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1.
Ad hoc networks formed without the aid of any established infrastructure are typically multi-hop networks. Location dependent contention and hidden terminal problem make priority scheduling in multi-hop networks significantly different from that in wireless LANs. Most of the prior work related to priority scheduling addresses issues in wireless LANs. In this paper, priority scheduling in multi-hop networks is discussed. We propose a scheme using two narrow-band busy tone signals to ensure medium access for high priority source stations. The simulation results demonstrate the effectiveness of the proposed scheme. Xue Yang received the B.E. degree and the M.S. degree from University of Electronic Science and Technology of China. She is currently a Ph.D. candidate at University of Illinois at Urbana-Champaign (UIUC). She is awarded Vodafone-U.S. Foundation Graduate Fellowship from 2003 to 2005. Her current research is in the areas of wireless networking and mobile computing, with the focus on medium access control, quality of service and topology control. Her research advisor is Prof. Nitin Vaidya at UIUC. For more information, please visit Nitin H. Vaidya received the PhD degree from the University of Massachusetts at Amherst. He is presently an Associate Professor of Electrical and Computer Engineering at the University of Illinois at Urbana-Champaign (UIUC). He has held visiting positions at Microsoft Research, Sun Microsystems and the Indian Institute of Technology-Bombay. His current research is in the areas of wireless networking and mobile computing. His research has been funded by various agencies, including the National Science Foundation, DARPA, BBN Technologies, Microsoft Research, and Sun Microsystems. Nitin Vaidya is a recipient of a CAREER award from the National Science Foundation. Nitin has served on the program committees of several conferences and workshops, and served as program co-chair for the 2003 ACM MobiCom. He has served as editor for several journals, and presently serves as Editor-in-Chief for IEEE Transactions on Mobile Computing, and as editor-in-chief of ACM SIGMOBILE periodical MC2R. He is a senior member of IEEE and a member of the ACM. For more information, please visit  相似文献   
2.
In this paper, we are interested in real-time flows requiring quantitative and deterministic Quality of Service (QoS) guarantees. We focus more particularly on two QoS parameters: the worst case end-to-end response time and jitter. We consider a non-preemptive scheduling of flows, called fp/dp*, combining fixed priority and dynamic priority established on the first node visited in the network. Examples of such a scheduling are fp/fifo* and fp/edf*. With any flow is associated a fixed priority denoting the importance of the flow from the user point of view. The arbritation between packets having the same fixed priority is done according to their dynamic priority. A classical approach used to compute the worst case end-to-end response time is the holistic one. We show that this approach leads to pessimistic upper bounds and propose the trajectory approach to improve the accuracy of the results. Indeed, the trajectory approach considers the worst case scenarios experienced by a flow along its trajectory. It then eliminates scenarios that cannot occur.  相似文献   
3.
The paper deals with the scheduling of periodic information flow in a FieldBus environment. The scheduling problem is defined from an analytical point of view, giving a brief survey of the most well-known solutions. One of these is called multicycle polling scheduling, which is based on the hypothesis that all the production periods of the periodic processes to be scheduled are harmonic. Although in some process control or manufacturing scenarios, this hypothesis may be acceptable, there are many real industrial processes to which it cannot be applied. The aim of the paper is to make a contribution towards solving the scheduling problem. It essentially concerns extension of the theory on which multicycle polling scheduling is based to a much more realistic and general scenario, where the periods of all the processes to be scheduled have arbitrary values. The authors present a new formulation of multicycle polling scheduling, called extended multicycle polling scheduling, and demonstrate that it comprises the scenario currently considered in the literature. Two algorithmic solutions for extended multicycle polling scheduling are then proposed, giving a computational complexity analysis which will highlight the capability of the algorithmic scheduling solutions to be performed on-line. The paper concludes by comparing the multicycle polling scheduling approach known in literature and the one presented in the paper. Comparison is performed by evaluating the use of available bandwidth to serve both periodic and asynchronous traffic in the two approaches.  相似文献   
4.
Analysis of Checkpointing for Real-Time Systems   总被引:3,自引:0,他引:3  
Predictable performance in the event of failuresis of paramount importance in most safety critical real-timesystems. Various hardware as well as software fault-toleranttechniques are employed towards this goal among which checkpointingis a relatively cost-effective scheme. Since checkpointing schemesdepend on time redundancy, they could affect the correctnessof the system by causing deadlines to be missed. This paper providesexact schedulability tests for fault tolerant task sets undera specified failure hypothesis and employing checkpointing toassist in fault recovery. The effects of checkpointing strategieson task response time are analysed and some insights for optimalcheckpointing are provided. The emphasis here is on utilizingthis analysis as an off-line design support tool.  相似文献   
5.
Builders of real-time systems often use priority scheduling in their systems without considering alternatives. This paper examines one alternative, pre-run-time scheduling, and show that when it can be applied it has significant advantages when compared to priority scheduling schemes.  相似文献   
6.
基于多分辨率模型的实时调度方法   总被引:1,自引:0,他引:1       下载免费PDF全文
在实时系统中,为了避免任务的计算结果发生时间逻辑错误,我们提出一种新的多分辨率模型。在该模型中,任务有多个计算时间,每个计算时间都对应一定的执行价值。任  务的计算时间越长,其执行价值越高。接着,我们提出了采用计算时间的数学期望值进行任务的优先级分配和可调度分析,从而可以利用已有的优先级分配和可调度分析方法   法,并在此基础上提出确定任务计算时间的方法。  相似文献   
7.
A Petri net approach to determining the conditions for stability of a re-entrant system with buffer priority scheduling policy is described in this paper.The concept of buffer boundedness based on the dynamic behavior of the markings in the system model is emphasized.The method is used to demonstrate the stability of the first buffer first served(FBFS)and the last buffer first served(LBFS)scheduling policies.Finally a sufficient condition for instability of systems with a positive feedback Joop(PFL) is established,and an example is given.  相似文献   
8.
林闯  戴琼海 《自动化学报》2000,26(6):770-775
描述了一种时间Petri网模型和方法,它能对具有缓冲优先调度可重入生产线系统进 行稳定性分析.基于系统模型标识的动态变化,以缓冲界限概念作为稳定性分析判据.这种方法 可用于具有固定优先次序调度策略的稳定性分析.推导了基本时间Petri网结构的稳定特性以 及具有正反馈环系统稳定的充分条件.这些研究结果可以用于多种实际系统的稳定性分析.  相似文献   
9.
基于双优先级的实时多任务动态调度   总被引:1,自引:1,他引:0  
刘怀  费树岷 《计算机工程》2005,31(18):16-18
提出了带有非周期服务器的双优先级调度算法.该算法将优先级带宽分为高带、中带和低带3部分.强实时任务实例到达后,优先级设置在低带,经过一段时间后将其优先级提升到高带;软实时任务的优先级设置在中带.分析了强实时任务实例优先级提升时间和任务集的可调度性.  相似文献   
10.
周期多帧任务的固定优先级调度算法的调度分析   总被引:3,自引:0,他引:3  
实时操作系统的核心问题--实时任务的调度是实时系统研究的重点之一。主要讨论了周期多帧任务的固定优先级调度算法的调度情况,证明了对于周期多帧任务DM算法不是最优的,同时也证明了对于累积单调周期多帧任务的DM算法是最优的。  相似文献   
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