A novel dynamic Multiple Ring-based Local Restoration for point-to-multipoint multicast traffic in WDM mesh networks

Optical networks with DWDM (Dense Wavelength Division Multiplex) can provide multiple data channels to supply high speed, high capacity to perform bandwidth-intensive multicast transmission service. Light-tree is a popular technique applied to support point-to-multipoint multicast services. Any failure during a multicast session would cause severe service loss or disruptions, especially when the faults occur near the source node. A novel ring-based local fault recovery mechanism, Multiple Ring-based Local Restoration (MRLR), for point-to-multipoint multicast traffic based on the minimum spanning tree (MST) in WDM mesh networks is proposed in this article. The MRLR mechanism dismembers the multicast tree into several disjoint segment-blocks (sub-trees) and reserves preplanned spare capacity to set up multiple protection rings in each segment-block for providing rapid local recovery. The MRLR scheme outperforms other methodologies in terms of the blocking probability, recovery time, and average hop count of protection path per session for different network topologies.     

Code sectoring methods in CDMA-based broadband point-to-multipoint networks

Code sectoring methods in broadband wireless point-to-multipoint (PMP) networks applying code-division multiple access (CDMA) are discussed in this paper. Interference reduction is the key factor in PMP network design, therefore antenna- and frequency-sectoring solutions are commonly applied. CDMA allows code sectoring strategies, moreover advanced interference suppression techniques (e.g., multiuser detection) can be utilized. The combination of different sectoring schemes and multiuser receivers in a CDMA-based PMP network provides the effective control of interference. In this study different CDMA code sectoring approaches are proposed and downlink interference analyses of a PMP network sector are presented.     

Estimating point-to-point and point-to-multipoint traffic matrices: an information-theoretic approach

Traffic matrices are required inputs for many IP network management tasks, such as capacity planning, traffic engineering, and network reliability analysis. However, it is difficult to measure these matrices directly in large operational IP networks, so there has been recent interest in inferring traffic matrices from link measurements and other more easily measured data. Typically, this inference problem is ill-posed, as it involves significantly more unknowns than data. Experience in many scientific and engineering fields has shown that it is essential to approach such ill-posed problems via "regularization". This paper presents a new approach to traffic matrix estimation using a regularization based on "entropy penalization". Our solution chooses the traffic matrix consistent with the measured data that is information-theoretically closest to a model in which source/destination pairs are stochastically independent. It applies to both point-to-point and point-to-multipoint traffic matrix estimation. We use fast algorithms based on modern convex optimization theory to solve for our traffic matrices. We evaluate our algorithm with real backbone traffic and routing data, and demonstrate that it is fast, accurate, robust, and flexible.     

基于无线传感器网络的车流量检测系统设计

由于城市中车辆增多,车流量检测在现代交通中已成为重要的一部分。掌握车流量信息,可以了解路面状况从而对做出合理决策有极大的帮助。如何准确实时地得到车流量数据成为道路交通的显著要求,本文中用TI公司的CC2530作为核心处理器单元,通过在主要路段设置热释电红外传感器检测节点,用ZigBee无线传输技术构建无线传感器网络,来实现对车流量的准确检测。本文网络版地址：http：//www.eepw.com.cn/article/276361.htm     

一种点对多点红外通信协议设计与实现

介绍一种基于转发机制的点对多点红外线通信协议设计方法。该方法采用采用轮询方式实现一个主控节点和多个从节点无线通信,当主控节点与某个从节点不能直接通信时,主控节点会选择一个能与之双方直接通信的第三方节点,通过第三方节点转发数据实现二者通信。数据传输时,节点与节点之间采用发送确认帧和超时重发策略。实验并在智能家居系统中验证了该协议能实现半径30m范围无线传感器节点数据可靠传输。     

The design and installation of the Cleveland,Ohio point-to-multipoint CATV fiber-optic transport system

Analog fiber-optic transmission system use is becoming commonplace and widespread for point-to-point CATV programme channel trunking applications. Owing to improvements in single-mode fiber, device technologies and availability of single-mode optical splitter/couplers, it is now technically and economically feasible to implement point-to-multipoint CATV trunking systems. This paper will describe the Cleveland, Ohio point-to-multipoint fiber-optic transport system design, the pros and cons of analog FM versus digital systems, the fiber plant and the end-to-end performance of the installed fiber-optic system. The multichannel FM/FDM fiber-optic system deployed by The Ohio Bell Telephone Company (OBT), an Ameritech company, was manufactured and installed by Catel Telecommunications, Inc. of Fremont, California.     

一种新的用于ATM网中ABR点对多点连接的反馈合并算法

本文提出了一种新的用于ＡＴＭ网中的ＡＢＲ点对多点连接的反馈合并算法。新算法不仅能同时解决“合并噪声”和“合并延迟”问题,而且由于提供一种根据反向资源管理信元的ＣＩ域判断支路拥塞程度的机制,因此即使在ＥＲ交换机与二进制交换机并存的网络环境中仍然性能优越,这是现有算法所无法做到的。我们的仿真结果清楚地表明了这一点。     

Constrained light-tree design for WDM mesh networks with multicast traffic grooming

Multicast applications such as IPTV, video conferencing, telemedicine and online multiplayer gaming are expected to be major drivers of Internet traffic growth. The disparity between the bandwidth offered by a wavelength and the bandwidth requirement of a multicast connection can be tackled by grooming multiple low bandwidth multicast connections into a high bandwidth wavelength channel or light-tree. Light-trees are known to be especially suited for networks that carry ample multicast traffic. In this paper, we propose new algorithms to address the problem of multicast traffic grooming. In particular, an Integer Linear Programming (ILP) formulation is proposed for optimal assignments of hop constrained light-trees for multicast connections so that network throughput can be maximized. Hop constrained light-trees improve the scalability of the approach by reducing the search space of the ILP formulation. Since solving the ILP problem is very time consuming for realistically large networks, we are motivated to propose a heuristic algorithm with a polynomial complexity, called Dividable Light-Tree Grooming (DLTG) algorithm. This algorithm is based on grooming traffic to constrained light-trees and also divides a light-tree to smaller constrained light-trees on which traffic is groomed for better resource utilization. Simulations show that the proposed DLTG heuristic performs better than other algorithms. It achieves network throughputs which are very close to the ILP formulation results, but with far lower running times.     

Logical topology design for dynamic traffic grooming in WDM optical networks

Traffic grooming in optical networks refers to consolidation of subwavelength client connections onto lightpaths. Depending on whether client connections are given in advance or randomly arrive/depart, traffic grooming is classified as static and dynamic. Dynamic traffic grooming has been traditionally performed through establishing/releasing lightpaths online. In this paper, the authors propose an alternate approach to design a static logical topology a priori and then route randomly arriving client connections on it to avoid frequent lightpath setup/teardown. Two problems are considered: 1) minimize resource usage constrained by traffic blocking requirements and 2) maximize performance constrained by given resources. These are formulated as integer linear-programming (ILP) problems. The numerical results show that the resource usage dramatically decreases when the blocking requirement is relaxed, and the grooming performance slowly increases when given more resources. In addition, the number of ports at client nodes has more profound impact on traffic grooming than the number of wavelengths.     

Algorithms for the global design of WDM networks including the traffic grooming

In this paper, we propose a model and algorithms for the global design problem of wavelength division multiplexing (WDM) networks including the traffic grooming. This problem consists in finding the number of fibres between each pair of nodes (i.e. the physical topology), finding the number of transponders at each node, choosing the set of lightpaths (i.e. the virtual topology), routing these lightpaths over the physical topology and, finally, grooming and routing the traffic over the lightpaths. Since this problem is NP-hard, we propose two heuristic algorithms and a tabu search metaheuristic algorithm to find solutions for real-size instances within a reasonable amount of computational time.     

The effect of IP traffic on WDM-based networks

In this letter me show that when IP traffic is loaded directly over WDM-based networks, the burstiness of the IP packets can have significant effects on the network performance through its influence on the fiber nonlinear effects, mainly the four-wave mixing effect provided the fiber input light power is high, the frequency spacing is narrow and IP traffic load is heavy     

The design of large-scale networks

The application of computer techniques to difficult large-scale network problems is discussed. The physical characteristics of two types of systems are described--computer-communication networks and cable television distribution systems. Two fundamental algorithms are presented, and applications to routing, reliability, and design of computer networks are given. The detailed engineering decisions that can be made by computer in the design of practical large-scale networks are illustrated by example for cable television systems. These examples are chosen to indicate the richness and difficulty of the problem of applying computers to network design.     

The distributed robust traffic controller for ATM networks

We propose an approach to design a distributed rate‐based traffic controller to flow‐regulate the best‐effort service (e.g. ABR) traffic and guaranteed service traffic through an ATM switch. The controller is distributed among the source nodes and has a very simple structure. Its local controller at each source node is open‐loop stable and only requires the knowledge of the buffer occupancy at the bottleneck switch. We show that this controller is fair and is not sensitive to the change of VCs over time. It does not have oscillation and can achieve a high utilization. Copyright © 2001 John Wiley & Sons, Ltd.     

Robust design of communication systems: The case of expedited forwarding of voice traffic in differentiated services networks

Design of experiments (DOE) is gaining acceptance in the community of telecommunication researchers, especially during the past several years. In this paper, a state‐of‐the‐art review on the use of DOE in the field of communication networks is presented, and the need for introducing a systematic robust design methodology to network simulations or testbed experiments is identified in ensuring robust behaviours of a network against uncontrollable sources of variation. Then, the Taguchi robust design methodology is applied for optimizing the expedited forwarding (EF) of voice traffic in a differentiated services network, and its step‐by‐step procedures are described in detail. The experimental data are collected using the ns‐2 simulator, and the SN ratio, a robustness measure, is analysed to determine an optimal design condition for each performance characteristic. The analysis results show that ‘type of queue scheduling schemes’ is a major control factor for ensuring robust behaviours of one‐way delay and jitter while ‘EF queue size’ is for throughput and loss rate. Finally, a compromised optimal design condition is identified using a desirability function approach adapted to multi‐characteristic robust design problems. Copyright © 2007 John Wiley & Sons, Ltd.     

Virtual topology design and flow routing in optical networks under multihour traffic demand

This article addresses the problem of finding a static virtual topology design and flow routing in transparent optical wavelength division multiplexing networks under a time-varying (multihour) traffic demand. Four variants of the problem are considered, using fixed or dynamically adaptable (meaning variable) flow routing, which can be splittable or unsplittable. Our main objective is to minimize the number of transceivers needed which make up for the main network cost. We formulate the problem variants as exact integer linear programs (ILPs) and mixed ILPs. For larger problem instances, we also propose a family of heuristics based on the concept of domination between traffic matrices. This concept provides the theoretical foundations for a set of techniques proposed to reduce the problem complexity. We present a lower bound to the network cost for the case in which the virtual topology could be dynamically reconfigured along time. This allows us to assess the limit on the maximum possible benefit that could be achieved by using optical reconfigurable equipment. Extensive tests have been conducted, using both synthetically generated and real-traced traffic demands. In the cases studied, results show that combining variable routing with splittable flows obtains a significant, although moderate, cost reduction. The maximum cost reduction achievable with reconfigurable virtual topologies was shown to be negligible compared to the static case in medium and high loads.     

The design of survivable directed networks

We study a survivable network design problem:the directed network design problem with connectivity constraints (DNCC). Some applications in telecommunications are presented. We discuss two integer linear programming models for DNCC, and relate these. The main body of the paper is a study of DNCC from a polyhedral point of view. We give several classes of nonredundant inequalities for polytopes associated with the problem. A cutting plane algorithm based on the polyhedral results is described and some computational results are given.     

The benefits of wavelength conversion in WDM networks withnon-Poisson traffic

The effects of wavelength conversion on wavelength routing optical networks with dynamic non-Poisson traffic are investigated. A model that characterizes any non-Poisson traffic by its first two moments is utilized. The arrival occupancy distribution of busy wavelengths for this model process is derived and is used to analyze the effects of wavelength conversion. The model predicts that traffic peakedness plays an important role in determining the blocking performance     

The use of priorities on token-ring networks for multimedia traffic

The authors consider the transport of multimedia traffic on a token-ring LAN. In order to guarantee acceptable QoS for multimedia traffic, resource management is required to insure that sufficient capacity from all shared resources is allocated to the priority traffic. Once a multimedia session is accepted and resources have been allocated, the next task is to insure that the high priority multimedia traffic actually obtains the resources which have been allocated to it     

Neural networks applied to traffic management in telephone networks

In this paper the application of neural networks to some of the network management tasks carried out in a regional Bell telephone company is described. Network managers monitor the telephone network for abnormal conditions and have the ability to place controls in the network to improve traffic flow. Conclusions are drawn regarding the utility and effectiveness of the neural networks in automating the network management tasks     

Neural networks for adaptive traffic control in ATM networks

Neural networks (NNs) have several valuable properties for implementing ATM traffic control. The authors present NN-based solutions for two problems arising in connection admission control, affecting the grade of service (GOS) at both the cell and call levels, and propose that neural networks may increase the network throughput and revenue