波长交换光网络中路由波长分配技术

路由波长分配问题是在给定连接的情况下,为该请求分配适当的光路进行传输。在无波长转换能力的情况下,需要为光路在其传输的链路上分配相同的波长,这就是波长连续性问题。物理层的光损伤极大的限制了光网络的能力,因此需要可感知损伤的路由波长分配算法来保证传输的质量。对于不同的感知损伤的路由波长分配方式,相应地,有不同的控制平面结构。     

一种改进TDM/WDM混合PON及其波长带宽分配机制

提出了一种改进的TDM/WDM混合型无源光网络结构,实现了波长共享,并通过增加备用波长,解决了突发业务的ONU需要大量占用带宽或者是业务不能得到及时发送的问题。对改进的混合无源光网络结构的动态波长带宽分配算法进行了研究,分析给出了增加备用波长后系统的波长分配算法。     

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.     

有限波长转换的OBS竞争解决机制探讨

对下一代光互联干线网最有前景的交换方式,光突发交换的现状及未来商用化的挑战进行了简单介绍,针对有限波长转换能力的光突发结构进行了深入的网络分析和建模,并从全网预先的资源规划方面,提出了竞争解决方案的初步设想和今后工作的重点.     

OBS中的一种原波长优先批调度算法

光突发交换网络(OBS)中心节点使用波长转换器减少突发丢失率,但波长转换器价格昂贵且技术不成熟,中心节点需要减少波长转换器的使用数目.大部分数据信道调度算法都没有考虑波长转换器数目.为此,提出一种原波长优先批调度算法基于相同波长转换器数目下进一步减少突发丢失率.仿真结果表明,这种批调度算法在波长转换器不足条件下,与其它...     

一种新型的动态路由和波长分配算法

本文讨论了WDM光网中，在动态业务流量和有限范围波长变换情况下的动态路由和波长分配（RWA）问题，基于Moone-Dijkstra算法，考虑到动态波长变换的可能和限制，提出了一种新型的、可实现动态最小代价路由和最佳虚波长通道的综合启发式算法（DMC－OVMP）。该算法对路由子问题和波长分配子问题既相互独立，又相互结合，优化了RWA，保证了网络信息传输的安全性。对中国教育和科研计算机网（CERNET）基于本算法进行了计算机仿真，实现了低的网络阻塞率。     

WDM网络中波长转换稀疏性与有限波长转换能力的研究

阐述稀疏波长转换和有限波长转换技术的概念,讨论了这两种技术对网络阻塞率和波长转换增益的影响,并给出了一种用于波长和波长转换器分配的启发式算法。     

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.     

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.     

基于同波长光纤延迟线集光突发交换结构及其性能分析

由于光突发交换机制本身就避免了光缓存的使用，但是现实中，光突发包之间竞争以及提供优先级服务又依靠光纤延迟线来解决。为此，我们设计了应用光纤延迟线的光突发交换网络核心节点结构。为了避免光纤延迟线色散引起的突发包输入排队缓存偏移，在该结构中设计了同波长光纤延迟线集。采用了空分交换矩阵，避免了波长转换的需要。为了有效运行该交换结构，我们提出了输入排队与自适应光缓存调度算法，而该算法不仅仅适用于光突发交换，也适合于光纤延迟线得到普遍应用的光分组交换。该调度算法能够提供优先级服务，避免队头阻塞，对该调度算法建立了严格的理论分析模型，并进行了仿真。仿真结果表明，与传统的延迟线竞争解决方案相比，这一调度算法能够改善交换性能1到2个数量级，是利用光纤延迟线解决光突发交换中竞争问题的一个较佳方案。     

Priority-based offline wavelength assignment in OBS networks

Optical burst switching (OBS) is a promising technique for wavelength division multiplexing (WDM) networks. In practice, wavelength converters (WCs) are either absent or only sparsely deployed in WDM networks due to economic and technical limitations. Thus, wavelength assignment is expected to be an important component of OBS networks. In this paper, an offline wavelength assignment scheme in OBS networks without wavelength conversion capability is proposed. The key idea of the scheme is to decide the wavelength searching order of each traffic connection at edge nodes according to the wavelength priorities determined by the calculated burst loss probabilities on different wavelengths. Simulation results indicate that the proposed scheme can reduce the network-wide burst loss probability significantly compared with other schemes. It is also illustrated that the performance of the proposed scheme can be further enhanced by a larger number of wavelengths per link and a reasonable delay bound at edge nodes.     

A novel optical burst switching scheme—logical cascaded private subnet with start wavelength assignment policy

Many recent studies have convincingly demonstrated that network traffic exhibits a noticeable self-similar nature, which has a considerable impact on network performance, and most studies of optical burst switching (OBS) networks are under a fundamental assumption that full wavelength conversion is available throughout the network. In practice, however, economic and technical considerations are likely to dictate a more limited and sparse deployment of wavelength converters in the optical network. Therefore, we present a novel scheme for OBS networks, called logical cascaded private subnet (LCPN) with start wavelength assignment policy. We define the concept of canoe relative to cluster in self-similar traffic, and introduce a new device named payload segregator at the edge node as a gateway to the core node in OBS Networks. According to the changes in the edge node framework, we put forward the concept of cluster private subnet and canoe private subnet in the core node correspondingly. A new start wavelength assignment policy is proposed for the absence of (full) wavelength conversion capabilities in the core node of OBS Networks. The performance study indicates that, our new scheme is robust under self-similar traffic and wavelength continuity constraint.     

OBS网络中的最小间隙组调度算法

根据OBS网络的结构和特点,分析了OBS网络核心节点的数据信道调度算法,提出了一种新的数据信道调度算法--最小间隙组调度(SGGS)算法,并详细讨论了该算法的具体实现.该算法将到达核心节点的控制包分组,然后将这一组控制包按数据包到达先后的次序调度数据信道,从而达到合理调度和使用数据信道,最终实现改善整个OBS网络性能的目的.     

OBS网络中的主动拥塞控制策略研究及性能分析

根据光突发交换(Optical Burst Switching--OBS)网络的结构和特点,分析了其核心节点在数据信道调度发生拥塞时拥塞控制策略的缺陷,提出了OBS网络中一种主动拥塞控制策略(ACC),详细讨论了该策略的具体实现过程.通过仿真验证,在OBS网络中采用该算法能减少突发数据包的丢包率,从而达到改善整个OBS网络性能的目的.     

QoS aware routing and wavelength allocation in optical burst switching networks using differential evolution optimization

The issue of burst losses imposes a constraint on the development of Optical Burst Switching (OBS) networks. Heavy burst losses strongly affect the Quality of Service (QoS) intended by end users. This article presents a QoS aware Routing and Wavelength Allocation (RWA) technique for burst switching in OBS networks. The RWA problem is modeled as a bi-objective Integer Linear Programming (ILP) problem, where objective functions are based on minimizing the number of wavelengths used and the number of hops traversed to fulfill the burst transmission requests for a given set of node pairs. The ILP model is solved using a novel approach based on a Differential Evolution (DE) algorithm. Analytical results show that the DE algorithm provides a better performance compared to shortest path routing, which is a widely accepted routing strategy for OBS networks.     

光突发交换网络中QoS方案的研究

光突发交换是构建下一代光网络的有效交换技术,在OBS网络中如何有效地支持QoS已成为一个重要的研究课题.介绍了光突发交换网络中基于偏置时间的QoS方案和波长分组QoS方案,最后提出了一种基于波长分组技术,结合突发分片技术和Min-Sv算法的QoS的解决方案,通过建立相应的模型时其进行了仿真,仿真结果表明所提出的方案可以更好地提供区分服务,同时有效地提高了信道的利用率,降低了整体的丢失率.     

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.     

Study on the problem of routing,wavelength, and time-slot assignment towards optical time-slot switching technology

Conventional optical burst switching (OBS) is incapable of providing connection-oriented service, and burst loss is more likely to occur with increasing of traffic load due to its inherent architecture where the burst size is variable. In this paper, we propose and evaluate the optical time-slot switching technology, in which the fixed-size time-slot is adopted as the basic switching granularity, and switching is done in the time domain, rather than the wavelength domain. Also, we prove that time-slot switching has an equivalent function to eliminate data conflict relative to wavelength converter. Subsequently, the routing, wavelength, and time-slot assignment problem is studied in this paper. An adaptive weight function is introduced to the routing and wavelength selection algorithm, then several useful approaches, such as the train approach, wagon approach and p-distribution approach, are presented for time-slot assignment and scheduling. The results show that our scheme can perform better than conventional OBS in the aspect of blocking performance, quality of service, and class of service.     

Wavelength Selection in OBS Networks Using Traffic Engineering and Priority-Based Concepts

A fundamental assumption underlying most studies of optical burst switched (OBS) networks is that full wavelength conversion is available throughout the network. In practice, however, economic and technical considerations are likely to dictate a more limited and sparse deployment of wavelength converters in the optical network. Therefore, we expect wavelength assignment policies to be an important component of OBS networks. In this paper, we explain why wavelength selection schemes developed for wavelength routed (circuit-switched) networks are not appropriate for OBS. We then develop a suite of adaptive and nonadaptive policies for OBS switches. We also apply traffic engineering techniques to reduce wavelength contention through traffic isolation. Our performance study indicates that, in the absence of full conversion capabilities, intelligent choices in assigning wavelengths to bursts at the source can have a profound effect on the burst drop probability in an OBS network.