【作者】 朱明；

【导师】 朱钢；

【作者基本信息】 南京航空航天大学 ， 通信与信息系统， 2016， 硕士

【摘要】 无线自组网不需要固定基础设施支持,组网快速灵活,抗毁性强,在军事和民用领域均有广阔的应用前景。近年来,随着网络多媒体业务类型和数量急剧增加,如何为多媒体业务流提供服务质量(QoS)保证受到了人们的广泛关注。在无线自组网多跳共享带宽受限的条件下,为了实现多媒体业务流的QoS保证,必须在数据链路层提出准确、实时的链路可用带宽预测方法,并将预测结果作为网络层路由选择的依据,实现跨层路由选择。本文的创新工作即围绕上述关键问题展开,具体包括:(1)在充分比较现有两类可用带宽预测方法的基础上,针对在无线自组网中进行可用带宽预测的两个难点问题:收发节点可用时长不同步和隐藏节点导致的传输失败问题,本文提出了一种基于分布式协调功能(DCF)协议的链路可用带宽预测方法。该方法首先定义了链路最大吞吐量,并将其视为该链路可用带宽的上限值。然后,方法要求链路两端收发节点利用自身载波检测能力获得各自的可用时长,并通过分析收发节点可用时长的不同步情况得到链路可用带宽的初步估计值。在此基础上,该方法通过讨论链路周围隐藏节点数据传输可能造成的两种传输中断情况,细致推导了隐藏节点导致的传输中断概率,并对链路可用带宽的初步估计值进行修正,最终得到链路可用带宽修正值。仿真结果证明了该链路可用带宽预测方法的准确性。(2)在充分验证链路可用带宽对路由协议性能重要影响的基础上,本文结合上述链路可用带宽预测方法和AODV路由协议,设计了基于链路可用带宽预测的跨层路由协议。该路由协议在路由发现的过程中综合考虑链路可用带宽和多跳路径的跳数,既保证了现有业务流的QoS,又为新业务流寻找到一条满足其带宽消耗的传输路径。为了实现对业务流的接入控制,该协议利用Hello分组在邻居节点间交互可用时长信息来进行链路可用带宽预测;在预测多跳路径的业务流带宽消耗过程中,充分考虑“流内竞争”问题,指出业务流在链路某一节点处的实际带宽消耗应是其需求带宽的竞争节点数倍。在上述两方面内容的基础上,该协议在路由发现的过程中对业务流进行接入控制,选择链路可用带宽满足带宽消耗且跳数较少的路由。仿真结果表明,该跨层路由协议能够有效地为网络中的现有业务流和新业务流提供QoS保证。更多还原

【Abstract】 Due to its independence of fixed infrastructure, quick networking, and strong anti-destroying, wireless ad hoc networks have been widely used in the field of military and civil communications. In recent years, with the rapid increase of multimedia business type and number, how to guarantee the quality of service(QoS) of multimedia business has received wide attentions from people. In the condition of multi-hop, shared and limited bandwidth in ad hoc networks, in order to realize the multimedia business flows’ QoS guarantee, we must put forward an accurate and real-time available bandwidth estimation method in the data link layer, so we can realize cross-layer routing according to available bandwidth results based on this method. Our innovative work centres on the above key problems, and the main innovation points are summarized as follows:(1). Based on the full comparison of the existing two kinds of available bandwidth estimation method, according to the two difficult problems when evaluating available bandwidth in ad hoc networks: the desynchrony in available period between transmitter and receiver, as well as the transmitting failures because of hidden nodes, we put forward a link available bandwidth estimation method based on distributed coordination function(DCF) protocol. Firstly, the method defines the maximum throughput in a link that can be seen as the upper limit of the available bandwidth in a link. Then, the method requires transmitter/receiver nodes to detect their own available periods using carrier sensing ability. Through analyzing the desynchrony in available period between transmitter and receiver, we get the preliminary estimate. Lastly, the method discusses the transmitting interruption because of hidden nodes in two cases to amend the preliminary estimate. Finally, we get the revised estimate. The simulation results verify the accuracy of the available bandwidth method.(2). Based on fully verying the link available bandwidth’s important influence on the performance of routing protocol, combined with the above link available bandwidth estimaton method and the AODV routing protocol, we design the cross-layer routing protocol based on link available bandwidth estimation. The routing protocol comprehensively considers link available bandwidth and hops of the multi-hop path in the routing discovery process, which not only ensures the QoS of existing business flows, but also finds a transmission path meeting their bandwidth consuption for the new business flows. In order to realize the admission control of business flows, the routing protocol evaluates available bandwidth of a link with the help of Hello packets that exchange available period information between neighbor nodes. In the process of predicting bandwidth consumption of multi-hop path, the routing protocol fully considers the “intra-flow contention”, pointing out that the business flow’s bandwidth consumption at a node should be contention count times its required bandwidth. Based on the above two aspects, the routing protocol conducts admission control of business flows, selecting the route with link available bandwidth satisfying bandwidth consumption and less route length. The simulation results show that the routing protocol can effectively provide Qo S guarantees for the exsting flows and new flows.更多还原