的时间复杂度．     

Optimal Dynamic Voltage Scaling in Energy-Limited Nonpreemptive Systems with Real-Time Constraints

Dynamic voltage scaling is used in energy-limited systems as a means of conserving energy and prolonging their life. We consider a setting in which the tasks performed by such a system are nonpreemptive and aperiodic. Our objective is to control the processing rate over different tasks so as to minimize energy subject to hard real-time processing constraints. Under any given task scheduling policy, we prove that the optimal solution to the offline version of the problem can be efficiently obtained by exploiting the structure of optimal sample paths, leading to a new dynamic voltage scaling algorithm termed the critical task decomposition algorithm (CTDA). The efficiency of the algorithm rests on the existence of a set of critical tasks that decompose the optimal sample path into decoupled segments within which optimal processing times are easily determined. The algorithm is readily extended to an online version of the problem as well. Its worst-case complexity of both offline and online problems is O(N²)     

Dynamic Voltage and Frequency Scaling For On-Demand Performance and Availability of Biomedical Embedded Systems

The goal of the study presented in this paper is to develop an embedded biomedical system capable of delivering maximum performance on demand, while maintaining the optimal energy efficiency whenever possible. Several hardware and software solutions are presented allowing the system to intelligently change the power supply voltage and frequency in runtime. The resulting system allows use of more energy-efficient components, operates most of the time in its most battery-efficient mode, and provides means to quickly change the operation mode while maintaining reliable performance. While all of these techniques extend battery life, the main benefit is on-demand availability of computational performance using a system that is not excessive. Biomedical applications, perhaps more than any other application, require battery operation, favor infrequent battery replacements, and can benefit from increased performance under certain conditions (e.g., when anomaly is detected) that makes them ideal candidates for this approach. In addition, if the system is a part of a body area network, it needs to be light, inexpensive, and adaptable enough to satisfy changing requirements of the other nodes in the network.      

Time Triggered Hybrid Scheduler with Dynamic Frequency Scaling for Distributed Real Time Embedded Systems

Wireless Personal Communications - In this paper, the time triggered hybrid scheduler (TTH) is implemented in the distributed real time embedded systems along with the operation of dynamic...     

Control System With High-Speed and Real-Time Communication Links

Recent technological advances have enabled distributed control systems to be implemented via networks. This allows feedback control loops to be closed over communication channels. This paper develops a control system with high-speed and real-time communication links. Two-degrees-of-freedom control is utilized in this servo control system, and sigma-delta modulation is employed to compress data and to transmit the signal over the transmission channels between the controller and the controlled plant. Simulation results show that the controller can compensate the possible existing noise in the transmission channels. In addition, the developed system is implemented in field-programmable gate arrays. We developed a real-time closed-loop control system that has a communication channel whose control-sampling period is 600 ns and can reduce the sampling period of the controller module to hundreds of nanoseconds.     

操作系统级低功耗动态电压缩放算法分析

低功耗的设计已经成为嵌入式系统设计中一个非常重要的方面，而动态电压调度（Dynamic Voltage Scaling DVS）又被认为是降低功耗的一种有效手段。本文对各类针对系统的动态电压缩放算法做了较系统的总结，给出了算法的模型，重点描述了操作系统级的两类动态电压缩放算法——基于间隔和基于任务的动态电压调度算法，概述了针对编译级的任务内动态电压调度算法。文章对三类算法作了分析与比较，由此给出了结论与观点，对以后动态电压缩放算法的研究做了预测。     

无线传感器网络的动态电压调节算法研究

对于能量有限的无线传感器网络,研究如何高效地利用有限能量具有重要意义.根据无线传感器网络多跳路由和拓扑易变的特点,提出一种基于任务驱动的含反馈的动态电压调节算法FB-DVS.该算法根据节点的任务集实时地调节节点的工作电压和频率,并通过反馈环节来修正误差,在保证任务实时性的前提下降低节点能耗.通过对仿真结果分析表明,改进的算法能有效地减少节点的能量消耗,延长无线传感器网络的生命周期.     

Frequency Scaling of Rain Attenuation for Satellite Communication Links

One year of copolarized signal data from the OLYMPUS satellite's 12, 20, and 30 GHz beacons were examined for frequency scaling of attenuation. The statistics of the ratios of attenuation in dB for the frequency pairs 30/20, 20/12, and 30/12 GHz computed at each 0.1 s-sample instant were found to be nearly independent of fade depth. It was found that attenuation in dB scales with frequency to the 1.9 power. Also, attenuation ratios computed from the separate statistics of attenuation at each frequency for the same level of occurrence are very close to those found from instantaneous attenuation ratios     

Control and Communication Challenges in Networked Real-Time Systems

A current survey of the emerging field of networked control systems is provided. The aim is to introduce the fundamental issues involved in designing successful networked control systems, to provide a snapshot assessment of the current state of research in the field, to suggest useful future research directions, and to provide a broad perspective on recent fundamental results. Reflecting the goals of the Special Issue itself, this paper surveys relevant work from the areas of systems and control, signal processing, detection and estimation, data fusion, and distributed systems. We discuss appropriate network architectures, topics such as coding for robustly stable control in the presence of time-varying channel capacity, channels with fixed versus adaptively variable data width, issues in data rate problems in nonlinear feedback problems, and problems in routing for stability and performance. In surveying current research on networked control systems, we find that recent theoretical advances and target applications are intimately intertwined. The common goal of papers in the Special Issue which follows is to describe key aspects of this relationship. We also aim to provide a bridge between networked control systems and closely related contemporary work dealing with sensor networks and wireless communication protocols     

Dynamic Base Station Selection for Personal Communication Systems with Distributed Control Schemes

Distributed control schemes allow base stations in personal communication systems to be placed at locations corresponding to high expected traffic. This flexible base station placement creates significant overlapping coverage areas that can be utilized to improve system performance [1]. A new technique for dynamic base station selection in systems with overlapping cells is considered and its effect on traffic performance is characterized. The technique realizes robust performance for personal communication systems in fluctuating and heavily tapered traffic. A mathematical analysis based on a state transition model is used to evaluate performance of a system that employs the proposed technique. The results indicate that improved blocking probability and carried traffic performance are obtainable. Computer simulations were undertaken confirm the analytical results.     

分布式天线系统在移动通信中的应用

移动通信在中国的发展势头未减,2G网络的优化以及3G网络的规划都对技术创新提出了更高的要求。分布式天线解决方案是当前和未来移动通信网络中无线资源管理的有效方式之一。介绍了分布式天线系统的种类和发展,探讨了分布式天线系统为移动通信运营商带来的好处。     

基于UML的嵌入式实时系统开发方法

嵌入式实时系统的严格约束条件增加了开发的复杂和困难.本文以空调系统为例,阐述了UML建模的基本过程,创建了各种可视化模型并进行了调试验证,大大缩短了系统开发时间,提高了设计质量,充分验证了使用UML技术在嵌入式实时系统开发中的可能和便利.     

Pinpointing Interrupts in Embedded Real-Time Systems Using Hashed Execution Contexts

Cyclic debugging is the process of iteratively re-executing a failed execution in order to determine the cause of the failure, i.e., the bug. In this process, being able to correctly reproduce the faulty execution is an absolute necessity. In sequential, deterministic, non-real-time software, this reproducibility is inherent. However, when the execution is preempted by interrupts, this has severe effects on program reproducibility, since, during the reproduction, it is required for interrupts to occur at the exact same instructions. Previously, this problem has been solved using instruction counters, that induce large execution-time perturbations, or by special hardware solutions which impose a risk of inexact results. In this paper, we propose an alternative method for pinpointing interrupts using hashed values of selected parts of the program execution context. Although our method in some cases can be ambiguous, we show that it serves as a pragmatic method for pinpointing and reproducing interrupts in embedded real-time systems. Moreover, our method does not rely on special hardware or compilers, is simple to implement and use, and requires little execution-time and memory.      

分布式实时通信网络在火控系统中的应用

通过对现代雷达火控系统通信基本特点的分析,提出一种适合于现代雷达火控系统的通信方式——基于ARCNET的多总线拓扑强容错令牌总线网,并对实时系统与实时通信的特征作了深入的分析。     

A Design Perspective for Real-Time Task Control in Distributed Systems

Industrial control systems have unique system requirements which often require diverse systems of cooperating components to achieve system goals. System requirements may be specified in the form of tasks which must be executed in sequential order. This paper presents a design perspective in which such problems can be decomposed and implemented by a distributed system in a modular-fashion. A System Scheduler is responsible for all flow control functions. Loosely coupled Task Processors respond to instructions from the scheduler to perform the control algorithm Parallelism, redundancy, and distributed control are presented as methods of improving system performance and reliability.     

Simultaneous On-Chip Bus Synthesis and Voltage Scaling Under Random On-Chip Data Traffic

This paper presents a statistical approach to synthesize an energy conscious the optimal bus width and the number of buses. The slack is exploited to maximize bus sharing and to reduce energy consumption by simultaneously scaling the voltage during the synthesis of on-chip communication bus. An assumption for bus synthesis is that a system has been partitioned and mapped onto the appropriate modules of a system-on-chip (SoC). Because of the diversity of applications to be run on a single SoC, there exists a variability of data size to be transferred among the on-chip communicating modules. This variability of data size is modeled as a random variable with a known distribution function. The resulting synthesis problem is relaxed to a convex quadratic optimization problem and solved efficiently using a convex optimization tool. The effectiveness of our approach is demonstrated by applying optimization to an automatically generated benchmark and a real-life application. By scaling voltage of a bus, a tradeoff between communication bus cost (bus width and the number of buses) and energy reduction is explored. The experimental results show the significant reduction in communication energy with scaling voltage. However, it offers a limitation to minimize the communication bus cost, if the voltage is scaled beyond its minimum limit. Furthermore, we also estimate the distribution of voltage under a random data size using an analytical method and the Monte Carlo simulation. The results show that the analytically estimated statistical parameters of voltage are close to the simulated results.     

A Real-Time Scheduler Design for a Class of Embedded Systems

We consider here the design aspect of a real-time scheduler for a class of embedded systems. For this purpose, we design a feedback controller for a reservation-based CPU scheduler for soft real-time systems. The execution time of soft real-time systems, such as multimedia systems, portable MP3 players, personal digital assistants, cellular phones, and embedded Web servers is highly variable. Hence, it is crucial to assign an adequate amount of CPU resources for the running tasks to guarantee the quality of service. On the other hand, it is also important not to allocate the large amount of resources to avoid waste. The purpose of this paper is to attain the aforementioned crucial objectives for a class of embedded systems under real-time computing constraints. Specifically, we provide an analytical model for a real-time scheduler in terms of a switched system with time-varying uncertainty. Moreover, by using Lyapunov stability in a linear matrix inequalities (LMIs) framework, we design a state feedback controller that stabilizes the switched system. This, in fact, achieves the regulation of scheduling errors caused by time-varying uncertainty to a desired level. We extend an LMI-framework-based control scheme to a relatively new control application domain, i.e., a soft realtime scheduling domain. We provide performance analysis under scheduler simulation environments and implement a feedback bandwidth server scheduler under a real-time kernel simulator. In the simulation studies, the advantages of the controller design scheme are clearly highlighted in comparison with some conventional existing open-loop systems.