【作者】 刘楠；

【导师】 林秀琴；

【作者基本信息】 北京邮电大学 ， 计算机科学与技术， 2013， 硕士

【摘要】 无线自组织网络完全由具有无线通信能力的移动节点组成,具有自组织、临时性、多跳路由、动态拓扑结构、节点对等通信和自愈性等特点。目前,被使用最广泛的无线自组织网络是IEEE802.11中定义的Ad Hoc网络。在应急通信场景下,Ad Hoc网络能够弥补公共电信网及其它传统无线网络依赖固定网络基础设施的缺陷,和卫星通信网等常用应急通信网络中节点要求高、传播时延大等不足。同时,在应急通信场景下,信道接入协议的好坏,能够直接影响到Ad Hoc网络的组网效率和节点间的通信质量,进而影响到应急通信网络在紧急救援中的工作能力,因此,对这部分技术的研究是非常重要的。本文在对Ad Hoc网络特点与性能、Ad Hoc网络组网技术、应急通信场景、以及现有Ad Hoc网络信道接入协议的广泛调研与分析的基础上,对Ad Hoc网络信道接入协议802.11DCF(Distributed Coordination Function)进行了改进与优化,设计了一种适应应急通信场景需求和特点的退避机制DEB (Dynamically Exponential Back-off),从而得出一种新的应急通信场景下的Ad Hoc网络信道接入协议ECS-DCF (Emergency Communication Supported DCF)。在协议设计完成之后,本文在实验室设计的分级Ad Hoc网络组网场景下,使用NS-3网络仿真工具分别对两种信道接入协议进行了仿真与测试,并对仿真结果进行了分析与比较。将本文中的分级Ad Hoc网络结构及与之对应的组网流程使用在应急通信场景下,能够有效地降低网络中的广播开销、路径损耗和消息、冲突概率,从而获得较高的组网效率与更合理的网络资源分配方式。本文根据应急通信场景下,节点接入需求的集中性与紧急事件的可重复性提出的退避机制和信道接入协议,能够为Ad Hoc网络提供更高的组网和节点接入效率,从而在一定程度上使应急通信场景下的分级Ad Hoc网络获得更好的性能表现。更多还原

【Abstract】 All nodes in wireless self-organized network are mobile nodes with wireless communication abilities. It is a kind of self-organized, temporary, multi-hop routing supported, dynamical topology supported, peer-to-peer and self-recovery wireless network. Currently, the most widely used wireless self-organized network is Ad Hoc network, which is defined in IEEE802.11standard. Ad Hoc network can work without the supports of network infrastructures, and has lower node ability requirement and networking delay than other new wireless network such as satellite communication network. Channel access technology is a very important part in Ad Hoc network technologies, especially in emergency communication. Channel access protocol has a great influence on networking efficiency and communication quality of the network. These factors affect the network communication ability in emergency relief directly.Firstly, the paper researches the characters and abilities of Ad Hoc network, Ad Hoc networking technologies, emergency communication, and some existing channel access protocols for Ad Hoc network. Secondly, based on the802.11DCF (Distributed Coordination Function) protocol, the paper designs a new channel access protocol, ECS-DCF (Emergency Communication Supported DCF), which has a new back-off mechanism called DEB (Dynamically Exponential Back-off) and suitable for emergency communication. Then, the paper simulates and tests the new protocol, with the networking process of hierarchical Ad Hoc network, which is designed in a related project in our lab, by using NS-3network simulation tool. Finally, the paper compares the performance of the two protocols, and makes analysis and conclusions by the results.The hierarchical Ad Hoc network structure and networking process in the paper reduces broadcasting cost, path loss and confliction probability in emergency communication network. Therefore, it has higher networking efficiency and reasonable resources allocation method. The channel access protocol and the back-off mechanism are based on the characters of emergency communication. They can provide higher networking and node accessing efficiency, and better performance to the hierarchical Ad Hoc network in emergency communication.更多还原