本文選題：視頻傳輸 + 網(wǎng)絡(luò)擁塞�。� 參考：《蘭州交通大學(xué)》2014年碩士論文

【摘要】：視頻實(shí)時(shí)傳輸過程中存在的問題隨著視頻點(diǎn)播、遠(yuǎn)程視頻傳輸?shù)榷嗝襟w飛速發(fā)展日益凸顯，視頻會議、視頻點(diǎn)播、遠(yuǎn)程教學(xué)、遠(yuǎn)程監(jiān)控等多媒體信息實(shí)時(shí)傳輸過程中包含大量數(shù)據(jù)，這使得用戶在網(wǎng)絡(luò)的傳輸容量和服務(wù)質(zhì)量提出更高的要求。突發(fā)數(shù)據(jù)延遲和包丟失會嚴(yán)重降低客戶端圖像質(zhì)量。因此，視頻傳輸對網(wǎng)絡(luò)帶寬，丟包率以及端到端的延遲都有一定的要求，由于網(wǎng)絡(luò)動態(tài)環(huán)境的大時(shí)滯性、非線性以及參數(shù)的時(shí)變特性，使得建立精確地?cái)?shù)學(xué)模型這一問題相對比較困難，本文在國內(nèi)外視頻實(shí)時(shí)傳輸研究現(xiàn)狀的基礎(chǔ)上，進(jìn)一步深入分析了視頻實(shí)時(shí)傳輸過程中存在的問題及現(xiàn)有的控制策略，將智能控制理論算法引入到視頻傳輸中，提出一種基于自適應(yīng)變論域模糊Smith預(yù)估PID控制策略。主要研究內(nèi)容如下： (1)根據(jù)流體理論對視頻傳輸系統(tǒng)擁塞控制機(jī)制進(jìn)行建模。 (2)模型的不精確性對視頻實(shí)時(shí)傳輸影響的研究。引入了模糊PID控制算法對視頻傳輸系統(tǒng)進(jìn)行控制，，通過仿真實(shí)驗(yàn)驗(yàn)證了模糊PID控制策略控制的優(yōu)越性，系統(tǒng)輸出能夠快速跟蹤穩(wěn)定值。若突發(fā)視頻流進(jìn)入系統(tǒng)，系統(tǒng)都能夠維持在期望值附近，然而當(dāng)參數(shù)鏈路容量有較大變化時(shí)，系統(tǒng)輸出隊(duì)列長度跟蹤效果較差。 (3)網(wǎng)絡(luò)環(huán)境的大時(shí)滯性對視頻實(shí)時(shí)傳輸影響的研究。采用了一種基于Smith預(yù)估的模糊PID實(shí)時(shí)視頻傳輸控制算法。該算法將模糊控制與Smith預(yù)估控制相結(jié)合，采取Smith預(yù)估策略補(bǔ)償系統(tǒng)滯后，同時(shí)運(yùn)用模糊控制在一定程度上克服了傳統(tǒng)Smith預(yù)估器對模型結(jié)構(gòu)與參數(shù)的精確性過于敏感、魯棒性差的缺點(diǎn)，使擁塞控制性能有明顯提高。仿真實(shí)驗(yàn)結(jié)果表明，該算法在大時(shí)滯的網(wǎng)絡(luò)環(huán)境下能很好地將路由器隊(duì)列長度收斂于期望值。 (4)自適應(yīng)變論域模糊Smith預(yù)估控制在視頻傳輸中的應(yīng)用研究。采用一種自適應(yīng)變論域模糊Smith預(yù)估控制策略，并應(yīng)用于視頻傳輸?shù)膿砣刂浦小Ｗ詈笸ㄟ^仿真表明，采用變論域模糊控制方法能保證系統(tǒng)的全局穩(wěn)定性以及控制精度，能使隊(duì)列快速收斂到目標(biāo)值，超調(diào)量較小，且當(dāng)網(wǎng)絡(luò)參數(shù)在較大范圍內(nèi)變動時(shí)，仍然保持較好的控制性能，并具有較好的穩(wěn)定性和魯棒性。
[Abstract]:With the rapid development of video on demand, remote video transmission and other multimedia, video conference, video on demand, distance teaching, etc.In the process of real-time transmission of multimedia information, such as remote monitoring, a large amount of data is included, which makes users require higher transmission capacity and quality of service in the network.Burst data delay and packet loss can seriously reduce client image quality.Therefore, video transmission has certain requirements for network bandwidth, packet loss rate and end-to-end delay, due to the large delay, nonlinear and time-varying characteristics of parameters in the dynamic network environment.It is relatively difficult to establish accurate mathematical model. Based on the current research situation of real-time video transmission at home and abroad, this paper further analyzes the existing problems and existing control strategies in the process of real-time video transmission.The intelligent control theory algorithm is introduced into video transmission, and a fuzzy Smith predictive PID control strategy based on adaptive variable theory is proposed.The main contents of the study are as follows:1) based on fluid theory, the congestion control mechanism of video transmission system is modeled.Research on the effect of imprecision of the model on real-time video transmission.The fuzzy PID control algorithm is introduced to control the video transmission system. The superiority of the fuzzy PID control strategy is verified by simulation experiments. The system output can track the stable value quickly.If the burst video stream enters the system, the system can be maintained near the expected value. However, when the parameter link capacity changes greatly, the system output queue length tracking performance is poor.3) the influence of large time delay on real-time video transmission.A fuzzy PID real-time video transmission control algorithm based on Smith prediction is adopted.The algorithm combines fuzzy control with Smith predictive control, adopts Smith prediction strategy to compensate for system lag, and uses fuzzy control to overcome the sensitivity of traditional Smith predictor to the accuracy of model structure and parameters to a certain extent.Because of the poor robustness, the congestion control performance is improved obviously.Simulation results show that the proposed algorithm can converge the router queue length to the expected value well in the network environment with large delay.Application of adaptive variable domain fuzzy Smith predictive control in video transmission.An adaptive variable domain fuzzy Smith predictive control strategy is adopted and applied to the congestion control of video transmission.Finally, the simulation results show that the variable domain fuzzy control method can guarantee the global stability and control accuracy of the system, make the queue converge quickly to the target value, reduce the overshoot, and when the network parameters change in a large range,It still maintains good control performance, and has good stability and robustness.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TP393.06;TP273.4

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