wAdAd hochoc 网络论文：基于忙音的网络论文：基于忙音的 AdAd hochoc 网络网络 MACMAC 协议研究协议研究【中文摘要】Ad hoc 网络,又称无线自组网,是由一组带有无线收发装置的节点组成的可快速搭建的网络,具有多跳、动态网络拓扑、分布式控制以及不依赖基站等特点,应用前景广泛,一直受到学术界和工业界的重视。MAC 协议用来协调各个节点对信道的共享访问、减少通信冲突,是 Ad hoc 网络的一个关键技术。现有的 IEEE 802.11 MAC 协议广泛应用于 Ad hoc 网络,但该协议会带来信道接入不公平性、隐终端和暴露终端等问题。当前很多研究都试图提高 Ad hoc 网络的性能,但这些协议只考虑了较为理想的网络环境,即接收节点的干扰范围等于其传输范围,无法解决大干扰域问题。由于忙音可以在载波侦听范围内被成功接收,应用到 MAC 协议中,可以有效解决大干扰域下的隐终端和暴露终端问题,因此基于忙音的 MAC 协议是当前的一个研究热点。本文从以下方面对 MAC 协议进行研究:(1)分析了 802.11 协议中二进制指数退避算法的不足,提出一种改进的退避算法,通过增大初始竞争窗口值,降低报文冲突概率,并在节点成功访问信道多次后主动退让,保证所有节点公平使用信道资源。(2)通过分析大干扰域问题,提出一种可变频率的双忙音 MAC 协议,利用忙音的频率和持续时间携带节点 id 信息,其它欲发送分组的节点根据当前通信双方的 id,判断自身是否在其干扰范围之内,从而决定是否发送分组。分析和仿真表明,该方法可以抑制隐终端并能同时缓解暴露终端问题。(3)对 Ad hoc 网络中的干扰积累现象进行了分析,并提w出一种基于 Hexagon 模型的 MAC 协议,该协议根据数据分组的冲突情况来调节接收端忙音的发射功率,当来自某一发送节点的分组传输失败时,接收节点将提高忙音的发射功率以扩大干扰控制半径,直至成功接收数据分组。分析和仿真表明,该协议可以提高接收端在多源干扰下正确收到数据的概率,更好的缓解了大干扰域下的隐终端问题。【英文摘要】Ad hoc network, also known as MANET, is a kind of network which consists of a set of nodes with wireless device for transmitting and receiving and can be quickly set up. As it has the features such as multi-hop, dynamic network topology, distributed control, and does not rely on base stations, it has a broad application prospect and has been subject to academic and industrial attention.Media access control protocol is used to coordinate nodes to access the shared channel and reduces conflicts, so it is a key technology to ad hoc network. Existing MAC protocols like IEEE 802.11 is widely used in ad hoc network, however, 802.11 will bring about the unfairness of channel access, hidden terminal and exposed terminal problems. Many studies have tried to improve the performance of ad hoc network, whereas, these MAC protocols usually consider only an ideal network environment, namely, the receivers interference range is equal to its wtransmission range, thus can not solve the large interference area problem.As busy tone can be successfully received in the carrier sensing range, it will effectively solve hidden terminal and exposed terminal problems in the large interference area once applied to the MAC protocol, which has been a current research focus. In this paper, we research the MAC protocol from the following aspects: Firstly, by analysising the shortcomings of the 802.11 binary exponential backoff algorithm, we propose an improved backoff algorithm. By enlarging the value of initial contention window, the algorithm could reduce probability of packet collision. Once a node has occupied channel successfully for several times, it will take the initiative to backoff to ensure equitable use of channel resource for all the nodes. Secondly, by analysising the large interference area problem, a variable frequency of dual busy tone based MAC protocol is proposed, which codes nodes id using frequency and duration of busy tone. Other nodes which intending to send packets obtain transmitter-receivers id, then evaluate whether they are within the receivers interference range, thus determine whether to send packets or not. Analysis and simulation show that, the wproposed protocol can prevent the hidden terminal in the large interference area and also alleviate the exposed terminal problem. Finally, we make an analysis of the interference accumulation phenomenon in ad hoc network and propose a Hexagon model based MAC protocol. The protocol adjusts the transmission power of receivers busy tone according to conflicts of data packet. When receiver fails to receive data packet, it will enhance the busy tone transmission power to enlarge interference control radius, so as to receive data packet successfully. Analysis and simulation show that, the protocol can improve the probability of the receiver to receive packet correctly in the case of multiple interference source, and better alleviate the hidden terminal problem in the large interference area.【关键词】Ad hoc 网络 退避算法 MAC 忙音 大干扰域【英文关键词】Ad hoc network Backoff algorithm MAC Busy tone Large interference area【目录】基于忙音的 Ad hoc 网络 MAC 协议研究 中文摘要 4-5 Abstract 5-6 第一章 绪论 10-13 w1.1 研究背景与意义 10-11 1.2 本文研究内容 11-12 1.3 本文组织结构 12-13 第二章 Ad hoc 网络 MAC 协议 13-23 2.1 MAC 协议分类 13-14 2.1.1 信道使用数目 13-14 2.1.2 信道接入方式 14 2.2 MAC 协议面临的主要问题 14-19 2.3 典型的 MAC 协议介绍 19-22 2.4 本章小结 22-23 第三章 IEEE 802.11 MAC 协议退避算法改进 23-35 3.1 现有的退避算法 23-24 3.2 一种改进的算法EIB 24-27 3.3 仿真工具 NS2 27-30 3.3.1 NS2 的基本原理 27-28 3.3.2 NS2 的无线网络模块 28-29 3.3.3 仿真流程 29-30 3.4 仿真与性能分析 30-34 3.4.1 吞吐量比较 32-33 3.4.2 公平性比较 33 3.4.3 时延比较 33-34 3.5 本章小结 34-35 第四章 可变频率的双忙音 MAC 协议 35-49 4.1 忙音简介 35 4.2 相关工作 35-37 4.3 问题描述 37 4.4 协议描述 37-42 4.4.1 获取位置信息 37-38 4.4.2 协议设计 38-39 4.4.3 忙音的模拟 39-41 4.4.4 通信规则 41-42 4.5 示例 42-43 4.6 仿真场景设置 43-46 4.7 网络性能分析 46-48 4.8 本章小结 48-49 第五章 基于 Hexagon 模型的 MAC 协议 49-61 5.1 相w关工作 49 5.2 问题描述 49-50 5.3 协议描述 50-55