树形全光网络中波长转换器配置算法

配置有限数量的波长转换器使网络阻塞率最低,是全光网络中需要解决的一个关键问题.通过考虑网络的直径、中心以及节点和链路的通信量,采用网络分解和迭代的方法,提出树形网络中基于赋权直径的波长转换器配置算法、基于节点加权中心的波长转换器配置算法,以及基于光路加权中心的波长转换器配置算法.算法演示表明,提出的3个算法总是将波长转换器放置在阻塞率较高的节点上,从而大大降低网络整体阻塞率.     

全光网波长转换器配置问题的一种启发式算法

波长转换技术可以消除全光网络中的波长一致性限制,降低网络阻塞率,因此在具有波长转换器的全光网中,如何通过合理配置、使用数量有限的波长转换器来最大程度的降低网络的阻塞率,这是全光网络需要解决的一个关键问题。因此对网络中通过节点的路由数量、通信量、路由长度及节点处于路由的中心距离进行分析,并给上述四个参数赋予一定的权重进行加权处理,提出了一种基于节点权的全光网络波长转换器配置算法,并针对一般拓扑网络进行了算法演示和分析。     

全光网络中波长转换器配置问题的蚁群算法

研究提高网络的利用率,在全光网络中放置波长转换器是打破波长一致性约束,为了降低网络阻塞率,提高网络通信能力的有效途径。但限于波长转换器的高昂成本,不可能为网络中的每个节点都配置波长转换器,所以波长转换器应以最优方案放置在网络中的个别关键节点上。提出了一种基于蚁群算法的波长转换器配置方法,通过蚁群算法寻找给定网络中任意源、目的节点之间的最优路径,并利用蚂蚁对最优路径的记录,统计路径在节点处发生波长转换的次数,将具有较高波长转换次数的节点作为网络中波长转换器放置节点。最后通过对一个5节点的网络进行算法演示和仿真分析,结果表明该算法能求得波长转换器的合理配置,得到较好的通信效果。     

度约束QoS组播路由遗传算法

有度约束的QoS组播路由问题在通信网络中具有重要意义。提出一种基于遗传算法的度约束组播路由算法,采用节点连接路径形式的编码方法构成一棵组播树的表示,设计了相应的具有树形结构的交叉和变异算子,以及节点度的改变算法。算法可以实现具有树形结构染色体的遗传进化。数值实验表明算法具有找到最优解的能力,特别适合于求解大规模网络有度约束的QoS组播路由问题。     

部分波长转换全光网阻塞概率的近似计算

该文基于链路波长占用独立性假设，改进了Birman 在1996年提出的分析模型，提出了一种部分波长转换全光网在固定式路由和随机分配波长条件下阻塞性能的近似分析方法，该方法可以适用于任何网络拓扑，任何业务量分布模式条件下网络中任意链路上配置任意数目转换器情况的研究，扩大了Birman模型的适用范围，对于转换器均匀放置的网络，在业务均匀分布或者业务量信中在短跳路径的情况下，近似计算能够较好地与计算机仿真相吻合，对于业务量集中在长跳路径的情况或者转换器非均匀放置的网络，近似计算能够很好地跟随计算机仿真结果。     

WDM光传送网中基于链路状态等级的动态路由与波长分配算法

提出了两种基于链路状态分级的路由与波长分配算法．分别为链路等级优先的动态路由与波长分配算法（LFLS-DRAW）和满足等级要求的动态路由与波长分配算法（RLSDRAW）算法．理论分析表明，基于链路状态分级的路由与波长分配算法的计算复杂度与同类算法相当，且与其它算法相比具有一定的优越性．仿真结果表明．基于链路状态分级的路由与波长分．配算法在计算时间和平均路由跳数相近的情况下．所选择路径的路由状态等级较高．具有较强的负载均衡能力，可以有效降低网络的拥塞概率．     

WDM网络中一种时延约束多播路由算法

文章提出了一种在有限波长转换器的WDM网络中,基于拉格朗日松驰的时延约束最小代价多播路由算法。该算法将WDM网络中的寻径与波长分配合成一步,并充分考虑到波长转换器的限制,利用拉格朗日松驰方法的特点,通过对松驰参数的变化得到每链路上的聚合代价,从而得到一棵近似于最优解的多播树。     

基于业务安全性的电力通信网双路由配置方法研究

针对现有电力通信业务路由配置方法集中于单路由算法无法从根本上保证信息安全传输的问题,提出基于业务安全性的最佳双路由算法ODR(Optimal Double Route),为每一条业务配置两条安全性最高的节点分离路径。首先,综合考虑站点和光缆的安全性,以及电力通信网的特殊性,构建通信网业务的双路由问题模型。其次,根据该问题模型改进Bhandari算法实现节点分离路径对的搜索。最后,通过实例测试业务配置结果,与最简单双路由算法RF(Remove-Find)相比,ORD算法的业务容量提高了9.07%,业务路径安全性高出20.4%,对于实际工程中的业务部署和网络规划具有一定的指导价值。     

波长连续WDM光网络中新的自适应RWA 算法

在对WDM波长路由光网络的路由和波长分配算法进行研究的基础上，提出了一种新的自适应动态路由算法和考虑路径优先级及网络公平性的波长分配算法，给出了具体分析及实现步骤。该算法能有效地利用网络资源，保证业务分布的均衡，较好地兼顾网络资源分配的合理性，有效地改善了全网的平均阻塞性能。     

全光网络中组播路由波长分配的一种遗传算法

在WDM网络中,组播是一种重要的通信需求。组播算法就是要建立一棵从源节点到目的节点的组播树,并给这棵组播树分配波长。但是在网络中有波长转换器的情况下计算的复杂性会大大增加。该文在分层图结构中基础上,提出了组播路由和波长分配的一种遗传算法,可以在满足时延约束的情况下,寻找费用最小的组播树,将路由和波长分配统一进行,同时考虑到了网络中波长转换器的存在。数值仿真实验结果表明该算法具有较好的平均性能和较低的时间复杂度。     

Assuming multiobjective metaheuristics to solve a three-objective optimisation problem for Relay Node deployment in Wireless Sensor Networks

This paper deals with how to efficiently deploy energy-harvesting Relay Nodes in previously established low-cost static Wireless Sensor Networks (WSNs), assuming a single-tiered network model. The purpose is to optimise three conflicting objectives: Average Energy Cost, Average Sensitivity Area, and Network Reliability. This is the so-called Relay Node Placement Problem (RNPP), which is an NP-hard optimisation problem. We find many works assuming heuristics in the current literature. However, it is not the case for metaheuristics, which usually provide good results solving such complex problems. This situation led us to consider a wide range of MultiObjective (MO) metaheuristics: the two standard Genetic Algorithms NSGA-II and SPEA2, the trajectory algorithm MO-VNS, the algorithm based on decomposition MOEA/D, and two novel swarm intelligence algorithms MO-ABC and MO-FA, which are based on the behaviour of honey bees and fireflies, respectively. These metaheuristics are applied to optimise a freely available data set. The results obtained are analysed considering two MO metrics: hypervolume and set coverage. Through a widely accepted statistical methodology, we conclude that MO-FA provides the best performance on average. We also study the efficiency of this approach, verifying that it is a good strategy to optimise such networks, including some limitations. Finally, we compare this proposal to another author approach, which assumes a heuristic.     

基于时延优化的软件定义网络控制层部署策略

当前大多数软件定义网络（SDN）中控制器的部署方案均重点考虑正常网络状态下传播时延对性能的影响,而忽略了链路故障状态下对时延的影响,针对此问题,提出了一种基于时延优化的控制层部署方案。首先,在综合考虑网络正常运行以及单链路故障等多种网络状态下的最坏情况时延最小化问题的基础上,以网络状态时延作为新的时延优化目标并建立了相应的数学模型。其次,提出了解决上述模型的两种启发式部署算法：基于贪婪算法的控制层部署算法（GA-CPA）和基于粒子群优化（PSO）算法的控制层部署算法（PSO-CPA）。最后,选取了真实网络拓扑及数据进行验证。仿真结果表明,GA-CPA和PSO-CPA两种部署算法均能在不同程度上降低网络状态时延,从而保证了大部分网络状态下的最坏情况时延维持在较低范围。     

Effects of type reduction algorithms on forecasting accuracy of IT2FLS models

Type reduction (TR) is one of the key components of interval type-2 fuzzy logic systems (IT2FLSs). Minimizing the computational requirements has been one of the key design criteria for developing TR algorithms. Often researchers give more rewards to computationally less expensive TR algorithms. This paper evaluates and compares five frequently used TR algorithms based on their contribution to the forecasting performance of IT2FLS models. Algorithms are judged based on the generalization power of IT2FLS models developed using them. Synthetic and real world case studies with different levels of uncertainty are considered to examine effects of TR algorithms on forecasts’ accuracies. As per obtained results, Coupland–Jonh TR algorithm leads to models with a higher and more stable forecasting performance. However, there is no obvious and consistent relationship between the widths of the type reduced set and the TR algorithm.     

Scheduling algorithms for multicast traffic in TDM/WDM networks with arbitrary tuning latencies

We consider all-optical Time Division Multiplexing (TDM)/Wavelength Division Multiplexing (WDM) broadcast and select networks with slotted operation. Each network access node is equipped with one fixed transmitter and one tunable receiver; tuning times are not negligible with respect to the fixed size slot time. We discuss efficient scheduling algorithms to assign TDM/WDM slots to multicast traffic in such networks. The problem is shown to be NP-hard; thus, heuristic algorithms based on the Tabu Search meta-heuristic are proposed, and their performance are assessed using randomly created request matrices based on two types of multicast traffic patterns. We show that significant advantages can be obtained by using these novel algorithms with respect to simpler greedy algorithms, even when restricting CPU times to realistic values to make the algorithms of practical use.     

无线传感器网络中利用部署知识的组合密钥预分发算法设计

在无线传感器网络(WSNs)的安全体系结构中,密钥预分发算法占据着极其重要的位置.然而,现有的密钥预分发算法通常都是在连通性、抵抗节点捕获的安全弹性和存储、通信和计算过载之间进行交换,很难使各项指标都很理想.为此,本文在对WSNs各种典型密钥预分发算法的特点进行详尽分析的基础上,通过利用部署知识和密钥空间的极限安全特性于组合模型中的方法,提出了一种新的适合于WSNs密钥预分发算法.理论分析及仿真证明了该算法在占用较小的内存和过载、局部完全连通的情况下,能使网络得到完美的安全弹性.     

Applying MOEAs to solve the static Routing and Wavelength Assignment problem in optical WDM networks

Wavelength-Division Multiplexing (WDM) in optical networks has revolutionized the Telecommunication field. This technology is able to exploit the enormous bandwidth capability of this kind of networks, allowing communication between end users via all-optical WDM channels (lightpath). Given a set of demands, the problem of setting up lightpaths by routing and assigning a wavelength to each connection is known as Routing and Wavelength Assignment (RWA) problem. There are two types of connection demands: static (demands are given in advance) and dynamic (demands are given in real-time). In this paper we present two different Multiobjective Evolutionary Algorithms (MOEA) with the aim of solving the static RWA problem. The first one is a population-based algorithm, the Differential Evolution (DE), but incorporating the Pareto Tournament concept (DEPT). The second one is a multiobjective version of the Variable Neighborhood Search (VNS), MO-VNS. In order to prove the goodness of our metaheuristics, we have compared them with the standard Fast Non-Dominated Sorting Genetic Algorithm (NSGA-II), typical heuristics in the Telecommunication field, and different varieties of Multiobjective Ant Colony Optimization Algorithms. On the whole, we conclude that our approaches have obtained very promising results.     

Comparative analysis of Traffic Patterns on <Emphasis Type="Italic">k-ary n-tree</Emphasis> using adaptive algorithms based on Burton Normal Form

k-ary n-trees are a particular type of Fat-Trees that belong to parametric family of topologies. In spite of their wide usage as an Interconnection Network topology, it has been quite unclear about the performance of Adaptive Routing Algorithms on them. In this paper, we consider a 4-ary 3-tree and analyze two Adaptive Routing Algorithms namely the Non-Minimal Adaptive Routing Algorithm and Minimal Adaptive Routing Algorithm. Specifically, the application of these algorithms on 4-ary 3-tree using various Traffic Patterns has been simulated. The six Traffic Patterns called BitTranspose, BitReversal, BitComplement, Uniform Distribution, k-shift and Ring are used as running examples throughout the paper. The simulation results show that the Network Latency for k-ary n-tree is much higher in case of the Non-Minimal Algorithm as compared to the Minimal Algorithm. However, in case of Ring Traffic, the results show a deviant behavior when compared to other patterns.     

全光波长变换技术及其在DWDM网络中的应用

全光波长变换技术是DWDM系统中的一项关键技术。它不仅可以充分利用波长资源,提供操作上的透明性和空闲波长调度的灵活性,还可以满足未来的动态路由分配需求。本文首先介绍了几种主要的全光波长变换技术的主要原理,继而阐述了其在DWDM网络中的应用。