An integrated survey in Optical Networks: Concepts, Components and Problems (original) (raw)
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Routing and Wavelength Assignment problem in Optical Networks
Wavelength assignment and routing has become the important issue in the optical networks. Using the efficient techniques the various network parameters can be optimized and the networks bandwidth can be utilized more efficiently. Most research in the literature was on the static routing and very few works was done on the dynamic routing. With Dynamic routing the network bandwidth can be used effectively and the best route for the data transmission can be calculated online. In this paper existing wavelength assignment and routing technique has been reviewed and analyzed. This literature work has been extended so the network routing strategy can be made better, which results in the efficient utilization of network resources.
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.
Efficient routing in optical networks
Journal of the ACM, 1996
This paper studies the problem of dedicating routes to connections in optical networks. In optical networks, the vast bandwidth available in an optical fiber is utilized by partitioning it into several channels, each at a different optical wavelength. A connection between two nodes is assigned a specific wavelength, with the constraint that no two connections sharing a link in the network can be assigned the same wavelength. This paper considers optical networks with and without switches, and different types of routing in these networks. It presents optimal or near-optimal constructions of optical networks in these cases and algorithms for routing connections, specifically permutation routing for the networks constructed here.
ICTACT Journal on Communication Technology, 2015
In wavelength division multiplexed all optical networks; lightpath establishes a connection between sending and receiving nodes bypassing the electronic processing at intermediate nodes. One of the prime objectives of Routing and Wavelength Assignment (RWA) problem is to maximize the number of connections efficiently by choosing the best routes. Although there are several algorithms available, improving the blocking performance in optical networks and finding optimal solutions for RWA problem has still remained a challenging issue. Wavelength conversion can be helpful in restricting the problem of wavelength continuity constraint but it increases complexity in the network. In this paper, we propose new weight dependent routing and wavelength assignment strategy for all optical networks without use of wavelength converters. Proposed weight function reduces blocking probability significantly, improving the network performance at various load conditions. Further, due to absence of wavelength converters, the cost and complexity of network reduces. Results show that the proposed strategy performs better than earlier reported methods.
Network Design Problems in Wavelength Division Multiplexing Optical Networks
In this study, we analyze a network design problem arising in Wavelength Division Multiplexing (WDM) networks where traffic is static, wavelength interchanging is allowed and the location and number of the wavelength interchangers are to be determined. Given a topology and traffic data, we try to find the fiber and wavelength interchanger configuration with the minimum cost, that can establish all given connections. We present different formulations of the problem and some valid inequalities. Finally, we propose a heuristic method of generating feasible solutions, apply the method on three different topologies with varying traffic data, and present the results. The method is based on the idea of partitioning the problem into two; routing problems and wavelength assignment and interchanger location problem. Our results prove to be close to the lower bounds we generate, and indicate that the fiber cost performance of the case where all nodes are wavelength interchangers can be attained using a relatively small number of wavelength interchangers.
A Routing and Wavelength Assignment Strategy for Successful Transmission in Optical Networks
Journal of Interconnection Networks, 2009
Optical Burst and Packet Switching (OBS/OPS) are techniques designed to serve higherlayer packet-based communication protocols by allowing statistical multiplexing. Since OBS and OPS networks provide connectionless transport, they both suffer from contention, which occurs when multiple communications want to use simultaneously the same wavelength in a link. This paper proposes a Routing and Wavelength Assignment (RWA) strategy based on the concept of (rooted) collision-free digraph, which represents all paths assigned by the routing to those communications sharing a wavelength. Using the proposed RWA strategy, the contention problem can be successfully solved by using simple mechanisms based on adding a suitable additional delay to burst/packet transmissions. Here we define and characterize the routing-antipodal networks, in which we can define n/2 pairs of arc-disjoint collision-free digraphs (with n being the number of nodes) that altogether include all arcs of the network. This implies that, using n/2 wavelengths, we can achieve connectivity between any pair of nodes under the wavelength-continuity constraint. Solutions with fewer wavelengths are also feasible. In particular, if the routingantipodal network has a trail that passes through all vertices at least once, one wavelength is enough to ensure connectivity between each pair of nodes. We also show that the line digraph technique provides us with a simple tool for obtaining proper collisionfree digraphs. The proposed method works in either a synchronous or an asynchronous transmission environment. Also, the arriving and length burst/packet distributions can be of any type, provided that the maximum theoretical offered load is not exceeded.
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.
Optimizing Routing and Wavelength Allocation in Optical Core Networks
2006
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 e...
Efficient wavelength assignment strategy for wavelength-division multiplexing optical networks
Optical Engineering, 2007
When a physical network and its required connections are given, the routing and wavelength assignment ͑RWA͒ is a problem. A suitable path and wavelength must be selected from among the many possible choices for each connection such that no two paths using the same wavelength pass through the same link. In the absence of wavelength conversion, a lightpath must use the same wavelength on all fiber links that it spans. In wavelength-division multiplexing ͑WDM͒ optical networks, there is a need to maximize the number of connections accepted and to minimize the number of connections rejected, i.e., the blocking probability. We propose a new strategy to assign the wavelength. Then we compare the performance of the proposed strategy with commonly used wavelength assignment strategies in terms of the number of attempts required to establish the given connection. The comparison shows that fewer attempts are required for the proposed strategy, leading to a reduced connection establishment time.