用于解决大规模波长路由光网中路由和波长分配问题的新启发式算法

本文提出了一种新的启发式算法,它将路由和波长分配问题分解为两个子问题分别进行优化求解,并以最小化波长需求作为目标函数。在不同通信负荷的情况下,我们以NSF网为例,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。数值结果表明所提出的算法可有效地应用于大规模波长路由光网。     

基于最小化平均分组跳的分组交换多跳光网的设计

本文研究了支持分组交换通信的波长路由光网的逻辑拓扑设计问题,并将它表示为混合整数线性规划问题(MILP),其目标函数为最小化平均分组跳数目.在约束条件中同时考虑了分组传输时延和排队时延.我们以6结点的网络为例,对于不同的收发机数目和时延边界,数值结果表明最小化平均分组跳数目等价于最小化网络拥塞.小的平均分组跳数目可以保证网络通信时具有较小的时延.最后,对于不同的通信模式,我们比较分析了网格的优化性能参数,这些结果有助于提出更好的启发式算法.     

WDM全光网络中一种分布式路由及波长分配协议

在全光网络中,光信号在全光域内传输,避免了光-电转换带来的延迟,因此全光网支持高数据率传输并提供巨大的网络容量。WDM(波分多路复用)技术的采用使得高速光传输线路与低速终端处理设备之间能够相互兼容。探讨了WDM全光网中的路由及波长分配问题,提出了一种用于WDM网络中的分布式路由及波长分配协议,具有开销小、阻塞率低以及良好的可扩展性,是一种比较实用的RWA协议。     

全光网络中动态业务下的阻塞性能分析

通过对自适应路由和动态备选路由算法的性能分析,研究了波长选择和波长交换这两种类型的全光网络在动态业务下的阻塞性能,并提出了将动态波长分配与自适应路由选择相结合的算法.数值结果表明:1)相比波长交换网络而言,多纤波长选择网络是更为经济且切实可行的选择;2)动态备选路由算法可以获得与自适应路由算法相似的性能,并且文中所提出的算法能够更好的提高网络的阻塞性能.分析表明:不同算法的性能与网络拓扑的连接度以及备选路由的数目密切相关.     

光传送网中结合传输损伤的路由和波长分配

在波长路由光网优化设计的过程中考虑了物理传输损伤造成的限制,提出了一种联合优化思路.将光信号在传输过程中的物理损伤作为问题公式的另一维约束,给出了相应的启发式算法,并按照由粗到细的机制对所提出的思路做了相应的评估,同时对负荷平衡问题作了初步的分析.数值结果表明这种算法可以获得与优化值相近的波长需求解,并且能够保证网络的传输性能,其业务分布随着备选路径的增加而趋向均衡.     

一种求解虚波长路径光网络波长资源优化问题的启发式算法

本文提出了一种虚波长路径光网络的启发式路由选择算法,它可以用来解决以最小化网络所需波长数目为目标的资源优化问题.该算法应用了基于最大概率路径的选路优化策略.对一个样例网络的数值分析结果表明该算法是有效的.     

波长转换受限条件下的最优组播波长分配算法

扩展了静态组播路由和波长分配问题,引入了范围受限的波长转换器,改进了优化目标,新的优化目标为整个组播连接使用的波长转换器数目最少,同时保证源节点到每个组播成员的路径上使用的波长转换器数目均小于指定值.利用动态规划,在两种连接建立策略下对问题进行了求解,所得解可用于衡量启发式组播波长分配算法的优劣.     

WDM多纤环网的优化设计

本文讨论了WDM多纤环网(MFR)的优化设计问题,为解决该问题提出了新的整数线性规划公式.所采用的优化目标是最小化平均结点端口数目,以此为优化目标可以保证所设计的多纤环网具有最大的经济有效性.利用所提出的算法,我们定量分析了采用不同路由方案(波长通道和虚波长通道)的几种MFR结构(单向和双向)的网络性能.本文所获得的结论可作为选择合适MFR结构的参考.     

动态波长路由的全光连接建立时间的优化方法

本文描述了在波长路由光网络中影响连接建立时间的限制因素，提出了预置光路的方法，通过对路由和波长分配算法的改进减小部分连接的建立时间。模拟计算表明，优化的算法可以使部分连接有效地利用预置光路，从而减小连接建立时间，提高网络的整体性能。     

分布式光网络中的波长和端口数目优化分析

研究了分布式Mesh光网络中动态业务疏导问题中的波长和端口优化问题,通过对分布式Mesh光网络中不同业务和网络拓扑情况下的网络结点波长和端口使用数目的仿真分析,得出网络中的合理波长和端口数目配置,为网络规划和设计提供依据.     

Wavelength conversion in multihop wavelength division multiplexed transport networks

In this paper, we have analyzed the wavelength conversion for a multihop wavelength division multiplexed (WDM) transport networks to minimize the blocking probability. The analytical model is presented for a static-routing for a multihop paths wavelength conversion. The results have been validated for three cases, without wavelength conversion, with wavelength conversion and limited wavelength conversion. We show that by using wavelength conversion, there is significant improvement in performance of these transport networks. Each of the three cases of wavelength conversion is discussed for different degrees of conversions. It is observed that the higher the degree of conversion is, the lower is the blocking probability. Also as the degree of conversion is increased further, the curve for limited range conversion moves towards the no conversion.     

A scheme of optical interconnection for super high speed parallel computer

An optical cross connection network which adopts coarse wavelength division multiplexing (CWDM) and data packet is introduced. It can be used to realize communication between multi-CPU and multi-MEM in parallel computing system. It provides an effective way to upgrade the capability of parallel computer by combining optical wavelength division multiplexing (WDM) and data packet switching technology. CWDM used in network construction, optical cross connection (OXC) based on optical switch arrays, and data packet format used in network construction were analyzed. We have also done the optimizing analysis of the number of optical switches needed in different scales of network in this paper. The architecture of the optical interconnection for 8 wavelength channels and 128 bits parallel transmission has been researched. Finally, a parallel transmission system with 4 nodes, 8 channels per node, has been designed.     

Delay-constrained anycast routing problem in WDM networks with wavelength conversions

Anycast routing and wavelength assignment problem has been intensively studied in wavelength-division multiplexing (WDM) networks, however, real-time application where packets have explicit expiration deadlines is not taken into consideration. In a WDM network, each link is associated with limited wavelengths available for channel connections. Data transmission over one wavelength to another requires wavelength conversion, which causes a long delay of message transmission. When the network and the set of anycast routing requests are given, the delay-constrained wavelength conversions anycast routing (DWCAR) problem is to find a set of light-paths, one for each source, for anycasting message to one member of the anycast destination group. The objective is to find a minimum number of wavelength conversions with the constraint that the sum of delays along every path must not exceed a given delay-bound. In this paper, we present a Tabu-search based delay-constrained anycast routing algorithm (TSDA) to solve this NP-complete problem, and compare it to a simple K shortest path based anycast algorithm (KSPA). Simulation results show TSDA achieves an average 40–50% improvement in required wavelength conversions.     

A new green multicast grooming protection algorithm in WDM optical networks

Since optical network carries a lot of traffic, survivability is very important to ensure the service continuity against network failures. Recently, multicast services become more popular to meet the huge multimedia demand in network, so that multicast survivability in optical network has got more attention. However, multicast survivability may lead to more energy consumption due to more redundant backup resources allocated. Since greening network is particularly important with the energy crisis keeping growing, green multicast survivability in optical network is a challenging issue. This paper focuses on the green multicast grooming protection problem in optical network and designs two auxiliary graphs that includes a virtual topology graph and an integrated graph to address the survivable multicast grooming, routing and wavelength assignment. Based on the auxiliary graphs, this paper proposes an efficient heuristic called green multicast grooming algorithm based on spanning path dedicated protection (GMG-SPDP), in which the network reliability and the energy efficiency are jointly taken into account. Simulation results show that, compared to other algorithms, the proposed GMG-SPDP not only has lower blocking probability and higher bandwidth utilization ratio, but also saves more energy.     

Performance analysis of traffic groomed optical network

In this paper we carry out the performance analysis of traffic groomed multilayer optical networks. It is seen that the number of wavelength channels required decreases as the wavelength grooming factor increases. We have evaluated blocking probability for different load and grooming factor. The performance of the network has been evaluated for different conditions; first for fixed number of links with grooming factor set to 3 and subsequently with increase in grooming factor up to 18 in steps. The load on each link is selected as 2, 5, 9, 12, 15 and 20 Erlangs and the blocking probability as function of number of optical channels has been evaluated. In this work the effect of number of wavelength channels, traffic load and grooming factor on network blocking probability has been studied. The investigation reveals that the blocking probability decreases with increase in wavelength channels. Similarly we found that the blocking probability increases with increase in traffic load which is quite evident. Further it is shown that when the grooming factor is increased to significant value (16), the number of wavelengths requirement (8) becomes relatively stable.     

An efficient algorithm for optimal manycast routing problem over WDM networks

In this paper, we discuss the problem of supporting resource optimization of manycasting service over wavelength division multiplexing (WDM) optical networks. Manycast is a novel group communication paradigm wherein the source is required to send data packets to a certain number of a set of pre-specified group members. Since it integrates the characteristic of multicast and anycast, manycast is attracting increasing interest from researchers over wavelength division multiplexing (WDM) optical networks. Splitter, cost, wavelength channel are three parameters which are taken into consideration for the first time in WDM. Finding a manycast tree which span the resource and selected nodes with minimum number of splitter, cost and wavelength channel is an NP-complete problem, and therefore we propose a simple and efficient heuristic solution: based-frequency manycast routing (BFM) algorithm to construct manycast trees with the aim of reducing the use of network resources. For a set of manycast requests, the simulation result shows BFM builds manycast trees with the smallest number of resources than other algorithms.     

Broadcasting, Scalability, and Reconfigurability Aspects in an All-Optical Network Architecture

All-optical networks are a sound answer to the huge data traffic demand expected for the forthcoming information society. Interesting networking aspects are the broadcasting, scalability, and reconfiguration in an all-optical environment. These issues are addressed in the present article for an all-optical network called MATRIX, which is time slotted and uses packet switching. The architecture enables the all-optical interconnection of a large number of nodes with both a small number of wavelengths and wavelength continuity based on a consequent exploitation of wavelength-division multiplexing and space-division multiplexing (i.e., multiple fibers per cable are used). For an efficient use of the resources, each node is equipped with multiple transmitters and receivers, respectively. Two different broadcasting schemes are investigated. An analytical model is developed, and the corresponding simulation results are in good agreement. It is further shown how different networks of arbitrary size can be interconnected to larger all-optical network clusters, thereby providing scalability not only with respect to the number of nodes but also to the geographical extension. Finally, wavelength reassignments allow change of optical paths through the network in case of changing traffic patterns or network failures in order to best exploit the available network resources. The total number of possible configurations is determined by the theory of Latin Squares.     

All-optical implementations for high-capacity TDMA networks

In this article we show how optical technology can allow the design of new optical devices that are able to perform some network functions in order to treat very high bit rate signals (100 Gbit/s). The multiplexing technique that we take into account is the Time Division Multiple Access (TDMA), and the network functions we consider are multiplexing, demultiplexing, synchronization, packet decoding, routing, and resolution of packet contention.

In order to show how these new optical devices can improve the network performance we propose two different network topologies: the first concerns a TDMA star network where the signal information is simultaneously broadcast to all users, while the second is a multihop network. The former is useful mainly for circuit switching, while the latter is suitable for packet switching.

Soliton propagation is used in order to avoid the problem of fiber chromatic dispersion.