导　　师： 高岭

学科专业： 081203

授予学位： 硕士

作　　者： ;

机构地区： 西北大学

摘　　要： 近年来,随着无线通信技术的飞速发展和广泛应用,下一代移动无线网将会以更高的数据接入速率来满足人们“随时、随地、与任何人”进行交互多媒体通信的需求。但是,无线网络通常具有误码率高、带宽低、时延大和移动频繁等特性,这使得无线链路有相对较高的差错率。在无线网络中,网络拥塞不再是数据丢失的唯一原因,如果直接沿用传统的TCP拥塞控制技术,很多情况下会造成数据发送速率不必要的降低,从而导致网络性能的下降。因此,在无线环境中如何有效的提高TCP性能自然成了一个重要的网络研究课题。 本文主要从三个方面对无线网络的拥塞控制机制进行研究。 首先,对Internet中传输控制协议的原理以及TCP拥塞控制算法中的关键技术进行了深入探讨和研究。分析总结了TCP的报文格式、TCP的连接、连接终止、连接复位以及TCP的状态机等;分析比较了几种主要的TCP拥塞控制算法/(Tahoe、Reno、NewReno、SACK和Vegas/),并对TCP拥塞控制算法的关键技术进行了详细的论述。 其次,探讨了无线网络下的TCP拥塞控制策略及无线网络下TCP协议的性能。主要涉及TCP拥塞控制策略:减缓数据发送速率的波动性,分离拥塞控制与差错控制,拥塞控制策略与应用的相关性;并针对无线传输错误对TCP吞吐量的影响进行了数学分析;总结了无线网络中拥塞判定的方法及当前无线网络中TCP拥塞控制的研究进展:并通过NS-2仿真实验比较分析了传统TCP协议版本在无线网络中的性能,在模拟试验的基础上总结了影响TCP性能的因素。 最后,提出了一种基于二次滤波带宽估计的TCP拥塞控制算法。首先对带宽估计协议进行了全面的解析评估,如带宽估计的吞吐量公式、公平性。尽管带宽估计协议的公平性可以得到证明,但是当源端对可用带宽估计不� With the fast development and widely application of wireless networking technologies, The next generation mobile wireless Internet will be expected to guarantee people enjoying interactive multimedia services 'with anybody, at anytime, in anyplace'. However, compare with the wired environment, the characters of wireless networks are high bit error rates, low bandwidth, long time delay, frequency moving and so on, so there are high error rate in wireless network. In wireless networks, congestion is not the only reason for data losing. If we use the traditional congestion control technique in wireless networks, it can make the sender decrease the sending rate unnecessarily and results the decrease of the network performance. Therefore, it is an important research project that how to improve the performance of TCP in wireless environment.The thesis includes three aspects to research the wireless network congestion control.First, the TCP theory and the key technology of TCP congestion control algorithm are researched in the thesis. There have analyzed the TCP message format, TCP link, link to terminate, link to reset and TCP state machine;At the same time we compare a few TCP congestion control algorithm /(such as Tahoe, Reno, NewReno, SACK and Vegas/) and discuss the key technology of TCP congestion control algorithm .Second, the TCP control strategies and the performance of TCP in the wireless network are analusised. The content is mainly about the TCP congestion control strategies which are the wave properties of the slacken data transmit rate, separating congestion control and error control, the relativity of the congestion control strategies and its application. And then there is the mathematical anaysis about the enfluence on the TCP throughput which is from the error of wireless transmission;And summerizes the congesion decision methods and analyses the research progress of the TCP congestion control in the wireless nerwork. We compare the performance of the transitional TCP in the wireless network using the N

关 键 词： 无线网络 拥塞控制 协议 仿真 带宽估计

领　　域： [自动化与计算机技术] [自动化与计算机技术] [电子电信] [电子电信]