【作者】 张幸；

【导师】 洪佩琳；

【作者基本信息】 中国科学技术大学 ， 通信与信息系统， 2009， 硕士

【摘要】 随着无线技术的发展和终端设备能力的提高,由无线节点自组织构建的多跳Ad Hoc网络逐渐成为无线通信领域的一个重要研究方向。为了满足不同业务对服务质量的需求,在Ad Hoc网络上提供QoS支持成为必然。然而,Ad Hoc网络的特性,诸如动态的拓扑结构、有限的网络资源以及无线信道的竞争性,给提供QoS支持带来了困难和挑战。QoS路由协议做为体系结构中的重要组成部分,引起了广泛的关注,其目标是在已知可用网络资源和应用需求时决定流的投递路径。已有路由协议采用不同的方式指导路由搜索。然而它们或是需要保存额外的网络信息或是基于表驱动的路由协议,存在可扩展性较差的问题。本文旨在设计一种路由协议,在维护较少拓扑信息的基础上,引导可用路径的建立而避免泛洪搜索的方式,所做研究如下:本文第三章提出了限制泛洪、智能查找的路由协议—MBQR(Multipoint-Based QoS Routing)。网络中的节点分布式地收集两跳范围内的局部拓扑信息。在此基础之上,根据某种策略在一跳邻居中选择能提供较好QoS支持的节点集(Multi-Point Relay,MPR)。当有数据要发送时,利用MPR节点集泛洪请求分组、智能引导路由搜索,从而快速地找到符合需求的较优路径,并且降低网络开销。仿真结果显示,MBQR协议相比较于基于AODV简单改进的QAODV协议,缩短了路由发现延时,并一定程度上提高了所建立的路由路径的带宽,对动态环境适应性更强。本文第四章将QoS资源评估和路由维护纳入路由协议框架之中,提出了改进的MBQR-MC(Multi-Constraint MBQR)路由协议。MBQR-MC借用已有的Hello机制,通过干扰范围(两跳范围)内的累积带宽消耗来估计节点的可用带宽,通过对时钟差的估计来衡量异步Ad Hoc网络中的端到端延时。同时引入节点稳定度来改进MPR选择机制,更好地捕捉网络的实际情况。仿真显示,改进的MBQR-MC协议能够较好的对可用资源进行评估,并选取更为稳定的MPR节点集,从而更好的引导路由路径的建立,减少分组的丢失。对于QoS路由来说,QoS路由失效检测和路径断开检测同样重要,这一点在很多其他QoS路由协议中都没有讨论。MBQR-MC包含一个完整的路由维护框架,实施基于目的端的QoS失效检测和基于冗余路径的快速路由恢复。仿真显示,当路由路径不再满足应用需求时,MBQR-MC能够检测出QoS失效,并切换到合适的冗余路径上。更多还原

【Abstract】 As the developing of wireless technology and improving of terminal devices, Ad Hoc has become one of the most important areas in wireless communication. In order to fulfill requirements of different applications, it is necessary to provide QoS on Ad Hoc instead of just best-effort service. However, characteristics of Ad Hoc network such as dynamic time-varying topology, limited resources and competed wireless channel bring a great many difficulties and challenges.QoS-aware routing is the most essential part of the whole QoS system.Its goal is to determine suitable routes for flows with the knowledge of available network resources and application requirements. Known protocols, which vary in the way of guiding search of routes, can not scale well because they need to conserve additional network information or are based on table-driven routing protocols.Therefore, this dissertation focused on devising a protocol, which could effectively guide route search based on maintenance of less topology information without consumptive flooding.A routing protocol named MBQR (Multipoint-Based QoS Routing) which is based on restricted flooding and intelligent search was presented in chapter 3. Network nodes collect local topology information within 2-hop range distributedly. Upon this, they choose MPR (Multi-Point Relay) sets which could provide better QoS support from 1-hop neighbors according to certain strategies. When there are application datas to transport, MPRs are used to restrict flooding and guide search intelligently in order to find an appropriate route quickly with less costs. The simulation results showed reduction in latency and improvement in bandwidth of established route compared to QAODV which is based on simple improvement of AODV. Meanwhile, MBQR was more adaptive to dynamic environment.Resources estimation and routing maintenance were also included in the routing framework, resulted a revised protocol called MBQR-MC (Multi-Constraint MBQR) in chapter 4. In this edition, available bandwidth of a node is estimated using existing hello algorithm by counting bandwidth consumption of nodes within the interference range. As for one way end-to-end delay, it is evaluated considering clock difference in MANET. Node stability, which reflects real network situation, is also introduced to improve MPR selection. MBQR-MC was proved to evaluate resources effectively and chose more stable MPRs, which actually reduced packets loss during simulation. Detection of QoS violation is as important as traditional route break detection, which was unfortunatelly not discussed in most QoS-aware routing protocols. MBQR-MC embraced an intact route recovery framework and implemented quick route recovery based on QoS violation detection in destination and redundant routes. Simple simulation showed that, MBQR-MC detected QoS violation when the current path could not satisfy application’s requirements and swiched to an appropriate one.更多还原