Routing and Wavelength Assignment problem in Optical Networks (original) (raw)

Comparative Analysis of Routing and Wavelength Assignment Algorithms used in WDM Optical Networks 1

Research Journal of Applied Sciences, Engineering and Technology, Maxwell Publications, 2014

This study aims at highlighting the Routing and Wavelength Assignment (RWA) problems in WDM Optical networks and describes the Routing Algorithms and their performance comparison. Since routing decisions play an important role in evaluating the blocking performance of a network it is critical to choose a wavelength assignment scheme that should take into account its compatibility with the chosen routing protocol in addition to its blocking performance. This study presents problems in Wavelength Assignment, describes various Routing schemes and different approaches to solve both the static and the dynamic RWA problems. RWA algorithms’ role is to assign a light-path (a route and a wavelength) to incoming calls in a network. RWA algorithms block calls if a continuous wavelength from source to destination cannot be found (wavelength blocking), thus degrading the performance of All Optical Networks, by call blocking. The failure of RWA algorithm to find an available wavelength on all links from source to destination causes congestion resulting in packet loss. This study examines the RWA algorithms and their problems in WDM Optical networks. The various measures taken to improve the blocking performance of WDM optical networks are also studied. We compared the performance of two wavelength assignment schemes, the Random wavelength assignment and the First-Fit wavelength assignment scheme via simulation. It was observed that the Random wavelength assignment algorithm performs well under low load, while for high load First Fit algorithm performs better.

Comparative Analysis of Routing and Wavelength Assignment Algorithms used in WDM Optical Networks

Research Journal of Applied Sciences, Engineering and Technology, 2014

This study aims at highlighting the Routing and Wavelength Assignment (RWA) problems in WDM Optical networks and describes the Routing Algorithms and their performance comparison. Since routing decisions play an important role in evaluating the blocking performance of a network it is critical to choose a wavelength assignment scheme that should take into account its compatibility with the chosen routing protocol in addition to its blocking performance. This study presents problems in Wavelength Assignment, describes various Routing schemes and different approaches to solve both the static and the dynamic RWA problems. RWA algorithms' role is to assign a light-path (a route and a wavelength) to incoming calls in a network. RWA algorithms block calls if a continuous wavelength from source to destination cannot be found (wavelength blocking), thus degrading the performance of All Optical Networks, by call blocking. The failure of RWA algorithm to find an available wavelength on all links from source to destination causes congestion resulting in packet loss. This study examines the RWA algorithms and their problems in WDM Optical networks. The various measures taken to improve the blocking performance of WDM optical networks are also studied. We compared the performance of two wavelength assignment schemes, the Random wavelength assignment and the First-Fit wavelength assignment scheme via simulation. It was observed that the Random wavelength assignment algorithm performs well under low load, while for high load First Fit algorithm performs better.

Routing and wavelength assignment in optical networks

IEEE/ACM Transactions on Networking, 2003

In this paper, we propose and evaluate a new approach for implementing efficient routing and wavelength assignment (RWA) in wavelength division multiplexing (WDM) optical networks. In our method, the state of a fiber is given by the set of free wavelengths in this fiber and is efficiently represented as a compact bitmap. The state of a multiple-fiber link is also represented by a compact bitmap computed as the logical union of the individual bitmaps of the fibers in this link. Likewise, the state of a lightpath is represented by a similar bitmap computed as the logical intersection of the individual bitmaps of the links in this path. The count of the number of 1-valued bits in the bitmap of the route from source to destination is used as the primary reward function in route selection. A modified Dijkstra algorithm is developed for dynamic routing based on the bitmap representation. The algorithm uses bitwise logical operations and is quite efficient. A first-fit channel assignment algorithm is developed using a simple computation on the bitmap of the selected route. The resulting bitwise routing algorithm combines the benefits of least loaded routing algorithms and shortest path routing algorithms. Our extensive simulation tests have shown that the bitwise RWA approach has small storage overhead, is computationally fast, and reduces the network-wide blocking probability. The blocking performance of our RWA method compares very favorably with three routing methods: fixed alternate routing, shortest path using flooding, and Dijkstra's algorithm using mathematical operations. Our simulation experiments have also evaluated the performance gain obtained when the network access stations are equipped with finite buffers to temporarily hold blocked connection requests. e.g., improving network robustness, increasing the efficiency of routing and wavelength assignment, enhancing the flexibility of network dimensioning, and improving fairness . In this paper, we address the issue of routing and wavelength assignment (RWA) and present an efficient RWA algorithm based on the logical link representation and fast bit-wise computation.

Wavelength Assignment Algorithm for optical networks

INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY

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 dynamic heuristic wavelength assignment algorithm for optical network with wavelength conversion

Network Architectures, Management, and Applications II, 2005

The blocking performance of wavelength routing WDM optical networks can be enhanced by applying routing and wavelength assignment. In this paper, we consider wavelength assignment problem in the optical network. Specifically, we propose a dynamic heuristic wavelength assignment algorithm, called Longest Segment (LS) algorithm, for WDM networks. In comparison to other proposed algorithms, the blocking performance of LS algorithm is better. In addition, the LS algorithm minimizes the usage of converters by chaining the minimum number of continuous segments which have at least one same available wavelength. Furthermore, the low algorithm' complexity is an another advantage of the algorithm.

Algorithm for wavelength assignment in optical networks

Scientific Research and Essays, 2015

Wavelength division multiplexing (WDM) is a technology which multiplexes many optical carrier signals onto a single optical fiber by using different wavelengths. Wavelength assignment is one of the important components of routing and wavelength assignment (RWA) problem in WDM networks. In this article, to decrease the blocking probability, a new algorithm for wavelength assignment-Least Used Wavelength Conversion algorithm is introduced and is an enhancement to the previously used Least Used Wavelength assignment algorithm. The performance of this wavelength assignment algorithm is evaluated in terms of blocking probability and the results show that the proposed technique is very promising in future. The Least Used Wavelength Conversion algorithm is compared with algorithms such as first-fit, best-fit, random and most-used wavelength assignment algorithm.

Routing and wavelength assignment over WDM optical networks

Proceedings of the 4th international IFIP/ACM Latin American conference on Networking - LANC '07, 2007

The increasing demand of bandwidth has found an answer in Optical Networks (ON). To take advantage of the different resources that ONs offer, several parameters need to be optimized to obtain good performance. Therefore, this work studies the Routing and Wavelength Assignment (RWA) problem in a multiobjective context. MultiObjective Ant Colony Optimization (MOACO) algorithms are implemented to simultaneously optimize the hop count and number of wavelength conversion for a set of unicast demands, considering wavelength conflicts. This way, a set of optimal solutions, known as Pareto Set, is calculated in one run of the proposed algorithm, without a priori restrictions. The proposed MOACO algorithms were compared to classical RWA heuristics using several performance metrics. Although, there is not a clear superiority, simulation results indicate that considering most of the performance metrics, MOACO algorithms obtain promising results when compared to the classical heuristics.

A heuristic priority based wavelength assignment scheme for optical networks

2012

We propose a heuristic priority based wavelength assignment (HPWA) scheme to minimize the blocking probability. In this scheme, the connection requests having same s-d pair are groomed first and then these groomed connection requests are served for routing and wavelength assignment according to their priority order. The priority order of each groomed connection request is estimated based on both the types of path (direct link physical path or indirect link physical path) first and then their traffic volume. The performance analysis of our proposed scheme is made in terms of blocking probability and compared the same with similar heuristic non-priority based wavelength assignment (HNPWA) scheme. Simulation study shows that the blocking probability of HPWA scheme is less than that of NPRWA. It is also seen that the performance of the proposed scheme is better in comparison to HNPWA, when the number of connection requests increases in the network.

Analysis of Routing and Wavelength Assignment in Large WDM Networks

Procedia Computer Science, 2014

In Wavelength Division Multiplexing (WDM) network, for a given connection request, a route has to be found, and a dedicated wavelength has to be assigned along that route. This problem of assigning route and wavelength to the connection request, using minimum network resources, is called Routing and Wavelength Assignment (RWA) Problem. This paper focuses on the analysis of proposed RWA algorithms in large WDM networks. We use simulations and analysis of randomly generated large networks under dynamic traffic and static traffic, with and without protection of the connection request. The protection of the primary route between source and destination is considered by setting up a dedicated backup path in case of failures. The wavelength requirements are analyzed using different wavelength assignment heuristics under different routing techniques for a set of connection requests. We find that, the fixed alternate routing packs connection requests into less number of wavelengths than the fixed routing and that most-used wavelength assignment heuristic performs slightly better than the first-fit wavelength assignment heuristic.

Dynamic Routing and Wavelength Assignment in Optical Networks by Means of Genetic Algorithms

Photonic Network Communications, 2004

We propose a novel genetic algorithm for solving the dynamic routing and wavelength assignment (DRWA) problem in wavelength-routed optical networks. The algorithm not only obtains low call blocking probability, but it also employs a very short computation time. Moreover, it is capable of providing fairness among connections, that is, to offer approximately the same quality of service (in terms of blocking probability) for all source-destination node pairs. Since requirements on optical network availability are highly severe, we also propose an extension of the algorithm to provide fault-tolerance capability at the optical layer. It is achieved by means of protection, where each optical connection request is provided with a pair of lightpaths (a primary and a backup lightpath). Again, the genetic algorithm proves to be highly efficient, in this case, at performing routing and wavelength assignment of pairs of lightpaths.