本文選題：移動通信 + TCP流量控制��； 參考：《華東師范大學(xué)》2014年碩士論文

【摘要】：近年來,移動終端的廣泛普及和移動應(yīng)用的高速發(fā)展推動著移動通信技術(shù)的不斷進步。人們對于移動通信的要求也越來越高,這促使移動通信的帶寬越來越高,延遲越來越短,可以支持的應(yīng)用越來越豐富。另一方面,TCP作為Internet協(xié)議中最為廣泛應(yīng)用的協(xié)議之一,在整個網(wǎng)絡(luò)中不可或缺。但是TCP在設(shè)計之初是為有線網(wǎng)絡(luò)提供可靠的、面向連接的傳輸服務(wù),并沒有將無線移動通信的因素考慮在內(nèi)。相對于有線環(huán)境而言,移動通信環(huán)境有著自身的特點：帶寬抖動,物理鏈路不可靠,差錯率高,丟包率高,信號易受干擾,信道切換,移動節(jié)點自身硬件能力不足等,都會造成非擁塞丟包,但是TCP無法區(qū)分丟包是否是由于擁塞引起的,導(dǎo)致TCP性能的下降。 為了解決上述問題,在2001年,由Mascolo等學(xué)者,提出了著名的TCP Westwood協(xié)議。TCP Westwood提出了一種帶寬預(yù)測的方式,當(dāng)TCP發(fā)生丟包或者超時時,通過預(yù)測帶寬來調(diào)整TCP的狀態(tài),以改善TCP的性能。TCP Westwood的帶寬預(yù)測比較準(zhǔn)確,可以反映出網(wǎng)絡(luò)帶寬的變化情況。TCP Westwood在丟包率較高的環(huán)境下的性能表現(xiàn)優(yōu)秀,可以判斷出丟包是否是由于擁塞引起的,成為了很多無線TCP改良算法的基礎(chǔ)。在移動通信中,由于節(jié)點的移動,或者是其他節(jié)點的加入或離開,帶寬會隨時發(fā)生變化,這種現(xiàn)象稱之為帶寬抖動。對于TCP協(xié)議而言,網(wǎng)絡(luò)狀況就像一個黑盒,TCP除了能夠得到ACK反饋之外,無法獲得其他的信息,所以對于帶寬抖動而言,會導(dǎo)致TCP不能隨時調(diào)整自己的狀態(tài)來應(yīng)對,造成性能的下降。TCP Westwood雖然提供了帶寬預(yù)測機制,但是它僅在TCP發(fā)生了丟包或者超時時才會啟用該機制,并沒有利用它的帶寬預(yù)測技術(shù)處理帶寬抖動,所以沒有對這一現(xiàn)象進行及時的處理。 本文主要著眼于處理移動通信中帶寬抖動的TCP協(xié)議的改進,主要基于TCPWestwood提出一種新的流量控制方案,稱之為Improved Westwood。通過采用TCPWestwood既有的帶寬預(yù)測技術(shù),用于分析、判斷帶寬的變化情況,調(diào)整TCP的狀態(tài),盡可能快地將TCP適配于當(dāng)前的網(wǎng)絡(luò)帶寬。 為了驗證Improved Westwood的性能,本文通過NS-2仿真實驗平臺進行實驗仿真。本文通過實際手機在3G網(wǎng)絡(luò)測速軟件得到實驗場景的參數(shù)來設(shè)計實驗場景。通過NS-2仿真實驗結(jié)合實際采集到的移動網(wǎng)絡(luò)通信數(shù)據(jù)確定流量控制策略的參數(shù)。然后通過一些場景驗證Improved Westwood與TCP Westwood在帶寬抖動環(huán)境下表現(xiàn)上的區(qū)別。接著跟其他TCP協(xié)議進行性能上的對比,驗證Improved Westwood改善了TCP在移動通信環(huán)境下的性能。
[Abstract]:In recent years, the widespread popularity of mobile terminals and the rapid development of mobile applications promote the continuous progress of mobile communication technology. The demand for mobile communication is becoming higher and higher, which makes the bandwidth of mobile communication become higher and higher, the delay is shorter and shorter, and the applications that can be supported are more and more abundant. On the other hand, as one of the most widely used protocols in Internet protocol, it is indispensable in the whole network. However, TCP was designed to provide reliable, connection-oriented transport services for wired networks, without taking wireless mobile communication into account. Compared with wired environment, mobile communication environment has its own characteristics: bandwidth jitter, unreliable physical link, high error rate, high packet loss rate, signal vulnerable to interference, channel switching, insufficient hardware capability of mobile node, etc. However, TCP can not distinguish whether the loss of packet is caused by congestion, which leads to the degradation of TCP performance. In order to solve the above problems, in 2001, Mascolo and other scholars proposed a famous TCP Westwood protocol .TCP Westwood proposed a bandwidth prediction method. When TCP lost packets or timed out, the state of TCP was adjusted by predicting the bandwidth. In order to improve the performance of TCP, the bandwidth prediction of TCP / Westwood is more accurate, which can reflect the variation of network bandwidth. The performance of TCP Westwood in the environment with high packet loss rate is excellent, and it can be determined whether the loss of packet is caused by congestion. It has become the basis of many improved wireless TCP algorithms. In mobile communication, the bandwidth will change at any time due to the movement of nodes or the addition or departure of other nodes. This phenomenon is called bandwidth jitter. For the TCP protocol, the network condition is like a black box TCP can get ACK feedback, but can not get any other information, so for bandwidth jitter, TCP can not adjust its state at any time to deal with it. Although it provides a bandwidth prediction mechanism, it only enables TCP when it loses packets or times out, and does not use its bandwidth prediction technology to handle bandwidth jitter. Therefore, this phenomenon has not been dealt with in a timely manner. This paper focuses on the improvement of TCP protocol which deals with bandwidth jitter in mobile communication, and proposes a new flow control scheme based on TCPWestwood, which is called Improved Westwood. The existing bandwidth prediction technology of TCPWestwood is used to analyze and judge the change of bandwidth, adjust the state of TCP, and adapt TCP to the current network bandwidth as quickly as possible. In order to verify the performance of Improved Westwood, this paper carries on the experiment simulation through the NS-2 simulation experiment platform. In this paper, the parameters of the experimental scene are obtained by using the mobile phone in 3G network speed measurement software to design the experimental scene. The parameters of the flow control strategy are determined by NS-2 simulation combined with the collected mobile network communication data. Then some scenarios are used to verify the difference between Improved Westwood and TCP Westwood in bandwidth jitter environment. Then compared with other TCP protocols, we verify that Improved Westwood improves the performance of TCP in mobile communication environment.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TP393.06

【參考文獻】

相關(guān)期刊論文 前2條

1 王遵彤;孫棟;喬非;吳啟迪;;分布式電梯群控系統(tǒng)多目標(biāo)調(diào)度算法[J];控制理論與應(yīng)用;2010年05期

2 江澤民;;對中國能源問題的思考[J];中國能源;2008年04期

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本文編號：1985799