Performance analysis of wavelength converters in WDM wavelength routed optical networks
17 Dec 1998-pp 239-246
TL;DR: A new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored and Multihop virtual topology is designed to minimize the number and overall cost of the converters.
Abstract: This paper attempts to study the impact of wavelength converters in WDM wavelength routed all-optical networks. A new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Multihop virtual topology is designed to minimize the number and overall cost of the converters. Blocking probabilities for static lightpath establishment (SLE) and dynamic lightpath establishment (DLE) are analyzed. In the case of SLE, arranging lightpaths in ascending order of their path length reduces blocking probability. Wavelength converters placed at nodes with high nodal degree further reduces the blocking probabilities. Simulation studies performed on a 28-node USA long haul network and a 20-node arbitrary mesh network, validate the above observations.
Citations
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21 Mar 1999
TL;DR: Investigation of heuristics for placing limited range wavelength converters in arbitrary mesh wavelength routed optical networks finds that limited range converters at a few nodes can provide almost the entire improvement in the blocking probability as the full range wavelengths placed at all the nodes.
Abstract: Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength converters play an important role in enhancing the fiber utilization and reducing the overall call blocking probability of the network. As the distortion of the optical signal increases with the increase in the range of wavelength conversion in optical wavelength converters, limited range wavelength conversion assumes importance. Placement of wavelength converters is a NP complete problem in an arbitrary mesh network. In this paper, we investigate heuristics for placing limited range wavelength converters in arbitrary mesh wavelength routed optical networks. The objective is to achieve near optimal placement of limited range wavelength converters resulting in reduced blocking probabilities and low distortion of the optical signal. The proposed heuristic is to place limited range wavelength converters at the most congested nodes, nodes which lie on the long lightpaths and nodes where conversion of the optical signals is significantly high. We observe that limited range converters at a few nodes can provide almost the entire improvement in the blocking probability as the full range wavelength converters placed at all the nodes. Congestion control in the network is brought about by dynamically adjusting the weights of the channels in the link thereby balancing the load and reducing the average delay of the traffic in the entire network. Simulations have been carried out on a 12-node ring network, 14-node NSFNET, 19-node European Optical Network (EON), 30-node INET network and the results agree with the analysis.
83 citations
TL;DR: A new algorithm for the sparse placement of full wavelength converters based on the concept of a k-minimum dominating set (k-MDS) of graphs is presented and has better blocking performance, has better time complexity, and avoids the local minimum problem.
Abstract: Optical wavelength converters are expensive, and their technology is still evolving Deploying full conversion capability in all nodes of a large optical network would be prohibitively costly We present a new algorithm for the sparse placement of full wavelength converters based on the concept of a k-minimum dominating set (k-MDS) of graphs The k-MDS algorithm is used to select the best set of nodes that will be equipped with full-conversion capability To allow placement of full wavelength conversion at any arbitrary number of nodes, we introduce a HYBRID algorithm and compare its performance with the simulation-based k-BLK approach We also extend the k-MDS algorithm to the case of limited conversion capability by using a scalable and cost-effective node-sharing switch design Compared with full search algorithms previously proposed in the literature our algorithm has better blocking performance, has better time complexity, and avoids the local minimum problem The performance benefit of our algorithms is demonstrated by simulation
25 citations
TL;DR: A new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored and Multihop virtual topology is designed to minimize the number and overall cost of the converters.
22 citations
TL;DR: This work proposes a combination of contention reduction through congestion control and bursts retransmission to eliminate completely bursts loss and shows that the proposed protocol is a viable solution for effectively reducing the conflict and increasing the bandwidth utilization for optical burst switching.
Abstract: Optical burst switching (OBS) is a proposed new communications technology that seeks to expand the use of optical technology in switching systems. However, many challenging issues have to be solved in order to pave the way for an effective implementation of OBS. Contention, which may occur when two or more bursts compete for the same wavelength on the same link, is a critical issue. Many contention resolution methods have been proposed in the literature but many of them are very vulnerable to network load and may suffer severe loss in case of heavy traffic. Basically, this problem is due to the lack of information at the nodes and the absence of global coordination between the edge routers. In this work, we propose another approach to avoid contention and decrease the loss. In this scheme, the intermediate nodes report the loss observed to the edge nodes so that they can adjust the traffic at the sources to meet an optimal network load. Furthermore, we propose a combination of contention reduction through congestion control and bursts retransmission to eliminate completely bursts loss. This new approach achieves fairness among all the edge nodes and enhances the robustness of the network. We also show through simulation that the proposed protocol is a viable solution for effectively reducing the conflict and increasing the bandwidth utilization for optical burst switching.
20 citations
TL;DR: This paper investigates heuristics for placing limited range wavelength converters in arbitrary mesh wavelength routed optical networks and observes that limited range converters at few nodes can provide almost the entire improvement in the blocking probability as the full range wavelength Converters placed at all the nodes.
18 citations
References
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TL;DR: The authors derive an upper bound on the carried traffic of connections for any routing and wavelength assignment (RWA) algorithm in a reconfigurable optical network and quantifies the amount of wavelength reuse achievable in large networks as a function of the number of wavelengths, number of edges, and number of nodes for randomly constructed networks as well as de Bruijn networks.
Abstract: Considers routing connections in a reconfigurable optical network using WDM. Each connection between a pair of nodes in the network is assigned a path through the network and a wavelength on that path, such that connections whose paths share a common link in the network are assigned different wavelengths. The authors derive an upper bound on the carried traffic of connections (or equivalently, a lower bound on the blocking probability) for any routing and wavelength assignment (RWA) algorithm in such a network. The bound scales with the number of wavelengths and is achieved asymptotically (when a large number of wavelengths is available) by a fixed RWA algorithm. The bound can be used as a metric against which the performance of different RWA algorithms can be compared for networks of moderate size. The authors illustrate this by comparing the performance of a simple shortest-path RWA (SP-RWA) algorithm via simulation relative to the bound. They also derive a similar bound for optical networks using dynamic wavelength converters, which are equivalent to circuit-switched telephone networks, and compare the two cases. Finally, they quantify the amount of wavelength reuse achievable in large networks using the SP-RWA via simulation as a function of the number of wavelengths, number of edges, and number of nodes for randomly constructed networks as well as de Bruijn networks. They also quantify the difference in wavelength reuse between two different optical node architectures. >
1,046 citations
"Performance analysis of wavelength ..." refers background in this paper
...In [18], approximate analytical models for networks with and without wavelength converters are studied....
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...It is dependent on four factors, namely, the network size and topology, the traffic distribution in the network, the number of wavelengths, and the Routing and wavelength assignment algorithm [18]....
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...The set of all lightpaths that have been setup between nodes constitutes the virtual topology[18]....
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TL;DR: In this paper, the authors present a review of various wavelength conversion techniques, discusses the advantages and shortcomings of each technique, and addresses their implications for transparent WDM networks, and discuss their potential advantages over the optoelectronic counterpart.
Abstract: WDM networks make a very effective utilization of the fiber bandwidth and offer flexible interconnections based on wavelength routing. In high capacity, dynamic WDM networks, blocking due to wavelength contention can he reduced by wavelength conversion. Wavelength conversion addresses a number of key issues in WDM networks including transparency, interoperability, and network capacity. Strictly transparent networks offer seamless interconnections with full reconfigurability and interoperability. Wavelength conversion may be the first obstacle in realizing a transparent WDM network. Among numerous wavelength conversion techniques reported to date, only a few techniques offer strict transparency. Optoelectronic conversion (O/E-E/O) techniques achieve limited transparency, yet their mature technologies allow deployment in the near future. The majority of all-optical wavelength conversion techniques also offer limited transparency but they have a potential advantage over the optoelectronic counterpart in realizing lower packaging costs and crosstalk when multiple wavelength array configurations are considered. Wavelength conversion by difference-frequency generation offers a full range of transparency while adding no excess noise to the signal. Recent experiments showed promising results including a spectral inversion and a 90 nm conversion bandwidth. This paper reviews various wavelength conversion techniques, discusses the advantages and shortcomings of each technique, and addresses their implications for transparent networks.
928 citations
"Performance analysis of wavelength ..." refers methods in this paper
...The all-optical conversion methods can be further grouped into two categories: those which employ coherent effects such as Four Wave Mixing(FWM) [5] and Difference Frequency Generation (DFG) and those which use cross-modulation such as absorption saturation of the semiconductor laser diode and gain Saturation of Optical Amplifier(SOA) [19]....
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02 Apr 1995
TL;DR: A traffic model for circuit switched all-optical networks (AONs) is introduced which is used to calculate the blocking probability along a path for networks with and without wavelength changers.
Abstract: We introduce a traffic model for circuit switched all-optical networks (AONs) which we then use to calculate the blocking probability along a path for networks with and without wavelength changers. We investigate the effects of path length, switch size, and interference length (the expected number of hops shared by two sessions which share at least one hop) on blocking probability and the ability of wavelength changers to improve performance. Our model correctly predicts unobvious qualitative behavior demonstrated in simulations by other authors.
560 citations
TL;DR: In this article, the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength-routing networks are studied and a blocking analysis of such networks is given.
Abstract: Unlike broadcast-and-select networks, wavelength-routing networks offer the advantages of wavelength reuse and scalability and are thus suitable for wide-area networks (WANs) We study the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength-routing networks. A blocking analysis of such networks is given. We first propose an analytical framework for accurate analysis of networks with arbitrary topology. We then introduce a model for networks with a variable number of converters and analyze the effect of wavelength converter density on the blocking probability. This framework is applied to three regular network topologies that have varying levels of connectivity: the ring, the mesh-torus, and the hypercube. The results show that either a relatively small number of converters is sufficient for a certain level of performance or that conversion does not offer a significant advantage. The benefits of conversion are largely dependent on the network load, the number of available wavelengths, and the connectivity of the network. Finally, the tradeoff between physical connectivity, wavelength conversion, and the number of available wavelengths is studied through networks with random topologies.
465 citations