Wavelength Assignment Problem Research Articles

Evaluation performance of genetic algorithm and tabu search algorithm for solving the Max-RWA problem in all-optical networks

In this paper, we deal with the static Routing and Wavelength Assignment (RWA) problem in networks with no wavelength converters, and where a given static set of connection demands is prearranged. Our objective is to maximize the number of optical connection-requests that can be established for a given number of wavelengths. A mathematical formulation for Max-RWA was presented. In this article, we implement and compare the performance of two random search algorithms namely: the genetic algorithm and the tabu search algorithm. Using these metaheuristics we solved approximately the wavelength assignment problem for Max-RWA while we computed its routing by a deterministic method which is the backtracking. Therefore we conducted many extensive experiments under different circumstances. Diagrams and representative numerical examples indicate the accuracy of our algorithms.

On the Optimal Design of a Spectrum-Switched Optical Network With Multiple Modulation Formats and Rates

Spectrum-switched optical networks (SSONs) are an attractive solution for core networks. With respect to wavelength-switched optical networks (WSONs), they achieve a higher spectrum efficiency thanks to the use of a flexible grid, instead of a fixed one. In SSONs, the well-known wavelength assignment (WA) problem of WSONs becomes a spectrum assignment (SA) problem. The SA problem aims at assigning a portion of the spectrum (called a frequency slot) to lightpaths. The width of the frequency slot depends on the requested bit rate and the modulation format adopted for the lightpath, and it is a multiple of the minimum bandwidth granularity, referred to as frequency slice. Thus, differently from WA, which assigns a single wavelength (or color) to each lightpath, SA assigns a set of colors (i.e., a set of frequency slices) to the lightpath. The shift from WA to SA introduces an additional constraint, which is related to the spectral adjacency of such frequency slices. This paper proves that the adjacency constraint in SA is not required and that by solving the WA problem (or the coloring problem) it is possible to derive a solution with spectrally adjacent slices in polynomial time. Based on such results, an integer linear programming formulation (ILP) for the optimal SA in a SSON with multi modulation formats and multi line rates (MMF/MLR) is presented for minimizing the network cost. The total cost of the network comprises the spectrum cost and the transponder card cost. Optimal results are presented for a MMF/MLR-SSON ring and show the amount of total occupied bandwidth and the network costs for different loads and ring lengths. Optimal selection of the modulation format and line rate is driven by the slice cost and the transponder card cost. Result comparison indicates that support of MMF and MLR is especially effective for improving spectrum utilization and allows spectrum saving up to 20% with respect to an SSON ring with single modulation format and line rate.

Routing and wavelength assignment in all optical networks using differential evolution optimization

The routing and wavelength assignment (RWA) problem, known to be an NP-complete problem, seeks to optimally establish routes and adequate wavelengths for the requested connections according to an objective function. This paper presents the use of a novel approach based on a differential evolution (DE) algorithm to the RWA problem in wavelength-routed dense division multiplexing (DWDM) optical networks. The proposed DE-RWA algorithm is modeled to optimize not only the network wavelength requirement ( $$ NWR $$ N W R , which is the minimum number of wavelengths needed to fulfill traffic demand) but also the average path length ( $$ APL $$ A P L ). We present the impact of the control parameters of the DE algorithm on the improvement of system's performance. Additionally, we present two strategies to improve the efficiency of the algorithm, knowing as the disjoint cut-set paths (DCS-P) algorithm and the use of a random mutation ( $$ random -M$$ r a n d o m - M ) parameter for DE. The proposed approach is evaluated for test bench optical networks with up to 40 nodes. Experiments show that the DE-RWA algorithm obtains results that equal the $$ NWR $$ N W R lower bound for networks with and without wavelength conversion capability, whereas reduce the $$ APL $$ A P L . The performance of the DE-based approach is compared against results obtained with the particle swarm optimization (PSO) and genetic algorithm (GA) models, showing that the DE-RWA outperform those algorithms. The presented DE-RWA model is simple to implement and could also be extended by adding other features such as impairment-aware, energy efficient, survivability among others in optical networks.

Designing a fine‐grained parallel differential evolution with Pareto tournaments for solving an optical networking problem

SUMMARYThe future of designing optical networks focuses on the wavelength division multiplexing technology. This technology divides the huge bandwidth of an optical fiber into different wavelengths, providing different available channels per link of optical fiber. However, when it is required to establish a set of demands, a problem comes up. This problem is known as routing and wavelength assignment problem. In this work, we have tackled the static routing and wavelength assignment problem by using multiobjective evolutionary computing. The algorithm applied is the differential evolution but modified with the Pareto tournaments concept for being adapted to the multiobjective context. By using OpenMP, an application programming interface that supports multiplatform shared memory multiprocessing programming, we have demonstrated that this algorithm is highly suitable to be parallelized. We have performed several experiments in multicore systems with two, four, and eight cores, obtaining 97.57% of mean efficiency. To ensure that our heuristic obtains relevant results, we have compared it with a parallel version of the standard fast nondominated sorting genetic algorithm. Finally, in order to show the goodness and effectiveness of the differential evolution with Pareto tournaments algorithm when dealing with this problem, we present diverse multiobjective comparisons with the nondominated sorting genetic algorithm and other approaches published in the literature. Copyright © 2013 John Wiley & Sons, Ltd.

QoT aware evolutionary programming algorithm for transparent optical networks

This paper presents an evolutionary programming algorithm to solve the quality of transmission (QoT) aware dynamic routing and wavelength assignment (DRWA) problem in transparent optical networks using wavelength division multiplexing (WDM). In this algorithm, the initial population is assumed to consist of a single individual and the algorithm uses only the mutation operator to explore the search space, both the features contributing to a reduction in algorithm execution time. A novel fitness function has been designed that takes into account the number of hops, the path cost, and the variance contributions due to the amplified spontaneous emission (ASE) noise and dynamic crosstalk at the nodes of each lightpath while evaluating a lightpath. This paper also proposes a new wavelength ordering assignment technique to reduce both the switch crosstalk and adjacent channel rejection crosstalk and hence, attempts to improve the mean blocking probability of the incoming call requests. This paper also, analyses the time complexity of the proposed algorithm.

Anycast routing and wavelength assignment problem in wavelength conversion WDM networks

Anycast routing and wavelength assignment without using wavelength conversion has been intensively studied in wavelength-division multiplexing (WDM) networks. In a realistic WDM network, semilightpath (a transmission path constructed by chaining together several lightpaths using wavelength conversion) is needed since wavelength-continuous path may not be available for a set of anycast requests. However, wavelength conversion is still expensive and results in degradation of signal quality. Therefore, efficient usage of wavelength conversion is of practical interest.In this paper, we first study the wavelength conversion-based anycast routing and wavelength assignment (WCARW) problem. When the network and the set of anycast requests are given, the WCARW is to find a set of paths and assign wavelengths to them. The goal of the WCARW is to minimize total number of wavelength conversions used over all paths subject to the end-to-end conversion bound constraints. For this NP-complete problem, we present a tabu-search anycast routing and wavelength assignment algorithm (TARWA), and compare it with the shortest anycast path routing and first-fit wavelength assignment algorithm (SAFF). Simulation results indicate that TARWA performs significantly better in terms of the number of wavelength conversions as well as blocking probability.

Routing Strategies in Survivable Optical Networks

Routing and wavelength assignment problem is one of the main problem in optical networks. The foremost problem is the routing problem after which the wavelength assignment is to be decided. In this paper we have proposed a routing strategy for optimization of the performance of the optical network in terms of blocking probability. The strategy proposed is better than the conventional algorithm in terms of blocking.Â

Wavelength Assignment Algorithm for optical networks

Wavelength assignment problem is one of the important problem in optical networks as on the first stage the route of the optical network is to be selected and after the route is selected then the wavelength is to be assigned to that route. In this paper we have proposed a wavelength assignment technique for the better performance of the optical network. The results have proved it better than the conventional algorithms.

A post-optimization method for the routing and wavelength assignment problem applied to scheduled lightpath demands

We consider here a NP-hard problem related to the Routing and Wavelength Assignment (RWA) problem in optical networks, dealing with Scheduled Lightpath Demands (SLDs). An SLD is a connection demand between two nodes of the network, during a certain time. Given a set of SLDs, we want to assign a lightpath, i.e. a routing path and a wavelength, to each SLD, so that the total number of required wavelengths is minimized. The constraints are the following: a same wavelength must be assigned all along the edges of the routing path of any SLD; at any time, a given wavelength on a given edge of the network cannot be used to satisfy more than one SLD. To solve this problem, we design a post-optimization method improving the solutions provided by a heuristic. The experimental results show that this post-optimization method is quite efficient to reduce the number of necessary wavelengths.

Binary quadratic programming formulation for routing and wavelength assignment problem in all-optical WDM networks

Routing and wavelength assignment (RWA) is the most concern in wavelength routed optical networks. This paper proposes a novel binary quadratic programming (BQP) formulation for the static RWA problem in order to balance traffic load among a network links more fairly. Subsequently, a greedy heuristic algorithm namely variable-weight routing and wavelength assignment (VW-RWA) is proposed to solve the developed BQP problem. In this method, the weight of a link is proportional to the link congestion. Performance evaluation results for different practical network topologies show that our proposed algorithm can decrease the number of required wavelengths in the network, blocking rate and variance of used wavelengths in each link. Besides, it is shown that the number of required wavelengths to establish call requests for a given network topology can be reduced at lower cost compared to other heuristics.

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.

Dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes

The wavelength selective switch-based reconfigurable optical add/drop multiplexers is a promising switching equipment for future reconfigurable wavelength-division multiplexing (WDM) mesh networks. However, its asymmetric switching property complicates the optimal routing and wavelength assignment problem. In an asymmetric switching scenario, using the classic Dijkstra's algorithm can lead to invalid paths traversing unconnected ports of an asymmetric node. To solve this problem, we propose both link-state (LS) and distance vector (DV) schemes for dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes. The proposed LS schemes include the asymmetric switching-aware (ASA) Dijkstra's algorithm, the $$K$$ -shortest path-based algorithm, and the entire path searching (EPS) algorithm. Simulation results show that the ASA-Dijkstra's algorithm will bring notable improvement of the blocking performance with low computational complexity, while the EPS algorithm has much higher complexity and is not suitable to be employed in large-scale networks. On the other hand, our proposed DV solution, i.e., the information diffusion-based routing (IDBR), can achieve the lowest blocking probability with the lowest computational complexity. Moreover, IDBR does not require the distribution of local asymmetric switching information like the LS schemes, thus having a high level of topology confidentiality.

Applying MOEAs to solve the static Routing and Wavelength Assignment problem in optical WDM networks

Wavelength-Division Multiplexing (WDM) in optical networks has revolutionized the Telecommunication field. This technology is able to exploit the enormous bandwidth capability of this kind of networks, allowing communication between end users via all-optical WDM channels (lightpath). Given a set of demands, the problem of setting up lightpaths by routing and assigning a wavelength to each connection is known as Routing and Wavelength Assignment (RWA) problem. There are two types of connection demands: static (demands are given in advance) and dynamic (demands are given in real-time). In this paper we present two different Multiobjective Evolutionary Algorithms (MOEA) with the aim of solving the static RWA problem. The first one is a population-based algorithm, the Differential Evolution (DE), but incorporating the Pareto Tournament concept (DEPT). The second one is a multiobjective version of the Variable Neighborhood Search (VNS), MO-VNS. In order to prove the goodness of our metaheuristics, we have compared them with the standard Fast Non-Dominated Sorting Genetic Algorithm (NSGA-II), typical heuristics in the Telecommunication field, and different varieties of Multiobjective Ant Colony Optimization Algorithms. On the whole, we conclude that our approaches have obtained very promising results.

Dynamic Routing and Resource Assignment Algorithm In sloted optical Networks

All-optical wavelength division multiplexing networks are the most promising candidate for the next generation wideband backbone networks. To improve the utilization of wavelength, time division multiplexing technology is introduced. The routing, wavelength and time-slots assignment problem was studied in such time-space switched networks. Two new dynamic algorithms were proposed which distribute slots of the session request on multiple different wavelengths of single fiber separately based on fixed alternate routing and adaptive routing policy. Especially in LLR-MWLB algorithm, network link weights adjust adaptively with the available time slots of each link and load balancing strategy is adopted. The effectiveness of the proposed algorithms is demonstrated by simulations and results show the better performance. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2336

Energy Efficient RWA Strategies for WDM Optical Networks

We consider the energy minimization problem in optical networks from an algorithmic perspective. Our objective is to plan optical WDM networks so as to minimize the energy expended, by reducing the number of energy-consuming components, such as amplifiers, regenerators, add/drop terminals, optical fibers, etc. We initially present an algorithm for solving the energy-aware routing and wavelength assignment problem based on an integer linear programming formulation that incorporates energy consumption and physical impairments (through a maximum transmission reach parameter) into routing and wavelength assignment. We then present a second algorithm that decomposes the problem and uses a linear programming relaxation to address the problem in large scale networks. Simulations are performed to evaluate and compare the performance of the proposed algorithms. In previously published works, energy minimization derives mainly from the reduction of the electronic processing of the traffic and the bypass in the optical domain, while the energy consumed by the optical devices is usually neglected. We focus on the optical layer and show that energy reductions can be obtained in that layer also.

An Adaptive Routing and Resource Assignment Algorithm with Load Balancing in WDM-TDM Networks

All-optical WDM networks are the most promising candidate for the next generation wideband backbone networks. To improve the utilization of wavelength, TDM technology is introduced into it. The routing, wavelength and time-slots assignment (RWTA) problem was studied in such time-space switched networks. A new adaptive algorithm was proposed which adopt adaptive network link weights and distribute slots of the session request on multiple different wavelengths adaptively with the remainder resource of the network. The effectiveness of the proposed algorithm is demonstrated by simulations and results show the better performance.

A proof of wavelength conversion not improving Lagrangian bounds of the sliding scheduled RWA problem

Extensive previous studies confirmed that wavelength conversion may only marginally improve the solutions to the static Routing and Wavelength Assignment (RWA) problem. This means that, for the static RWA problem, certain RWA schemes that do not use wavelength conversion can achieve a performance almost as good as the one from the best RWA scheme. Previous research work on sliding scheduled RWA problems, where a given set of lightpath demands are allowed to slide within their time windows, has also indicated in limited simulation results that the benefit of using wavelength conversion is marginal. However, the observation cannot be conclusive without the solid mathematical proof. We are thus motivated to investigate whether schedule sliding really requires wavelength conversion to achieve a better performance. In this paper, we prove that wavelength conversion does not improve the Lagrangian bound of the sliding scheduled RWA problem. In most test cases, this bound is very close to the best achieved objective function value. Our proof implies that, for those cases, the improvements achieved by making use of wavelength conversion are very marginal.

Multicast Traffic Grooming based Light-tree in WDM Mesh Networks

Abstract Multicast applications such as video conferencing, weather forecasting and on-line multi player gaming are major areas of Internet traffic growth. The disparity between bandwidth offered by a wavelength and the bandwidth requirement of a multicast connection can be purposefully solved by grooming low bandwidth connection requests into a high bandwidth wavelength channel in an optical network. In this paper, we discuss multicast traffic grooming problem using light-tree approach with static multicast connection requests. As higher layer electronic ports such as transmitters and receivers are dominant cost factors in a WDM mesh networks, it is critical to reduce their number when grooming multicast traffic into high bandwidth trees. This paper propose a heuristic algorithm called Saturated-Light-Tree based Multicast Traffic Grooming (SLTMTG) that solves grooming, routing and wavelength assignment problems. SLTMTG algorithm is based on grooming of multicast traffic to constrained light-trees in which traffic is groomed for better resource utilizations. This approach is used to minimize the grooming cost as well as wavelength requirement. Here, proposed approach tries to satisfy all connection requests. The performance of proposed algorithm has compared with existing Multicast Traffic Grooming (MTG) algorithm. The results are compared on several standard networks to measure cost and wavelength utilization.

QoT-aware Grooming, Routing, and Wavelength Assignment (GRWA) for Mixed-Line-Rate translucent optical networks

A Mixed Line Rate (MLR) optical network is a good candidate for a core backbone network because of its ability to provide diverse line rates to effectively accommodate traffic demands with heterogeneous bandwidth requirements. Because of the deleterious effects of physical impairments, there is a maximum transmission reach for optical signals before they have to be regenerated. Being expensive devices, regenerators are expected to be sparsely located and used in such a network, called a translucent optical network. In this paper, we consider the Grooming, Routing, and Wavelength Assignment (GRWA) problem so that the Quality of Transmission (QoT) for connections is satisfied, and the network-level performance metric of blocking probability is minimized. Cross-layer heuristics to effectively allocate the sparse regenerators in MLR networks are developed, and extensive simulation results are presented to demonstrate their effectiveness.

A Comparative Study on Multiobjective Swarm Intelligence for the Routing and Wavelength Assignment Problem

The future of designing optical networks is focused on the wavelength division multiplexing (WDM) technology. This technology divides the huge bandwidth of an optical fiber into different wavelengths, providing different available channels per link of fiber. However, when it is necessary to establish a set of demands, a problem comes up. This problem is known as a routing and wavelength assignment (RWA) problem. Depending on the traffic pattern, two varieties of a RWA problem have been considered in the literature: static and dynamic. In this paper, we present a comparative study among three multiobjective evolutionary algorithms (MOEAs) based on swarm intelligence to solve the RWA problem in real-world optical networks. Artificial bee colony (ABC) algorithm, gravitational search algorithm (GSA), and firefly algorithm (FA) are the selected evolutionary algorithms, but are adapted to multiobjective domain (MO-ABC, MO-GSA, and MO-FA, respectively). In order to prove the goodness of the swarm proposals, we have compared them with a standard MOEA: fast nondominated sorting genetic algorithm. Finally, we present a comparison among the metaheuristics based on swarm intelligence and several techniques published in the literature, coming to the conclusion that swarm intelligence is very suitable to solve the RWA problem, and presumably that it may obtain such quality results not only in diverse telecommunication optimization problems, but also in other engineering optimization problems.