波长变换器均匀旋转的Mesh—Torus的性能分析

本文主要研究了在WDM的Mesh-Torus中,部分网络节点使用波长转换器能给网络带来的好处。文中比较了在非泊松业务下,波长转换器按二项式分布和均匀分布旋转时在阻塞率、转换增益和公平性方面能带来的好处,证明了波长转换器均匀旋转在链路负荷均匀的情况下的Mesh-Torus中是一种优化配置。     

片上网络中3D拓扑结构的性能评估

3D结构的片上网络(3D NoC)结合了3D集成(3D IC)和NoC技术的优势,相比2D NoC具有更为优越的性能.然而,目前大多数关于3D NoC结构的研究都集中在3D Mesh结构上.介绍了利用NIRGAM仿真器实现的另一种拓扑结构--3D Torus.在均衡负载模式和对称随机负载模式下分析评价了3D Torus网络延迟和吞吐率.结果表明,3D Torus拓扑结构的性能高于3D Mesh结构.     

波长转换对抗毁多光纤网状WDM网络的性能影响

目前研究波长转换器对WDM网络性能影响的文献一般都是针对单光纤网络并且不考虑网络抗毁的要求。该文使用整数线性规划建模和动态系统仿真的方法,分别研究了静态业务和动态业务下,多光纤网状WDM网络在满足抗毁要求时,节点配置波长转换器对网络性能的影响,以此对使用波长转换器获得的好处给出较为全面的结论。     

DWDM网中全光波长转换器的研究

全光波长转换器（AOWC）是未来DWDM网络中关键性器件之一，文章介绍了DWDM网中几种AOWC的实现方法、原理和进展情况，还简单介绍了波长转换器在DWDM网中的最优化放置问题。     

基于光波长转换的光分组交换系统的性能分析与仿真

提出并分析了一种具有波分复用的光分组交换架构中置入波长转换器的模型,在该结构中每个输入线都共享波长转换器,讨论了在均衡和非均衡条件下,网络丢包率和波长转换器数目的关系,仿真结果表明该模型能在降低丢包率的同时又能减少波长转换器的数目.     

一种基于WDM和OCDMA的全光分组网络的阻塞率分析

提出混合波分复用(WDM)和光码分多址(OCDMA)网络结构方案,并建立数学模型讨论该网络结构的阻塞率.通过数学模型分析,使用波长转换器对阻塞率的影响,讨论并比较了几种稀疏波长转换器的算法.仿真结果表明:在尽可能地增加每个波长通道中标签链路的数目的情况下,在部分节点的所有波长放置波长转换器时的网络阻塞率最小.     

波长变换对光网络中阻塞性能的影响

在网状光网络中建立稀疏波长变换模型,定性的计算了有和没有波长转换器网络的阻塞概率。研究了在这两种网络中通道长度对阻塞概率的影响,以及波长转换器对提高网状光网络的阻塞性能的影响。建模结果表明,对大容量的网状网,波长变换器能大大降低网络的阻塞概率,但对一个波长数目不定且业务量接近饱和的网络作用不大。     

基于WDM和OCDM的光分组网络的阻塞率分析

本文介绍了标签转换器和波长转换器的实现原理。光分组网络中不同的节点配置不同的器件直接影响网络的性能，本文研究了仅配置波长转换器或仅配置标签转换器以及混合配置波长转换器和标签转换器时基于WDM和OCDM的光分组网络的阻塞率，为光分组网络的实际应用提供一定的参考价值。     

混合光波长转换在波分复用光网络中的应用

在全光网络中，如何合理利用波长转换来降低光网络的阻塞率是一个非常关键的问题。研究了最新的波长转换体系结构和波长转换手段，提出一种全新的混合波长转换方法，在减少网络中波长转换器个数的同时，维持拥塞概率类似于全波长转换。提出了5种不同的波长转换器使用策略，并利用数值模拟的方法，比较了这5种不同的波长转换器使用策略，分析结果，得出了最小化光网络的阻塞概率的波长转换使用策略。结合混合波长转换和波长转换器使用策略，进一步提出了光网络中优化波长转换器配置的遗传算法，通过对14个节点的美国自然科学基金网(NSF Net)的数值模拟，结果表明它是十分有效的，在减少光网络中波长转换器数量，且不增加光网络波长数量的情况下，基本保持原有网络性能。     

光网络中支持区分业务的损伤感知QoS机制

光网络中物理层损伤会造成明显的信号质量下降。为了保证QoS(服务质量),必须在RWA(路由和波长分配)算法中考虑这些损伤及其引起的变化。文章提出了一种损伤感知的差异化路由与波长算法,并针对规则Mesh网络与Cernet网络进行了数值仿真,结果表明,在满足QoS要求的情况下优先保证网络中高等级业务的波长分配,能降低高等级业务的阻塞率,并能提高网络总体的资源利用率。     

On optimal converter placement in wavelength-routed networks

Wavelength converters increase the traffic-carrying capacity of circuit-switched optical networks by relaxing the wavelength continuity constraints. We consider the problem of optimally placing a given number of wavelength converters on a path to minimize the call-blocking probability. Using a simple performance model, we first prove that uniform spacing of converters is optimal for the end-to-end performance when link loads are uniform and independent. We then show that significant gains are achievable with optimal placement compared to random placement. For nonuniform link loads, we provide a dynamic programming algorithm for the optimal placement and compare the performance with random and uniform placement. Optimal solutions for bus and ring topologies are also presented. Finally, we discuss the effect of the traffic model on the placement decision     

星形波长路由光网络中的波长分配

文章主要研究了网络中心与其它节点之间由两条光纤成双向传输链路的情况，给出了均匀和顾机两种业务条件下网络中所需波长数的理论下限范围，利用图着色理论构造启发式算法解决了星形网络中的波长分配问题，最后通过实际波长分配验证了算法的有效性。     

Design and Analysis of Circular Microstrip Patch Antenna for White Space TV Band Application

The wide range of wireless sensor network applications has made it an interesting subject for many studies. One area of research is the controlled node placement in which the location of nodes is not random but predetermined. Controlled node placement can be very effective when either the price of the sensor nodes is high or the sensor coverage is of a specific type and it is necessary to provide special characteristics such as coverage, lifetime, reliability, delay, efficiency or other performance aspects of a wireless sensor network by using the minimum number of nodes. Since node placement algorithms are NP-Hard problems, and characteristics of a network are often in conflict with each other, the use of multi-objective evolutionary optimization algorithms in controlled node placement can be helpful. Previous research on node placement has assumed a uniform pattern of events, but this study shows if the pattern of events in the environment under investigation is geographically dependent, the results may lose their effectiveness drastically. In this study, a controlled node placement algorithm is proposed that aims to increase network lifetime and improve sensor coverage and radio communication, assuming that the event pattern is not uniform and has a geographical dependency. The proposed placement algorithm can be used for the initial placement or, for repairing a segmented network over time. In this study, multi-objective evolutionary optimization algorithms based on decomposition (MOEA/D) have been used, and the performance results have been compared with other node placement methods through simulation under different conditions.

     

一种波长转换范围受限全光网中的波长分配算法

本文研究了波长转换范围受限全光网中的动态路由和波长分配问题,提出了一种固定备选路由条件下新的路由和波长分配算法.算法引入了波长相关性的概念,用波长关联权值定量描述了各路由的前后链路上不同波长之间的相互依赖关系.在建立连接时首先使用那些依赖性强,对其他路由影响小的波长,从全局的角度出发选择最优的路由和波长分配方案.计算机仿真表明,本文算法能够适用于稀疏网络和网状网,在均匀业务强度或者大部分业务量来自于长跳路由的情况下,本文算法能够显著降低网络阻塞概率和使用的波长转换器数目,有效提高系统性能.     

Reliability and routability consideration for MCM placement

This paper presents a methodology based on the fuzzy logic approach for the placement of the power dissipating chips on the multichip module substrate. Our methodology considers both thermal distribution and routing length constraints during multichip module placement. In this paper, the main design issue is the coupled placement for reliability and routability. The objective of the coupled placement is to enhance the system performance and reliability by obtaining an optimal cost during multichip module placement. For reliability considerations, the design methodology is addressed on the placement of the power dissipating chips to achieve uniform thermal distribution. The thermal placement analysis is based on the modified fuzzy force-directed placement method. Placement for routability is based on minimizing the total wire length estimated by semi-perimeter method. The placement trade-off between routability and reliability is illustrated by varying a weighting factor. Case studies of the coupled placement are presented. In addition, the thermal distribution of the coupled placement results is simulated with the finite element method.     

Contention resolution and QoS provisioning using sparse fiber delay lines in WDM networks

In this paper, we combine fiber delay lines (FDL) and optical wavelength conversion (OWC) as the solution for the burst contention problem in optical burst switching (OBS). We present a placement algorithm, k-WDS, for the sparse placement of FDLs at a set of selected nodes in the network. The algorithm can handle both uniform and non-uniform traffic patterns. Our extensive performance tests show that k-WDS provides more efficient placement of optical fiber delay lines than the well-known approach of placing the resources at nodes with the highest experienced burst loss. Performance results are also given to compare the benefit of using FDLs alone, OWCs alone, as well as a mixture of both FDLs and OWCs. A new algorithm, A-WDS, for the placement of an arbitrary numbers of FDLs and OWCs is presented and evaluated under different uniform and non-uniform traffic loads using network simulation of the NSFNET topology and randomly generated graphs. The paper is concluded by presenting the design of a cost-effective optical switch equipped with variable-delay FDL bank. Based on the switch design, a scheme to provide differentiated services for multiple classes of traffic is presented and evaluated.     

Wavelength Converters Placement in All Optical Networks Using Particle Swarm Optimization

Placement of wavelength converters in an arbitrary mesh network is known to be a NP-complete problem. So far, this problem has been solved by heuristic strategies or by the application of optimization tools such as genetic algorithms. In this paper, we introduce a novel evolutionary algorithm: particle swarm optimization (PSO) to find the optimal solution to the converters placement problem. The major advantage of this algorithm is that does not need to build up a search tree or to create auxiliary graphs in find the optimal solutions. In addition, the computed results show that only a few particles are needed to search the optimal solutions of the placement of wavelength converters problem in an arbitrary network. Experiments have been conducted to demonstrate the effectiveness and efficiency of the proposed evolutionary algorithm. It was found that the efficiency of PSO can even exceed 90% under certain circumstances. In order to further improve the efficiency in obtaining the optimal solutions, four strategic initialization schemes are investigated and compared with the random initializations of PSO particles.     

Design techniques of two‐layer architectures for WDM optical networks

A general method for designing multilayered WDM optical networks, based on the combined use of single‐and multi‐hop connection modes, is presented. It takes into account variable values for the number of users and wavelengths in each cluster. Closed form expressions are derived for the transmission capacity and the optimum number of channels for intra‐cluster communications, either in the case of uniform or non‐uniform traffic distribution. The analytical approach is particularly useful in the presence of constraints on the number of wavelengths, due to technological limits or non‐linear phenomena, when sub‐optimal solutions must be necessarily addressed. The proposed method is integrated with the adoption of well‐known selection procedures, like simulated annealing or genetic algorithms, to reduce the computational effort. Copyright © 2001 John Wiley & Sons, Ltd.     

Sparse Wavelength Conversion in Wavelength-Routed WDM Optical Networks*

A wavelength-routed optical network can suffer inefficiencies due to the wavelength-continuity constraint (under which a signal has to remain on the same wavelength from the source to the destination). In order to eliminate or reduce the effects of this constraint, a device called a wavelength converter may be utilized. Due to the high cost of these wavelength converters, many studies have attempted to determine the exact benefits of wavelength conversion. However, most of these studies have focused on optical networks that implement full wavelength conversion capabilities. An alternative to full wavelength conversion is to employ only a sparse number of wavelength converters throughout the network, thereby reducing network costs. This study will focus on different versions of sparse wavelength conversion--namely, sparse nodal conversion, sparse switch-output conversion, and sparse (or limited) range conversion--to determine if most of the benefits of full conversion can be obtained using only sparse conversion. Simulation and analytical results on these three different classes of sparse wavelength conversion will be presented. In addition, this study will present heuristic techniques for the placement of sparse conversion facilities within an optical network.