A Novel Solution to the Dynamic Routing and Wavelength Assignment Problem in Transparent Optical Networks

We present an evolutionary programming algorithm for solving the dynamic routing and wavelength assignment (DRWA) problem in optical wavelength-division multiplexing (WDM) networks under wavelength continuity constraint. We assume an ideal physical channel and therefore neglect the blocking of connection requests due to the physical impairments. The problem formulation includes suitable constraints that enable the algorithm to balance the load among the individuals and thus results in a lower blocking probability and lower mean execution time than the existing bio-inspired algorithms available in the literature for the DRWA problems. Three types of wavelength assignment techniques, such as First fit, Random, and Round Robin wavelength assignment techniques have been investigated here. The ability to guarantee both low blocking probability without any wavelength converters and small delay makes the improved algorithm very attractive for current optical switching networks.Comment: 12 Pages, IJCNC Journal 201

Application of Ant Colony Optmization to the Routing and Wavelength Assignment problem

The transmission capacity of a link in today's optical networks has increased significantly due to wavelength-division multiplexing (WDM) technology. A unique feature of optical WDM networks is tight coupling between routing and wavelength selection. A lightpath is implemented by selecting a set or sequence of physical links between the source and destination nodes, and reserving a wavelength on each of these links for the lightpath. Thus, in establishing an optical connection we must deal with both routing (selecting a suitable path, i.e., sequence of physical links) and wavelength assignment (allocating an available wavelength for the connection (source-destination pair)). The resulting problem is referred to as the routing and wavelength assignment (RWA) problem, and is significantly more difficult than the routing problem in electrical networks. In this thesis, we offer a new heuristic algorithm to solve the RWA problem using Ant Colony Optimization (ACO) meta-heuristic. An edge disjoint path problem and a partition coloring problem are used to formulate the algorithm

Performance analysis of realistic optical time division multiplexed wavelength routed networks

Application of optical time division multiplexing (OTDM) in wavelength routed optical networks greatly enhances the flexibility of bandwidth assignment because OTDM provides time division sub-channels in a wavelength to match the processing speed of electronic devices. Different types of such OTDM wavelength-routed (OTDM-WR) networks, assuming different levels of sophistication of the OTDM technology, have been proposed. The performance of these OTDM-WR networks improves with the time-slot routing capability of the intermediate nodes of the network. However, as the transmission rate increases up to hundreds of gigabits per wavelength channel, electronic processing of the time slots limits the achievable performance of the OTDM-WR networks. All-optical signal processing can overcome the electronics bottleneck, but the available all-optical signal processing capability is rather limited and cannot yet utilize the full potential of time-slot routing. Even with such limitations, current technologies, such as fast wavelength converters and micro-electromechanical system (MEMS) optical switches, can significantly enhance the performance of existing wavelength-routed networks by adding the OTDM capability, albeit limited. We develop time-slot routing schemes that require fast wavelength converters only and study the performance of these schemes by simulations on Manhattan street networks and a network with the topology of the AT&T North America OC-48 fiber network.published_or_final_versio

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 network

Attack-Aware Routing and Wavelength Assignment of Scheduled Lightpath Demands

In Transparent Optical Networks, tra c is carried over lightpaths, creating a vir- tual topology over the physical connections of optical bers. Due to the increasingly high data rates and the vulnerabilities related to the transparency of optical network, security issues in transparent wavelength division multiplexing (WDM) optical net- works have become of great signi cance to network managers. In this thesis, we intro- duce some basic concepts of transparent optical network, the types and circumstances of physical-layer attacks and analysis of related work at rst. In addition, based on the previous researches, we present a novel approach and several new objective cri- terions for the problem of attack-aware routing and wavelength assignment. Integer Linear Programming (ILP) formulation is used to solve the routing sub-problem with the objective to minimize the disruption of physical-layer attack as well as to opti- mize Routing and Wavelength Assignment (RWA) of scheduled transparent optical network

OPTIMIZING ROUTING AND WAVELENGTH ALLOCATION IN OPTICAL CORE NETWORKS

Optical networks using wavelength division multiplexing (WDM) technology have emerged as an attractive solution for meeting rapidly growing demands forBandwidth. WDM allows the same fiber to carry many signals independently as long as each uses a different wavelength. Connections must therefore be routed and assigned to wavelengths such that no two calls use the same wavelength on the same link. This is known as the routing and wavelength assignment (RWA) problem. If full conversion is available at all nodes, the WDM network is equivalent to a circuit-switchednetwork; however, the high cost of wavelength converters often makes it desirable to keep the amount of conversion used in the network to a minimum. Since the performance of this architecture is tightly linked to the efficient establishment of light paths, a detailed investigation of the lightpath establishment problem is conducted.This study addresses an important problem in wavelength routed all-optical WDM networks: how to efficiently utilize a limited number of resources on statically routed optical core. We first formulate a routing scheme to balance channels across the network and then introduce a wavelength allocation scheme to reduce number of wavelength channel and wavelength conversion. Both theoretical and simulation results are presented. By using the proposed routing scheme and wavelength assignment algorithm, only a very small number of wavelength converters are needed to achieve same performance as that of the full-Complete Wavelength conversion. This objective is achieved in the study by evolving the routing and wavelength assignment scheme using very simple and intuitive steps

An efficient shared path protection based on quality of service in WDM networks.

With the explosive growth of the Internet in the past decade, survivability and high-bandwidth have become the most critical characteristics for networks. Determining the most efficient and reliable network configuration is a significant challenge in current optical network research. WDM (Wavelength Division Multiplexing) has become one of the most important features of optical networks because of its highly improved utilization of network capacity. The design of WDM networks can be analyzed from two perspectives: Network Design, and Routing & Wavelength Assignment (RWA). Network design includes physical topology design and configuration design. Routing and Wavelength Assignment (RWA) involves mapping lightpaths into the physical topology and assigning wavelength to these lightpaths. In this thesis, we concentrate on RWA, and propose a new formulation for dynamic lightpath allocations in fault-tolerant optical networks. We use WDM shared-path protection to achieve fault tolerance. Our formulation can accommodate three different qualities of service (QoS), each requiring a different amount of resources. We generate an efficient MILP formulation for dynamic lightpath allocation based on the QoS, and show through simulations, that it can be used for a practical-sized WDM networks. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2002 .H8. Source: Masters Abstracts International, Volume: 42-01, page: 0259. Adviser: Arunita Jaekel. Thesis (M.Sc.)--University of Windsor (Canada), 2003