A Distributed Memetic Algorithm for the Routing and Wavelength Assignment Problem

In this paper a novel approach for modelling Routing and Wavelength Assignment (RWA) problem in wavelength-routed Dense Wavelength Division Multiplexing (DWDM) optical networks is proposed. A new idea based on Artificial Bee Colony (ABC) algorithm is introduced for solving RWA problem which is known to be an NP-hard problem. In the proposed ABC-RWA approach every food source represents a possible and feasible lightpath between each original and destination node pair in demand matrix. The positions of food sources are modified by some artificial bees in the population where the aim is to discover the places of food sources. The food source with the highest nectar value seems to be a solution which is evaluated by the fitness function. The simulation results demonstrate the ability and efficiency of proposed approach for solving RWA in real-world optical networks. The proposed approach could be extended for dynamic RWA schemes in real-time applications and employed by network resilience architectures.

In WDM networks, static Routing Wavelength Assignment (RWA) problem is NP-complete. The Integer Linear Programming (ILP) is too complicated to implement. In most existing algorithms, it is usually split into routing and wavelength assignment, which is not completely precise. Mainly motivated by that imprecision, the Layered-Graph model was introduced into static RWA problem, which can consider the routing and wavelength assignment jointly. Three proposed algorithms using this model are described in this paper. Their performances are also evaluated by series of exhaustive simulations.

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.

This paper proposes the optimal design of lightpath Routing and Wavelength Assignment (RWA) problem in Wavelength Division Multiplexing (WDM) networks without wavelength conversion. We formulate RWA as a mixed Integer Linear Programming (ILP) problem where the objective is to minimize the cost of wavelength assignment to the fiber links in the network. The Lagrangean relaxation technique and the optimization-based heuristics are used to solve this problem. Two sets of computational experiments are performed to test the algorithms for the maximum carried traffic and minimum wavelength requirements in three different network topologies (GTE, ARPA, OCT network). Based on solution quality to the computational experiments, the error gaps between the upper bound and the lower bound are close enough that the near optimal solutions could be obtained. On the other hand, we also show that the solution quality degrade gracefully under more and more heavy traffic network environment. By assessing solution quality and the computational time, we propose the efficient and effective optimization-based algorithms based on the Lagrangean relaxation method for the RWA problem in the WDM networks without wavelength conversion.

The hierarchical routing and wavelength assignment problem in Automatic Switched Optical Network (ASON) is researched. Based on our analysis, three adaptive algorithms called MLLR (Multi-Layer Least Loaded Routing Algorithm), WMLCR (Wavelength-graph-based Multi-Layer Least Congestion Routing Algorithm) and BMR (Backtracking-based Multi-Layer Routing Algorithm) are proposed. A platform named AHORSP (ASON based hierarchical optimal routing & signaling platform) supporting our routing scheme is proposed and demonstrated. The simulation shows that the proposed algorithms can have comprehensive application on the basis of their convenience to be realized, low BP performance and acceptable operation time.

We consider the problem of routing and wavelength assignment problem (RWA) in wavelength-routed networks, which consists of the Wavelength Division Multiplexers (WDM) and optical cross-connect (OXCs) devices interconnected via point-to-point WDM links. Assume that none of the OXCs has wavelength conversion capability. The paper shows that the problem of RWA can be solved simultaneously by employing an efficient graph theoretic formulation, named as multi-layered graph model. On the basis of this notion, a heuristic RWA algorithm for static case is proposed. The numerical examples confirm that the proposed approach for static lightpath establishment (SLE) can obtain better solution for the number of requested lightpaths. The paper also considers the dynamic lightpath establishment (DLE) problem. We propose another heuristic DLE algorithm based on alternate-lightpath routing, according to a global selection criterion. We make a comparison of blocking probability according to different selection criterion. The performance of the proposed DLE algorithms is also evaluated and compared with that of the conventional algorithm via simulation of an arbitrary mesh network, where lightpath requests are assumed to arrive according to a Poisson process with exponentially distributed holding times.

The routing and wavelength assignment (RWA) problem is a classic and challenging problem in wavelength-division multiplexing (WDM) optical networks and has shown to be NP-hard. This paper studies the min-RWA problem with the objective of minimizing the number of required wavelengths and presents a new powerful neighborhood called Shift-and-Shaking (SAS). The proposed SAS integrates a high-level shift move to change the wavelength of one lightpath and two low-level ejection chain-based shaking (ECS) procedures to find the best routings for the related lightpaths. This new neighborhood is embedded into a simple iterated local search algorithm, called SAS-ILS, for solving min-RWA. The proposed SAS-ILS is tested on three sets of totally 113 widely studied instances in the literature. Comparison with other state-of-the-art algorithms shows that the SAS-ILS is able to improve 22 previous best known results, while matching the best known results for the remaining ones within short computational time.

The most promising technology for exploiting optical networks is the Wavelength Division Multiplexing (WDM). When it is necessary to establish a set of demands, a problem comes up, this problem is known as: Routing and Wavelength Assignment problem (RWA problem). In this paper, we present a Hybrid OpenMP+MPI version of the Differential Evolution (DE), but adapted to a multiobjective context (DEPT), for solving this problem. We have studied the behavior of the Hybrid DEPT algorithm by comparing it with an MPI version of the DEPT algorithm. For this comparison, we have used a real-world topology (NTT, Japan) and a homogeneous cluster composed of 16 multi-core nodes, each node with 8 cores (a total of 128 cores). We can conclude that using a Hybrid OpenMP+MPI version of the DEPT algorithm is very suitable to solve the RWA problem in a reasonable time.

A new method to design logical topologies based on genetic algorithms is presented. Not only does the algorithm determine which nodes should be connected by means of lightpaths with the aim of minimizing congestion, but it also solves the routing and wavelength assignment problem. In this way, the algorithm guarantees that the logical topology obtained can be embedded in the optical network subject to the available set of resources. The algorithm is effective in terms of both congestion and fairness. For instance, when compared with other work, the congestion is significantly reduced (from 20% to 75% depending on the matrix of traffic considered), and the fairness, when evaluated in terms of the Jain index, is generally higher than 0.94. Moreover, the algorithm brings advantages when employed in dynamic scenarios where the logical topology is frequently reconfigured, as it is fast and, in contrast to other algorithms previously proposed, the calculation process can be stopped at any time (if required) in order to give the best virtual topology found up to the moment.

In this paper, we compare the cost of the survivable optical transport solutions with subwavelength switching gran-ularity. The focus is on Time-Domain Wavelength Interleaved Network (TWIN) and Packet Optical Add/Drop Multiplexer (POADM) network. Both technologies exploit optical slot switching: TWIN on a physical mesh topology, and POADM on a physical ring. The cost model accounts for the node components, the transponder cost and the cost of wavelength use per km of fiber. For the first time, a single network dimensioning model supporting protection is proposed for these metro technologies. The network planning solution is based on linear programming, and addresses the routing and wavelength assignment problem (RWA) and the optimal scheduler calculation. We consider dedicated protection, which consist in doubling the capacity of each operational conthe network and shared protection, in which the protection capacity is potentially shared between multiple backup flows. By running the linear programming optimization we study the impact of different protection models on the cost of networks in different configurations and identify the scenarios for which each of the technologies is best suited.

We propose a comprehensive scalable algorithm simultaneously assessing the routing, scheduling and virtualization in Time-Domain Wavelength Interleaved Network (TWIN). TWIN is an energy-efficient optical burst switching technology for metropolitan area and data center intra- and interconnections, with destinations using separate allocated sets of wavelengths for the reception. Given the costs of the optical transponders and the wavelength use per km of fiber length, the proposed algorithm solves the routing and wavelength assignment problem, and in the same time allocates the time slots to traffic flows (performs the slot scheduling), so that the total network cost is minimized. The algorithm also enables the construction of overlayed virtual networking domains at minimum cost, which share the transponders and network links, and can employ different scheduling policies. The performance of the algorithm is compared with the pre-existing optimal dimensioning solution for single virtualization domain based on Integer Linear Programing, for different scenarios. The obtained results show that the network cost is within 27% of the optimal.

In this paper, the routing and wavelength assignment problem in all optical networks is considered. A solution to the RWA problem is proposed through a Genetic Algorithm (GA) based approach to search for the most suitable set of paths from many possible ones. We use GAs to solve this problem by introducing a new fitness function based on the mean value of occurrence of the common edges between the different genes of a single chromosome. In addition, we further improve performance and particularly execution times by considering the maximum quantity of edge disjoint paths (EDPs) to initialize the population with some indigo chromosomes. These EDPs are pre-computed and inserted in the GA-RWA problem. The proposed approach has been evaluated on the NSF network topology and compared with other similar schemes.

In an all-optical WDM network; optical fibers are used to transmit data followed by WDM technology. An optical fiber carries light along its length path at high rates and with little loss. Several wavelengths on a single fiber can be used to transfer data, when using wavelength-division multiplexing. In this way, several data transmissions at very high speed can take place on a single fiber. The routing and wavelength assignment (RWA) problem consists of finding a path and a wavelength for a set of data connections. The objective is typically to maximize the profit of established data by achieving as much as possible lightpath for transmitting optical signal (max-RWA). The RWA is NP-hard, thus much research has been conducted to finding a good way of approaching the RWA. This work mainly focuses on the analyzes work RWA problem based on integer linear programming (ILP) and reliable heuristics for variant topology of WDM networks. For performance analysis heuristics method as well as others variants of solution for RWA problem also had been implemented which results give some interesting observation about resources as well as optimal solution.

In this chapter we study the planning (offline) problem in WDM networks. In such networks, the signal quality of transmission (QoT) degrades due to physical-layer impairments, making necessary the use of regeneration at some intermediate nodes for certain lengthy lightpaths. Because of physical effects, routing choices made for one lightpath affect and are affected by the choices made for the other lightpaths. This interference among the lightpaths is particularly difficult to formulate in a planning algorithm, since in this version of the problem, we start without any established connections, and the utilization of lightpaths is the variable of the problem. We present a way to formulate inter-lightpath interference as additional constraints on the routing and wavelength assignment (RWA) problem. We initially present algorithms to solve the problem of planning a transparent all-optical WDM network, that is, a WDM network without regeneration capability. Then, we turn our attention to translucent WDM optical networks and present a series of algorithms that choose the regeneration sites and the number of regenerators required on these sites, solving the regenerator placement and the RWA problem for a given set of requested connections.

The emergence of translucency in WDM networks as a trade-off between the low cost of full transparency and high signal quality provided by full opacity has led to immense interest in translucent network design by the research community in recent years. Efficient translucent network design necessitates the judicious choice of regeneration sites and number of regenerators in order to maintain a predefined quality of transmission and to reduce the overall network cost. In this paper, we explicate a framework that corroborates the offline version of Physical Layer Impairment Aware Routing and Wavelength Assignment (PLI-RWA) problem in translucent networks. The originality of the proposed PLI-Signal Quality Aware RWA (PLI-SQARWA) algorithm lies in finding the routes which use fewest amounts of regenerators and constituting an efficient Regenerator Placement (RP) algorithm to place regenerators before wavelengths are assigned leading to maximal use of regenerators as wavelength converters. Subsequently, in the WA phase, for any further wavelength contention resolutions; we resort to optical wavelength converters. A relevant difference between existing studies and the proposed algorithm is that PLI-SQARWA provisions both, regeneration and wavelength conversion which guarantees zero signal and wavelength blocking. We proceed to the performance comparison of PLI-SQARWA with a heuristic for RWA and RP called COR2P (Cross-Optimization for RWA and RP) and the comparison results reveal that PLI-SQARWA outperforms COR2P in terms of number of network regenerators and time delay while demonstrating similar blocking performance to COR2P at various traffic loads. The results also suggest that to minimize time delay due to Optical-Electrical-Optical (OEO) conversions, using optical wavelength converters for only wavelength contention resolution is a judicious choice rather than resorting to regenerators. Finally, it can be inferred from the study that there exists a trade-off between the overall network cost and the maximum tolerable delay.