本文關(guān)鍵詞： 流媒體 分段方式 超幾何分布 靜態(tài)調(diào)度 緩存替換策略　出處：《北京交通大學》2015年碩士論文　論文類型：學位論文

【摘要】：流媒體系統(tǒng)在實際中應(yīng)用廣泛,但大量圖形數(shù)據(jù)在網(wǎng)絡(luò)傳輸時出現(xiàn)響應(yīng)速度慢、網(wǎng)絡(luò)擁塞嚴重、緩存利用率低等問題。尤其在硬件帶寬較低情況下,如服務(wù)器網(wǎng)卡讀寫能力不足、PCI時鐘頻率低、總線位寬數(shù)低于64位等情況下。本文針對該類問題提出一種基于預(yù)期使用價值的緩存替換策略,并以基于斐波那契數(shù)列劃分的變動分段方式為基礎(chǔ)實現(xiàn)流轉(zhuǎn)化。 本論文主要分為三個部分： 第一,從流媒體關(guān)鍵技術(shù)出發(fā),通過對其在不同傳輸協(xié)議、不同編碼方式下數(shù)據(jù)段平均接收分段數(shù)、平均下載時間進行統(tǒng)計,分析調(diào)度策略在流媒體數(shù)據(jù)傳輸中的重要性。通過評估C/S網(wǎng)絡(luò)結(jié)構(gòu)得出其作為緩存替換策略測試平臺的合理性。此外,本文也闡述了靜態(tài)調(diào)度算法的分段方式在調(diào)度策略中和緩存替換策略成果及其在點播系統(tǒng)中的重要意義。 第二,本文為預(yù)期使用價值算法的實現(xiàn)提出一種將斐波那契數(shù)列相結(jié)合的數(shù)據(jù)分段方式,并通過Ns2仿真軟件對新的數(shù)據(jù)分段方式進行模擬統(tǒng)計。分析中發(fā)現(xiàn)新算法在減小對磁盤資源的占用和降低延時方面都比其余算法具有更好的效果。然后從用戶點播體驗和用戶行為特征入手提出基于預(yù)期使用價值的緩存替換策略。 第三,針對基于預(yù)期使用價值算法,通過二次編碼Ns2仿真環(huán)境的底層C++代碼來拓展Ns2仿真環(huán)境功能模塊,對編譯分級結(jié)構(gòu)中TclObject基類添加派生類。通過建立啞鈴型網(wǎng)絡(luò)拓撲結(jié)構(gòu),分別對服務(wù)器響應(yīng)延時、客戶端請求延時、目標節(jié)點延時、網(wǎng)絡(luò)吞吐量等指標進行測試,得出ULH算法優(yōu)于傳統(tǒng)的LRU、LFU算法。最后將全部策略嵌入到實際網(wǎng)絡(luò)平臺中,對流媒體播放效果進行實驗,得到了較好的圖像傳輸效果。
[Abstract]:Streaming media system is widely used in practice, but a large number of graphics data in the network transmission problems such as slow response speed, serious network congestion, low cache utilization, especially in the case of low hardware bandwidth. For example, the server network card is not able to read and write, the PCI clock frequency is low, the bus bit width is less than 64 bits, and so on. This paper proposes a cache replacement strategy based on the expected use value for this kind of problems. And based on the Fibonacci series division of the variable segmentation as the basis for the realization of flow transformation. This thesis is divided into three parts:. First, according to the key technology of streaming media, the average number of data segments received and the average download time under different transmission protocols and different encoding methods are counted. The importance of scheduling strategy in streaming media data transmission is analyzed, and the rationality of C- / S network structure as a test platform for cache replacement policy is obtained by evaluating the structure of C- / S network. This paper also describes the achievements of static scheduling algorithms in scheduling policies and cache replacement policies and its significance in on-demand systems. Secondly, this paper proposes a data segmentation method which combines Fibonacci series for the realization of the expected use value algorithm. Through the Ns2 simulation software, the new data segmentation method is simulated and counted. It is found that the new algorithm is more effective than the other algorithms in reducing the cost of disk resources and the delay. Based on the characteristics of broadcast experience and user behavior, a cache replacement strategy based on expected use value is proposed. Thirdly, based on the expected use value algorithm, the function module of the Ns2 simulation environment is extended by the lower C code of the secondary coding Ns2 simulation environment. By establishing the dumbbell network topology structure, we test the server response delay, the client request delay, the target node delay, the network throughput and so on. It is concluded that the ULH algorithm is superior to the traditional LRUL-LFU algorithm. Finally, all the strategies are embedded into the actual network platform, and the streaming media playback effect is tested, and the better image transmission effect is obtained.
【學位授予單位】：北京交通大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TP333

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