智能光网络中RWA问题的研究

在ASON中．路由和波长分配（RWA）算法是其中一个关键问题。由于当前网络中业务增长迅速．而网络中可用资源有限．因此要使用合理的RWA算法来优化网络资源。本文分别阐述了静态RWA、动态RWA以及RWA算法中的其他问题．并主要对路由和波长问题进行了分析和研究。     

智能光网络中RWA问题的研究

在ASON中,路由和波长分配（RWA）算法是其中一个关键问题。由于当前网络中业务增长迅速,而网络中可用资源有限,因此要使用合理的RWA算法来优化网络资源。分别阐述了静态RWA、动态RwA以及RWA算法中的其它问题,并主要对路由和波长问题进行了分析和研究。     

静态环型波长路由光网络中RWA问题的研究

RWA问题是静态环型波长路由光网络中的一个核心问题.随着RWA优化算法求解方式的简化,算法的运算效率得到了提高,但却牺牲了解的优化性能.如何使优化效率和时间效率协调统一是当前环网波长路由光网络中RWA优化算法设计的难点.本文对静态波长路由光网络中RWA问题进行了阐述,综述了当前国内外的RWA算法,并对静态环网中几种新的算法进行了分析研究.     

GMPLS协议中的路由和波长分配技术

因特网工程工作组（IETF）制定的通用多协议标签交换协议（GMPLS）,作为光网络的控制平面协议,推动了光网络的智能化进程。路由和波长分配问题（RWA）是光网络智能化的核心问题之一。在介绍RWA算法和GMPLS协议的基础上,分析了不同RWA算法、不同RWA机制对网络信息的需求,描述了GMPLS协议为解决RWA问题所做的标准化工作,并分析了与RWA相关的网络信息分发格式。     

波长路由光网络中RWA算法的设计分析

文章通过对波长路由光网络中路由与波长分配(RWA)问题的研究,介绍了求解路由子问题和波长分配子问题的常用方法,总结了3种类型的RWA问题的优化解决方法,最后对目前RWA算法设计中存在的问题进行了分析并阐述了解决此类问题的重要性.     

多光纤ASON网络动态路由优化算法

本文研究了多光纤波分复用光网络中的动态路由和波长分配问题，提出了基于分层图模型的一种新的多光纤网络的动态路由优化算法，该算法将连接请求的建立转化为在分层图模型中为该请求寻找一条最优路径，这使得设计者可以同时考虑路由和波长分配的问题，从而取得更好的效果。模拟结果显示基于分层图模型的(MFD—RWA：MultiFiber Dynamic：Routing and Wavelength Assignment)算法优于传统的动态最短路径算法。     

智能光网络ASON中波长分配算法探讨

WDM网络的高速发展，使得各种路由波长算法（RWA）的研究和应用比较成熟，而随着IP应用的爆炸式增长，ASON技术具有巨大的发展潜力，相对于WDM的RWA算法的研究，ASON中RWA算法的研究有待进一步的细化，本文在WDM网络的波长分配算法的基础上，详细地阐述了波长分配算法在ASON中的要求及改进。     

稀疏波长变换网络性能分析与研究

文章对动态业务模型下的稀疏波长变换网络性能进行了分析与研究，对波分复用（WDM）网络中引入波长变换器后的网络性能进行了系统的仿真，分析了波长变换器数量、波长变换器位置、波长变换范围以及路由波长算法等因素对网络性能的影响。     

备用路由下一种新的WDM动态路由波长分配算法

基于波长转换度的空闲波长图模型,提出了一种用于WDM光网络在备选路由下的动态RWA算法。路由选择采用K条最短路径算法进行,备选路由集中首选最佳路由时考虑链路的代价、跳数和每一个链路上不可用波长数。通过计算机模拟,分析这3个参数对网络的阻塞率的影响,结果表明本算法中所选定研究的3个参数中选定路由的不可用波长数对网络阻塞率的影响程度比通道的代价,跳数对网络的影响程度大,这个结论对算法中这3个参数数值的选取提供了依据,使算法能够依据实际网络情况动态选取参数,降低网络阻塞率。     

WDM光网络中动态RWA算法仿真的实现

在WDM光网络中，在给定一组连接请求后，需要为之建立路由并分配波长，这被称为路由和波长分配问题（RWA）。由于当前光网络中的业务呈现爆炸式的增长，而光网络中的可用资源却是有限的，因此如何使用合理的RWA算法来优化网络资源的利用就显得尤为重要。目前已有很多文献提出了基于各种优化目标的RWA算法，也都通计算机仿真的方法测试和评估了算法的性能。计算机仿真是进行算法性能评估的主要手段，但是关于算法仿真的实现，—般的文献都涉及的很少，本文主要研究了WDM光网络中动态RWA算法计算机枋真的实现。     

一种波长转换受限WDM网络的动态路由和波长分配算法

本文基于分层图模型,提出了在节点波长转换范围受限和波长转换器数目受限情况下,解决WDM网络的动态路由和波长分配问题的一种算法.通过计算机仿真,研究了本算法的性能以及这两种波长转换受限情况对网络阻塞率的影响.     

Ant Colony Optimization for Dynamic RWA in WDM Networks with Partial Wavelength Conversion

Dynamic routing and wavelength assignment (RWA), which supports request arrivals and lightpath terminations at random times, is needed for rapidly changing traffic demands in wavelength division multiplexed, (WDM) networks. In this paper, a new distributed heuristic algorithm based on ant colony optimization for dynamic RWA is put forward. We consider the combination of route selection and wavelength assignment as a whole using a multilayer-graph model. Therefore, an extended multilayer-graph model for WDM networks with limited wavelength conversion is presented. Compared with other RWA methods, the Ant Colony heuristic algorithm can achieve better global network optimization and can reduce communication overhead cost of the networks. Simulation showed that a lower blocking probability and a more rational wavelength resource assignment can be achieved.     

一种公平的多优先级WDM光网络波长分配算法

文章研究了波分复用(WDM)光网络中动态业务下的波长分配问题,在无波长转换器的条件下,提出了一种加入了公平性考虑的动态门限算法.该算法在支持多优先级的动态门限法的基础上,通过更新初始优先级减少了不同距离光路连接请求间的阻塞率差别,改善了公平性.计算机仿真结果说明了该算法的有效性.     

WDM网络中支持QoS的路由与波长分配算法

针对波分复用(wDM)网络中的路由与波长分配问题。提出了一种支持服务质量(QoS)的约束搜索算法。基于多目标规划模型,这种搜索算法可为网络各节点创建路由表,根据路由表信息求出非支配路径集合,从而一次性完成寻找路由和分配波长两项任务。仿真实例证明了该算法的有效性。     

基于多约束条件的WDM光网络多播动态路由算法

针对WDM光网络多播动态路由分配问题,提出了一种多约束条件下的路由分配算法.对WDM光网络中的多约束因素进行了系统分析,阐述了算法的实现步骤,并对CERNET和NSFNET两种网络进行了仿真实验和对比.     

WRON中基于波长相关性的波长分配算法

基于节约网络资源和降低网络的阻塞率和波长分配代价的思想,在WRON网络的动态路由波长分配算法中考虑波长相关性.根据波长之间转换度变化,详细定义波长转换器的可转换波长之间的波长转换度,并定义了一个利用二进制数表示的空闲波长指示参数,利用该参数对链路上的空闲波长进行表示,用蚁群系统的蚁群波长信息素更新的计算公式来更新这个指示参数,简化波长分配的过程.通过仿真,证明本算法能够达到节约波长资源,降低网络的阻塞率和波长分配代价的目的.     

Routing Algorithms in WDM Networks under Mixed Static and Dynamic Lambda-Traffic

Dynamic traffic is becoming important in WDM networks. In the transition towards full dynamic traffic, WDM networks optimized for a specific set of static connections will most likely also be used to support on-demand lightpath provisioning. Our paper investigates the issue of routing of dynamic connections in WDM networks which are also loaded with high-priority protected static connections. By discrete-event simulation we compare various routing strategies in terms of blocking probability and we propose a new heuristic algorithm based on an occupancy cost function which takes several possible causes of blocking into account. The behavior of this algorithm is tested in well-known case-study mesh networks, with and without wavelength conversion. Moreover, Poissonian and non-Poissonian dynamic traffics are considered.     

WDM网络中的一种波长分配算法

本文研究了动态业务下，采用固定选路和备用选路的波分复用光传送网中的波长分配问题，提出了一种波长分配算法-相对最小影响算法。与己朋的利用全网信息分配波长的算法相比，该算法能更精确地描述波长分配对全网状态的影响，使网络资源的充分利用成为可能。计算机仿真表明，该波长分配算法性能较好。     

Dynamic routing and wavelength assignment in the presence of wavelength conversion for all-optical networks

Blocking probability has been one of the key performance indexes in the design of wavelength-routed all-optical WDM networks. Existing research has demonstrated that an effective Routing and Wavelength Assignment (RWA) algorithm and wavelength conversion are two primary vehicles for improving the blocking performance. However, these two issues have largely been investigated separately; in particular the existing RWA algorithms have seldom considered the presence of wavelength conversion. In this paper, we firstly demonstrate that the existing dynamic RWA algorithms do not work well in the presence of wavelength conversion as they usually only take into account the current traffic, and do not explicitly consider the route lengths. We then propose a weighted least-congestion routing and first-fit wavelength assignment (WLCR-FF) algorithm that considers both the current traffic load and the route lengths jointly. We further introduce an analytical model that can evaluate the blocking performance for WLCR algorithm. We carry out extensive numerical studies over typical topologies including ring, mesh-torus, and the 14-node NSFNET; and compare the performance of WLCR-FF with a wide variety of existing routing algorithms including static routing, fixed-alternate routing and least-loaded routing. The results conclusively demonstrate that the proposed WLCR-FF algorithm can achieve much better blocking performance in the presence of sparse or/and full wavelength conversion.     

Multicast wavelength assignment with sparse wavelength converters to maximize the network capacity using ILP formulation in WDM mesh networks

In general, multicast routing and wavelength assignment (MC-RWA) can be subdivided in routing and wavelength assignment issues in wavelength-division multiplexing (WDM) mesh networks. Previous studies on WDM multicast have mainly focused on WDM multicast routing. The multicast wavelength assignment problem is studied in this paper. A unicast routing path can be established by a lightpath in an all-optical network. However, in the multicasting case, a multicast routing tree can be established by a single light-tree or several lightpaths, or a combination of several light-trees and lightpaths. We propose a wavelength assignment algorithm for finding an optimal combination of lightpaths and light-trees to construct a newly required multicast session. First of all, two cost functions are given to evaluate the establishing cost for each feasible wavelength, and then find a set of wavelengths that covers all destinations with the minimal cost using Integer Linear Programming (ILP) formulation. We focus on maximizing the total number of users served in a multicast session and the network capacity. The simulation results show that the proposed algorithm can improve system resource utilization and reduce the blocking probability compared with the First-Fit algorithm.This research was partially supported by the Grant of National Science Council, R.O.C. (NSC 94-2745-E-155-007-URD).