自相似及其对网络性能影响的研究

【作者】 梁恩志；

【导师】 吴援明；

【作者基本信息】 电子科技大学 ， 信号与信息处理， 2003， 硕士

【摘要】 本文给出了自相似的几种常见定义，描述了该随机过程在数学和物理上的一些特征，并讨论了如何识别一个序列是否是自相似或长相关的以及如何定量分析其相关性强弱的问题。本文总结了前人的研究成果，给出了几种常见产生自相似的方法和几种估计自相似参数的方法，并对ON/OFF模型叠加产生自相似业务进行了仿真实验，得到了实验结果，从实验结果可以看出，仿真结果和理论值比较接近，这说明利用ON/OFF模型叠加产生自相似业务是可行的。在网络性能分析中，排队性能是一个重要的指标。传统的排队理论中，分析排队的方法有很成熟的理论，经典方法是利用拉普拉斯变换来处理，前提条件是拉普拉斯变换要存在。重尾分布的拉普拉斯变换不存在，这给重尾分布服务时间的分析带来了很大的困难，因此需要用新的方法解决这个问题。这里介绍一种称为TAM(Transform Approximation Method)的方法，这个方法能较好的解决重尾分布拉普拉斯变换不存在的问题。丢失率CLP(cell loss probability)是网络性能分析中的另一个重要指标，本文给出了一种输入是自相似过程的ATM(Asynchronous Transfer Mode)复用器中估计丢失率的方法，这种方法基于大偏差理论。从仿真实验结果可以看出，这种方法比原有的方法更准确，这为以后带宽、缓冲器大小的设计提供了理论依据。更多还原

【Abstract】 In this paper, several mathematical definitions of self-similarity are given, and some of their properties are described. The method of justifying a self-similar process and getting its autocorrelation coefficient (or self-similar parameter) are also discussed. Achievements which are achieved by scientific research of predecessors are summarized. Some methods of how to generate self-similar process and a few means of estimating self-similar parameter are given. Self-similar traffics are generated by using of ON/OFF model with heavy-tailed distribution and results are given. The results of experiment accord with the theory. This identicalness indicates that the method of getting results by using of ON/OFF model is feasible.In network performance, queueing performance is an important indicator. Methods of queueing analysis in traditional theory are based on mature theory. Laplace transform is a crucial mathematical tool which is used by classical methods. It is the heavy-tailed distributions that may not possess all of their moments, and, therefore certainly not their Laplace transforms that brings the difficult to analyzing heavy-tailed distribution service time. In order to solve this problem, a new method is proposed in this paper.CLP (cell loss probability) is another main factor in network performance. A method of estimating the CLP in an ATM (asynchronous transfer mode) multiplexer which is fed by a self-similar arrival process is advanced in this paper. The approach is based on theory of large deviations, and the simulation tests show that it is more accurate than the existing approximation results. The analysis and results provide the theoretical basis of designing buffers and bandwidth.更多还原