Wavelength Converter Placement Research Articles

Wavelength Assignment Techniques with Converters for All Optical Networks (AONs)

We present an optical routing and wavelength assignment (RWA) technique for the best placement of the wavelength converters. The wavelength converter placement was considered independently at the complete nodes and partial nodes. In comparison to existing approaches, our technique performs better and requires fewer wavelength converters to get the required performance. As much as 7%, the likelihood of blocking is decreased. The study also demonstrates that the top four nodes have the biggest influence over the blocking performance of the network. It is clear that placing the converters in the right location is just as crucial to improving performance as simply adding more converters.

Implementation of Adaptive Algorithm to Optimize the Placement of Wavelength Converters

The Wavelength Converters in WDM Optical Network, is one the essential component in today’s advanced research, but at the same time they are very expensive and it should be used in limited number to make effective use of Wavelength Converters. The two main criteria to be achieved is to reduce the overall blocking probability at an affordable cost and the other performance measures are within reasonable limits. To equip the node with the Wavelength converter for any network is crucial. There should be a minimal blocking probability at those particular nodes chosen to place the Wavelength Converter. A large margin decrease in the blocking probability will be easy for the placement of Wavelength Converter. Compared with the previous method of allocation, the results of the proposed adaptive algorithm can significantly reduce the blocking probability at higher range. The implementation of Adaptive algorithm shows that it is more cost effective to optimize the blocking performance. The blocking performance improvement hence led to the comparison of performance and efficiency other conventional methods with the proposed Adaptive algorithm is done.

Wavelength Converter Based Optimized RWA for All Optical Networks

Wavelength converters are used in WDM networks to avoid call blocking and minimizing the blocking probability. Optimal placement of wavelength converters restricts the call blocking probability, the complexity and improves the overall network performance of the network. In this paper, we propose a new weight dependent routing and wavelength assignment algorithm for the optimal placement of the wavelength converters. The wavelength converter placement was considered separately at all the nodes and the partial nodes. Our algorithm outperforms the previously reported studies and requires a lesser number of wavelength converters to achieve the required performance. It reduces the blocking probabilities up to 5.4% and shows that the first four nodes primarily control the blocking performance of the network. The study also reveals that instead of merely increasing the number of converters, their placement at the right location plays a crucial role in improving the performance. Initially, although an increase in the number of the wavelengths also improves the network performance, the further increase does not contribute much to the reduction of the blocking probability.

Wavelength Assignment Vs. Wavelength Converter Placement in Wavelength-Routed Optical WDM Networks

In this paper, we deal with the wavelength assignment and the converter placement problem in wavelength-routed optical WDM Mesh networks. Our objective is to try to assign wavelengths in an efficient manner with/without wavelength conversion to get a very low blocking probability and optimize the performance of the overall network. Thus, we implement and compare the performance of two proposed algorithms namely DWA “Dynamic Wavelength Assignment” and SWA “Static Wavelength Assignment” with well-known algorithms. We first present a literature review about previously proposed approaches, and then we introduce and evaluate our implemented approaches. We also discuss the wavelength converter placement problem in mesh networks. We finally corroborate our theoretical findings through extensive simulations.

Placement of Wavelength Converters in Dynamically Routed All Optical Networks in presence of Tunable Transceivers

Efficient routing with optimal resources is one of the challenging tasks in the design of DWDM networks. Wavelength Converter (WC) is an important resource, as the placement of WCs affects the network performance and the quantity of WCs affects the cost of the network. With the help of WCs the network performance can be maximized by removing the wavelength continuity constraint. As WCs are very expensive, selecting the candidate nodes for the placement of WCs in a network is important. In this paper we have proposed an optimized approach for the placement of WCs in the presence of tunable transceivers (TTRs) and fixed transceivers (FTRs). The performance analysis has been carried out for above approaches. Observation shows that sparse partial wavelength converters with various loads requires only 2.4% converters. When tunable transceivers are used an average reduction of 73% in blocking probability and average saving of 91% in required number of converters.

Wavelength Converters Placement in Optical Networks Using Bee Colony Optimization

Wavelength converters placement (WCP) in all-optical WDM networks belongs to the class of hard combinatorial optimization problems. So far, this problem has been solved by various heur ...

Probability based dynamic-alternate routing and the corresponding converter placement algorithm in all-optical WDM networks

This paper proposes a new dynamic-alternate routing algorithm and its corresponding converter placement algorithm in order to reduce the connection blocking probability for all-optical WDM networks. The main idea in the proposed dynamic-alternate routing algorithm is to try to route the traffics according to a predefined optimal probability distribution. The problem for finding the optimal probability distribution was shown as a convex optimization problem. The problem can be solved by flow deviation method or other standard optimization techniques. Simulation results show that the proposed routing algorithm yields lower connection blocking probabilities than the previous works. The proposed routing algorithm produces similar traffic pattern as the optimal traffic pattern. The similarity between the traffic pattern produced by the proposed dynamic-alternate routing algorithm and the optimal traffic pattern can be further employed for solving other network designing problems such as converter placement problem. Since the optimal traffic pattern can be easily predicted, the optimal traffic pattern which minimizes the blocked traffic intensity is utilized for finding the locations of wavelength converters. The key idea is to place the wavelength converters at the nodes where they are needed most. Simulations have been performed to study the performance of the proposed wavelength converter placement method. The simulation results have shown that the proposed placement method combined with the proposed probability based dynamic-alternate routing algorithm yields smaller connection blocking probability than the two converter placement methods with their corresponding alternate routing algorithms.

Differential evolution optimization applied to the wavelength converters placement problem in all optical networks

The placement of wavelength converters in an arbitrary mesh network is known to belong to the class of NP-complete problems. So far, this problem has been solved by heuristic strategies or by the application of optimization tools such as genetic algorithms (GAs). In this paper we introduce the application of Differential Evolution (DE) to the problem of the placement of wavelength converters to obtain the optimal solution. Many comparative studies confirm its robustness and efficiency, showing that in many cases DE outperforms many other well known evolutionary computational approaches in terms of convergence speed and quality of solutions. The major advantage of the DE algorithm rests in the fact that it does not need to build up a search tree or to create auxiliary graphs as other methods do. Furthermore, the method typically requires few control parameters, and the computed results show that only a small population is needed to obtain the optimal solution for the placement of wavelength converters in an arbitrary network. We present experiments that demonstrate the effectiveness and efficiency of the proposed evolutionary algorithm.

Reduction Of Blocking Probability In Shared Protected Optical Network

0 B ABSTRACT - 1 B In this paper we have proposed a restricted shared protection scheme in wavelength convertible optical network. In our proposed approach we have included both alternate path routing and partial placement of wavelength converters for reduction of blocking probability. The simulation result shows the performance of our proposed approach is better than the existing protection schemes.

Sparse-partial wavelength conversion: Converter placement and wavelength assignment

Wavelength conversion has been shown as one of the key techniques to improve blocking performance in a wavelength-routed all-optical WDM network. Given that wavelength converters nowadays remain very expensive, how to make effective use of a limited number of wavelength converters becomes an important issue. In this paper, we present and analyze the Sparse-Partial Wavelength Conversion (SPWC) network architecture, which has the inherent flexibility that can facilitate network carriers to upgrade the legacy optical backbone to support wavelength conversion. We explore the efficiency of partial wavelength conversion and demonstrate that SPWC architecture can significantly reduce the number of wavelength converters, yet achieve excellent blocking performance with a proper wavelength converter placement scheme. We also propose a wavelength assignment scheme called Minimum Converter Allocation (MCA), which can further improve the utilization of the wavelength converters. Simulation results indicate that, with the proposed MCA wavelength assignment algorithm, the performance of a wavelength-routed WDM network with only 1%–5% of wavelength conversion capability is very close to that with Full-Complete Wavelength Conversion capability.

Placement of wavelength converters and light splitters in a WDM network using the generic graph model

Previous studies on the placement issue mainly focus on the availability of wavelength converters or light splitters on each node and normally the placement of wavelength converters and light splitters are considered in isolation. In this paper, by extending our previous work on the generic graph model, we study the placement of wavelength converters and light splitters as well as how their capabilities will affect the cost efficiency and performance in a holistic manner. In our study, both the sparse and limited capability strategies are considered, so is the coexistence of both wavelength converters and light splitters in the same network. The dynamic multicast traffic model is used for the simulation study. Four proposed algorithms, namely, WCF-I, WCF-D, LSF-I and LSF-D, for finding the optimal configuration of wavelength converters and light splitters are studied. The configuration includes information on the availability as well as the capability (and limitation) of the devices on each node in the network. Three metrics: cost efficiency (CE), request blocking probability (RBP) and average multicast tree cost (AMTC) are used to compare the different algorithms. All of the proposed algorithms manage to find a placement configuration with higher CE and comparable RBP, compared to the case of wavelength converters and light splitters having full capability of wavelength conversion and light splitting on all the nodes. From the results, we conclude that the presence of wavelength converters contributes more to improving the cost efficiency than the presence of light splitters when traffic load is not high. We also conclude that the sparse strategy has more impact on the performance than the limited strategy. In addition, our results led us to believe that the configuration that is obtained for a specific traffic load is not necessary the optimal configuration for other traffic loads.

Reduction of Blocking Probability in Restricted Shared Protected Optical Network using Alternate Path Routing and Wavelength Converter Placement

In this paper, we have proposed a restricted shared protection scheme in wavelength convertible optical network. In our proposed approach, we have included both alternate path routing and partial placement of wavelength converter for reduction of blocking probability. With computer simulation, we have evaluated the performance of our proposed approach, by comparing it with the existing shared protection.

Dynamic Traffic Grooming in Optical Networks with Wavelength Conversion

Traffic grooming in wavelength division multiplexing (WDM) optical networks refers to routing and aggregating low-rate client traffic onto wavelength granularity lightpaths. When client traffic randomly arrives/departs, it is called dynamic traffic grooming. This paper focuses on dynamic traffic grooming when the optical network has sparse wavelength conversion, and aims to examine the impact of wavelength conversion and converter placement on dynamic traffic grooming. We have developed both an analytical model for performance evaluation, and an adaptive traffic load-based (ATL) heuristic algorithm for converter placement, accompanied with a discussion of various converter placement heuristics. Numerical results indicate that the ATL heuristic can obtain similar performance as the greedy heuristic with lower computation complexity.

Performance analysis of multi-fiber WDM network with limited-range wavelength conversion

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength conversion technology and wavelength converters play an important role in enhancing fiber utilization and in reducing the overall call blocking probability of the network. In this paper, we develop a new analytical model to calculate the average blocking probability in multi-fiber link networks using limited range wavelength conversion. Based on the results obtained, we conclude that the proposed analytical model is simple and yet can effectively analyze the impact of wavelength conversion ranges and number of fibers on network performance. Also a new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Finally, we analyze network performance with the proposed scheme. It can be observed from numerical simulations that limited range converters placed at a few nodes can provide almost the same blocking probability as full range wavelength converters placed at all the nodes. We also show that being equipped with a multi-fiber per-link has the same effect as being equipped with the capability of limited range wavelength conversion. So a multi-fiber per-link network using limited range wavelength conversion has similar blocking performance as a full wavelength convertible network. Since a multi-fiber network using limited range wavelength conversion could use fewer converters than a single-fiber network using limited range wavelength conversion and because wavelength converters are today more expensive than fiber equipment, a multi-fiber network in condition with limited range wavelength conversion is less costly than a single fiber network using only limited range wavelength conversion. Thus, multi-fiber per-link network using limited range wavelength conversion is currently a more practical method for all optical WDM networks. Simulation studies carried out on a 14-node NSFNET, a 10-node CERNET (China Education and Research Network), and a 9-node regular mesh network validate the analysis.

Converter Placement in Wavelength-routed Networks with Dynamic Traffic Demand

The blocking performance of wavelength division multiplexing (WDM) all-optical networks can be improved by employing wavelength conversion. In this paper, we study wavelength converter placement problem in wavelength-routed WDM networks with dynamic traffic demands. It is considered that under different routing and wavelength assignment (RWA) algorithms, the path usage probabilities are significantly different. Therefore, in this paper the converter placement algorithm and RWA policies are considered jointly.

Placement of Light Splitters and Wavelength Converters for Efficient Multicast in All-Optical WDM Networks

This paper studies the problem of light splitter placement (LSP) and wavelength converter placement (WCP) in all-optical WDM networks to enable optimal provisioning of static and dynamic traffic through efficient photonic multicast connections. To solve the LSP-WCP problem under static traffic provisioning, an Integer Linear Programming model is formulated to achieve the optimal solution in the sense that the total number of wavelength channels required by the multicast requests is minimized. To solve the LSP-WCP problem under dynamic traffic provisioning, a complementary-combined LSP-WCP heuristic is proposed to minimize the multicast traffic blocking probability, and is proved through extensive simulations.

Dependency-based analytical model for computing connection blocking rates and its application in the sparse placement of optical converters

In this paper, we present a new analytical model that captures link dependencies in all-optical wavelength-division multiplexing (WDM) networks under uniform traffic and enables the estimation of connection-blocking probabilities more accurately than previously possible. The basic formula of the dependency between two links in this model reflects their degree of adjacency, the degree of connectivity of the nodes composing them, and their carried traffic. Our validation tests have shown that the analytical dependency model gives accurate results and successfully captures the main dependency characteristics observed in the simulation measurements. The usefulness of the model is illustrated by showing how to use it in enhancing a simulation-based algorithm that we recently proposed for the sparse placement of full wavelength converters in WDM networks. To analytically handle the presence of wavelength converters, a lightpath containing converters is divided into smaller subpaths, such that each subpath is a wavelength-continuous path, and the nodes shared between these subpaths are full wavelength-conversion-capable. The blocking probability of the entire path is obtained by computing the probabilities in the individual subpaths. We validate the analytically-based sparse placement algorithm by comparing it with its simulation-based counterpart using a number of network topologies.

A binary (0-1) linear program formulation for the placement of limited-range wavelength converters in wavelength-routed WDM networks

We investigate the problem of optimally placing limited-range wavelength converters at a subset of nodes in wavelength-routed wavelength-division-multiplexing (WDM) networks. We consider two different aspects of the converter-placement problem: 1) the placement minimizing the network-wide blocking probability; and 2) the placement minimizing the number of wavelength-convertible nodes to meet the performance constraints. We present a binary (0-1) linear program (BLP) formulation in which the end-to-end blocking probability is expressed as a linear function of converter locations so that standard linear program (LP) optimization packages can be employed to obtain the optimal solution of the problems. We also present a new analytical model for estimating the end-to-end blocking probabilities. Experiments have been conducted over four network topologies, including 19-node European optical network (EON), 24-node USA backbone network (UBN), 32-node HYPERCUBE, and 36-node MESH-TORUS. We demonstrate that the optimal solutions of the converter-placement problems can be obtained within a reasonable computation time.

Wavelength Converters Placement in All Optical Networks Using Particle Swarm Optimization

Placement of wavelength converters in an arbitrary mesh network is known to be a NP-complete problem. So far, this problem has been solved by heuristic strategies or by the application of optimization tools such as genetic algorithms. In this paper, we introduce a novel evolutionary algorithm: particle swarm optimization (PSO) to find the optimal solution to the converters placement problem. The major advantage of this algorithm is that does not need to build up a search tree or to create auxiliary graphs in find the optimal solutions. In addition, the computed results show that only a few particles are needed to search the optimal solutions of the placement of wavelength converters problem in an arbitrary network. Experiments have been conducted to demonstrate the effectiveness and efficiency of the proposed evolutionary algorithm. It was found that the efficiency of PSO can even exceed 90% under certain circumstances. In order to further improve the efficiency in obtaining the optimal solutions, four strategic initialization schemes are investigated and compared with the random initializations of PSO particles.

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.