一种按需式双信道的Ad Hoc网络路由方法

为了提高Ad Hoc网络的信道带宽和降低通信时的相互影响，在单信道的Ad Hoc网络多路径路由方法基础上，提出了按需式的采用双信道的路由策略。在物理上，整个网络存在两个独立的信道。通过一次路由发现，获得两条节点不相交路径，按照每包分配策略，把数据交替在两个信道的不同路径上进行传输。在提高带宽的同时，降低了数据传输冲突，从而改善网络性能。     

波长路由树形全光网中波长转换器配置算法

在波长路由全光网中,波长转换以及路由和波长分配算法（RWA）是降低网络阻塞率、改善网络性能的两个重要方法。研究了树形网络中波长转换器的配置问题,结合树形网络的特点,对影响波长转换器配置的主要因素进行了分析。综合路径长度、路径通信负荷以及节点的度,提出了基于网络直径的波长转换器配置算法和基于网络中心的波长转换器配置算法。通过算法演示和仿真,表明提出的两种算法各有优点。     

光通信网络中路由与波长分配的算法研究

光通信网络作为下一代网络的主要网络之一,在整个通信网中起着至关重要的作用。目前光通信中主要是采用基于DWDM(密集波分复用)技术组成的光网络,随着波分数量的增加,DWDM网络中的路由与波长分配问题显得十分重要,需要有一种有效的算法来使有限的波长资源得到充分地利用。本文根据原有的数学分析模型,提出了一种分层图模型,并根据此模型提出了一种用来解决DWDM网络中出现的波长分配问题的一种算法,并通过计算机仿真来表明此算法提高了波长资源的利用率,降低了网络的阻塞率。     

波长路由光网络相关问题分析

光纤凭借着带宽大和传输损耗小的特点逐渐代替了铜缆,并且是干线网一种重要传输介质。文章重点对波长路由光网进行了深入的探究和分析,详细指出波长路由光网络所具有的优势,同时针对波长路光网络中的RWA问题和波长路由光网络中故障管理的问题进行了分析。     

基于WDM传输网的动态路由算法

波分复用技术(WDM)作为一种公认的最佳光纤扩容技术已被广泛应用在国际和国内长途骨干网上。路由算法与波长分配(RWA)是WDM网中的重要技术之一,评价RWA算法的一个重要标准是网络阻塞率。采用合适的路由算法可以大大降低网络的阻塞率。该文采用一种结合了再生节点选择的动态RWA算法来解决WDM网中的波长路由问题,并通过光纤通道拓扑的优化算法来进一步优化。通过建模仿真,研究了NSFNET网络优化前后阻塞率的变化,仿真的结果证明采用该优化算法可以降低网络的阻塞率。     

一种稀疏波长转换光网络中的波长分配算法

研究了具有波长转换功能的WDM光网络的分类以及已有的几种波长分配算法，分析了波长分配算法的一般流程。文中以波长变换次数最少做为所提出的波长分配算法的主要优化目标，根据WDM光网络中的节点是否具有波长转换的功能，结合等价光路由替换的思想，提出了在稀疏有限波长转换光网络中的一种启发式的波长分配算法。仿真实验表明，当光网络中的连接请求量较大时，该算法的阻塞率低于已有的一些波长分配算法，连接能力有了较大提高。     

一种改进的基于最少信道切换的路由算法

在Ad Hoc网络中,如何基于多信道有效地利用网络中的频谱资源,提高网络的性能,已经成为近几年来研究的热点。在DSDV路由协议的基础上,提出了一种基于减少网络中的信道切换的路由算法——OLCH-DSDV,该算法采用最小切换时延的信道分配策略,尽量减少信道切换产生的时延,从而降低了网络时延,提高了吞吐量。该算法要求源节点通过自身维护的路由和信道使用信息,选择到达目的节点的最优路径,也就是需要最少信道切换的路径。仿真结果表明该路由改进算法在有效提高系统吞吐量的同时,也有效地减少了网络中的传输时延。     

基于蚁群的无线传感器网络能量均衡非均匀分簇路由算法

无线传感器网络(WSN)路由中,节点未充分考虑路径剩余能量及链路状况进行的路由会造成网络中部分节点网络寿命减少,严重影响网络的生存时间。为此,将蚁群优化算法与非均匀分簇路由算法相结合,提出一种基于蚁群优化算法的无线传感器非均匀分簇路由算法。该算法首先利用考虑节点能量的优化非均匀分簇方法对节点进行分簇,然后以需要传输数据的节点为源节点,汇聚节点为目标节点,利用蚁群优化算法进行多路径搜索,搜索过程充分考虑了路径传输能耗、路径最小剩余能量、传输距离和跳数、所选链路的时延和带宽等因素,最后选出满足条件的多条最优路径,完成源目的节点间的信息传输。实验表明,该算法充分考虑路径传输能耗和路径最小剩余能量、传输跳数及传输距离,能有效延长无线传感器网络的生存期。     

并行LU分解的通信模式在WDM环网上的波长分配算法

波长分配是光网络设计的基本问题，设计波长分配算法是洞察光网络通信能力的基本方法．不同的并行算法具有不同的通信模式，如何在光互连网上实现这些通信模式，是当前一个颇受关注的研究领域．本文基于WDM环网络，针对矩阵的并行LU分解，构造了一种并行LU分解的通信模式，讨论了将该通信模式嵌入在环形光网络中的波长分配问题．在解决该问题的过程中，得到了将一种特殊的二分图结构的通信模式嵌入在环网中的波长分配算法．通过分析和证明得到了在WDM环网上实现该并行LU分解通信模式所需的最小波长数．     

基于WAPG动态路由与波长分配的优化算法

多粒度交换能减少交换节点中的交换矩阵规模及复用器和解复用器的数目,很大程度降低了网络成本,但使得光纤网络路由与波长分配问题变得更加复杂.通过分析多粒度光网络交换节点的结构和动态路由与波长分配的特点,定义5种不同的逻辑链路权重标注方法,提出一种基于路径图波带分配的路由与波长分配模型,达到减少波长碎片的目的.模拟结果表明,该方法能有效地减少多粒度光网络中的波长转换数和降低网络成本.     

All-to-All Optical Routing in Chordal Rings of Degree 4

We consider the problem of routing in networks employing all-optical routing technology. In such networks, information between nodes of the network is transmitted as light on fiber-optic lines without being converted to electronic form in between. We consider switched optical networks that use the wavelength-division multiplexing (or WDM) approach. A WDM network consists of nodes connected by point-to-point fiber-optic links, each of which can support a fixed number of wavelengths. The switches are capable of redirecting incoming streams based on wavelengths, without changing the wavelengths. Different messages may use the same link concurrently if they are assigned distinct wavelengths. However, messages assigned the same wavelength must be assigned edge-disjoint paths. Given a communication instance in a network, the optical routing problem is the assignment of {routes} to communication requests of the instance, as well as wavelengths to routes so that the number of wavelengths used by the instance is minimal. We focus on the all-to-all communication instance I _A in a widely studied family of chordal rings of degree 4, called optimal chordal rings . For these networks, we prove exact bounds on the optimal load induced on an edge for I _A , over all shortest-path routing schemes. We show an approximation algorithm that solves the optical routing problem for I _A using at most 1.006 times the lower bound on the number of wavelengths. The previous best approximation algorithm has a performance ratio of 8. Furthermore, we use a variety of novel techniques to achieve this result, which are applicable to other communication instances and may be applicable to other networks. Received July 22, 1998; revised October 14, 1999.     

WDM全光网络中Multicast的寻径与波长分配算法

在WDM全光网络中实现实时Multicast功能是计算机网络的应用要求,也是现代计算机网络的重要特征。该文提出了一种在WDM全光网络中实现实时Multicast的算法。该算法以辅助的波长图为基础,将寻径与波长分配统一进行,构造满足延迟约束的、具有较低成本的Multicast树,实现Multicast功能。     

A survey on physical layer impairments aware routing and wavelength assignment algorithms in optical networks

Optical networks are moving from opaque and translucent architectures towards all-optical (transparent) architectures. In translucent architectures a small amount of regeneration (e.g. optical–electronic–optical conversion) is available in the network. The incorporation of the physical impairments in the routing and wavelength assignment (RWA) problem in transparent optical networks has recently received some attention from the research communities. This work compiles a comprehensive survey of the proposed algorithms that address this issue. The physical layer impairments and related classification in optical networks are initially presented followed by physical layer impairments (PLI) constrained and aware RWA algorithms. Algorithmic approach, current PLI-RWA proposals, impact of wavelength conversion on these algorithms, protection and resilience considerations, and proposed extensions to control planes are covered in this work. Further research topics are presented in this study.     

基于遗传算法的动态RWA问题的研究

针对WDM光传送网中的动态路由选择和波长分配(RWA)问题,提出了一种基于遗传算法的动态RWA方法。将遗传算法与相对容量影响(RCI)波长分配算法相结合,以实现对RWA算法的改进。仿真结果表明,与现有最短路径算法[1]相比,该算法能有效提高网络资源利用率,促进波长资源的合理分配。     

Optical packet switching with multiple path routing

The performance of packet-switching wavelength routed optical networks critically depends on packet contentions at the intermediate routers. This paper shows through simulations that deflection routing is an effective technique for packet-switching wavelength routed optical networks with irregular meshed topologies. It is shown that multiple path routing (MPR) as the deflection rule mitigates the blocking of packets substantially in cross-connected all-optical networks leading to a significant reduction in hardware volume and cost of all-optical IP routers. The effectiveness of the blocking reduction critically depends on the network topology, and meshed topologies with a high number of interconnections benefit of the largest gain from deflection routing.     

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。     

Wavelength Conversion in All-Optical Networks with Shortest-Path Routing

We consider all-optical networks with shortest-path routing that use wavelength-division multiplexing and employ wavelength conversion at specific nodes in order to maximize their capacity usage. We present efficient algorithms for deciding whether a placement of wavelength converters allows the network to run at maximum capacity, and for finding an optimal wavelength assignment when such a placement of converters is known. Our algorithms apply to both undirected and directed networks. Furthermore, we show that the problem of designing such networks, i.e., finding an optimal placement of converters, is MAX SNP-hard in both the undirected and the directed case. Finally, we give a linear-time algorithm for finding an optimal placement of converters in undirected triangle-free networks, and show that the problem remains NP-hard in bidirected triangle-free planar networks.     

Simple, Efficient Routing Schemes for All-Optical Networks

All-optical networks promise data transmission rates several orders of magnitude higher than current networks. The key to high transmission rates in these networks is to maintain the signal in optical form, thereby avoiding the prohibitive overhead of conversion to and from the electrical form, and to exploit the large bandwidth of optical fibers by sending many signals at different frequencies along the same optical link. Optical technology, however, is not as mature as electronic technology. Hence it is important to understand how efficiently simple routing elements can be used for all-optical communication. In this paper we consider two types of routing elements. Both types can move messages at different wavelengths to different directions. If in the first type a message wants to use an outgoing link that is already occupied by another message using the same wavelength, the arriving message is eliminated (and therefore has to be rerouted). The second type can evaluate priorities of messages. If more than one message wants to use the same wavelength at the same time, then the message with the highest priority wins. We prove nearly matching upper and lower bounds for the runtime of a simple and efficient protocol for both types of routing elements, and apply our results to meshes, butterflies, and node-symmetric networks. Received January 6, 1998, and in final form July 17, 1998.     

WDM全光网络中优化组播路由的遗传算法

在WDM网络中，路由和波长分配是紧密联系在一起的，即在建立光连接的过程中，不但需要确定路由，还要为该路由分配合适的波长资源。该文给出了一种遗传算法以解决在给定一组时延受限的组播请求的情况下，如何为这些组播请求建立合适的组播路由树，从而使得该组组播树所占用的波长数最小的问题。通过使用一种合适的二维染色体编码表示，并设计适合问题的交叉和变异操作，从而算法可以有效地搜索假设空间，实验模拟结果表明了该算法具有快速有效的特点。     

Traffic grooming, routing, and wavelength assignment in WDM transport networks with sparse grooming resources

While a single fiber strand in wavelength division multiplexing (WDM) has over a terabit-per-second bandwidth and a wavelength channel has over a gigabit-per-second transmission speed, the network may still be required to support traffic requests at rates that are lower than the full wavelength capacity. To avoid assigning an entire lightpath to a small request, many researchers have looked at adding traffic grooming to the routing and wavelength assignment (RWA) problem. In this work, we consider the RWA problem with traffic grooming (GRWA) for mesh networks under static and dynamic lightpath connection requests. The GRWA problem is NP-Complete since it is a generalization of the RWA problem which is known to be NP-Complete. We propose an integer linear programming (ILP) model that accurately depicts the GRWA problem. Because it is very hard to find a solution for large networks using ILP, we solve the GRWA problem by proposing two novel heuristics. The strength of the proposed heuristics stems from their simplicity, efficiency, and applicability to large-scale networks. Our simulation results demonstrate that deploying traffic grooming resources on the edge of optical networks is more cost effective and results in a similar blocking performance to that obtained when distributing the grooming resources throughout the optical network domain.