基于改进蚁群算法的卫星光网络波长分配方法

路由与波长分配是下一代光网络的需要解决的核心问题之一。本文采用智能蚁群算法,研究了卫星光网络的路由与波长分配问题,为通信请求寻找最优的数据传输光路径。基于请求区域受限策略(Restricted Request Area,RRA)和链路波长负载平衡策略,建立了考虑传输延迟和波长连续性约束的双主星分布式星群节点结构光网络系统模型。利用智能蚁群路由和波长分配(Smart Ant Colony Routing AndWavelength Assignment,SAC-RWA)算法求解系统模型,以找到具有稀疏波长转换的卫星光网络中最小成本波长路径。所提出的算法允许单个蚂蚁同时完成路由和波长分配,仿真结果表明,RRA能够明显改进卫星光网络的性能,以略微增加拥塞率的代价显著降低了计算复杂度。     

软件定义卫星光网络蚁群优化波长路由技术

针对卫星光网络中网络拓扑动态时变和业务类型多样化的问题,研究了在软件定义网络架构下保障服务质量的路由技术,提出了一种基于多业务的卫星光网络蚁群优化波长路由算法。通过改进蚁群算法的启发函数,将波长空闲率、时延、时延抖动、丢包率作为蚂蚁选路的重要依据,为业务选择了满足多种服务质量的最优路径;采用分组波长分配方法对不同等级的业务进行了区分服务,为不同业务分配了不同的波长集。仿真结果表明:与CL-ACRWA算法和Dijkstra算法相比,降低了卫星光网络的平均时延、平均时延抖动、平均丢包率,提高了波长利用率,同时也降低了高优先级业务的网络拥塞概率。     

基于精英蚂蚁算法的动态路由和波长分配研究

为了更有效地解决密集波分复用光网络中动态路由和波长分配问题,提高光网络中资源利用率,该文提出了一种基于精英策略蚂蚁系统算法的动态路由和波长分配问题的解决方法。在仿真中通过将精英策略蚂蚁算法应用到经典的美国国家科学基金会网络中,动态地完成路由和波长的分配。仿真结果表明,精英策略蚂蚁算法能够降低网络阻塞率,有效提高密集波分复用光网络的带宽资源利用率,并且随着波长数目或者网络负载的不断增加,这种优势更加明显。     

一种快速动态分布式光链路建立方法

提出一种改进的波长分配算法,用于波长路由光网络中快速动态分布式光链路的建立。该算法采用提前释放和超时释放两种波长和链路释放机制,减少了网络拥塞,更适合波长路由网络的实际运行规则。通过在美国自然科学基金网(NSF)上的仿真计算,与以前的研究结果相比,该算法可以减少网络的阻塞率8％,同时缩短了光链路建立的时间。     

基于强化学习的光传送网路由波长优化

针对光传送网中动态业务的路由和波长问题,提出一种基于强化学习的深度路由波长分配算法DeepRWA。算法基于软件定义网络架构,通过强化学习灵活地调整控制光传送网,实现光网络路由波长分配策略优化。针对路由选择问题,结合链路上的波长使用情况,使用A3C算法选择合适的路由,使得阻塞率最小;针对波长分配问题,使用首次命中算法选择波长。考虑阻塞率、资源利用率、策略熵、价值损失、运行时间及收敛速度等多个指标,利用14节点NSFNET网络拓扑仿真实验。结果表明:当信道中包含18个波长时,与传统KSP-FF算法相比,所提出的路由波长分配算法的阻塞率降低了0.06,资源利用率提高了0.02,但运行时间有增加;在波长数超过45以后,与传统KSP-FF算法相比,所提算法保持阻塞率和资源利用率的同时,运行时间开始降低;当信道中包含波长数为58时,与传统KSP-FF算法相比,所提算法运行时间减少了0.07 ms。由此可见,提出的算法使路由选择和波长分配得到了优化。     

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.     

Hadoop平台下一种改进蚂蚁算法的QoS路由研究

随着未来云计算的发展,各种云服务的应用将需要更高的网络性能。链路拥塞导致的数据包传输时延或数据包丢弃使得网络无法保障业务的QoS。目前普遍使用的链路状态路由算法不具有拥塞响应机制。本文通过在拥塞节点间发送连接蚂蚁寻找新路由来解决拥塞问题。NS2仿真结果表明,该算法能加快新的路由搜索,满足QoS的需求,并有效控制丢包率,时延等性能。     

WDM光网络中一种新的备用路由算法

文章基于负载均衡和禁忌搜索提出一种新的备用路由算法,实现了优化解搜索及对链路负载方差和拥塞的优化.路由选择后,采用首次命中按长通道优先原则为各光通道分配波长.在环网和网状网静态业务模式下对不同路由算法进行了仿真,仿真结果表明,新算法能充分利用网络资源安排最佳路由,有效降低了对波长的需求.     

认知网络中的拥塞规避多径路由算法

链路拥塞导致的数据包传输延时或者数据包丢弃使得网络无法保证业务的Q0S,而目前普遍使用的链路状态路由算法不具有拥塞响应机制.本文针对以上问题,提出了一种能够快速规避拥塞的多径路由算法,该算法通过改进蚂蚁算法,在拥塞发生时采用双向蚂蚁寻路的方法,提高了新路径搜索的速度;使用新的寻路准则使其更满足认知网络的QoS需求.使用...     

一种基于改进蚁群算法的光网络动态RWA机制

动态RWA(路由与波长分配)问题是智能光网络的核心问题.文章提出一种解决动态RWA问题的改进蚁群算法,在转移概率中加入了链路的空闲率作为约束条件,同时还引入了随机扰动防止搜索过早收敛于局部最优路径.仿真结果表明,改进算法与传统Dijkstra+ FF(首次命中)算法相比,可以显著降低阻塞率,提高资源利用率.     

WDM网络中基于负载平衡的动态波长路由算法

在WDM网络中，路由和波长分配（RWA）算法是一个焦点问题．当前的RWA算法多是考虑路径跳数或全网拥塞程度，并没有分析各个链路的具体情况．文中提出一种WDM网络中能实现负载平衡的路由算法——最大波长跳数比值（MWHR）算法。基本思想是：根据各备选路径的跳数和其经过的各链路上的可用波长数信息。计算该路径的优先选取权值，优先选取权值最大的路径．仿真表明，该算法在保证较低的阻塞率情况下，能有效的将业务负载均衡分布在网络中的所有链路上．     

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.     

基于蚁群系统的分布式RWA算法研究

针对波分复用(WDM)光网络中动态选路和波长分配(RWA)问题，提出了一种基于蚁群算法的分布式动态RWA方法。将蚁群算法与分层图模型结合，实现了RWA的并行计算。仿真结果表明，与现有最短路径法相比，该算法能有效地降低光路阻塞率，促进波长资源的合理分配，同时分布式的计算方式也降低了现代频繁变化的大型光网络的通信开销。     

部分共享波长转换光网络动态路由的改进算法

提出了一种应用于部分共享波长转换（PWC）的波长路由光网络（WRON）中的基于节点阻塞的动态路由算法,它不需要共享复杂的波长转换信息,而是将各节点的阻塞特性考虑到路由过程中。为评价算法性能,在14节点的国家科学基金网（NSFNET）拓扑中进行了仿真。结果表明,新的路由算法显著改善了网络的阻塞性能和建路失败的概率,尤其是随着网络负载的降低,网络性能的改善更显著。     

一种基于改进蚁群算法的光网络波长路由分配算法

路由与波长分配(RWA)是下一代光网络的需要解决的核心问题之一。论文提出了一种基于改进蚁群算法的光网络RWA算法SA-DRWA算法。算法在转移概率中加入了链路的空闲率作为约束条件,同时还引入了随机扰动以防止传统蚁群算法中迭代次数较少时就过早收敛于局部最优路径的缺点。理论分析表明,SA-DRWA算法可以有效地实现光网络中的负载均衡。对不同网络拓扑中算法的性能进行了仿真,结果表明,SA-DRWA算法比传统Dijkstra+FF算法在阻塞率及资源利用率等方面有明显改进,在规则网格型网络中阻塞率和资源利用率分别改善了0.23。     

Effects of wavelength routing and selection algorithms onwavelength conversion gain in WDM optical networks

Wavelength-division multiplexing (WDM) technology is emerging as the transmission and switching mechanism for future optical mesh networks. In these networks it is desired that a wavelength can be routed without electrical conversions. Two technologies are possible for this purpose: wavelength selective cross-connects (WSXC) and wavelength interchanging cross-connects (WIXC), which involve wavelength conversion. It is believed that wavelength converters may improve the blocking performance, but there is a mix of results in the literature on the amount of this performance enhancement. We use two metrics to quantify the wavelength conversion gain: the reduction in blocking probability and the increase in maximum utilization, compared to a network without converters. We study the effects of wavelength routing and selection algorithms on these measures for mesh networks. We use the overflow model to analyze the blocking probability for wavelength-selective (WS) mesh networks using the first-fit wavelength assignment algorithm. We propose a dynamic routing and wavelength selection algorithm, the least-loaded routing (LLR) algorithm, which jointly selects the least-loaded route-wavelength pair. In networks both with and without wavelength converters the LLR algorithm achieves much better blocking performance compared to the fixed shortest path routing algorithm. The LLR produces larger wavelength conversion gains; however, these large gains are not realized in sufficiently wide utilization regions and are diminished with the increased number of fibers     

Ant colony optimization based load balancing routing and wavelength assignment for optical satellite networks

An ant colony optimization (ACO) based load balancing routing and wavelength assignment (RWA) algorithm (ALRWA) was put forward for the sake of achieving a fairy load balancing over the entire optical satellite networks. A multi-objective optimization model is established considering the characteristic of global traffic distribution. This not only employs the traffic intensity to modify the light path cost, but also monitors the wavelength utilization of optical inter-satellite links (ISLs). Then an ACO algorithm is utilized to solve this model, leading to finding an optimal light path for every connection request. The optimal light path has the minimum light path cost under satisfying the constraints of wavelength utilization, transmission delay and wavelength-continuity. Simulation results show that ALRWA performs well in blocking probability and realizes efficient load balancing. Meanwhile, the average transmission delay can meet the basic requirement of real-time business transmission.     

Wavelength converter placement under different RWA algorithms in wavelength-routed all-optical networks

Sparse wavelength conversion and appropriate routing and wavelength assignment (RWA) algorithms are the two key factors in improving the blocking performance in wavelength-routed all-optical networks. It has been shown that the optimal placement of a limited number of wavelength converters in an arbitrary mesh network is an NP-complete problem. There have been various heuristic algorithms proposed in the literature, in which most of them assume that a static routing and random-wavelength assignment RWA algorithm is employed. However, the existing work shows that fixed-alternate routing and dynamic routing RWA algorithms can achieve much better blocking performance. Our study further demonstrates that the wavelength converter placement and RWA algorithms are closely related in the sense that a well-designed wavelength converter placement mechanism for a particular RWA algorithm might not work well with a different RWA algorithm. Therefore, the wavelength converter placement and the RWA have to be considered jointly. The objective of this paper is to investigate the wavelength converter placement problem under the fixed-alternate routing (FAR) algorithm and least-loaded routing (LLR) algorithm. Under the FAR algorithm, we propose a heuristic algorithm called minimum blocking probability first for wavelength converter placement. Under the LLR algorithm, we propose another heuristic algorithm called weighted maximum segment length. The objective of the converter placement algorithms is to minimize the overall blocking probability. Extensive simulation studies have been carried out over three typical mesh networks, including the 14-node NSFNET, 19-node EON, and 38-node CTNET. We observe that the proposed algorithms not only outperform existing wavelength converter placement algorithms by a large margin, but they also can achieve almost the same performance compared with full wavelength conversion under the same RWA algorithm.     

MC-BRM: A distributed RWA algorithm with minimum wavelength conversion

There are two strategies for solving Routing and Wavelength Assignment (RWA) in wavelength-routed networks: centralized and distributed. Centralized approaches are appropriate for small networks with light traffic, whereas distributed approaches are suitable for large networks with heavy traffic. Solving RWA problem in distributed algorithms can be generally divided into two phases: routing phase and wavelength assignment phase. Allocating a wavelength over a physical path for a connection request can be performed by one of two major strategies: Backward Reservation Method (BRM) and Forward Reservation Method (FRM). In this work, we assume that every node in the network can be equipped with a number of wavelength converters. Wavelength converters are usually chosen in a free policy. However, we propose a distributed algorithm, called Minimum-Conversion Backward Reservation Method (MC-BRM), that attempts to establish light-paths with minimum number of wavelength conversions. The MC-BRM algorithm can efficiently reduce the number of required wavelength conversions in the network. Besides improving blocking probability, MC-BRM can lead to better fairness in establishing light-paths with different number of hops. Finally, we make the worst case analysis for estimating wavelength conversion usages in individual nodes.