WDM网络中基于阻塞公平性的业务疏导和波长分配

在具有多速率级别连接请求的WDM网络中，通过为较高速率的请求预留更多的波长集合，结合网络节点对较低速率业务更强的输导能力，解决网络的阻塞公平性和全网的流量问题。在中国教育科研网的仿真实验，本文的策略比First-fit算法取得了更好的阻塞公平性能，并接纳了更多的网络流量。当负载为170Erlang时，多接纳的流量约为12％。     

WDM网状网中的基于平面构造的业务量疏导算法

将多个低于一个波长带宽的低速业务流复用到一个波长上传输的业务量疏导已经得到越来越多 的研究。WDM/SDH环网中的业务量疏导已得到大量研究,WDM网状网中的业务流疏导问题研究相对较少。该文研究静态环境下波长数目受限的业务量疏导问题,提出了一种基于平面构造的启发式业务量疏导算法。仿真结果表明该算法比已知的算法具有更好的性能。     

一种WDM疏导网络动态组播路由算法

对无波长变换能力的波分复用（WDM）疏导网络中的组播路由和波长分配（MRWA）问题进行了研究，提出了动态组播流量疏导算法（DMTGA）。这种算法根据当前网络资源使用情况，结合流量疏导和负载均衡，对链路权重进行动态配置，构建满足组播业务请求带宽需求的组播树。在不同的网络负载下对算法进行仿真，对比分析了DMTGA对业务请求接入率、平均网络资源利用率和全网负载分布的影响。     

WDM疏导网络中一种新的多播业务路由算法

研究了波分复用(WDM)网状网中动态多播业务量疏导,提出一种新的辅助疏导模型,其可以描述当前网络资源状况和节点分光特点,并动态更新.进而提出一种有效的多播业务量疏导启发式算法(MGA),将业务的多播选路和波长分配同时完成.仿真表明,该算法在波长连续性限制、网络波长和节点收发器数目有限的情况下,具有较低网络阻塞率.     

线性预编码OFDM系统的迭代接收机

线性预编码是OFDM系统在频率选择性衰落信道中利用频率分集的有效方法.为了进一步提高性能,本文提出了一种线性预编码OFDM系统的迭代接收机,该迭代接收机采用基于线性最小均方误差准则(LMMSE)的turbo均衡算法及其简化方法,具有很低的计算复杂度.本文同时还提出通过使用长度不小于等效离散时间信道的时延扩展长度的线性预编码器和迭代接收机,可获得完全的频率分集增益.仿真表明本文提出的方法在多径干扰严重的信道条件下的误码率性能接近AWGN下界.     

光网络选路和波长分配研究

文章在叙述了光网络中选路和波长分配(RWA)要解决的基本问题后,对有关方面的近年研究作了综述,主要包括:虚拓扑重构、业务量疏导的RWA、多播RWA、抗毁网络的RWA.抗毁问题涉及WDM网络的抗毁选路、区分可靠性、网状网的快速恢复、多故障下的抗毁.     

光交换通信网络路由与波长分配研究

本文采用了作者提出的Lagrange松弛框架下子问题序贯求解的新方法，解决了具有大量相同连接的路由与波长分配问题，大大改善了对偶解质量。数值计算验证了新方法的有效性。     

多播格状WDM光网络中流量疏导的一种启发性算法

波分复用技术的开发应用及网络业务信息的多样化促进了多播技术的应用和发展.由于网络中波长带宽与节点间业务信息需求之间的巨大反差,使流量疏导成为必要,以节约网络资源和成本.但多播的出现使流量疏导算法变得更复杂多样.本文提出了对多播格状网络中的静态流量进行有效疏导的一种启发性算法,并取得较为优化的结果.     

Ant Colony Optimization for Dynamic RWA in WDM Networks with Partial Wavelength Conversion

Dynamic routing and wavelength assignment (RWA), which supports request arrivals and lightpath terminations at random times, is needed for rapidly changing traffic demands in wavelength division multiplexed, (WDM) networks. In this paper, a new distributed heuristic algorithm based on ant colony optimization for dynamic RWA is put forward. We consider the combination of route selection and wavelength assignment as a whole using a multilayer-graph model. Therefore, an extended multilayer-graph model for WDM networks with limited wavelength conversion is presented. Compared with other RWA methods, the Ant Colony heuristic algorithm can achieve better global network optimization and can reduce communication overhead cost of the networks. Simulation showed that a lower blocking probability and a more rational wavelength resource assignment can be achieved.     

多播光网络研究中几个问题的探讨

波分复用(WDM)技术的开发和应用使得网络中的信息容量得到了极大的提高，而网络中业务信息的多样化则促进了多播技术的应用和发展。多播的出现使网络的节点结构、虚拟拓扑连接方式及路由和流量疏导算法变得更加复杂多样。为此对光网络中各种多播方式及节点结构并对现有的路由和波长分配算法进行了评述。在此基础上提出了对这类光网络中的信息流量进行疏导时应遵循的几个基本原则，目的是提高波长容量的利用率，减少网络中所用的波长和分插复用器（ADM）数，降低网络的成本和费用。     

Grooming of Arbitrary Traffic in Optical WDM Mesh Networks Using a Genetic Algorithm

In this paper, a genetic algorithm is proposed for grooming of arbitrary traffic in optical mesh networks. Traffic streams are routed in the wavelength division multiplexing (WDM) grooming networks that comprise both fiber links and established lightpaths. Chromosomes are split into multiple versions when multiple shortest routes are found. The selection strategy is based on a comparison between chromosomes. A variety of cost functions are proposed for the routing algorithm and two comparison methods are considered in the selection procedure. Computer simulations are performed with randomly generated traffic patterns. The results show that the algorithm is effective for traffic grooming (TG) problems, and also for routing and wavelength assignment problems.     

一种WDM网状网中基于共享保护的业务量疏导算法

在WDM网络中业务的带宽需求远低于一个波长所提供的带宽,业务量疏导可以聚集低速业务到大容量的光路中从而有效地利用波长带宽资源.目前大多数业务量疏导的研究限于环形网,考虑对WDM网状网中低速业务可靠疏导的文献更少.该文综合考虑WDM网状网生存性及业务量疏导,提出了基于波长分层图的共享保护业务量疏导算法(SPTG-LG,Shared Protection Traffic Grooming algorithm ba,sed on wavelength Layered-Graph),并对算法进行了仿真和分析.     

波分复用光传送网中备用选路下的选路和波长分配算法

本文研究了动态业务下,波分复用光传送网的选路和波长分配问题,提出了一种基于备用选路的选路和波长分配算法.与文献中已有的利用全网信息的备用选路的算法相比,该算法能更加精确地描述建立光路对全网的影响,选择对网络状态影响最小的路由-波长对来建立光路,促进网络资源的有效利用.计算机仿真表明,不论在规则的格型环网还是非规则的网络中,在阻塞率性能方面,在大多数情况下该算法优于文献中已有的备用选路算法;同时它也能改善公平性.     

Dynamic Routing in WDM Grooming Networks

Traffic grooming in optical networks has gained significant importance in recent years due to the prevailing sub-wavelength traffic requirement of end-users. In this paper, a methodology for dynamic routing of fractional-wavelength traffic in WDM grooming networks is developed. To evaluate the performance of routing algorithms, a new performance metric that reflects the network utilization is also proposed. The performances of shortest-widest path, widest-shortest path, and available shortest path routing algorithms are evaluated on a class of WDM grooming networks by considering traffic of different capacity requirements. The effect of dispersity routing, where higher capacity requests are broken into multiple unit capacity requests, is also investigated. The most interesting counter-intuitive result that is observed is that increasing the grooming capability in a network could result in degrading the performance of the widest-shortest path algorithm.     

Shared Sub-Path Protection Algorithm in Traffic-Grooming WDM Mesh Networks

In this paper, we investigate the problem of dynamically establishing dependable connections in wavelength division multiplexing (WDM) mesh networks with traffic-grooming capabilities. We first develop a new wavelength-plane graph (WPG) to represent the current state of the network. We then propose a dynamic shared sub-path protection (SSPP) scheme based on this WPG. To establish a dependable connection, SSPP first searches a primary path for each connection request, and then it segments the found path into several equal-length sub-paths, and computes their corresponding backup paths, respectively. If two sub-paths in SSPP are fiber-disjoint then their backup paths can share backup resources to obtain optimal spare capacity. Based on dynamic traffic with different load, the performance of SSPP has been investigated via simulations. The results show that SSPP can make the tradeoffs between resource utilization and restoration time.     

Routing Mechanisms Employing Adaptive Weight Functions for Shortest Path Routing in Optical WDM Networks

Optical dense wavelength division multiplexed (DWDM) networks are an attractive candidate for the next generation Internet and beyond. In this paper, we consider routing and wavelength assignment in a wide area wavelength routed backbone network that employs circuit-switching. When a session request is received by the network, the routing and wavelength assignment (RWA) task is to establish a lightpath between the source and destination. That is, determine a suitable path and assign a set of wavelengths for the links on this path. We consider a link state protocol approach and use Dijkstras shortest path algorithm, suitably modified for DWDM networks, for computing the shortest paths. In [1] we proposed WDM aware weight functions that included factors such as available wavelengths per link, total wavelengths per link. In this paper, we present new weight functions that exploit the strong correlation between blocking probability and number of hops involved in connection setup to increase the performance of the network. We also consider alternate path routing that computes the alternate paths based on WDM aware weight functions. The impact of the weight functions on the blocking probability and delay is studied through discrete event simulation. The system parameters varied include number of network nodes, wavelengths, degree of wavelength conversion, and load. The results show that the weight function that incorporates both hop count and available wavelength provides the best performance in terms of blocking probability.     

考虑功率限制的WDM光网有效设计

提出了一种基于禁忌搜索技术的启发式算法有效波长与路由分配(RWA-TS-P)来解决考虑功率限制的WDM光网的优化设计。该算法建立在局部搜索贪婪算法RWA-greedy之上,引入了功率验证过程来保证建立光路的功率有效性。通过环网和网状网的设计实例验证了算法的性能。数值结果表明,该算法能够在保证网络中建立的所有光路功率有效性的前提下最优地配置网络资源,同时具有可以控制的计算复杂性。     

Link-State-Based Algorithms for Dynamic Routing in All-Optical Networks with Ring Topologies

The increased usage of large bandwidth in optical networks raises the problems of efficient routing to allow these networks to deliver fast data transmission with low blocking probabilities. Due to limited optical buffering in optical switches and constraints of high switching speeds, data transmitted over optical networks must be routed without waiting queues along a path from source to destination. Moreover, in optical networks deprived of wavelength converters, it is necessary for each established path to transfer data from source to destination by using only one wavelength. To solve this NP-hard problem, many algorithms have been proposed for dynamic optical routing like Fixed-Paths Least Congested (FPLC) routing or Least Loaded Path Routing (LLR). This paper proposes two heuristic algorithms based on former algorithms to improve network throughput and reduce blocking probabilities of data transmitted in all-optical networks with regard to connection costs. We also introduce new criteria to estimate network congestion and choose better routing paths. Experimental results in ring networks show that both new algorithms achieve promising performance.     

A comparative path establishment study on routing performance of MLR WDM optical networks

In this paper, we investigate the effect of path establishment method priorities over routing performance in mixed line rate (MLR) wavelength division multiplexed (WDM) optical networks. The survivable routing with rate and wavelength assignment (SRRWA) problem is presented and an efficient shared backup path protection solution is proposed. We prepared detailed simulation scenarios with all possible prioritizations and observed their performances. The simulation results show that assigning higher priority to single hop methods as compared with multi‐hop methods yields better performance. In both methods, it has been observed that assigning higher priority to grooming reduces the communication cost and the traffic blocking ratio while enhancing the resource utilization.     

Routing and Wavelength Assignment in Optical Networks Using Logical Link Representation and Efficient Bitwise Computation

In this paper, we propose and evaluate a new approach for implementing efficient routing and wavelength assignment (RWA) in wavelength division multiplexing (WDM) optical networks. In our method, the state of a fiber is given by the set of free wavelengths in this fiber and is efficiently represented as a compact bitmap. The state of a multiple-fiber link is also represented by a compact bitmap computed as the logical union of the individual bitmaps of the fibers in this link. Likewise, the state of a lightpath is represented by a similar bitmap computed as the logical intersection of the individual bitmaps of the links in this path. The count of the number of 1-valued bits in the bitmap of the route from source to destination is used as the primary reward function in route selection. A modified Dijkstra algorithm is developed for dynamic routing based on the bitmap representation. The algorithm uses bitwise logical operations and is quite efficient. A first-fit channel assignment algorithm is developed using a simple computation on the bitmap of the selected route. The resulting bitwise routing algorithm combines the benefits of least loaded routing algorithms and shortest path routing algorithms. Our extensive simulation tests have shown that the bitwise RWA approach has small storage overhead, is computationally fast, and reduces the network-wide blocking probability. The blocking performance of our RWA method compares very favorably with three routing methods: fixed alternate routing, shortest path using flooding, and Dijkstra’s algorithm using mathematical operations. Our simulation experiments have also evaluated the performance gain obtained when the network access stations are equipped with finite buffers to temporarily hold blocked connection requests.