移动IP中的切换策略

移动切换是移动IP中的关键技术之一，对于移动IP的性能有着重要的意义。对移动IPvl6基本切换策略、分级移动IPvl6切换策略和快速切换协议切换策略进行了分析，阐述了各种策略的流程，并重点探讨了它们的优缺点。最后给出了关于移动IP切换策略的一些结论和建议。     

策略网管技术的研究现状及QOS应用

随着网络的发展和多媒体应用的增加,如何实现网络管理的智能化及提供服务质量保证已经成为目前网络管理研究的重点,基于策略的网络管理被认为是解决这两个难题的有效途径.本文详细介绍了策略网管的研究现状、框架结构及QoS应用,并分析了其优势及尚待解决的问题.     

移动IP无缝切换技术研究

移动IP协议是宏移动管理方案,但它不支持无缝切换.针对移动I P的不足,人们提出了许多改进方案来增强其性能.根据切换过程的技术特征,文章从基于缓存和转发机制的切换、基于减少组件延时的切换、基于上下文转移的切换和基于候选访问路由器发现策略的切换等角度,对增强移动IP性能的各种无缝切换技术进行了研究.     

WATM资源分配调度和切换策略研究

近年来，ATM和无线通信两种技术得到了极为快速的发展。WATM（Wireless ATM）作为ATM网络的无线延伸的一种解决方案吸引了学术界和工业界广泛的兴趣。重点分析了WATM资源分配调度和对切换策略的研究。     

LEO移动卫星系统的一种基于动态多普勒的切换技术

切换技术是移动通信系统中的关键技术之一。对于LEO移动卫星通信系统而言,切换不光考虑小区之间、还得引入星际切换,因此,其复杂程度远远高于地面蜂窝系统。近几年来,随着LEO移动业务的蓬勃发展,众多的切换机制应运而生,并在实际应用中得到了检验和发展。介绍了一种基于动态多普勒的切换排序技术,对其原理及切换过程进行了详细的阐述。     

IP微移动的切换管理

IP微移动是一种能够在移动过程中有效改善移动节点通信质量的移动性管理方式,其核心部分为切换管理。该文首先分析了IP微移动的切换过程,并从网络层切换和链路层切换的关系及其交互性的新视角提出了切换管理的分类方法,详细分析和研究了目前典型的IP微移动协议的特点和存在的问题,并给出对这些协议的性能比较,最后讨论了IP微移动切换管理的未来研究方向。     

移动IP中的S-MIP切换方法

有两种比较常用的减少切换时延的方法．第一种是通过分层管理的架构来减少家乡网络的注册时间，第二种是通过地址预先配置来减小地址长度的方法来解决延迟的快速切换机制。S-MIP切换方法是建立在分层和快速切换方法之上的。它能够实现与L2层相似的较少的数据包丢失和切换的时延。     

基于Q学习的异构无线网络动态切换策略

提出了一种基于Q学习的动态切换策略,用于最大化用户体验(QoE).基于Q学习的动态切换策略选择最佳网络,不仅利用当前网络状态还利用了未来网络状态和用户终端状态.不同于其他动态规划算法,该算法不需要获取无线网络环境的信息,而是通过利用用户终端过去经验来学习最优策略.仿真结果显示,该动态切换策略能以较少网络间切换次数来接近甲骨文优化算法性能,从而使用户体验得到更优质的网络音频服务.     

移动切换资源预留技术研究

论文介绍了移动通信中的QoS、资源预留协议及为保证各业务QoS的资源预留切换方案。在移动切换中对基于QoS保证的资源预留方案的研究现状进行了综述,并在资源预留方法方面提出了一种设想,最后指出了今后资源预留技术研究的趋势。     

一种基于策略和移动代理的网络管理体系结构

网络管理是一项复杂的系统工程，传统的客户机／服务器模式的缺点日益明显，已经无法胜任对大型的分布异构网络的管理。通过对基于移动代理的网络管理和基于策略的网络管理的分析研究，结合两种技术的优点，提出了一种具有良好的适应性的自动化网络管理体系结构，并进行性能分析。最后通过简单原型系统的实现和域间服务质量(QoS)配置的实例研究，验证了该体系结构的有效性和灵活性。     

移动IP在无线局域网下的一种快速切换方法

针对移动IP在无线局域网下的应用,提出了一种新的基于链路层的移动IP快速切换方法,通过在无线局域网的无线接入点间加入特定的MAC网桥来减少移动节点在切换时产生的切换时延,进而减少移动节点上行和下行方向上的数据包的丢失,达到对移动IP切换进行优化的目的。此方法在无线局域网实际环境中进行了性能测试,结果证明优化后的时延较之原来普通移动IP切换时延有明显降低。     

蜂窝重叠情况下移动IP切换延时分析

从理论上首次对移动 IP 切换过程中的切换延时和乱序分组进行了建模和分析,分别得到了各自的概率分布公式。并且根据这个结果,优化了重叠区域的半径。结果表明:本模型准确地描述了移动 IP 的切换行为,它对于评价移动 IP 的切换性能非常有用。     

Improvements on “IP – IAPP”: A fast IP handoff protocol for IEEE 802.11 wireless and mobile clients

One of the most critical issues in introducing Wireless LAN (WLAN) real-time and delay sensitive applications, such as Voice over IP (VoIP), is guaranteeing IP service continuation during inter-subnet Basic Service Set (BSS) transitions. Even though WLANs offer very high channel bandwidth, they exhibit long network-layer handoff latency. This is a restraining factor for mobile clients using interactive multimedia applications such as VoIP or video streaming. In a previous work, we presented a novel fast and efficient IP mobility solution, called “IP-IAPP”, which offers constant IP connectivity to the 802.11 mobile users and successfully preserves their ongoing sessions, even during subnet handoffs (fast recovery of active connections). It is an 802.11-dependent IP mobility solution, which accelerates the network reconfiguration phase after subnet handoffs and significantly reduces the IP handoff latency. It restores L3 connectivity almost simultaneously to the L2 connectivity after a subnet handoff, due to a zero-delay movement detection method. As a result, even the most demanding next generation WLAN applications such as Voice over WLAN (VoWLAN) suffer insignificant disruption. In this paper we present an improved version of the IP-IAPP mobility mechanism (new optimized protocol procedures). Certain extensions have also been incorporated to the initial proposal, for the provision of more advanced services: (a) secure inter-AP IP-IAPP communications, (b) zero patching on the clients s/w, and (c) support of clients which use a dynamic IP address. Performance measurements out of further and more complex testing verify that the proposed method outperforms other existing mobility solutions, and still introduces the lesser imperative amendments to the existing 802.11 wireless LAN framework. Ioanna F. Samprakou received her B. Eng in Computer Engineering and Informatics in 2000 and her MSc. in the same area in 2003 from the University of Patras, Greece. She is currently a Ph.D canditate at the University of Patras. She has joined Atmel SA in 2002, where she is a Senior Wireless System Eng at the System Concept and Design group. She specializes in wireless technologies, and mobile communications, and holds a patent in the field of IP mobility. She has led teams in developing wireless 802.11 products such as Wi-Fi APs, STAs, and VoIP phones. Previously she has worked for the Research & Academic Computer & Technology Institute of Patras (RACTI) as an R&D computer engineer. She is a member of the Technical Chamber of Greece. Christos J. Bouras obtained his Diploma and PhD from the Computer Science and Engineering Department of Patras University (Greece). He is currently an Associate Professor in the above department. Also he is a scientific advisor of Research Unit 6 in Research Academic Computer Technology Institute (CTI), Patras, Greece. His research interests include Analysis of Performance of Networking and Computer Systems, Computer Networks and Protocols, Telematics and New Services, QoS and Pricing for Networks and Services, e – learning, Networked Virtual Environments and WWW Issues. He has extended professional experience in Design and Analysis of Networks, Protocols, Telematics and New Services. He has published 200 papers in various well-known refereed conferences and journals. He is a co-author of 7 books in Greek. He has been a PC member and referee in various international journals and conferences. He has participated in R&D projects such as RACE, ESPRIT, TELEMATICS, EDUCATIONAL MULTIMEDIA, ISPO, EMPLOYMENT, ADAPT, STRIDE, EUROFORM, IST, GROWTH and others. Also he is member of, experts in the Greek Research and Technology Network (GRNET), Advisory Committee Member to the World Wide Web Consortium (W3C), IEEE Learning Technology Task Force, IEEE Technical Community for Services Computing WG 3.3 Research on Education Applications of Information Technologies and W 6.4 Internet Applications Engineering of IFIP, Task Force for Broadband Access in Greece, ACM, IEEE, EDEN, AACE and New York Academy of Sciences. Theodore E. Karoubalis. received his B. Eng in Computer Engineering and Informatics in 1992 and his Ph.D. in the same area in 1996 from the University of Patras, Greece. He has joined ATMEL Hellas SA at 1998. Since 1998 he is the Manager of PSLi software dpt. and since 2002 he is the manager of System and Concepts dpt. His interests include systems on chip, embedded applications, wireless systems etc. He is a member of IEEE and the Technical Chamber of Greece.     

GPON系统中基于QoS的动态带宽分配算法的研究

为了实现吉比特无源光网络(GPON)带宽分配的公平性,降低网络的丢包率及传输延时,研究了GPON系统传输汇聚层的帧结构及带宽分配的实现方法,提出了一种新的动态带宽分配(DBA)算法--基于QoS的二层动态带宽分配算法.性能分析与对比表明,这种算法对不同用户和不同等级的业务都具有很好的公平性,并可以降低低等级业务的传输延时.     

基于动态分布结构的一种微观移动切换方法

提出了一种在动态分布结构下微观移动的切换方法,它可根据移动主机进入微观局网收到的首次注册信息,动态地选择微观移动的网关,调整微观局网结构,分布了网络负载。通过用比较分析的方法和仿真实验对切换时间进行了计算和验证,表明此方法减少了微观移动网关的切换时延。     

基于移动IPv6的平滑切换算法研究

切换时延和数据包丢失一直是制约移动IPv6发展的关键因素.文章针对现有切换算法及存在的问题进行了分析,然后在现有算法的基础上提出了一种改进算法.仿真实验结果表明,该算法能有效地抑制因移动节点的网络切换而导致的通信节点拥塞控制机制的启动,提高了移动网络数据流的正确率和吞吐量,进而提高了移动网络的通信质量.     

Fast handoff with reducing waste rate approach for wireless resources management in UMTS mobile networks

3G Wideband CDMA systems adopt the Orthogonal Variable Spreading Factor code tree as the channelization codes management for achieving high data rate transmission in personal multimedia communications. It assigns a single channelization code for each accepted connection. Nevertheless, it wastes the system capacity when the required rate is not powers of two of the basic rate. One good solution is to assign multiple codes for each accepted connection but it causes two inevitable drawbacks: long handoff delay and new call setup delay due to high complexity of processing with multiple channelization codes, and high cost of using more number of rake combiners. Especially, long handoff delay may result in more call dropping probability and higher Grade of Service, which will degrade significantly the utilization and revenue of the 3G cellular systems. Therefore, we propose herein an adaptive efficient codes determination algorithm based on the Markov Decision Process analysis approach to reduce the waste rate and reassignments significantly while providing fast handoff. Numerical results demonstrate that the proposed approach yields several advantages, including the lowest GOS, the least waste rate, and the least number of reassignments. Meanwhile, the optimal number of rake combiners is also analyzed in this paper. This research was supported in part by the National Science Council of Taiwan, ROC, under contract NSC-93-2213-E-324-018.     

动态路由模拟策略研究

网络模拟路由策略的基本目标是真实地反映模拟数据包的转发过程。拓扑变化会影响路由选择结果。现：有模拟器在处理动态路由时会让所有节点同时感知到拓扑变化信息，这与实际网络中的情况并不相符。给出并分析动态路由模拟抽象模型，进而提出计算不同节点对拓扑变化感知时间的策略；提出动态MTree_Nix路由策略，以静态路由表和拓扑变化消息序列作为动态路由表，通过比较节点的感知时间查找路由。实验结果表明，此算法能够更真实地模拟网络中的动态路由，并且具有较高的模拟效率。     

快速层次移动IPv6的乒乓切换研究

针对现有的预测式FMIPv6(快速移动IPv6)没有提供域内乒乓切换机制,因而可能导致大量远程注册开销和系统通信开销的问题,在FMIPv6的基础上引入HMIPv6(分层移动IPv6)层次结构,提出了一种基于FHMIPv6(快速层次移动IPv6)的乒乓切换优化方案。分析结果表明,与FHMIPv6相比,所提方案在乒乓切换模式下能够有效减少时延和丢包率,进一步提高吞吐量。     

Optimization of the transmission mechanism for wireless TCP

A novel method which can detect the possible handoffs for mobile nodes is proposed in this article. The method can be deployed on mobile nodes. So when a possible handoff occurs, mobile nodes can detect and take some necessary actions in time. In this study, the method is also used to optimize the transmission mechanism of Q-TCP. Moreover, the simulation results show that Q-TCP can provide better quality of service （QoS） for mobile nodes when they are moving among different agents.