多波长光网络的动态路由等效算法

针对多波长光网络的特点，提出了一种动态路由和波长分配的等效算法。采用波长图、增加虚拟源节点和目的节点等技术，把多波长网络转化为等效的单波长网络，避免了求解路由和波长分配两个复杂子问题，简化了算法的程序设计。利用最短径算法进行路由和波长分配可以求得问题的最优解，从而有效地降低了网络阻塞率。仿真结果表明：与FAR-2D算法相比，在4和8波长的全波长转换网络中，采用等效算法阻塞率最大降幅分别达到0．02、0．025。     

多纤多波长光网络的动态路由等效算法

针对多光纤多波长光网络的特点,提出了一种动态路由和波长分配的等效算法。采用波长图、增加虚拟源节点和目的节点、引入光纤数量矩阵等技术,把多纤多波长网络转化为等效的单波长网络,大大简化了算法程序的复杂度。采用最短径算法作为算法的基础,可求得每次业务在全网范围内的路由和波长分配的最优解。仿真结果表明,当网络呼叫量为60时,全波长转换情况下,2纤、4纤网络的阻塞率分别为0.1116、4.3×10-5。     

稀疏波长变换的WDM光网络阻塞率的分析与计算

本文主要对具有稀疏波长变换的WDM全光网的阻塞率进行分析,首先提出一种模型分析了无波长变换器的L跳路径端到端阻塞率,接着对部分波长变换器的L跳路径的阻塞率进行求解,随后分析了全网的平均阻塞率。研究得到的主要结论是,波长变换器使用的有效性取决于网络的连接度。     

一种新型的动态路由和波长分配综合算法

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-OVWP)。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。以中国教育和科研计算机网(CERNET)为拓扑背景，基于本算法进行了计算机仿真，并对实验结果进行了比较分析，证明本算法可充分利用网络信息获取较低的阻塞率。     

抗毁性WDM网状光网络中的P圈快速构造算法

p圈法是抗毁性网状WDM光网络中一种十分优秀的保护算法,在p圈配置到网状光网络的过程中,圈构造算法是设计的第一步.文中提出了一种快速圈挖掘算法(FCMA),本算法基于k-最短路由算法构造最小p图,通过圈扩展算法获得更多性能优良圈,文中给了启发式算法的具体步骤.通过计算机仿真表明,该算法实现快速圈构造,性能优于其它同类算法,适合网状光网络中的p圈快速构造.     

应用业务预测的动态带宽分配算法

当前以太无源光网络中动态带宽分配算法主要是基于轮询机制.其中限制带宽分配算法根据各个ONU发送的队列长度能够动态分配带宽,但是这种算法不能实时获得各个ONU的队列长度.因此,利用维纳滤波的方法对自相似业务流量进行预测,预测的结果应用于限制动态带宽分配,得出一种改进的动态带宽分配算法.这种改进算法通过预测ONU的队列长度,更确切地反映了其状态信息,有利于OLT进行准确地带宽分配.对这种算法进行了仿真分析,在业务负载介于0.1～0.5的情况下,平均包时延比较接近0.1ms,达到了改进目的.     

光交换技术在通信网络中的应用

光纤网络作为高速有效的代名词已经深入人心,在通信系统中也已经大规模的实现部署和应用。而实现透明的、高生存性的全光通信网是宽带通信网的发展目标。光交换技术作为全光通信网络中的一项重要基础技术,其发展和应用很大程度上决定未来光通信网络的前进方向。对光交换技术的概念及发展和其在通信中应用的情况作概要的介绍,以供广大科研工作者研究和探讨。     

以太无源光网络单级多功能ONU内调度算法

针对以太无源光网络(EPON),为各类业务提供服务质量支持,特别是保障时延敏感型业务的服务质量,提出一种调度算法,应用到EPON的光网络单元(ONU)中.我们设法让这个单级调度算法具备多级调度功能.通过理论分析和仿真测试,证明本算法具有灵活的优先级机制和公平调度功能.     

基于带宽借贷的EPON动态带宽分配算法

针对以往以太网无源光网络(EPON)动态带宽算法中存在的带宽分配不公平性问题,提出了基于带宽借贷机制的动态带宽算法LLR和LWR,其基本思想为当某光网络单元(ONU)有空余带宽时,光线路终端(OLT)将此ONU多余带宽借贷给重负载ONU,当债权ONU遇到带宽不足的情况时,OLT将会安排负债ONU偿还其未满足请求部分带宽.通过在正常使用和存在"贪婪"用户的两种情况下的仿真,分析了这两种算法的平均时延和丢包率特性.仿真结果表明这两种算法能为正常使用用户提供有保障的公平性服务,消除了以往算法在若干用户过量使用的情况下所有用户都受影响的问题,使动态带宽分配更加公平.     

EPON上行接入动态带宽分配算法的研究

以太无源光网络的上行方向需要一种多址接入技术来防止以太数据包的碰撞。时分多址技术应用广泛,而波分多址技术极具潜力,是发展的方向。基于时分多址技术,提出了一种改进的动态带宽分配算法,结合了轮询机制和申请的优先级。通过建模仿真,证明了该算法可以取得较小的平均包延时和较高的带宽利用率。     

基于最小化波长需求的波长路由光网的优化设计

讨论了波长路由光网的资源优化设计问题,提出了一种新的整数线性规划（ILP）公式,用于解决波长通道（WP）和虚波长通道（VWP）的路由选择和波长分配问题,它的优化目标是最小的网络需求,以中国高速信息示范网（CAINONET）为例,分析了波长通道（WP）和虚波长通道（VWP）路由方案之间在波长需求方面的差别,同时还研究了网络波长重用度的问题。     

任意拓扑结构全光WDM网络中波长转换器配置的遗传算法

波长转换是应用在全光WDM网络中打破波长一致性约束、降低网络阻塞概率的一种有效技术,但限于波长转换器的高昂成本以及其对信号失真度的影响,目前还不可能为网络中的每个节点均配置波长转换器,所以波长转换器需要以最优方案配置在网络中的个别关键节点上,本文提出了一种在任意拓扑结构的网络中,基于遗传算法的波长转换器配置算法,并对该算法在NSFNET网络上进行了计算机仿真,模拟结果显示该算法非常有效.     

All-optical wavelength reuse with simultaneous upstream data and PPS timing signal transfer for flexible optical access networks

All-optical wavelength reuse is a viable approach for realization of low cost colourless ONUs. We experimentally demonstrate a novel all-optical wavelength reuse technique with simultaneous upstream data and pulse-per-second signal transfer, exploiting EDFA gain saturation with a holding beam. A DFB laser is modulated with 8.5 Gbps data and transmitted downstream over 24.7 km fibre. A saturated EDFA located at the ONU is adopted to reduce the extinction ratio of the downstream data from 6.2 dB to 839.1 mdB. This allows for data rewrite and wavelength reuse for upstream transmission. Receiver sensitivities of ?20.19 dBm and ?19.60 dBm are achieved at back-to-back analysis and 24.7 km downstream link respectively. A holding beam is further exploited to attain simultaneous carrier reuse and PPS clock upstream transfer. PPS jitter stability of 1.01 × 10^-08 ns and 6.64 × 10^-08 ns are attained respectively. This work offers a convenient all-optical wavelength reuse solutions for optical access networks.     

Realization of wavelength conversion with hyperbolic secant femtosecond pulse in normal dispersion regime

Realization of wavelength conversion based on second-order femtosecond dark solitons with hyperbolic secant pulse is presented. This is achieved by introducing localized dispersion perturbation along the optical fiber. We demonstrate that an initial 30 fs second-order pulse decays to similar sub-pulses by applying perturbation using a step increment of β₂ from 6.3 to 15.75 ps² km^?1. This shows that the realization of a 1 × 2 channel wavelength converter for femtosecond pulses is possible. Recent research shows the possibility of realizing wavelength conversion generated from picosecond solitons neglecting nonlinear effects. However, employing the same method for femtosecond pulses fails due to the manifestation of nonlinear effects. In this paper, pulse deformation under different levels of perturbation was tested, and appropriate perturbation leading to similar sub-pulses is achieved.     

Cross-dock job assignment problem in space-constrained industrial logistics distribution hubs with a single docking zone

This paper addresses a cross-dock operations problem in space-constrained industrial logistics distribution hubs. In these hubs, the number of incoming trucks exceeds the number of docks available, and inbound trucks and orders arrive at random. The solution lies in minimising the waiting time of trucks by coordinating the pick up/delivery sequences of inbound and outbound orders in the storage zones. A mathematical model and a meta-heuristics algorithm, which is based on a genetic algorithm, are developed to address the problem. This research is innovative because the proposed algorithm allows the insertion of inbound orders that arrive at random into the schedule, without causing any significant disturbance to the original outbound order schedule. Computational experiments are conducted to examine the performance of the algorithm under heavy and normal cross-dock conditions. Results show that the algorithm reduces the total makespan of storage operations by 10% to 20% under heavy and normal conditions. The research study benefits manufacturers by increasing cross-docking efficiency in industrial logistics systems characterised by limited temporary storage capacity and the random arrival of inbound trucks.     

Distributed multicast routing algorithm with dynamic performance in multimedia networks

The delay and delay variation-bounded multicast tree (DVBMT) problem is known to be NP-complete. In this paper, we propose an efficient distributed dynamic multicast routing algorithm to produce routing trees with delay and delay variation constraints. The proposed algorithm is fully distributed, and supports the dynamic reorganizing of the multicast tree in response to changes for the destination. Simulations demonstrate that our algorithm is better in terms of tree delay and routing success ratio as compared with other existing algorithms, and performs excellently in delay variation performance under lower time complexity, which ensures it to support the requirements of real-time multimedia communications more effectively.