【作者】 窦志斌；

【导师】 张连芳；

【作者基本信息】 天津大学 ， 计算机应用技术， 2006， 硕士

【摘要】 随着无线通信技术的进步,多跳无线Ad hoc网络再次成为当前无线网络研究的一个重要领域。和3G网络、WLAN不同,无线Ad hoc网络是不需要任何基础设施的网络,任意两个节点间的通信,通过一定的路由协议,经多跳传输来完成。由于无线通道易受干扰和节点移动的原因,Ad hoc网络的拓扑经常发生变化,这给无线Ad hoc网络路由设计带来很多困难。而在无线Ad hoc网络上传输多媒体业务更是一个极具挑战性的研究课题。如何扩展无线Ad hoc网络路由协议,使其支持多媒体业务传输,是本文本文的主要研究目标。众多的无线Ad hoc网络路由协议中,动态源路由协议(DSR,Dynamic Source Routing)是一个有代表性的协议。DSR是一类on demand、源路由协议。源路由特点使其具有面向连接的优点,但另一方面是DSR存在着较大的控制开销和链路失效的判断机制不佳的问题。此外DSR协议以及其它的无线Ad hoc网络路由协议都忽视了近几年兴起的多媒体业务传输的要求,没有针对多媒体业务带宽大,延迟小,容忍一定程度的丢包等特点进行考虑和优化。本文首先针对DSR试验床代码架构的不合理,借鉴了另外一种路由协议AODV的程序架构,对原始的DSR试验床代码进行了架构上的重建。其次,拓展DSR路由协议,增加QoS路由和准入控制机制,对在Ad hoc网络中发起的任何一个新的多媒体业务都要进行准入控制,判断它是否能够获得所需的带宽,延迟等等资源,根据衡量的结果来决定是否准入。针对多媒体业务传输对延迟有较严格要求和无线网络的拓扑的可变性的特点,试验床中本文提出了备用路径机制,即在使用主路径进行业务的传输的过程中,维护一条备用路径,当主路径失效后,马上切换到备用路径,从而避免频繁的重新找路而带来的延迟。在本文的最后,我们对扩展的DSR协议试验床进行了户外真实场景下的试验,通过对试验数据分析,新改进的DSR协议在视频业务的投递率上,路径的失效次数上,准入控制上都大大优于原始的DSR协议,基本上能够保证多媒体视频业务在Ad hoc网络中各个节点以步行的速度移动的情况下正常的传输。因此对DSR协议进行的改进和扩展达到了令人满意的效果。更多还原

【Abstract】 Among the numerous routing protocols of the wireless Ad hoc networks, the Dynamic Source Routing protocol is very representative. It was proposed by Carnegie Mellon University in 1996. During the development of wireless network, although this routing protocol is improving from time to time, due to the characteristic of DSR, it has the problem of expensive control overhead and the mechanism of judging link failure does not work well. Furthermore, the DSR routing protocol and other wireless Ad hoc routing protocols ignore the requirements of multimedia traffic transmission. They don’t take care of and optimize the transmission of multimedia traffic which has the characteristic of large bandwidth, low delay, tolerance of low packet loss ratio. With the technology improvement in wireless network, more and more applications and business require multimedia support, so how to extend the wireless routing protocol to support multimedia traffic is out topic of this paper. In this paper, due to the low efficient and unreasonable architecture of DSR test-bed program, we firstly rebuild the whole architecture of DSR test-bed program according to architecture of AODV test-bed program. Secondly, we extend the DSR routing protocol, add the QoS support and admission control mechanism. For each new multimedia traffic in Ad hoc wireless network, the admission control mechanism judges weather the QoS parameters such as bandwidth, delay meet the new multimedia traffic requirements. If so, the new traffic is allowed to enter the network.At last, in order to solve the large delay of route discovery in real Ad hoc network which could greatly degrade the quality of multimedia traffic, we proposed backup route mechanism. During the traffic transmission using the primary route, we maintain a backup route. When the primary route breaks down, this mechanism guarantee traffic will switch to the backup route with no delay which avoid delay of re-finding route.At last, in order to test the extension and improvement of original DSR, we have done a series of experiments outdoors. According to analyzed experimental data and compared with original DSR routing protocol, the new DSR routing protocol has great improvements in packets delivery ratio, the times of route failure, admission control. It could guarantee the transmission of multimedia traffic when each node in Ad hoc wireless network is moving less than or equal than the walking speed. In a word, the success of the experiments shows that after our improvement and extension to the original DSR protocol it has been able to support the real-time multimedia traffic’s transfer very well and been getting more useful in our daily life.更多还原