A Lagrangean relaxation approach for QoS networks CFA problems

This paper is about design methodologies for packet networks, under the constraints of end-to-end quality of service (QoS) metrics. The network modeling also considers the dynamics of today's packet networks. We are particularly considering the problem of capacity and flow assignment where the routing assignments and capacities are considered to be decision variables. An efficient Lagrangean relaxation-based heuristic procedure is developed to find bounds and solutions for a corporate virtual private network (VPN), where the traffic is mostly based on TCP connections. Numerical results for a variety of problem instances are reported.     

Lagrangean Based Methods for Solving Large-Scale Cellular Network Design Problems

The cellular network design (CND) problem is formulated as a comprehensive linear mixed integer programming model integrating the base station location (BSL) problem, the frequency channel assignment (FCA) problem and the topological network design (TND) problem. A solution algorithm based on Lagrangean relaxation is proposed for solving this complex cellular network design problem. Pursuing the optimum solution through exact algorithms to this problem appears to be unrealistic considering the large scale nature and NP-hardness of the problem. Therefore, the solution algorithm strategy consists in computing effective lower and upper bounds for the problem. Lower bounds are evaluated through a Lagrangean relaxation technique and subgradient method. A Lagrangean heuristic is developed to compute upper bounds based on the Lagrangean solution. The bounds are improved through a customized branch and bound algorithm which takes in account specific knowledge of the problem to improve its efficiency. Thirty two random test instances are solved using the proposed algorithm and the CPLEX optimization package. The results show that the duality gap is excessive, so it cannot guarantee the quality of the solution. However, the proposed algorithm provides optimal or near optimal solutions for the problem instances for which CPLEX also provides the optimal solution. It further suggests that the proposed algorithm provides optimal or near optimal solutions for the other instances too. Finally, the results demonstrate that the proposed algorithm is superior to CPLEX as a solution approach for the CND problem.     

Hierarchical Ring Network Design Using Branch-and-Price

We consider the problem of designing hierarchical two layer ring networks. The top layer consists of a federal-ring which establishes connection between a number of node disjoint metro-rings in a bottom layer. The objective is to minimize the costs of links in the network, taking both the fixed link establishment costs and the link capacity costs into account.Hierarchical ring network design problems combines the following optimization problems: Clustering, hub selection, metro ring design, federal ring design and routing problems. In this paper a branch-and-price algorithm is presented for jointly solving the clustering problem, the metro ring design problem and the routing problem. Computational results are given for networks with up to 36 nodes.     

基于软交换的下一代网络体系结构

软交换的出现是传统电信话音网络走向开放体系架构的发展结果。它在下一代网络的呼叫与控制中将起到核心作用。本文介绍了软交换技术的产生背景，分析了基于软交换的开放网络体系结构，把软交换网络与传统电信网络进行了比较，指出软交换将在下一代网络的演进发展中起到关键性的作用。     

双归属环形网络拓扑规划算法设计

本文研究了一种高效的双归属环形网络拓扑规划算法,提出了在满环与非满环间调整节点的启发式搜索算法,当节点数在1 500个以内时,本算法都能很快求解,而现有算法通常只能处理几百个节点的中等规模网络.本文首先给出了相关数学模型,然后详述了初始拓扑生成过程及采用的启发式优化算法.最后通过将CPLEX规划结果、人工规划结果和算法规划进行比对,验证算法性能.     

NGN和软交换

文章介绍了下一代网络(NGN)的标准化进程和基于软交换的网络演进,探讨了软交换与IP多媒体子系统(IMS)的关系.文章认为运营商在面对网络演进时需要采用平滑过渡的手段,所以对新的网络设备提出了新的要求:对于核心网络,运营商希望能够支持多种流量、多种业务,具有丰富的协议、大容量和高性能;对于边缘网络,运营商要求具有丰富的接口能力;对于业务,运营商希望提供灵活有效的业务平台和用户可接受的新型终端设备;对于网络管理和维护,运营商则需要智能化的管理体系.     

基于软交换的下一代网络组网结构

下一代网络将是基于软交换系统的通信网络。在研究各种软交换系统互联机制的基础之上,结合软交换基于IP网络构建、信令与媒体分离等特点提出了基于软交换系统的下一代网络中可以采用的各种组网结构,比较了各种方式的优缺点,指明了其适用范围。最后给出了现有通信网向下一代通信网络演进过程中网络体系结构的演进方案。     

期待中的下一代网

下一代网是一个正在探索中的问题。本文从以下视角探讨了下一代网：提出下一代网的时代背景，什么是下一代网，下一代网中的三个世界，发展下一代网的主要驱动力和障碍，下一代网的初期发展情况，对下一代网的市场预测，在下一代网上开展哪些服务，下一代网运营商如何对它们提供的服务定价，发展下一代网需要新的管制框架和建立战略伙伴关系。     

Lagrangean relaxation for service location in large‐scale networks with QoS constraints

Current trends in computing indicate that there is a great potential for service‐oriented computing and similar technologies, such as application‐oriented networks (AONs), where services can relocate to adapt to the conditions of the underlying network. In such environments, providing and consuming services and establishing a relationship between consumers (users of services) and producers (providers of services) are still challenging and vastly researched aspects. Bearing this in mind, we define a service location and planning (SLP) problem that uniquely matches producers to consumers and accounts for realistic parameters such as, quality of service (QoS) constraints of throughput and delay, and network constraints of underlying link layer bandwidth capacities, and cost of meeting consumer requests. Our contribution lies in the mathematical formulation of the SLP problem as an integer linear programming (ILP) problem that can be solved optimally for small‐scale networks and extending this work using Lagrangean relaxation (LR) approximation techniques to solve the SLP problem for large‐scale networks. Copyright © 2009 John Wiley & Sons, Ltd.     

利用网络处理器构建弹性分组环模块

弹性分组环作为解决城域网的问题的一个方案被提出后,迅速成为研究的热点,但专用的RPR芯片还未商品化。提出了一种利用不支持RPR协议的网络处理器借助协议转换器来构建RPR模块的设计方案。协议转换器的主要功能是RPR/Ethernet帧转换和接口转换。文章介绍了RPR模块的结构和功能,并讨论了协议转换器的实现。     

下一代网络业务体系架构研究

本文提出了一种应用于下一代网络的面向服务的业务体系架构。该架构的优势在于：通过开放业务能力实现了业务应用的灵活创建,从而缩短了业务生成周期,降低了开发成本;同时,通过引入面向服务的思想进行开放能力互联大大增加了业务网的健壮性。     

基于仿真的复杂通信网络设计方法

随着现代通信网络规模扩大化以及网络的结构复杂化,传统的网络设计方法越来越难以满足复杂通信网设计的需要,将网络仿真建模和分析与复杂通信网络设计相融合,给出了基于仿真的复杂通信网络设计流程,为复杂通信网络设计提供了一个定量分析和设计的方法。基于仿真的网络设计方法以网络指标需求为目标,采用循环递推的方式,反复修正网络设计,最终获得一个满足网络指标需求的最优网络设计方案。     

新一代城域MSTP解决方案

在城域网领域随着企业和城市家庭用户对高宽带业务需求的增加，现有的城域网络资源的利用已达到了极限，无法广泛提供充足且高性价比的宽带资源，因此形成了“宽带瓶颈”，限制了城域领域的信息流通，阻碍了新应用的推广，光桥科技推出的一代解决方案将突破这个瓶颈，近一步降低运营成本。     

基于IP的第三代移动通信系统的网络平台结构

研究未来基于IP的第三代移动通信系统的网络平台。首先讨论第三代移动通信系统业务和网络能力需求；然后给出基于IP的第三代移动通信系统的网络平台（IP^2)的一般结构。     

下一代网络技术

简要论述了下一代网络结构、功能和特点 ,分别介绍了在下一代网络中起重要作用的DWDM、MPLS、软交换、IPv6等技术。     

基于IP技术的下一代电信网

关于下一代电信网的话题已成为当前电信行业的一个热点。因此首先介绍了下一代电信网的演进策略和体系架构，然后介绍了下一代电信网的关键技术及其主要特点，最后指出了下一代电信网中有待解决的一些问题。     

下一代网络提供业务的方式

本对目前网络提供业务的方式以及下一代网络提供业务的方式进行了介绍，并阐述了下一代网络所提供的业务的特点。     

涡街提频振荡水柱驱动压电发电理论分析

海洋波浪能频率低(0.3～1 Hz),海浪进入振荡水柱气室压缩空气形成高速气流。在高速气流通道内放置绕流圆柱钝体,采用卡门涡街效应提高波浪能振荡水柱采集气室气压激振频率,实现高频驱动压电发电,提高海洋能量转换效率。推导波浪进入气室形成振荡的水气动力转换理论,计算了气室初级压强和流速。分析了低频高压气流经钝体形成卡门涡街高频涡流激振提频过程,计算出气压作用于钹型压电发电结构输出的电量。研究气体流速、钝体等系统参数与输出能量的关系。计算结果表明,周期为0.65～1.1 s的海浪进入气室经提频作用于钹型压电发电结构,稳定输出电能可达70～80 mW,为新型波浪能采集技术提供了理论基础。     

基于EPON的FTTH网络设计与实现

针对用户的不同情况,采用基于EPON的FTTH方案建设宽带接入网络,分别描述了设备选择、组网,并针对具体的业务要求,提出了有针对性的解决方案,同时,还考虑了布线、施工中的注意事项和规范,以及运营商关注的运维方案.     

基于TCP／IP协议的校园网构筑

１９９４年３月国家教委启动了中国教育计算机网络项目。ＣＥＲＮＥＴ将覆盖全国大专院校等教育科研机构，已于１９９４年１０月与国际ｉｎｔｅｒｎｅｔ联网。这样，全国有条件的大学开始了基于Ｉｎｔｅｒｎｅｔ的校园网络建设工作。