嵌入服务通告与发现的ZRP协议

服务通告和发现在MANET(Mobile Ad hoc Networks)网络中,是一个十分重要的组成部分.现有的服务通告和发现协议不是为MANET网络设计的.文章提出了一个适合MANET、基于ZRP(Zone Routing Protocol)的服务通告及发现协议.服务的通告与发现存在于ZRP路由控制分组中,避免了周期性的通告给MANET网络带来的负载,节约了有限的带宽和设备的能耗.     

MANET中一种新的基于节点位置的按需路由算法

移动Ad hoc网络(MANET)是一种由无线移动主机/节点组成的动态自治网络.在MANET中进行有带宽保证的按需路由选择具有重要意义.本文提出一种新的按需路由算法LABGR(Location Aided Bandwidth Guaranteed Routing).LABGR以节点当前位置信息为基础,在路由选择过程中把路径稳定性和节点能量受限问题结合起来,采用受限扩散路由方法,利用多种机制避免在全网中进行扩散,限制路由请求过程中被影响的节点数目,有效提高了路由请求效率并且保证了链路带宽.本文还对LABGR算法特性进行了深入分析.     

提供QoS保障的无线多跳路径可用带宽估计模型与方法

该文对多跳路径的可用带宽估计问题进行了研究,提出了在估计过程中必须将全局QoS保障作为可用带宽的估计原则。对多跳路径的干扰进行了定性分析与定量计算,并利用排队网络理论建立了路径性能分析模型,利用该模型能得出路径中各个业务流的QoS参数。在此基础上设计了能提供QoS保障的可用带宽估计方法。该文所提出的估计方法以QoS需求不被破坏为约束条件,克服了现有工作将无约束的最大可达吞吐量作为可用带宽从而导致业务的QoS可能受到影响这一缺陷。仿真实验证明了分析模型与可用带宽估计方法的准确性。     

MANET中的关键技术探讨

由于移动自组网(MANET)具有多跳的无线连接、动态拓扑及有限带宽等特征,给其路由协议带来了很多挑战.文中简要介绍了MANET的概念、特点,重点分析了MANET中的关键技术(无线资源管理与空中接口理论技术.路由技术、互联网接入技术、地址自动分配技术、域名系统和服务质量保证技术),同时对无线资源管理与空中接口理论技术、域名系统及服务质量保证技术的实现进行了简单的推测.     

MANET仿真软件的分析与研究

网络仿真软件是网络性能理论分析、评估网络设计方案以及网络故障诊断的有力工具由于MANET自身环境的复杂性．对其的设计．仿真以及优化显得更加的困难本文介绍了3种主流网络仿真软件：商业软件OP-NET Modeler和免费软件NS-2及GloMoSim,分析了其各自的特点及适用范围。接下来详细介绍了目前在研究领域广泛使用的NS仿真软件的原理,并给出了使用NS仿真软件进行网络仿真和MANET仿真的一般步骤．最后对全文作出总结。     

一种基于端到端测量的路径性能参数估计算法

现有的网络性能估计技术不能实现对路径容量和可用带宽的同时测量。该文通过对存在拥塞链路的路径作随机分析,得到了一种对路径可用带宽的近似估计式,并通过对Kapoor(2004)中的方法进行改进, 提出了一种基于端到端的可以同时对单拥塞路径的容量及可用带宽进行估算的算法。在较准确估算路径容量的同时,达到了用同一组样本实例同时估计路径容量和可用带宽的目的。仿真验证了算法的有效性和准确性。     

一种认知网络中的带宽分配方法研究

认知网络作为一种新型的网络概念和技术,近年来其重要性得到了广泛的认同。在认知网络中,如何根据用户业务需求及带宽资源状况动态进行带宽分配是一个重要的问题。通过对用户权重的估计分析,提出了一种基于权重估计的改进带权Max-Min带宽分配算法,仿真试验证明该算法可改善对用户业务流QoS的整体保障能力。     

MANET分簇策略的仿真研究与实现

无线移动自组织网络（MANET）是一种无需基础设施支持的无线网络,而MANET分簇策略的性能研究有着广泛的应用。本文对MANET分簇策略仿真平台进行研究与实现,并对现有的MANET分簇算法进行仿真分析。本文所提出的平台不仅能统计和分析分簇策略的性能,还能对MANET分簇过程的实时状态进行仿真和输出。与现有的通用型网络模拟平台相比,该平台是针对MANET所设计的,具有交互性好、可扩性强、便于分簇策略优化改进等特点。     

基于Laguerre变换的宽带LFM信号频谱压缩数字接收方法

该文提出了一种新的宽带线性调频(LFM)信号频谱压缩数字接收方法。文中分析了Laguerre变换的频率卷绕特性以及对LFM信号的频谱压缩特性,利用数字域Laguerre变换构建可变压缩度的频谱压缩网络,使信号带宽始终处于接收机处理带宽以内,相应达到改变接收机带宽的目的,有利于减小后续基带信号处理的数据量。压缩信号可利用频谱恢复网络实现信号的重构,LFM信号的初始频率和调频斜率在频谱恢复后仍可较精确估计。仿真结果验证了方法的正确性和有效性。     

Ad hoc网络技术讲座第3讲Ad hoc网络采用QoS信令机制的研究

信令机制通常是网络中最复杂的功能部件之一,本文首先介绍了移动Adhoc网络(MANET)中采用QoS信令机制的必要性,然后详细说明和分析了RSVP及其改进协议在MANET中应用的可行性。接着讨论了一种适合于MANET的带内信令机制——INSIGNIA信令机制及其改进协议,最后对全文进行了总结。     

Bandwidth estimation: metrics, measurement techniques, and tools

In a packet network, the terms bandwidth and throughput often characterize the amount of data that the network can transfer per unit of time. Bandwidth estimation is of interest to users wishing to optimize end-to-end transport performance, overlay network routing, and peer-to-peer file distribution. Techniques for accurate bandwidth estimation are also important for traffic engineering and capacity planning support. Existing bandwidth estimation tools measure one or more of three related metrics: capacity, available bandwidth, and bulk transfer capacity. Currently available bandwidth estimation tools employ a variety of strategies to measure these metrics. In this survey we review the recent bandwidth estimation literature focusing on underlying techniques and methodologies as well as open source bandwidth measurement tools.     

IP网可用带宽快速检测方法SSP的研究与应用

在IP网中,可用带宽是最重要的网络资源,是网络传输性能的决定因素,可用带宽的实时检测具有重要的研究和现实意义.本文对当前典型的端到端的可用带宽测量工具Pathload进行了研究,分析了Pathload工具检测算法的优点以及不足,提出了一种快速而精确的带宽测量方法--SSP,通过它可以快速检测到端到端路径的可用带宽值,为有效利用网络资源、支持QoS服务和多媒体实时业务提供了保证.     

基于延迟参数的可用带宽主动估测算法

可用带宽是重要的网络资源,但它的实际测量存在许多困难。该文基于延迟趋势模型,提出一种端到端的可用带宽估测算法SSP(SRdeg and SRdet Parameters),设计了反映网络传输性能的参数SRdeg 和SRdet ,通过端系统对参数进行计算,主动调整发送速率,从而快速估测到网络的可用带宽,达到有效利用网络资源的目的。在NS2平台进行了参数和SSP算法的性能测试实验,并与当前的带宽估测工具Pathload进行了比较。实验结果表明,SSP算法估测带宽的精度和效率都高于Pathload。     

基于位置加权的电力通信网站点带宽估算方法

提出一种电力通信网站点通信带宽估算方法,涉及电力通信网领域?所述方法包括如下几个步骤：首先根据电力通信网拓扑图,确定电力通信网站点在电力通信网中的局部重要度和全局重要度;接着对电力通信网站点的局部重要度和全局重要度进行融合,得到电力通信网站点的实际重要度值;然后根据所述实际重要度值确定每一个站点通信带宽估算模型中的数据业务冗余系数;最后根据站点通信带宽估算模型计算电力通信网站点的规划带宽?提出的方法利用站点在网络拓扑中的位置计算站点的重要度,并将节点重要度引入站点通信带宽估算中,克服了传统站点通信带宽估算结果不够精确的问题?     

Accurate estimation of capacities and cross-traffic of all links in a path using ICMP timestamps

The estimation of the link capacity and its available bandwidth in an end-to-end path is crucial for network management, admission control and flow control for adaptive applications. This paper introduces an estimation mechanism able to accurately estimate the available bandwidth of all links in an end-to-end path, through its capacity and cross-traffic estimation. The estimation procedures resort to the dispersions of packet pairs and trains using the concepts of ICMP Timestamp and Traceroute that, efficiently used together, enable the measurement of the dispersions in all links in the path. These mechanisms were evaluated through simulation experiments, where we analyzed the influence of the several network parameters on each estimation mechanism. The results show that these estimation methods are able to accurately estimate both the capacity and the cross-traffic of all links in a path with moderate length and with low overhead.     

The Mobility Issue in Admission Controls and Available Bandwidth Measures in MANets

This paper is focused on the QoS (Quality of Service) in IEEE 802.11 MANETs (Mobile Ad hoc Networks). The QoS support like resources allocation in any network is relied to the ability to estimate the availability of these resources. The bandwidth is main resource, which the estimation of its availability is an open issue to research in MANets. In order to improve the available bandwidth measurements, this paper proposes a new approach named IBEM (Improved Bandwidth Estimations through Mobility incorporation) in IEEE 802.11 MANets. Seen that the measurement failures in MANets are due to neglecting some features of such networks, and mobility is the principal characteristic. The mobility is neglected in all existing bandwidth measurement approaches. The proposed approach aims to incorporate the mobility criteria in the available bandwidth estimations with specific manner. The comparative results with bandwidth estimation methods in the literature testify the improvement brought by this approach.     

无线自组织网络中基于QoS保障准则的可用带宽估计

对无线自组织网络中可用带宽估计问题进行了研究,提出了在估计过程中必须将全局服务质量（QoS）保障作为可用带宽的估计准则。建立了无线自组织网络中非饱和条件下异构的分析模型,该模型能将业务流的QoS度量映射为网络参数,在此基础上设计了能提供QoS保障的可用带宽估计算法。本文所提出的估计算法将包括时延、丢包率与吞吐量在内的QoS需求不被破坏作为可用带宽估计的约束条件,克服了现有的工作将无约束的最大可达吞吐量作为可用带宽因而导致业务的QoS可能受到影响这一缺陷,从而使得估计结果更加合理与准确。仿真实验证明了分析模型与可用带宽估计算法的准确性。      

DIChirp: direct injection bandwidth estimation

Ideally, network bandwidth estimation algorithms should be independent of the end system performance. If end system capabilities are involved, then the measurement will be of the system throughput and will not indicate a correct assessment of network bandwidth. Packet dispersion‐based active bandwidth estimation schemes including Pathload, TOPP and pathChirp use delay correlation where the network‐induced delay on packets transmitted at certain rates is translated into bandwidth estimation. Since packet dispersion‐based active measurement schemes use delay correlation, bandwidth estimations are distorted by the host protocol stack‐induced delay variations. Studies revealed that the host protocol stack‐induced delay variations due to context switching are stovepiped in the network‐induced delay variations and impact the measurement process. This study explores the delay variations introduced by the host protocol stack in packet dispersion‐based techniques. The impact of host protocol delay variations and context switching on bandwidth estimation is analyzed and a new active bandwidth estimation tool minimizing the impact of context switching is proposed. Direct Injection Chirp (DIChirp) bypasses the TCP/IP protocol stack and directly interfaces with the network hardware. It uses the kernel for scheduling the outgoing packets, thus achieving more accurate estimation of bandwidth. Experiments revealed that the host protocol and context switching‐induced delay variations can be as high as 800µs and could result in bandwidth estimation errors near 20%. Experiments also revealed that the DIChirp is superior to the pathChirp implementation in performance estimation since the datapath utilized by DIChirp is less prone to delay variations induced by context switching. Copyright © 2007 John Wiley & Sons, Ltd.     

Dynamic Bandwidth Allocation in WDM Passive Star Networks with Asymmetric Traffic

When asymmetric traffic is offered to a WDM passive star network, the offered bandwidth must be allocated is such a way that each station takes a portion of the available bandwidth proportional to its needs. When the traffic characteristics are fixed and a priori known, then, the bandwidth allocation scheme can be based on these characteristics. Unfortunately, the traffic characteristics are often unknown and time-variable. In this paper, a dynamic bandwidth allocation scheme is presented, which is based on the network feedback information in order to be capable of adapting to the changing traffic characteristics. According to the proposed scheme, a set of learning automata processes the network feedback information and dynamically allocates the available bandwidth to the stations according to their needs.