本文選題：流媒體 + 擁塞控制　； 參考：《蘭州理工大學(xué)》2014年碩士論文

【摘要】：伴隨著流媒體的廣泛應(yīng)用和人們對(duì)高服務(wù)質(zhì)量的追求,流媒體傳輸技術(shù)成為網(wǎng)絡(luò)應(yīng)用的一大熱點(diǎn)。流媒體集音頻視頻及圖文于一體,具有數(shù)據(jù)量大、低時(shí)延、低抖動(dòng)等特性。流媒體數(shù)據(jù)在網(wǎng)絡(luò)中傳輸時(shí)常采用的是UDP協(xié)議,而非TCP。但是UDP并不提供任何的擁塞控制機(jī)制,這使得服務(wù)質(zhì)量不能得到有效保障。并且流媒體傳輸會(huì)消耗大量的網(wǎng)絡(luò)資源,擁塞控制的缺乏將會(huì)影響到網(wǎng)絡(luò)的正常運(yùn)行。因此,為流媒體傳輸引入適當(dāng)?shù)膿砣刂茩C(jī)制勢(shì)在必行。實(shí)踐證明,最有發(fā)展前景的擁塞控制算法應(yīng)該在保證媒體流QoS的同時(shí),又注重與TCP數(shù)據(jù)流的友好共處。 基于以上要求,本文首先分析了擁塞產(chǎn)生的原因、擁塞控制的特點(diǎn)和研究意義,其次對(duì)流媒體和實(shí)時(shí)流式傳輸作了詳細(xì)的闡述,接著研究了TCP擁塞控制的基本原理、支持實(shí)時(shí)傳輸?shù)腞TP和RTCP協(xié)議,然后重點(diǎn)研究了基于速率的擁塞控制算法TFRC(TCP-Friendly Rate Control protocol)。針對(duì)TFRC算法中缺乏對(duì)單向延遲抖動(dòng)的控制、發(fā)送速率變化波動(dòng)性大、慢啟動(dòng)時(shí)間過(guò)長(zhǎng)等不足,本文對(duì)TFRC算法進(jìn)行改進(jìn),提出一種更適合流媒體傳輸?shù)膿砣刂扑惴?稱之為FS-TFRC (Improved TFRC in respect of Fairness and Smoothness)。利用RTCP反饋信息包獲取計(jì)算吞吐率的參數(shù)RTT和丟包率p,根據(jù)吞吐量模型來(lái)計(jì)算相應(yīng)的發(fā)送速率,從而起到平滑發(fā)送速率的作用。特別是在慢啟動(dòng)階段利用FS-TFRC降低了慢啟動(dòng)時(shí)間,將單向傳輸延遲抖動(dòng)作為反饋信號(hào)來(lái)修正FS-TFRC的發(fā)送速率,同時(shí)采用一種自適應(yīng)閾值調(diào)節(jié)方案,根據(jù)歷史情況動(dòng)態(tài)的調(diào)整抖動(dòng)延遲閡值。最后通過(guò)仿真實(shí)驗(yàn),驗(yàn)證了改進(jìn)算法FS-TFRC在降低時(shí)延、減緩抖動(dòng)和保證平滑性等方面都取得了較好的結(jié)果,能夠更好地適應(yīng)流媒體實(shí)時(shí)傳輸。
[Abstract]:With the wide application of streaming media and the pursuit of high quality of service, streaming media transmission technology has become a hot spot in network applications. Streaming media with audio, video and text in one, with a large amount of data, low delay, low jitter and other characteristics. Streaming media data is often transmitted in the network using UDP protocol, not TCP. However, UDP does not provide any congestion control mechanism, which makes the quality of service can not be effectively guaranteed. And streaming media transmission will consume a lot of network resources, the lack of congestion control will affect the normal operation of the network. Therefore, it is imperative to introduce appropriate congestion control mechanism for streaming media transmission. It has been proved that the most promising congestion control algorithm should not only guarantee the QoS of media flow, but also pay attention to the friendly coexistence with TCP data stream. Based on the above requirements, this paper first analyzes the causes of congestion, the characteristics and significance of congestion control, and then describes the streaming media and real-time flow transmission in detail, and then studies the basic principle of TCP congestion control. RTP and RTCP protocols are supported for real-time transmission, and then the rate-based congestion control algorithm (TFRC(TCP-Friendly Rate Control protocol) is studied. In view of the lack of one-way delay jitter control in TFRC algorithm, the fluctuation of transmission rate and the long time of slow start, this paper improves the TFRC algorithm and proposes a congestion control algorithm which is more suitable for streaming media transmission. It is called FS-TFRC improved TFRC in respect of Fairness and Smoothnessen. The RTCP feedback packet is used to obtain the parameter RTT and the packet loss rate p.The corresponding transmission rate is calculated according to the throughput model, which plays the role of smoothing the transmission rate. Especially in the slow start stage, FS-TFRC is used to reduce the slow start time, the one-way transmission delay jitter is used as the feedback signal to correct the transmission rate of FS-TFRC, and an adaptive threshold adjustment scheme is adopted at the same time. Adjust the jitter delay threshold dynamically according to the historical situation. Finally, the simulation results show that the improved algorithm FS-TFRC has achieved better results in reducing delay, reducing jitter and ensuring smoothness, and can better adapt to real-time streaming media transmission.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TP393.06

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本文編號(hào)：1911426