在ATM网络中估计QoS的一种算法

文章采用两态的离散Ｍａｒｋｏｖ业务流模型，根据排队长度与业务流系统状态的关联性来计算其总业务流的ＱｏＳ参数，并通过仿真对分析结果进行了验证。     

一种支持QoS的无线MAC协议

WAND（Wireless ATM Network Demonstrate)是欧洲ACTS（Advanced Connunication Technologies and Services)支持的项目之一。在WAND中采用一种基于集线器式、自适应TDMA方式的MAC协议－基于预约和竞争的移动接入ATM方案（MASCARA）,它通过预约与竞争方法,为无线ATM（WATM）终端提供支持QoS的宽带无线接入。通过分析MASCARA议框架结构、各组成单元功能以及MASCARA时间帧结构,阐明了这种WATM MAC协议的优越性。     

一种提供良好QoS保障的Ad Hoc网络MAC协议

为有效减小Ad Hoc网络实时业务节点的信道接入时延,提升对多媒体业务的服务质量(QoS)保障,在研究时隙分配类多址协议的基础上,设计了一种新的基于时隙重构的分组预约协议。新协议时隙结构简单,具有较好的冲突化解能力,通过对空闲数据时隙的重构利用以及层级式的接入控制,取得了较好的时延保障性能。     

一种能有效支持QoS的光突发装配技术

提出了一种新的光突发装配技术，目的在于增强光突发交换(OBS)网络的服务质量(QoS)能力。该技术由自适应门限突发装配算法和基于优先级的随机化的偏移时间设置方案构成。该装配算法特别适合于多类别分组混合装配，能让所有类别的分组公平有效地使用装配能力，能较好地与IP层的QoS机制相匹配。偏移设置方案将突发控制分组(BCP)与突发数据(BP)间的偏移时间分成QoS偏移和随机偏移，前者由改进的JET协议按照有选择性的突发段丢弃机制(BSSD)确定，后者则由令牌桶机制确定。BSSD仅丢弃包含有低类别分组的突发段，而非整个突发。计算机仿真结果表明，本文提出的突发装配技术在性能上具有优越性。     

MANET中一种QoS模型的分析与改进

QoS模型是对QoS的一种综合解决方案.文章就MANET中一种扩展性强的QoS模型INSIGNIA进行了研究与分析,讨论了多种已有的对INSIGNIA模型改进方式的具体过程,总结归纳这些改进中的所要解决的问题和解决效果,考虑控制成本花费和借助路由协议和其他协议层的信息应对动态网络的方式,最后提出了合适的改进解决思路和步骤.     

一种支持QoS的OBS网络数据信道调度协议

综合考虑了突发包所经历跳数和突发包的长度等因素,文章给出了一种新型的支持服务质量(QoS)的光突发交换(OBS)数据信道调度协议--考虑跳数的改进型JET模式下的优先级抢占(H-PPJET)协议.文章在OBS网络环境中对H-PPJET协议进行了仿真,并与JET模式下的优先级抢占(PPJET)协议进行了对比,仿真结果表明,H-PPJET协议改善了网络的吞吐量和丢包率性能.     

OBS网络中一种基于蚁群探测的路由机制

光突发交换技术是最具发展潜力的光交换技术之一,而减少突发丢失是其首要问题。传统的静态路由机制不能随着网络负载的变化而更改路由,不能有效应对动态业务。为此,在研究现有动态负载平衡路由机制的基础上,提出了一种基于蚁群探测的路由机制。蚁群根据节点出度链路上的负载变化选择下一跳节点,当转发到目的节点时收集蚁群探测到的所有备选路径,然后根据备选路径中记录的链路负载选择可使丢包最小的路径,通过选择更加合理的路由,达到减少突发丢失率的目的。仿真结果表明,与其他算法相比,所提出的机制表现出比较好的性能,有效降低至少15%突发丢失率。     

一种基于虚拟突发的OBS网络业务疏导机制

提出了一种基于虚拟突发光突发交换的(OBS)网络业务疏导机制TG-VB(traffic grooming based on virtual burst)。作为一种多粒度动态业务疏导机制,TG-VB将常规突发通过"逻辑汇聚"组成虚拟突发,增大核心网中业务传输粒度;同时,TG-VB根据虚拟突发整体传输、整体调度的特点,为汇聚的常规突发动态地选择最优的共用传输路径。仿真结果表明,与采用传统疏导机制的OBS网络相比,TG-VB能够有效地减轻核心节点的通信处理开销,降低对网络节点端口数量的需求;在相同负载条件下,TG-VB可极大地提高波长信道利用率。     

为实时业务提供QoS保证的MAC机制性能研究

分析的MAC机制在IEEE802．11DCF机制的基础上提供了QoS增强。由于实时业务对时延要求敏感。因而提出的实时业务分析模型并未考虑退避重传。和尽力而为业务相比较。实时业务获得了高的饱和吞吐量和低的接入延时，但是以较高的帧丢失率为代价。为了保证实时业务的QoS要求，使用QoS参数P0．Qos来限制帧丢失率。经过分析得出，在保证帧丢失率上限和最大吞吐量的条件下，可求得最优初始窗口，获得较好的网络性能。     

LOBS网络的QoS分析

网络的服务质量(QoS)是下一代IP over WDM光因特网中一个很重要的问题。光标签突发包交换技术(LOBS)作为一种新出现的光交换技术,必须支持QoS。文章主要介绍了LOBS网络的特点,并回顾和总结了已有的光突发交换(OBS)网络QoS方案,讨论了在LOBS中的QoS准则。     

无线局域网MAC层QoS研究

在分析无线网协议提供QoS保证方面存在的问题的基础上，讨论了IEEE802．11e的两个新的策略：增强的分布式协调功能和混合协调功能。通过对受控竞争机制的分析．指出了IEEE802．11e仍存在的不足及未来的发展方向。     

一种新的自适应负载均衡的QoS多径路由机制

针对MANET中AODV,DSR等典型按需路由协议未考虑负载均衡导致网络拥塞和性能急剧下降的严重不足,提出了新的路由机制-ALBQM(Adaptive Load Balance QOS Multipath).ALBQM主要包括:(1)QoS可用带宽的负载感知模型,减少网络冲突和拥塞;(2)采用最大不相关多径并行通信,自适应分配数据流量,提高数据递交率.基于OPNET网络仿真平台对ALBOM应用于DSR进行性能验证,与DSR及其多径路由SMR相比,在重负载网络中有更好的性能表现-在不增加额外控制开销的条件下提升数据递交率,减少端到端平均延迟及路由错误总数.     

MANET的建模和性能分析

简要介绍了自组织网络相比于传统蜂窝网络的优点和研究难点,阐述了基于IEEE 802.11的移动Ad Hoc网络的MAC层的工作原理并从数学理论上分析了吞吐量,接着介绍了软件建模的流程,并给出了理论与仿真的比较分析,同时获得基于IEEE 802.11的MANET吞吐量的最大值以及达到该最大值时网络所承受的业务量的理论值和实际值。     

一种基于IEEE 802.11的多速率自适应MAC协议

提出了一种新颖的基于连续ACK帧统计信息的IEEE 802.11多速率自适应MAC协议EARF(EnhancedARF),其主要思想是:每一个速率有各自的成功阈值——速率升高的门限值,并且该值根据信道状况(用延时因子量化)动态地变化。协议不需对现有的IEEE 802.11标准做任何修改,因此易于通过编写驱动程序实现。仿真表明在大多数信道条件下,该协议性能较现有的基于ACK帧统计的速率自适应协议如ARF,ARF3-10都有较大的提高。     

MAC Layer Admission Control and Priority Re-allocation for Handling QoS Guarantees in Non-cooperative Wireless LANs

Providing QoS guarantee with appropriate service differentiation in IEEE 802.11 wireless LANs is quite desirable. However, users may be selfish and thus rigorously try to maximize their performance by demanding high services even though the network has already saturated. On the other hand, user misbehaviors such as misuse of priority and over-rate transmission pose further harm to performance of existing flows. These application layer non-cooperation makes successful resource allocation very challenging with existing contention based CSMA/CA channel access. In this paper, we propose a MAC layer coordinated QoS framework of admission control and priority re-allocation for quality of services of real-time applications in wireless LANs. Our focus is on priority based MAC schedulers where each user can set its flow priority in order to receive appropriate level of services. With channel condition information such as available bandwidth and mean delay exchanged among neighboring stations, users can enforce admission control based on the perceived channel status and may re-allocate their priorities to accommodate existing flows as desired. User misbehaviors are identified by estimating the flow transmitting rate and matching priority setting, or even punished by assigning appropriate low priorities. Extensive simulations results show that the proposed framework can effectively coordinate wireless users on keeping reserved transmission rate, using appropriate MAC priority, and allocating sufficient resource. Ming Li received his B.S. and M.S. in Engineering from Shanghai Jiao Tong University, China, in 1995 and 1998, respectively. He is currently a Ph.D. candidate in department of Computer Science, University of Texas at Dallas, where he received M.S. degree in Computer Science in Dec. 2001. His research interest includes QoS schemes for mobile ad-hoc networks and multimedia over wireless networks. B. Prabhakaran is with the faculty of Computer Science Department, University of Texas at Dallas. He has been working in the area of multimedia systems: animation & multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. Dr. Prabhakaran received the prestigious National Science Foundation (NSF) CAREER Award in 2003 for his proposal on Animation Databases. He has published several research papers in various refereed conferences and journals in this area. He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

QoS provisioning for large-scale multi-ap WLANs

Large-scale deployment of IEEE 802.11 wireless LANs (WLANs) with a high density of access points (APs) has become commonplace due mainly to its potential for numerous benefits, such as ubiquitous service coverage, seamless handover, and improved link quality. However, the increased AP density can induce significant channel contention among neighboring cells, thus causing severe performance degradation and throughput imbalance between cells. There have been a plethora of research efforts to improve the WLAN performance, but most of them focused only on single WLAN environments without accounting for inter-cell contention. The de facto QoS-provisioning mechanism for WLANs, i.e., the Enhanced Distributed Channel Access (EDCA), is no exception to this. The EDCA focuses only on inter-flow priority distinction and has not considered the effect of inter-cell contention which significantly restricts its efficiency. This paper presents an enhanced QoS provisioning framework that takes into account inter-cell level differentiation as well as inter-flow level priority, which may be viewed as extension of QoS provisioning from a single-WLAN domain to a multi-WLAN domain. We also propose an architecture for managing multi-AP systems in which a central controller regulates the wireless channel occupancy of APs by adaptively configuring the cell-level QoS parameters. Our extensive simulation results show that the proposed inter-AP cooperative QoS scheme overcomes the limit of legacy 802.11e and provides a high level of fairness in large-scale densely-deployed WLANs.     

A 802.11 Based Slotted Dual-Channel Reservation MAC Protocol for In-Building Multi-Hop Networks

In this paper, we propose a novel slotted Dual-Channel Reservation (DCR) MAC protocol that uses 802.11 primitives for providing both Quality of Service (QoS) and fairness. RTS/CTS handshaking is transmitted on a separated control channel to prevent successive collisions of RTS and CTS packets with existing data transmission. Furthermore, contention for channel access may be initiated by sender as well as receiver depending on the channel status for better fairness. A simple slot reservation algorithm in the data channel provides high efficiency. The main conclusion is that reservation access benefits both delay performance, and efficiency as well as fairness—the reason being that not only an exposed terminal can regain the channel more easily because of dramatically reduced contention (RTS-CTS) traffic, but also a hidden terminal receives less collisions in handshaking since any node winning a slot will quit contending on the control channel. Therefore, it is highly recommended to use reservation access even if the prevailing traffic is data, e.g. TCP. To enhance delay performance, we devise a fake packet repeating mechanism that can reserve the slot for a connection even if the user temporarily has no packets to transmit. Simulations based on key metrics—throughput, fairness index and mean delay are performed to validate the new protocol and quantify its advantages. The limitations of the proposed DCR-802.11 protocol due to need for global clock synchronization and dual channels are also discussed.Jing Zhu received the B.S. and M.Sc. degrees both in electronic engineering from Tsinghua University, Beijing, P. R. China, in 2000 and 2001, respectively, and Ph.D. in electrical engineering from University of Washington (Seattle) in 2004. Currently, he is a research scientist in the Communications Technology Lab at Intel Corp. He is an IEEE member. His main research interest is high-performance wireless networking and its applications, e.g. Internet-on-Move, Digital Home, and Intelligent Transport System, focusing on cross-layer protocol optimization.Sumit Roy received the B. Tech. degree from the Indian Institute of Technology (Kanpur) in 1983, and the M. S. and Ph. D. degrees from the University of California (Santa Barbara), all in Electrical Engineering in 1985 and 1988 respectively, as well as an M. A. in Statistics and Applied Probability in 1988. His previous academic appointments were at the Moore School of Electrical Engineering, University of Pennsylvania, and at the University of Texas, San Antonio. He is presently Prof. of Electrical Engineering, Univ. of Washington where his research interests center around analysis/design of physical and data link layer of communication systems, with a topical emphasis on next generation mobile/wireless networks. He is currently on academic leave at Intel Wireless Technology Lab working on high speed UWB radios and next generation Wireless LANs. His activities for the IEEE Communications Society includes membership of several technical committees and technical program committees for conferences, and he serves as an Editor for the IEEE Transactions on Wireless Communications and Wiley Journal on Wireless Communications and Mobile Computing.     

Ad Hoc网络中提供QoS保障的MAC协议的研究

在Ad Hoc网络中提供QoS保障是一个复杂的系统问题,而MAC协议是上层应用的服务质量能否得到最终保障的一个关键因素.文章阐述了Ad Hoc网络中QoS MAC协议的提出背景,说明了QoS MAC协议的设计策略.详细分析和讨论了在Ad Hoc网络的MAC层提供QoS支持的各种机制及方法.     

Power Management Based Grid Routing Protocol for IEEE 802.11 Based MANET

MANET(Mobile Ad Hoc Network)is a collection of wireless mobile nodes forming a temporary communica-tion network without the aid of any established infrastructure or centralized administration.The lifetime of a MANETdepends on the battery resources of the mobile nodes.So energy consumption may one of important design criterions forMANET.With changing the idle model to sleep model in the grid environment,this paper proposes a new energy-awarerouting protocol.Performance simulation results show that the proposed strategy can dynamic balance the traffic load in-side the whole network,extend the lifetime of a MANET,and without decreasing the throughput ratio.