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On the behavior of different TCP algorithms over a wireless channel with correlated packet losses

performance Evaluation Review 1999年第1期27卷 155-165页

作者： Anjum, Farooq Tassiulas, Leandros ISR Dept. of Electrical Engg. Univ. of Maryland College Park MD United States

In this paper, we investigate the behavior of the various algorithms of TCP, the internet data transport protocol, over wireless links with correlated packet losses. For such a scenario, we show that the performance of NewReno is worse than the performance of Tahoe in many situations and even OldTahoe in a few situations on account of the inefficient fast recovery method of NewReno. We also show that random loss leads to significant throughput deterioration when either the product of the square of the bandwidth-delay ratio and the loss probability when in the good state exceeds 1 or the product of the bandwidth-delay ratio and the packet success probability when in the bad state is less than two. The performance of Sack is always seen to be the best and the most robust thereby arguing for the implementation of TCP SACK over the wireless channel. We also show that under certain conditions the performance depends not only on the bandwidth-delay product but also on the nature of timeout whether coarse or fine. We have also investigated the effects of reducing the fast retransmit threshold.

关键词： network protocols Algorithms Bandwidth Communication channels (information theory) Correlation theory internet Packet switching Wireless telecommunication systems Correlated packet losses Transmission control protocol (TCP)

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Enterprise network control and management: Traffic flow models

Enterprise network control and management: Traffic flow mode...

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conference on Multimedia systems and Applications ii

作者： Maruyama, W George, M Hernandez, E LoPresto, K Uang, Y Lockheed Martin Mission Syst Interact Technol Ctr Sunnyvale CA 94089 USA

ISBN: (纸本)0819434388

The exponential growth and dramatic increase in demand for network bandwidth is expanding the market for broadband satellite networks. It is critical to rapidly deliver ubiquitous satellite communication networks that are differentiated by lower cost and increased Quality of Service (QoS). There is a need to develop new network architectures, control and management systems to meet the future commercial and military traffic requirements, services and applications. The next generation communication networks must support legacy and emerging network traffic while providing user negotiated levels of QoS. network resources control algorithms must be designed to provide the guaranteed performance levels for voice, video and data having different service requirements. To evaluate network architectures and performance, it is essential to understand the network traffic characteristics.

关键词： network management traffic flows bandwidth QoS network protocols packet distributions SNMP RMON TCP UDP HTTP FTP

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Statistical evaluation and modelling of internet dial-up traffic

Statistical evaluation and modelling of Internet dial-up tra...

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conference on performance and control of network systems iiI

作者： Färber, J Bodamer, S Charzinski, J Univ of Stuttgart Stuttgart Germany

ISBN: (纸本)0819434345

In times of internet access being a popular consumer application even for "normal" residential users, some telephone exchanges are congested by customers using modem or ISDN dial-up connections to their internet Service Providers (ISPs). In order to estimate the number of additional lines and switching capacity required in an exchange or a trunk group, internet access traffic must be characterized in terms of holding time and call interarrival time distributions. In this paper, we analyse log files tracing the usage of the central ISDN access line pool at University of Stuttgart for a period of six months. Mathematical distributions are fitted to the measured data and the fit quality is evaluated with respect to the blocking probability caused by the synthetic traffic in a multiple server loss system. We show how the synthetic traffic model scales with the number of subscribers and how the model could be applied to compute economy of scale results for internet access trunks or access servers.

关键词： internet traffic modelling ISDN access trace evaluation

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Nonlinear adaptive inverse control via the unified model neural network

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3722卷 153-162页

作者： Jeng, Jin-Tsong Lee, Tsu-Tain Hwa-Hsia Coll of Technology and commerce Chung-Ho City Taiwan

In this paper, we propose a new nonlinear adaptive inverse control via a unified model neural network. In order to overcome nonsystematic design and long training time in nonlinear adaptive inverse control, we propose the approximate transformable technique to obtain a Chebyshev Polynomials Based Unified Model (CPBUM) neural network for the feedforward/recurrent neural networks. It turns out that the proposed method can use less training time to get an inverse model. Finally, we apply this proposed method to control magnetic bearing system. The experimental results show that the proposed nonlinear adaptive inverse control architecture provides a greater flexibility and better performance in controlling magnetic bearing systems.

关键词： Feedforward neural networks

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TCP-friendly rate adjustment protocol for continuous media flows over best effort networks

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performance Evaluation Review 1999年第1期27卷 220-221页

作者： Padhye, Jitendra Kurose, Jim Towsley, Don Koodli, Rajeev University of Massachusetts Amherst MA 01002 United States Nokia Research Center Burlington MA 01803 United States Nokia Research Center

Due to the close interaction between transport control protocols (TCP) congestion control and error control, TCP itself can not be used for continuous media (CM) applications. However, by taking a formula-based approach towards CM congestion control, differentiated services can be realized in which CM flows compete only against one another, and not against TCP. To this end, a TCP-friendly rate adjustment protocol, called CMTCP, is developed for continuous media flows over best-effort channel. TCP-friendliness is achieved by changing the sending rate, corresponding to measured loss rate and roundtrip times. Simulation and prototype tests show a throughput close to that of a TCP connection traveling over the same network path.

关键词： network protocols Algorithms Computer simulation Congestion control (communication) Data communication systems internet Telecommunication networks Telecommunication services Telecommunication traffic Best effort networks Continuous media networks Rate adjustment congestion control protocols

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Virtual Personal Computers and the Portable network 18

Virtual Personal Computers and the Portable Network

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18th IEEE International performance, Computing and Communications conference

作者： Duran, JW Laubach, A Motorola SPS Portable Network Project Austin TX USA

ISBN: (纸本)0780352599

Three categories of remote computing (client/server) in use and development today are the network Computer (Java), the Web Browser interface and Remote Screen/Keyboard. The Remote Screen/Keyboard model offers the greatest flexibility the 'thinnest clients': and the strongest immunity to the need for upgrades to users' terminals. It also allows the use of lightweight, ultra-portable, wireless terminals while still providing access to the most complex applications (including internet access, corporate information systems, and E-mail), and to all the files normally available from a user's desktop computer. The terminals control users' Virtual Personal Computers, which reside an sewers in the network. The authors have constructed a test system with which users satisfy their computing needs using terminals ranging from one to sir pounds, connected by a variety of wireless and wireline means. performance and usage statistics collected so far, along with coming wireless packet data systems, suggest that the Virtual Personal Computer/Portable network model is attractive to users and Mill soon be economically viable.

关键词： Personal computers

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Sensory based expert monitoring and control

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Proceedings of SPIE - The International Society for Optical Engineering 1999年 3722卷 122-133页

作者： Yen, Gary G. Oklahoma State Univ Stillwater United States

A new algorithm based on fuzzy neural networks called Incremental Learning Fuzzy Neuron network (ILFN) was developed for pattern classification. To demonstrate the performance of the resulting classifier, simulation was carried out using the Westland vibration data set. Comparisons between the ILFN and some existing methods showed that in terms of classification performance, the ILFN is competitive with or even better than many well-known classifiers. Results from the simulation studies show that the real-time and on-line ILFN classifier is efficient for fault classification and identification in machine condition monitoring.

关键词： Expert systems

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Spoken language interface for a network management system

Spoken language interface for a network management system

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conference on Multimedia systems and Applications ii

作者： Remington, R Lockheed Martin Mission Syst Interact Technol Ctr Sunnyvale CA 94089 USA

ISBN: (纸本)0819434388

Leaders within the Information Technology (IT) industry are expressing a general concern that the products used to deliver and manage today's communications network capabilities require far too much effort to learn and to use, even by highly skilled and increasingly scarce support personnel. The usability of network management systems must be significantly improved if they are to deliver the performance and quality of service needed to meet the ever-increasing demand for new internet-based information and services. Fortunately, recent advances in spoken language (SL) interface technologies show promise for significantly improving the usability of most interactive IT applications, including network management systems. The emerging SL interfaces will allow users to communicate with IT applications through words and phases - our most familiar form of everyday communication. Recent advancements in SL technologies have resulted in new commercial products that are being operationally deployed at an increasing rate. The present paper describes a project aimed at the application of new SL interface technology for improving the usability of an advanced network management system. It describes several SL interface features that are being incorporated within an existing system with a modern graphical user interface (GUI), including 3-D visualization of network topology and network performance data. The rationale for using these SL interface features to augment existing user interfaces is presented, along with selected task scenarios to provide insight into how a SL interface will simplify the operator's task and enhance overall system usability.

关键词： spoken language interface speech recognition natural language interface human computer interface network management systems multi-modal user interface usability information appliances

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Optimization of connection oriented, mobile, hybrid network systems

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1999年第2期17卷 373-384页

作者： ElBatt, TA Ephremides, A Univ Maryland Dept Elect Engn College Pk MD 20742 USA

In this paper, we consider the extension of a cellular system by means of satellite channels. Specifically, we consider an area covered by a number of cells, that is also covered by a number of spot beams. We consider connection-oriented service, and call durations are assumed to be exponentially distributed. Also, users are mobile and, as such, they may cross cell and/or spot-beam boundaries, thus necessitating handoffs, We incorporate the possibility of call dropping due to unsuccessful hand-off attempts, in addition to satellite propagation delays along with the probability of new call blocking, and formulate a specific multifaceted cost function that must be ultimately minimized. The minimization is to be carried out by choosing: 1) the optimal partitioning of channels between the cellular and the satellite systems, and ii) the call admission and assignment policy, subject to the constraints of a demand vector that consists of an exogenous (new-call) generation process and an internal (handoff-based) process that results from the mobility model, Two subproblems of this complex optimization problem are solved by means of numerical techniques and by means of so-called standard clock simulation techniques. In this solution method, we employ the ordinal optimization approach which focuses on preserving the performance rank, rather than the performance prediction of the different control policies. We find that the "double" coverage, through both cellular and satellite resources, results in substantial improvement over pure terrestrial or pure satellite systems for parameter values that correspond to practical environments.

关键词： Blocking probability call assignment channel allocation dropping probability hybrid mobile networks optimization

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ATM-based TH-SSMA network for multimedia PCS

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1999年第5期17卷 824-836页

作者： Win, MZ Qiu, XX Scholtz, RA Li, VOK AT&T Labs Res Newman Springs Lab Wireless Syst Res Dept Red Bank NJ 07701 USA Univ So Calif Dept Elect Engn Inst Commun Sci Los Angeles CA 90089 USA Univ Hong Kong Dept Elect & Elect Engn Hong Kong Peoples R China Univ Hong Kong Versitech Ltd Hong Kong Peoples R China

Personal communications services (PCS) promise to provide a variety of information exchanges among users with any type of mobility, at any time, in any place, through any available device, To achieve this ambitious goal, two of the major challenges in the system design are: i) to provide a highspeed wireless subsystem with large capacity and acceptable quality-of-service (QoS) and ii) to design a network architecture capable of supporting multimedia traffic and various kinds of user mobility. A time-hopping spread-spectrum wireless communication system called ultra-wide bandwidth (UWB) radio is used to provide communications that are low power, high data rate, fade resistant, and relatively shadow free in a dense multipath environment. Receiver-signal processing of UWB radio is described, and performance of such communications systems, in terms of multiple-access capability, is estimated under ideal multiple-access channel conditions. A UWB-signal propagation experiment is performed using the bandwidth in excess of 1 GHz in a typical modern office building in order to characterize the UWB-signal propagation channel. The experimental results demonstrate the feasibility of the UWB radio and its robustness in a dense multipath environment. In this paper, an ATM network is used as the backbone network due to its high bandwidth, fast switching capability, flexibility, and well-developed infrastructure. To minimize the impact caused by user mobility on the system performance, a hierarchical network-control architecture is postulated. A wireless virtual circuit (WVC) concept is proposed to improve the transmission efficiency and simplify the network control in the wireless subsystem. The key advantage of this network architecture and WVC concept is that the handoff can be done locally most of the time, due to the localized behavior of PCS users.

关键词： ATM broadband network multimedia multiple access personal communications services (PCS) spread spectrum time-hopping UWB radio

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