New coprimeness over multivariable polynomial matrices and its application to control delay systems

This paper presents a new notion of coprimeness over multivariable polynomial matrices, where a single variable is given priority over the remaining variables. From a characterization through a set of common zeros of the minors, it is clarified that the presented coprimeness is equivalent to weakly zero coprimeness in the particular variable. An application of the presented coprimeness to control systems with non-commensurate delays and finite spectrum assignment is also presented. Because the presented coprimeness is stronger than minor coprimeness, non-commensurate delays are difficult to deal with in algebraic control theory. The “rational ratio condition” between delays, which can reduce non-commensurate delays to commensurate delays, proves to be both powerful and practical concept in algebraic control theory for delay systems.     

Effective-capacity-based stochastic delay guarantees for systems with time-varying servers, with an application to IEEE 802.11 WLANs

Many network applications rely on stochastic QoS guarantees. With respect to loss-related performance, the effective bandwidth/capacity theory has proved useful for calculating loss probabilities in queues with complex input and server processes and for formulating simple admission control tests to ensure associated QoS guarantees. This success has motivated the application of the theory for delay-related QoS too. However, up until now this application has been justified only heuristically for queues with variable service rate. The paper fills this gap by establishing rigorously that the effective bandwidth/capacity theory may be used for the asymptotically correct calculation and enforcement of delay tail-probabilities in systems with variable rate servers too. Subsequently, the paper applies the general results to IEEE 802.11 WLANs, by representing each IEEE 802.11 station as an On/Off server and employing the effective capacity function for this model. Comparison of analytical results with simulation validates the effectiveness of the On/Off IEEE 802.11 model for delay-related QoS, complementing earlier results on loss-related performance.     

逻辑语言剪枝算子的过程语义及其实现

论述了逻辑程序设计中剪枝算子的作用及传统剪枝算子的过程性语义和说明性语义不一致问题;介绍了新型逻辑程序语言〔淑划中的COTRTT11t剪枝算子;通过引入一组定义描述其过程语义,并进一步阐述了剪枝算子和延迟计算规则之间的关系,讨论了Godel语言的剪枝策略及控制机制,从而为逻辑程序语言的实现提供了依据。     

高速以太网时延仿真分析

随着以太网技术的不断发展,以太网已成为未来通信领域的核心技术之一。而影响用户业务体验服务质量(QoS)的参数通常包括时延、抖动、丢包率等。对于实时的语音和视频业务来说,业务数据的端到端时延则最为关键。主要在熟悉以太网标准的基础上,总结端到端时延的主要构成因素,对各个时延所占比重进行理论分析。最后对10G/100G以太网进行仿真模型设计,验证了理论分析的正确性。     

基于延迟敏感的组播路由遗传算法的研究

1 引言为了保证多媒体实时业务流的QoS传输,所采用的路由技术之一是通过组播路由(multicast routing)为实时应用寻找最佳路径。以往,人们对非受限组播路由问题研究较多,但由于它们都未考虑QoS的延迟标准,因此,对多媒体实时传输的要求显得束手无策。Widyono阐述了受限Bellman-Ford(CBF)算法,它的性能较优,但其计算时间随着网络规模的增大而呈指     

CSMA/CD的建模和性能分析

文章对CSMA／CD（载波侦听多址访问／冲突检测）网络建立分析模型,主要对其时延、吞吐量和介质利用率进行了性能分析,分析了该三项性能指标随网络参数的变化。最后总结出了CSMA／CD网络的优缺点。     

Dejittering in the transport of MPEG-2 and MPEG-4 video

When multimedia information is transported over a packet-switched network, the quality of presentation can be degraded due to network delay variation or jitter. This paper presents a dejittering scheme that can be used in the transport of MPEG-4 and MPEG-2 video to absorb any introduced network jitter, thus preserving the presentation quality of transported media streams. The dejittering scheme is based on the statistical approximation of delay variation in the arrival times of video packets carrying encoded clock reference values and a filtering and re-stamping mechanism. In addition, a brief overview of the MPEG-4 system is presented.     

分段延迟微分方程线性-方法数值解渐近稳定性

This paper deals with the stability analysis of numerical solutionof linear -methods for delay differential equations. We focuson the linear test equation x(t)=ax(t)+bx(［t］), where a,b areconstants and ［t］ is the largest-integer function. Sufficent conditionsare given for the numerical solution to be asymptotic stable     

基于VP的ATM网中多项服务质量路由算法

ＡＴＭ网传统的路由方案所考虑的仅是可连接性,对于基于ＶＰ的ＡＴＭ网,提出了一种以代价和时延多服务品质,基于Ｄｉｊｋｓｔｒａ算法的路由算法,算法简单易行,计算复杂度低。     

Statistical Analysis and Modeling of Jobs in a Grid Environment

The existence of good probabilistic models for the job arrival process and the delay components introduced at different stages of job processing in a Grid environment is important for the improved understanding of the Grid computing concept. In this study, we present a thorough analysis of the job arrival process in the EGEE infrastructure and of the time durations a job spends at different states in the EGEE environment. We define four delay components of the total job delay and model each component separately. We observe that the job inter-arrival times at the Grid level can be adequately modelled by a rounded exponential distribution, while the total job delay (from the time it is generated until the time it completes execution) is dominated by the computing element’s register and queuing times and the worker node’s execution times. Further, we evaluate the efficiency of the EGEE environment by comparing the job total delay performance with that of a hypothetical ideal super-cluster and conclude that we would obtain similar performance if we submitted the same workload to a super-cluster of size equal to 34% of the total average number of CPUs participating in the EGEE infrastructure. We also analyze the job inter-arrival times, the CE’s queuing times, the WN’s execution times, and the data sizes exchanged at the kallisto.hellasgrid.gr cluster, which is node in the EGEE infrastructure. In contrast to the Grid level, we find that at the cluster level the job arrival process exhibits self-similarity/long-range dependence. Finally, we propose simple and intuitive models for the job arrival process and the execution times at the cluster level.