Wavelength-division Multiplexing Routing Research Articles

Millimeter-Wave Radio-Over-Fiber Network for Linear Cell Systems

We discuss and propose millimeter-wave linear cell systems for signal distribution on railway radiocommunication systems between train and trackside, and a foreign object debris detection system for airport runways using the radio-over-fiber network technology. Linear cell configurations based on wavelength-division multiplexing (WDM) and power-splitter-based distribution networks are discussed and demonstrated experimentally. A single-sideband modulation for data transmission in an intermediate frequency over a fiber system is successfully transmitted with an ultrafast wavelength-tunable laser diode for WDM routing to track the train car within 3 $\mu$ s. Radar signal distribution by an optical double-sideband suppressed-carrier modulation mitigates the dispersion effect of the fiber cable to transmit a 32-GHz signal into the remote radar heads.

Forward-Looking WDM Network Reconfiguration with Per-Link Congestion Control

We study reconfigurations of wavelength-routed Wavelength Division Multiplexing (WDM) networks in response to lightpath demand changes, with the objective of servicing more lightpath demands without additional network resources from a long-term network operation point of view. For the reconfiguration problem under study, we assume WDM network operators are provided with lightpath demands in batches. With limited network resources, our problem has two unique challenges: balancing network resource allocations between current and future lightpath demands, and modeling future lightpath demands. The first challenge implies making tradeoffs between accepting as many current immediate lightpath demands as possible and reserving a certain amount of network resources for near future predicted lightpath demands. The second challenge implies modeling future predicted lightpath demands, which are not exactly known or certain as the current lightpath demands. Our proposed model allows a natural separation between the operation of the optical layer and the user traffic layer (predominantly the IP-layer), while supporting their interactions, for which we propose a new formulation for per-link congestion control, associated with a mathematical solution procedure. Our simulation results reveal that by properly controlling resource allocations in the current session using our proposed mechanism, rejections in future sessions are greatly reduced.

Converter Placement in Wavelength-routed Networks with Dynamic Traffic Demand

The blocking performance of wavelength division multiplexing (WDM) all-optical networks can be improved by employing wavelength conversion. In this paper, we study wavelength converter placement problem in wavelength-routed WDM networks with dynamic traffic demands. It is considered that under different routing and wavelength assignment (RWA) algorithms, the path usage probabilities are significantly different. Therefore, in this paper the converter placement algorithm and RWA policies are considered jointly.

Layered-routing approach for solving multicast routing and wavelength assignment problem

We have developed a new layered-routing approach to address the problem of all-optical multicast over wavelength-routed wavelength division multiplexing (WDM) networks. We model the WDM network as a collection of wavelength layers with sparse light- splitting (LS) and wavelength conversion (WC) capabilities. We apply the degree constraint technique to solve the problem. The approach is capable of completing multicast routing and wavelength assignment (MCRWA) in one step. We propose two generic frameworks to facilitate heuristic development. Any heuristic that is derived from either Prim’s or Kruskal’s algorithm can be easily imported to solve the MCRWA problem. One example is given for each framework to demonstrate heuristic development. Extensive simulations were carried out to measure the performance of heuristics developed from the frameworks. The results show that the STRIGENT scheme is suitable for hardware design and it is advisable to deploy light splitters and wavelength converters to the same node for better performance.

Wavelength assignment with sparse wavelength conversion for optical multicast in WDM networks

This paper addresses the problem of multicast wavelength assignment for sparse wavelength conversion (MWA-SWC) in wavelength-routed wavelength-division-multiplexing (WDM) networks. It aims to optimally allocate the available wavelength for each link of the multicast tree, given a sparse wavelength conversion network and a multicast request. To our knowledge, little research work has been done to address this problem in literature.In this paper, we propose a new technique called MWA-SWC algorithm to solve the problem. The algorithm first maps the multicast tree from the sparse conversion case to the full conversion case by making use of a novel virtual link method to carry out the tree mapping. The method provides a forward mapping to generate an auxiliary tree as well as a reverse mapping to recover the original tree. Applying the auxiliary tree, we propose a dynamic programing algorithm for the wavelength assignment (WA) aiming to minimize the number of wavelength converters (NWC) required. Simulation results show that our new algorithm outperforms both random and greedy algorithms with regard to minimizing the NWC. Testing on various scenarios by varying the number of wavelength conversion nodes in the tree has confirmed the consistency of the performance. The primary use of the MWA-SWC algorithm is for static traffic. However, it can also serve as a baseline for dynamic heuristic algorithms. Typically, the MWA-SWC algorithm will provide great benefit when the number of available wavelengths on each link of the multicast tree is relatively large and the performance advantage is significant.

Multicast traffic grooming in wavelength-routed WDM mesh networks using dynamically changing light-trees

In this paper, we address the online multicast traffic grooming problem in wavelength-routed wavelength division multiplexing (WDM) mesh networks with sparse grooming capability. We develop a multicast dynamic light-tree grooming algorithm (MDTGA) that can support multihop traffic grooming by taking advantage of light-trees. In this algorithm, a light-tree can be dropped, branched, and extended when a route is to be established for a new request; a light-tree can also be contracted when some branches carry no effective traffic after requests depart from the network. The difficulty of the algorithm lies in the dynamic characteristic of light-trees. We implement MDTGA on a new auxiliary-graph model. For the purpose of comparison, we also implement a lightpath-based grooming algorithm by putting a constraint on the optical-splitting capability of the nodes. Through extensive simulations, we find that MDTGA has much better performance than the lightpath-based algorithm.

A binary (0-1) linear program formulation for the placement of limited-range wavelength converters in wavelength-routed WDM networks

We investigate the problem of optimally placing limited-range wavelength converters at a subset of nodes in wavelength-routed wavelength-division-multiplexing (WDM) networks. We consider two different aspects of the converter-placement problem: 1) the placement minimizing the network-wide blocking probability; and 2) the placement minimizing the number of wavelength-convertible nodes to meet the performance constraints. We present a binary (0-1) linear program (BLP) formulation in which the end-to-end blocking probability is expressed as a linear function of converter locations so that standard linear program (LP) optimization packages can be employed to obtain the optimal solution of the problems. We also present a new analytical model for estimating the end-to-end blocking probabilities. Experiments have been conducted over four network topologies, including 19-node European optical network (EON), 24-node USA backbone network (UBN), 32-node HYPERCUBE, and 36-node MESH-TORUS. We demonstrate that the optimal solutions of the converter-placement problems can be obtained within a reasonable computation time.

Photonic network R&D activities in Japan-current activities and future perspectives

R&D activities on photonic networks in Japan are presented. First, milestones in current ongoing R&D programs supported by Japanese government agencies are introduced, including long-distance and wavelength division multiplexing (WDM) fiber transmission, wavelength routing, optical burst switching (OBS), and control-plane technology for IP backbone networks. Their goal was set to evolve a legacy telecommunications network to IP-over-WDM networks by introducing technologies for WDM and wavelength routing. We then discuss the perspectives of so-called PHASE II R&D programs for photonic networks over the next 5 years until 2010, by focusing on the report that has been recently issued by the Photonic Internet Forum (PIF), a consortium that has major carriers, telecom vendors, and Japanese academics as members. The PHASE II R&D programs should serve to establish a photonic platform to provide abundant bandwidth on demand, at any time on a real-time basis, through the customer's initiative to promote bandwidth-rich applications, such as grid computing, real-time digital-cinema streaming, medical and educational applications, and network storage in e-commerce.

Randomized routing and wavelength requirements in wavelength-routed WDM multistage, hypercube, and de Bruijn networks

This paper considers randomized routing in wavelength-routed wavelength division multiplexed (WDM) networks. Randomized routing is advantageous when compared to deterministic routing, as it is simple, oblivious, and suitable for centralized as well as distributed implementation. Recently, there has been a considerable interest in studying regular graphs such as shuffle networks and de Bruijn networks as a possible physical topology for wavelength-routed WDM networks (IEEE/ACM Trans. Network 3(3) (June 1995) 269; IEEE/ACM Trans. Network 2(1) (February 1994) 70; Comput. Networks ISDN Systems 30(24) (December 1998) 2349). In Pankaj and Gallager (1995), permutation routing has been taken as a benchmark problem to accept a network and a deterministic algorithm has been proposed for routing permutation traffic without any blocking in an N-node wrapped-around multi-stage shuffle network using O( log 3 N) wavelengths. In this paper, we look at the possible application of probabilistic techniques on a class of wrapped-around multi-stage networks called 2-multinets and study the wavelength requirements for routing permutation traffic, allowing a negligible blocking of sessions. We adopt the routing scheme proposed in (J. ACM 31 (1984) 507) for fast packet routing to find routes in the circuit-switched wavelength-routed WDM networks and analyze the wavelength requirements for different models. The models differ in their routing node architecture and wavelength selection policy. Our analysis shows that the permutation routing problem can be solved on these models with an overwhelming probability using O( log 2 N) wavelengths. We also study the routing problem on 2-multinets for a class of 1-expectedly bounded connection requests. For this class also, we propose two models and obtain similar bounds on the number of wavelengths required. We confirm the theoretical results by extensive simulation experiments. The theoretical as well as experimental results show that the number of wavelengths required is reduced significantly when randomized routing techniques are used. Finally, we discuss how the results obtained for 2-multinets can be extended to hypercubes and de Bruijn networks.

Next-generation WDM network design and routing: introduction to the feature issue

Feature Issue on Next-Generation WDM Network Design and Routing (WDMN). The ever-increasing volume of Internet traffic is the major driver behind the increased efforts toward designing switches, routers, and new techniques and technologies that are capable of sustaining such tremendous demands. Optical networking and wavelength-division multiplexing (WDM) have emerged in the past decade as the technology and the technique of choice for efficiently exploiting the large bandwidth offered by optical devices at a very competitive cost per carried bit. To bring such technologies all the way from mere hardware to user-ready devices, there remains a large gap to be filled with protocols, frameworks, algorithms, and designs that make effective and efficient use of this optical fiber bandwidth. Research in the area has been focused recently on many aspects of optical networks. Of particular interest to <a href=

Dynamic lightpath restoration based on bidirectional initiation for wavelength-routed WDM networks

Dynamic restoration is one of the basic survivability paradigms for surviving single-link failures in wavelength-routed wavelength division multiplexing (WDM) networks. In dynamic restoration, no spare network resources are reserved before a network failure occurs. The network must dynamically discover spare network resources to recover the disrupted network services after a network failure occurs. Accordingly, dynamic restoration is efficient in resource utilisation but slow in service recovery. Fast provisioning of service recovery is a great concern with dynamic restoration. A bidirectional initiation restoration mechanism (BIRM) is proposed for dynamic path restoration in wavelength-routed WDM networks. BIRM differs from existing path restoration mechanisms in that it allows both the source node and the destination node of a broken lightpath to respectively initiate a path restoration process in the event of a link failure. The purpose is to reduce the path restoration time so that a backup path can be established quickly for each broken lightpath that traverses a failed link. Based on BIRM, a dynamic path restoration protocol is also presented. Moreover, the performance of BIRM is evaluated through simulation experiments in terms of the path restoration time and request blocking probability.

Wavelength rerouting in optical networks, or the Venetian Routing problem

Wavelength rerouting has been suggested as a viable and cost-effective method to improve the blocking performance of wavelength-routed wavelength-division multiplexing (WDM) networks. This method leads to the following combinatorial optimization problem, dubbed Venetian Routing. Given a directed multigraph G along with two vertices s and t and a collection of pairwise arc-disjoint paths, we wish to find an st-path which arc-intersects the smallest possible number of the given paths. In this paper we prove the computational hardness of this problem even in various special cases, and present several approximation algorithms for its solution. In particular we show a non-trivial connection between Venetian Routing and Label Cover.

On multicast routing for wavelength-routed WDM networks with dynamic membership

Future broadband networks must support integrated services and offer flexible bandwidth usage. In our previous work in [1], we explored the optical link control (OLC) layer on the top of optical layer that enables the possibility of bandwidth on-demand (BoD) service directly over wavelength division multiplexed (WDM) networks. Today, more and more applications and services such as video-conferencing software and Virtual LAN service require multicast support over the underlying networks. Currently, it is difficult to provide wavelength multicast over optical switches without optical/electronic conversions although the conversion takes extra cost. In this paper, based on the proposed wavelength router architecture (equipped with ATM switches to offer O/E and E/O conversions when necessary), a dynamic multicast routing algorithm is proposed to furnish multicast services over WDM networks. The goal is to join a new group member into the multicast tree so that the cost, including the link cost and the optical/electronic conversion cost, is kept as low as possible. The same algorithm can be applied to other wavelength routing architectures with redefinition of electronic copy cost. The effectiveness of the proposed wavelength router architecture as well as the dynamic multicast algorithm is evaluated by simulation.

Multicasting in WDM networks

Wavelength-division multiplexing (WDM) networks are believed to be a promising candidate to meet the explosive increase of bandwidth demand in the Internet. In this article, we survey the problems of and approaches to multicasting in WDM networks. In particular, we address the issues in the context of three types of WDM networks: broadcast-and-select, wavelength-routed, and optical burst-switched (OBS) WDM networks. Broadcast-and-select WDM networks are typically for WDM LANs?MANs, and can be either single-hop or multihop. Various multicast scheduling algorithms (MSAs) are discussed for single-hop networks. For multihop networks, we discuss how channel sharing can be employed to effectively support multicast. In a wavelength-routed WDM network, supporting multicast leads to the multicast routing and wavelength assignment (MC-RWA) problem, which has been discussed for different scenarios, including sparse-splitting networks. We also discuss the problem of efficiently supporting multicast in optical burst-switched (OBS) networks, where the overheads due to control packets and guard bands need to considered.

Coloring all directed paths in a symmetric tree, with an application to optical networks*

AbstractLet T be a symmetric directed tree, i.e., an undirected tree with each edge viewed as two opposite arcs. We prove that the minimum number of colors needed to color the set of all directed paths in T, so that two paths of the same color never use the same directed arc of T, is equal to the maximum number of different paths that contain the same arc of T. The proof implies a polynomial time algorithm for actually coloring the paths with the minimum number of colors. When only a subset of the directed paths is to be colored, the problem is known to be NP‐complete; we describe certain instances of the problem which can be efficiently solved. These results are applied to WDM (wavelength‐division multiplexing) routing in all‐optical networks. In particular, we solve the all‐to‐all gossiping problem in optical networks. © 2001 John Wiley &amp; Sons, Inc. J Graph Theory 38: 183–196, 2001

A Distributed Control Protocol for Wavelength Routing with Fairness Improvement in WDM Networks

This paper considers the problem of distributed routing with fairness improvement in wavelength-routed wavelength-division multiplexed (WDM) networks with dynamic traffic conditions. The wavelength continuity constraint imposed by WDM networks causes increased blocking of connection requests. The performance loss is more for connections with longer hop counts, when compared to that for connections with shorter hop counts. This is further worsened when distributed routing is used due to the reservation conflicts. We propose a distributed control protocol to select a usable wavelength and route and to improve fairness among connections with different hop counts. The proposed dynamic priority based fairness improvement scheme(DPFS) improves fairness among connections by enforcing dynamically varying priority based control to the connection requests over access to a subset of the available wavelengths. while allowing a free access to the remaining wavelengths. We study the effectiveness of the proposed protocol through extensive simulation experiments. The results show that the proposed scheme improves fairness significantly with an acceptable level of degradation in the overall network performance.

A time optimal wavelength rerouting algorithm for dynamic traffic in WDM networks

In this paper, we consider wavelength rerouting in wavelength routed wavelength division multiplexed (WDM) networks with circuit switching, wherein lightpaths between source-destination pairs are dynamically established and released in response to a random pattern of arriving connection requests and connection holding times. The wavelength continuity constraint imposed by WDM networks leads to poor blocking performance. Wavelength rerouting is a viable and cost effective mechanism that ran improve the blocking performance by rearranging certain existing lightpaths to accommodate a new request. Recently, a rerouting scheme called move-to-vacant wavelength retuning (MTV-WR) with many attractive features such as shorter disruption period and simple switching control, and a polynomial time rerouting algorithm, for this scheme, to minimize the weighted number of rerouted lightpaths have been proposed. This paper presents a time optimal rerouting algorithm for wavelength-routed WDM networks with parallel MTV-WR rerouting scheme. The algorithm requires only O(N/sup 2/W) time units to minimize the weighted number of existing lightpaths to be rerouted, where N is the number of nodes in the network and W is the number of wavelength channels available on a fiber link. Our algorithm is an improvement over the earlier algorithm proposed in that it requires O(N/sup 3/W+N/sup 2/W/sup 2/) time units, which is not time optimal. The simulation results show that our algorithm improves the blocking performance considerably and only very few lightpaths are required to be rerouted per rerouting. It is also established through simulation that our algorithm is faster than the earlier rerouting algorithm by measuring the time required for processing connection requests for different networks.

Efficient algorithms for wavelength rerouting in WDM multi-fiber unidirectional ring networks

In this article, we consider wavelength rerouting in wavelength-routed Wavelength-Division Multiplexed (WDM) multi-fiber unidirectional ring networks with circuit switching. The wavelength continuity constraint imposed by WDM networks leads to poor blocking performance. Wavelength rerouting is a viable and cost effective mechanism that can improve the blocking performance by rearranging certain existing lightpaths to accommodate a new request. Recently, in Ref. [1], a rerouting scheme called ‘Parallel Move-To-Vacant Wavelenth Retuning (MTV-WR)’ with many attractive features such as shorter disruption period and simpler switching control has been proposed. A polynomial time rerouting algorithm has also been proposed in Ref. [1] to minimize the weighted number of rerouted lightpaths in WDM networks with the parallel MTV-WR rerouting scheme. However, this algorithm is not time optimal and works correctly when the fiber links, wavelength channels, and lightpaths are all bidirectional. We present here a time-optimal rerouting algorithm to minimize the number of rerouted lightpaths in wavelength-routed WDM multi-fiber unidirectional ring networks with parallel MTV-WR rerouting scheme. This algorithm requires only O( NFW) time units, where N is the number of nodes in the network, F is the number of fiber links between two consecutive nodes, and W is the number of wavelength channels available on a fibre link. We also present on O( NF 2 W) time rerouting algorithm to minimize the weighted number of rerouted lightpaths. The simulation results show that the rerouting algorithms improve the blocking performance considerably and only very few lightpaths are required to be rerouted per rerouting. The results also show that, for a given network load per wavelength per fiber, increasing the number of wavelengths or the number of fibers, leads to an improved performance by the networks with rerouting, without any rerouting and with full wavelength conversion capability at the routing nodes.