Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/6142
標題: 可變位元速率視訊交通之控制—使用小波估計自我相似參數值
Variable Bit Rate (VBR) Video Traffic Control: A Wavelet Approach for Self-Similar Parameters Estimation
作者: 葉禮彬
Yeh, Li-Bin
關鍵字: Hurst parameter;赫氏參數;self-similarity;congestion control;random early detection;throughput;自我相似性;壅塞控制;隨機事先偵測;貫通率
出版社: 電機工程學系
摘要: 
近年來,在ATM網路中的可變位元速率之視訊(VBR video)已經證實具有自我相似性(self-similar)。若忽略這種特性,將會使我們在網路效能分析上產生過度樂觀的預估值,進而導致網路資源分配不足。換句話說,自我相似的特性對網路的效能有很大的影響。赫氏參數(Hurst parameter)是用來描述自我相似程度多寡的重要參數。為了要能判別網路的交通是否具有自我相似性,我們需要使用一些判別的方法來測試其赫氏參數值。本篇論文,我們使用小波轉換(wavelet transform)作為判別赫氏參數的方法。小波的重要特徵是它的觀念和使用方法容易,而且在於測量交通資料的斜率。小波的其它優點是我們可以任意的選擇vanishing moment來消除先前的取樣結果。此外,藉由小波係數的能量變化,我們可以正確地估計赫氏參數值。我們應用FIR多層類神經網路來分析和預測ATM網路中自我相似性交通流量的狀態,FIR多層類神經網路能準確地預測在下一個時槽即將進入網路的總資料數。利用此一資訊,我們可以估計在ATM網路中的可變位元速率之視訊交通的頻寬需求。實驗的結果顯示,我們可以得到最小的有效頻寬需求。另外我們也利用隨機事先偵測(random early detection)的方法來作交通壅塞控制,模擬的結果顯示,我們使用隨機事先偵測的方法可以得到更高的貫通率(throughput)。

More recently, the variable-bit-rate (VBR) video over ATM networks is found to exhibit self-similar characteristics. Neglecting the self-similarity would lead to overly optimistic performance predictions and inadequate network resources allocation. In other words, the presence of self-similarity has serious implications on the performance of networks. A key parameter characterizing self-similar processes is the Hurst parameter H, which is designed to capture the degree of self-similarity. In order to determine if a given time series exhibits self-similarity, a method is needed to estimate H for a given time series. In this thesis we present an estimation tool by using wavelet transform. An important feature of the wavelet-based tool is the conceptual and practical simplicity, consisting essentially in measuring the slope. The other advantage of wavelet-based tool is that we can arbitrary choose vanishing moment to remove pre-selected trends. Moreover, the Hurst parameter can be accurately estimated from the power-law behavior of wavelet coefficients. A finite-duration impulse response (FIR) multilayer network is used to predict the number of incoming cells at the next period. Based on the information provided by the FIR multilayer network, we apply the wavelet-based tool to measure the Hurst parameters of predicted data. Then we use the Norros formula to estimate the bandwidth requirement for each predicted data. The results show that the lowest effective bandwidth requirement for MPEG1 video traffic over ATM networks can be obtained. Then we use the random early detection (RED) algorithm for traffic congestion control based on the predictive bandwidth. The simulation results indicate that the actual data has higher throughput by using RED.
URI: http://hdl.handle.net/11455/6142
Appears in Collections:電機工程學系所

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