一种波分复用全光网波长分配算法

研究了动态业务下，无波长变换的波分复用全光风采用固定选路时的波长分配问题，提出了一种中心式的波长分配算法－最小影响算法。该算法能精确地描述某个波长的分配对全网状态的影响，因而能够更有效地使用网络资源。计算机仿真表明，如果用阻塞概率来衡量，该波长分配算法优于文献中已有的典型算法。     

全光网静态路由选择和波长分配的分层图算法

文章提出一种将路由选择和波长分配结合起来的启发式的路由选择和波长分配(RWA)算法．通过这种新的分层图算法和限制光跳距的加权系数来优化全光网的静态路由选择和波长分配，使建立光连接时所需的波长数达到最少．最后对实际的ARPANet等5种光网络进行了计算机仿真，证明了本算法比以前的算法有更好的性能．     

波分复用光网中的一种新型波长分配算法

目前网络承载业务的趋势是以IP为中心的数据业务,从而促进了以WDM光网络向高速和宽带多波长的应用和普及,为了进一步提高网络的性能并提高资源利用率,出现了光网络控制面技术.路由选择与波长分配问题是WDM光传输网络控制面中非常重要的问题之一.目前实际应用最广泛的波长分配算法是First-Fir(FF)算法.本文基于FF算法,研究动态业务下波分复用光网络在固定选路下的波长分配问题,提出了一种新的波长分配启发式算法——Joint First Fit.计算机仿真试验表明,与常用的FF算法相比,该算法显著的降低了网络呼叫阻塞率,有利于提高网络资源的利用率.     

一种波分复用全光网波长分配算法

研究了动态业务下 ,无波长变换的波分复用全光网采用固定选路时的波长分配问题 ,提出了一种中心式的波长分配算法—最小影响算法。该算法能精确地描述某个波长的分配对全网状态的影响 ,因而能够更有效地使用网络资源。计算机仿真表明 ,如果用阻塞概率来衡量 ,该波长分配算法优于文献中已有的典型算法     

WDM全光网自适应路由和波长分配算法

研究了无波长转换WDM全光网的路由和波长分配算法（RWA）。通过对已有算法的分析和比较,提出了一种自适应最小跳数路由算法（ADMH）。此算法以最小跳数路由为基础,同时考虑网络状态的变化,因而不仅能尽量少使用网络资源,也能使网络资源的分布保持均衡。计算机模拟仿真的结果表明,这种算法性能在各种网络参数条件下优于或等于已有算法。     

波分复用全光网络路由和波长分配算法

本文根据波分复用全光网络路由和波长分配（ＲＷＡ）实现过程的不同把算法划分为两大类;路由和波长分配分解法和路由和波长分配并行法。对这两类分别讨论了动态和静态ＲＷＡ算法。     

全光网复用段共享保护环的实现

本文介绍了全光网中保护的重要性，全光网复用段共享环的保护过程以及将全光网和SDH的保护进行了比较，并给出了本次实现保护倒换的试验结果。     

一种基于WDM四纤环网的波长分配算法

介绍了一种基于WDM四纤共享保护环网进行波长分配的算法.该算法采用矩阵形式表示波长分配情况,它可以用最少的波长数目经由最短通道实现环网上各站点之间的全连接.最后,对偶数站点的波长分配方法加以改进,用比较简洁的过程获得了相同的波长分配结果.     

波分复用全光网中的一种新的波长分配算法

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．提出了一种新的波长分配算法，新算法在已市算法的基础上进行了改进，与已有算法相比，该算法能更精确地描述波长分配对全厨状态的影响。计算机仿真表明，如果用阻塞率来衡量，该波长分配算法优于文献中已有的波长分配算法。     

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。     

静态波长路由光网络中路由和波长分配算法的统计修正

本文采用统计的方法对以网络最小所需波长数为优化目标的路由和波长分配算法进行了修正.数值模拟计算表明,经过统计方法修正之后,可以求得更接近波长下限的网络所需波长数.另外本文还首次提出用统计的方法对路由和波长分配算法进行比较,通过比较两个算法在经过统计修正之后求得的网络所需波长数的分布可以知道它们的优劣.     

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。     

QoS-Friendly Wavelength Assignment in Dynamic Wavelength-Routed Optical Networks

In-band crosstalk has been widely considered as a major transmission impairment that significantly impacts the bit error rate (BER) performance of lightpaths in circuit-switched all-optical wavelength-routed networks. Such crosstalk usually occurs when multiple wavelengths pass through an optical crossconnect node, and the magnitude of the crosstalk is largely dependent on the wavelengths assigned to the lightpaths. Traditional wavelength assignment (WA) schemes pay little regard to the physical layer quality of service (QoS), and hence cannot provide optimized network performance in practical networks with imperfect physical transmission media. In this paper, we first present our categorization of in-band crosstalk based on the location of crosstalk generation, then we propose two QoS-friendly WA approaches, one of which selects the wavelength based on the estimated BERs, and the other based on the weighted crosstalk number counting. The two approaches have different computation complexities. Numerical results show that both approaches can significantly improve the BER blocking rate by suppressing the created in-band crosstalk, but the BER-based approach generally gives the better performance at the price of more extensive computation.This work was supported in part by DARPA Grants #N66001-00-1-8949 and #66001-01-1-8932 (co-funded by NSA).     

Routing and Wavelength Assignment in Optical Networks Using Logical Link Representation and Efficient Bitwise Computation

In this paper, we propose and evaluate a new approach for implementing efficient routing and wavelength assignment (RWA) in wavelength division multiplexing (WDM) optical networks. In our method, the state of a fiber is given by the set of free wavelengths in this fiber and is efficiently represented as a compact bitmap. The state of a multiple-fiber link is also represented by a compact bitmap computed as the logical union of the individual bitmaps of the fibers in this link. Likewise, the state of a lightpath is represented by a similar bitmap computed as the logical intersection of the individual bitmaps of the links in this path. The count of the number of 1-valued bits in the bitmap of the route from source to destination is used as the primary reward function in route selection. A modified Dijkstra algorithm is developed for dynamic routing based on the bitmap representation. The algorithm uses bitwise logical operations and is quite efficient. A first-fit channel assignment algorithm is developed using a simple computation on the bitmap of the selected route. The resulting bitwise routing algorithm combines the benefits of least loaded routing algorithms and shortest path routing algorithms. Our extensive simulation tests have shown that the bitwise RWA approach has small storage overhead, is computationally fast, and reduces the network-wide blocking probability. The blocking performance of our RWA method compares very favorably with three routing methods: fixed alternate routing, shortest path using flooding, and Dijkstra’s algorithm using mathematical operations. Our simulation experiments have also evaluated the performance gain obtained when the network access stations are equipped with finite buffers to temporarily hold blocked connection requests.     

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.     

多粒度全光网中的多层联合路由

多粒度交换技术利用波带级路由以及光纤级路由,可有效降低光交叉连接器的复杂度.但多粒度交换增加了光网络的逻辑层次结构,使得网络中的路由与资源分配问题更为复杂,因此,在多粒度全光网中实现多层联合路由是提高网络性能的关键.本文对多粒度交叉连接结构进行了分析,并对多粒度全光网中的多层联合路由问题进行了研究.     

Provisioning Methods for Bit-Rate-Differentiated Services in Hybrid Optical Networks

This paper addresses the problem of routing and wavelength assignment of bit-rate-differentiated optical services in a hybrid network. Hybrid optical networks are composed of resources, such as fiber links and photonic/electronic switches, that vary in their capabilities and transmission qualities. These networks are also responsible for the realization of optical services with varying quality-of-service (QoS) guarantees. In such networks, it is required to have a cost-effective assignment of the optical and electronic resources to these services in order to maximize the revenue of the network operator. This paper deals with optical services that are defined according to their tolerance to transmission impairments. We first divide the provisioning problem into two phases: (1) routing and (2) wavelength assignment and regeneration reservation. In the routing phase, a set of k-routes are generated to select from in the second phase, where each route optimizes a specific aspect of the problem (e.g., number of hops, maximum accumulated noise, etc.). The second phase, using the information about the resources along each route, attempts at finding the best wavelength allocation on that route such that the signal quality meets the service-level agreement (SLA). The second phase also uses the minimum number of regenerator ports on intermediate nodes for the purpose of wavelength translation and signal clean-up. Comparisons of the above scheme with a probing-based method, reveal substantial enhancements to the blocking performance with a maximum running time increase of 60%. In addition, the use of multiple routes provides higher reduction in the blocking probability over single-routing schemes. Moreover, the proposed, non-pessimistic, provisioning approach has a major impact on reducing the regeneration budget of the network.     

Dynamic Deflection Routing with Virtual Wavelength Assignment in Optical Burst-Switched Networks

In optical burst-switched networks, one of the most significant issues is contention resolution. There have been several deflection routing techniques as contention resolution. While contention is resolved by traditional deflection routing, it cannot guarantee that the control packet will reserve all the wavelengths successfully to the destination on the alternate path, especially when traffic load in a network is high. Therefore, in this paper, we propose a Deflection Routing with Virtual Wavelength Assignment (DR-VWA) algorithm in order to provide a higher resource guarantee for loss-sensitive traffic bursts. The proposed DR-VWA scheme (1) dynamically decides the alternate path with the least traffic load and (2) allows high-priority bursts in terms of loss to be assigned available wavelengths over the path virtually. The proposed scheme is evaluated through simulation, and it is shown that significant improvement with regard to burst loss and wavelength conversion cost can be achieved.This work was supported in part by the Korea Science and Engineering Foundation (KOSEF) through OIRC project and by the US National Communications System (NCS).     

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.     

Routing Mechanisms Employing Adaptive Weight Functions for Shortest Path Routing in Optical WDM Networks

Optical dense wavelength division multiplexed (DWDM) networks are an attractive candidate for the next generation Internet and beyond. In this paper, we consider routing and wavelength assignment in a wide area wavelength routed backbone network that employs circuit-switching. When a session request is received by the network, the routing and wavelength assignment (RWA) task is to establish a lightpath between the source and destination. That is, determine a suitable path and assign a set of wavelengths for the links on this path. We consider a link state protocol approach and use Dijkstras shortest path algorithm, suitably modified for DWDM networks, for computing the shortest paths. In [1] we proposed WDM aware weight functions that included factors such as available wavelengths per link, total wavelengths per link. In this paper, we present new weight functions that exploit the strong correlation between blocking probability and number of hops involved in connection setup to increase the performance of the network. We also consider alternate path routing that computes the alternate paths based on WDM aware weight functions. The impact of the weight functions on the blocking probability and delay is studied through discrete event simulation. The system parameters varied include number of network nodes, wavelengths, degree of wavelength conversion, and load. The results show that the weight function that incorporates both hop count and available wavelength provides the best performance in terms of blocking probability.