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题名	移动网络中传输协议性能的研究
作者	孙向辉
学位类别	博士
答辩日期	2004
授予单位	中国科学院声学研究所
授予地点	中国科学院声学研究所
关键词	移动互联网 传输控制协议 移动性 切换 网络性能 本地移动管理 协议栈
其他题名	Studies on Performance of Transport Protocol in Mobile Network
中文摘要	近年来，随着科学技术的不断发展，通信领域发生了很大变化。其中有两项业务的增长速度之快超乎了人们的预测和想象，一个是互联网，另外一个是移动、通信。在技术革新和市场需求的推动下，这两种技术不断趋向融合，这就是移动互联网。移动互联网的出现给人们带来了很大的方便，人们不再被有线束缚，而是可以在任何时候、任何地点通过多种接入方式接入网络，获取信息或者和其他人进行通信。TCP（传输控制协议）是互联网上使用最为广泛的可靠传输协议，人们平时使用的许多应用，如电子邮件、网页浏览和文件传输等都是使用TCP协议传输数据。TCP协议是基于有线网络的特征设计的，有线网络的特征是链路延时小、误码率低，在有线网络中报文丢失的主要原因是由于网络中出现拥塞，TCP协议的拥塞控制机制在有线网络中工作的很好，但是在无线移动网络环境中遇到了很大问题。无线移动网络的一个重要特征是移动切换，切换对TCP的性能有很大的影响。本文主要探讨了提高移动网络中TCP的性能问题：首先，从多个方面详细分析了TCP在切换过程中遇到的问题，比较了几种现有的解决方案，然后提出了EHN-HP（Explicit Handoff Notification-Handoff Process）机制，EHN-HP机制针对切换这个特殊的事件在原有TCP的慢启动阶段和拥塞避免阶段的基础上引入了一个专门处理切换过程的阶段一一切换处理阶段（HandoffProcess），在这个阶段中采用了重新设置切换后慢启动门限以及重新估算切换后超时重传定时器的机制。经过模拟仿真的结果可以看出，EHN-HP机制有效的改善了TcP在切换中遇到的性能下降的问题。针对现在为了解决本地移动性提出的本地移动管理方案，文章给出了一种MAP（Mobility Allchor Point）缓存机制，通过在MAP缓存切换时的报文，提高了TCP在本地移动中的性能。这样，移动终端在本地范围内同一个MAP下进行移动切换时，使用MAP机制方案；移动终端在MAP之间，或者跨管理域进行切换，以及进行垂直切换时，使用EHN-HP机制，在不同的切换场景下采用这两种方案，可以提高TCP在各个层次移动切换情况下的性能。EHN-HP机制和MAP缓存机制需要传输层和网络层知道链路层的切换信息，在现有的传统TCP江P协议模型中，可以通过层与层之间简单的接口来实现，但是这种简单的通信机制效率较低，而且对QoS、安全等其它功能支持不完善。由此，文章在最后给出了一种交叉层设计的TCP／IP协议栈模型，使用这种模型，协议栈可以更好的支持EHN-HP机制和MAP缓存机制，以及QoS、安全性等其它功能，提高协议栈的效率。
英文摘要	With the developing of science technology, the communication field changes very rapidly. There are two services whose deployment speeds are very fast, one is Internet, and the other is mobile communication. The technology innovations and the market needs drive these two services to integrate. This integration leads to Mobile Internet. Mobile Internet can take people more convenient. People can access the Internet and communicate other people anytime and anywhere, without limited by wireline. TCP (Transport Control Protocol) is the most widespread reliable transport protocol on the Internet. Many applications transmit the packets using TCP, such as Email, WWW and FTP. TCP is designed on the basis of wireline network, whose characters include little delay, and low BER. In the wireline network, the main reason of packet loss is congestion, and the congestion control mechanism of TCP works very well to deal with this kind of loss. But TCP meets many problems in wireless mobile network. One of the characters of wireless mobile network is mobile handoff, which leads to very large performance degradation to TCP. This dissertation mainly explores some issues about improving TCP performance in mobile network as follows: First, we analyze some problems that TCP can meet in mobile network from some aspects in detail. After comparing some proposed schemes, we propose a new scheme, EHN-HP (Explicit Handoff Notification - Handoff Process). This scheme takes a new phase, Handoff Process, which is used to process the events in the handoff specially, to original TCP protocol. In this new phase, the ssthresh is reset to a new value and the RTO is re-calculated using the new RTT sample after handoff. We simulate this scheme using NS-2 and get some simulation results. Through analysis of these results, we can conclude that the proposed EHN-HP scheme can improve the TCP performance during the mobile handoff. Second, to improve the TCP performance in the local mobility management, we propose the MAP-buffer scheme. Through keeping some packets in MAP buffer for a TCP connection that is about to handoff, this scheme can avoid the packet loss when handoff takes place in local region. Thus we can give a total performance improvement scheme of TCP in the mobile network: when terminal's handoff takes place below a MAP in the local region, MAP-buffer scheme can be used, when handoff takes place between MAPs, management regions, or in vertical handoff, EHN-HP scheme can be used. Using these two schemes, we can improve the TCP performance when terminals move in the total mobile network. Finally, this dissertation proposes a cross-layer TCP/IP protocol stack model. Using this model, TCP/IP stack can support the EHN-HP scheme and MAP-buffer scheme more efficiently, and other functions.
语种	中文
公开日期	2011-05-07
页码	107
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/842]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	孙向辉. 移动网络中传输协议性能的研究[D]. 中国科学院声学研究所. 中国科学院声学研究所. 2004.

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