基于QualNet仿真平台的Ad Hoc网络组播路由协议研究

近年来，对Ad Hoc网络组播路由协议的研究越来越被人们关注，但是目前所设计的组播路由协议在性能上都有一些不足，针对不同的网络应用环境选择和设计适合的组播协议十分重要．本文利用QualNet仿真平台对MAODV和ODMRP两种组播路由协议进行仿真，分析与比较了它们在各种网络环境中的性能．     

基于PIM-SM的域内组播设计

PIM-SM是一个不依赖于某一特定单播路由协议的组播路由协议,为组播数据转发提供路由信息。介绍了IP组播原理,分析了组播通信的优点,概述了组播路由协议。研究了基于PIM-SM的组播网络设计与实现方法,并给出了相关的网络配置方案。     

ODMRP组播协议的改进算法及其仿真

ODMRP组播协议非常适合于带宽限制大、移动性强和节点能量受限的Adhoe网络。为了进一步提高该协议的性能，该文设计出一种改进方案。该方案首次提出“假死”状态的概念，将其应用于原协议中，以提高路由的有效性。文中，原协议和改进方案的仿真算法在仿真工具GloMoSim中实现，同时仿真结果显示该算法比原协议在数据分发率和网络有效性等性能有很大改善。所以，该改进方案有效地提高了ODMRP协议的性能，使之更加适用于Adhoe网络。     

基于OPNET的按需组播路由协议仿真

按需组播路由协议(ODMRP)是一种针对移动自组织网络的组播路由协议,该协议在源节点和接收节点之间建立网格进行数据传输,具有冗余路径、不依赖单播路由、健壮性高等特点.目前尚缺乏对于ODMRP的建模和仿真研究.针对此问题,基于OPNET仿真环境完成了对ODMRP的建模,建立了该协议的有限状态机(FSM)、节点模型、网络模型以及包格式,基于C语言编程实现了路由的建立、更新、维护和数据传输过程.通过设置不同的参数和统计量,仿真检验了协议性能,包括网络的端到端延时和数据包递交率与节点移动速度和组播组尺寸之间的定量关系,证明了所建立的协议模型的功能正确性.仿真结果表明,ODMRP协议适用于诸如战场通信、灾难救助、体育比赛、大型会展等需要临时组网进行组播通信的应用场合.     

基于ODMRP的链路状态预测组播路由算法

ODMRP协议是无线自组网环境下的一种按需式组播路由协议。论文提出了一种基于链路状态预测的ODMRP协议改进,即LSF-ODMRP路由协议。该协议继承了ODMRP协议的按需式路由发现和更新,并采用了链路状态预测机制LSF(Link Status Forecasting),大大减少了路由失效数并缩短了分组投递延迟,提高了网络性能。通过对LSF-ODMRP协议的模拟仿真实验比较,验证了协议的改进效果。     

三种Ad Hoc网络组播协议的性能分析与比较

近年来，Ad hoc网络的组播路由协议研究受到广泛关注，但已经提出的各种组播协议中还没有一种在MANET定义的各种性能指标方面都处于领先，因此对不同协议的分析和比较能帮助人们在不同的应用环境下选择和设计更适合的组播协议。本文首先分别介绍了3种典型的组播路由协议：ODMRP、ADMR、DRMR，然后对其控制开销进行了计算分析，最后利用NS2仿真软件对3种协议进行仿真，分析与比较了它们在各种网络环境下的性能。     

无线Mesh网络组播路由协议

组播服务是无线Mesh网络面向实际应用的一种重要服务,网络层组播路由协议则是服务实现的核心支撑协议.无线Mesh网络独有的结构特征、性能要求以及多射频、多信道和多速率的引入使得许多传统组播路由协议无法直接进行应用,近几年来,已有不少针对特定无线Mesh网络的组播路由协议相继提出.归纳总结了协议的设计目标、原则和分类方法;阐述了各类典型协议的主要机制,并就这些协议的技术特点和性能差异进行了详细比较;最后结合无线Mesh网络的发展趋势和协议面向实际混合业务环境的实用化目标分析了多射频、多信道以及多速率对组播路由的影响,指出了基于实测环境和实际业务需求建立组播路由跨层优化模型与具体优化机制的重要性.     

两种Ad hoc网络组播路由协议的性能比较和分析

目前研究人员已提出多种Adhoc网络组播路由协议,根据MANET制定的路由协议性能评价标准,还没有一种组播路由协议能满足所有的性能要求,因此对协议在各种应用环境下的性能进行测试和比较,有助于人们选择和设计组播路由协议。该文首先介绍了两种组播路由协议—ODMRP和DBRMP的基本思想,接着提出这两种协议的控制开销计算方法,并对它们的性能进行了定性比较,最后使用了NS-2仿真平台对两种组播路由协议在各种应用环境下的性能进行了仿真,并根据仿真结果详细比较和分析了两种协议在各种应用环境下的性能特点。     

无线自组织网络组播路由协议的研究

组播通信在无线自组织网络应用中越来越重要。该文首先针对不同的组播路由方式,选出具有代表性的四种组播路由协议PUMA、ODMRP、MAODV和FLOOD,然后从理论和仿真实验两个层面上对四种协议进行了比较。仿真结果表明,PUMA在场景规模适中,节点移动速度较慢的情况下报文投递率和端到端延迟要优于其他三种协议,这为未来自组织网络可靠组播的研究奠定基础。     

几种Ad Hoc网络组播路由协议的分析与比较

Ad Hoc网络是一种不依赖于固定设施的,自组织的无线网络,其组网快捷、方便,具有广阔的发展前景.在典型的Ad Hoc网络应用中,网络主机通过按组工作来完成一项特定的任务.因此,组播在Ad Hoc网络中是一个十分重要的功能.按照参与组播路由的结点构成的网络拓扑结构的不同,分别介绍了基于树的组播路由协议AMRIS,基于格网的组播路由协议ODMRP、CAMP、FGMP,和基于混合的组播路由协议AMRoute,并对它们各自的工作方式进行了分析,最后对它们各自的特点进行了比较.     

能量驱动的移动Ad Hoc网络概率组播路由协议

在ODMRP协议中，由于采用周期性地广播Join-Query包来更新成员信息和路由信息，因此网络中流动着大量平凡的Join-Query控制包，造成网络开销增大，网络拥塞。采用能量驱动的概率转发的方法，根据每个节点的能量资源信息为每个节点设置相应的转发投递概率，抑制网络中的Join-Query控制包。模拟结果显示，能量驱动的MANET概率组播路由协议(p-ODMRP)在投递率满足需求的情况下，网络的控制开销减小20%左右，增加了网络寿命，协议的综合性能有明显提高。     

E-ODMRP: Enhanced ODMRP with motion adaptive refresh

On-Demand Multicast Routing Protocol (ODMRP) is a multicast routing protocol for mobile ad hoc networks. Its efficiency, simplicity, and robustness to mobility render it one of the most widely used MANET multicast protocols. At the heart of the ODMRP’s robustness is the periodic route refreshing. ODMRP rebuilds the data forwarding “mesh” on a fixed interval and thus the route refresh interval is a key parameter that has critical impact on the network performance. If the route refresh rate is too high, the network will undergo too much routing overhead, wasting valuable resources. If it is too low, ODMRP cannot keep up with network dynamics, resulting in packet losses due to route breakages. In this paper, we present an enhancement of ODMRP with the refresh rate dynamically adapted to the environment. Simulation results show that the Enhanced ODMRP (E-ODMRP) reduces the packet overhead by up to a half yet keeping a packet delivery ratio comparable to that of the original ODMRP. E-ODMRP compares favorably with other published multicast schemes.     

Design of a Scalable Multicast Scheme With an Application-Network Cross-Layer Approach

This paper develops an efficient and scalable multicast scheme for high-quality multimedia distribution. The traditional IP multicast, a pure network-layer solution, is bandwidth efficient in data delivery but not scalable in managing the multicast tree. The more recent overlay multicast establishes the data-dissemination structure at the application layer; however, it induces redundant traffic at the network layer. We propose an application-oriented multicast (AOM) protocol, which exploits the application-network cross-layer design. With AOM, each packet carries explicit destinations information, instead of an implicit group address, to facilitate the multicast data delivery; each router leverages the unicast IP routing table to determine necessary multicast copies and next-hop interfaces. In our design, all the multicast membership and addressing information traversing the network is encoded with bloom filters for low storage and bandwidth overhead. We theoretically prove that the AOM service model is loop-free and incurs no redundant traffic. The false positive performance of the bloom filter implementation is also analyzed. Moreover, we show that the AOM protocol is a generic design, applicable for both intra-domain and inter-domain scenarios with either symmetric or asymmetric routing.     

可变核心的Ad hoc组播路由协议

针对Ad hoc网络中信源节点增加时ODMRP按需组播路由协议会产生大量的控制开销,提出了一种优化的基于可变核心算法的组播路由协议VCMP(variable core multicast route protocol).该协议的核心不必事先固定,而是能根据当前的网络拓扑和组成员关系进行变化,利用核心的帮助,能解决ODMRP环境中所会出现的控制开销问题,使整个网络中的控制包大大的减少.仿真结果表明VCMP确实有更好的性能.     

Link stability based multicast routing scheme in MANET

The group-oriented services are one of the primary application classes that are addressed by Mobile Ad hoc Networks (MANETs) in recent years. To support such services, multicast routing is used. Thus, there is a need to design stable and reliable multicast routing protocols for MANETs to ensure better packet delivery ratio, lower delays and reduced overheads. In this paper, we propose a mesh based multicast routing scheme that finds stable multicast path from source to receivers. The multicast mesh is constructed by using route request and route reply packets with the help of multicast routing information cache and link stability database maintained at every node. The stable paths are found based on selection of stable forwarding nodes that have high stability of link connectivity. The link stability is computed by using the parameters such as received power, distance between neighboring nodes and the link quality that is assessed using bit errors in a packet. The proposed scheme is simulated over a large number of MANET nodes with wide range of mobility and the performance is evaluated. Performance of the proposed scheme is compared with two well known mesh-based multicast routing protocols, i.e., on-demand multicast routing protocol (ODMRP) and enhanced on-demand multicast routing protocol (EODMRP). It is observed that the proposed scheme produces better packet delivery ratio, reduced packet delay and reduced overheads (such as control, memory, computation, and message overheads).     

基于跨层设计的CLRM-HWMP路由协议研究

在研究HWMP路由协议的基础上引入跨层设计方法,综合考虑数据链路层的数据帧传输成功率DFTE(Data Frame Transmission Efficiency)、网络层的可用带宽和节点跳数作为跨层路由度量值CLRM(Cross-Layer Routing Metric),提出一种综合路由判据的跨层路由协议CLRM-HWMP路由协议.该协议有效解决单一的路由量度判据在提高无线Mesh网络性能方面的局限问题.通过NS-3仿真工具对无线Mesh网络中的HWMP路由协议和提出的CLRM-HWMP跨层路由协议进行分析对比,实验结果表明:提出的CLRM-HWMP路由协议有效降低了节点间端到端时延、提高了数据包投递成功率和网络吞吐量.     

一种基于分群的移动自组网多播路由协议

为提高多播协议的可扩展性,提出一个基于分群的高效多播路由协议(ECMRP)。采用改进的基于权重的分群算法对移动自组网中的移动节点进行分层管理,并应用软状态方法在群首间建立多播树,减小当网络拓扑结构动态变化时重构、维护多播树结构的控制开销。仿真实验结果表明,该算法在路由开销和分组投递率上均优于多播按需距离矢量和按需多播路由协议,更适合于高动态、大规模的自组网。     

Moving routing protocols to the user space in MANET middleware

Mobile Ad Hoc Network (MANET) middleware must be aware of the underlying multi-hop topology to self-adapt and to improve its communication efficiency. For this reason, many approaches rely on specific cross-layer communications to interact with the network protocols in the kernel space. But these solutions break the strict layering of the network stack and hinder the portability of middleware and applications.The main argument of this paper is to move the routing protocols to the user space to simplify the development, testing, deployment and portability of middleware and applications. If routing is just another software component in the user space, cross-layering can be elegantly solved using advanced software engineering techniques like component frameworks and explicit APIs. As a consequence, a slight performance cost must be paid to achieve portability and easy deployment. But we will demonstrate that the performance obtained by a user-space routing protocol is satisfactory for a wide range of applications.We have implemented the unicast MANET OLSR protocol in Java (jOLSR) and, on top of it, we have created a novel overlay multicast protocol (OMOLSR). We have then integrated both routing protocols (jOLSR, OMOLSR) as software components in a well-known group communication toolkit (JGroups). Modifying the JGroups toolkit, we have devised a topology-aware group communication middleware for MANETs (MChannel). In our MChannel middleware, group membership is obtained directly from OMOLSR multicast trees and failure detection is obtained from jOLSR active probing. We have validated our approach in several real testbeds to demonstrate the feasibility and efficiency of our middleware.