【作者】 乔延华；

【导师】 刘剑飞；

【作者基本信息】 河北工业大学 ， 通信与信息系统， 2007， 硕士

【摘要】 移动Ad hoc网络是由一组带有无线通信收发装置的移动终端节点组成的一个多跳、临时、无中心网络,并以其灵活、健壮、投资少等特性,广泛用于军事、自然灾害应急处理、移动会议等领域。路由是Ad hoc网络研究的关键技术之一,也是影响网络整体性能最重要的因素之一。目前大部分的路由研究着眼于找到一条连接源节点和目的节点的路由,并不考虑当前的网络流量和数据流的传输要求,一旦网络中的数据流量超过了网络所能承受的限度,数据流的传输质量将无从保证。随着多媒体等业务引入Ad hoc网络,对文件传输的实时性就有了更高的要求,因此,如何在网络中提供QoS保证具有越来越重要的意义。本文从Ad hoc网络的基本概念入手,对Ad hoc网络的路由协议进行了详细的分析研究。通过NS-2仿真,比较分析了移动Ad hoc网络四种典型路由协议AODV、DSR、DSDV和TORA在不同业务连接数下的性能,较为详细地分析了仿真过程以及仿真脚本,通过nam直观图观看网络运行的具体过程,给出了四种典型协议在不同业务连接数下的分组传送率、平均端到端时延和归一化路由开销三种性能的比较结果,对四种协议进行了比较分析。通过对无线移动Ad hoc网络四种典型路由协议的研究和仿真,发现AODV协议具有良好的性能,能够支持QoS且易于扩展,但又存在不能提供QoS保障、延时较大、路由开销较大等弊端。鉴于此,本文针对无线Ad hoc网络中的按需距离矢量路由协议AODV,提出了一种改进的路由协议I-AODV。该协议是在AODV协议的基础上引入QoS保障机制扩展而成,它将带宽作为QoS路由保障的参数,并通过减少控制消息分组的传送次数来减少路由开销,更好地保障了无线自组网的服务质量。通过在NS-2中对AODV和I-AODV进行仿真比较,结果表明,该协议能较大地改善AODV路由协议的实时性能,路由开销也有了一定量的减少。更多还原

【Abstract】 Ad hoc network is a dynamic multihop wireless network that is set up with multiple wireless devices without any infrastructure. With the flexibility, robustness and less investment, it has been widely used in military, emergency of natural disaster and mobile conference fields and etc..Routing is one of the key technologies in Ad hoc network, it is also the most important factor influencing the network performance.Much works on Ad hoc routing recently are aimed at finding a path connecting the source node and the destination node, they don’t consider the transmission requirement of network traffic, once the data traffic exceed the maximum limit of network, the transmission quality of the data flow can’t be guaranteed. With the appearance of the business required strict QoS (such as multimedia technology), it needs higher real-time performance when transmitting files. Thus providing QoS in Ad hoc networt is of great importance.The concept of Ad hoc network is introduced in this paper and the routing protocol of Ad hoc network is introduced in detail. An attempt has been made to compare the performance of four prominent routing protocols (AODV, DSR, DSDV and TORA) for mobile Ad hoc network. By comparing the packet delivery ratio, average end-to-end delay and normalized routing overhead with different node connections for these four routing protocols, the simulation method and results are presented, the dynamic effect can be seen by the“nam”. According to the theoretical research and simulation results, we can find that AODV has better performance, it can support QoS and it can be extended easily. But it also has some flaws, such as poor QoS guarantee, long delay and high routing overhead. Therefore, an improved protocol (I-AODV) in mobile Ad hoc network is proposed and implemented in NS-2.The protocol is an expansion of AODV protocol. Taking bandwidth as the parameter for QoS, and decreasing the routing overhead by reducing the times of transmitting control packets, it provides better assurance for QoS in Ad hoc network. The simulation results show that it improves the real-time and normalized routing overhead performance of AODV.更多还原