Network Design Problems in Wavelength Division Multiplexing Optical Networks (original) (raw)

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.

WDM Optical Networks: A Complete Design

Journal of Communication and Information Systems, 2005

Different integer linear programming (ILP) have been proposed for design of optical networks. The traditional approaches divide design into two separate problems: virtual topology design (VTD), in which best connections among nodes are derived from traffic demand; and routing-and-wavelength assignment (RWA), in which physical paths are accommodated in the physical topology to support the requested connections. We propose an iterative linear programming approach to solve both problems jointly under multiple objectives such as congestion avoidance, fiber load and wavelength pool minimization. The solution of the VTD problem generates a request for a set of paths to be supplied by the physical topology. Physical paths are then allocated in order to minimize some objective functions that are akin to a linear programming formulation. If no feasible solution is found, VTD program supplies a next best solution until all paths are routed. Some objective functions (e.g. maximum fiber load) may be oblivious to the persistence of cycles in the final solution, which may even be dismembered from the source-to-destination link sequence. These anomalies may be eliminated by re-optimizing the solution using the total number of hops as a new objective function, subject to the minimal value of maximum fiber load that was determined in the previous optimization step. The final design phase is the assignment of wavelengths to paths or sections thereof, making best use of available wavelength conversion resources. Our formulation allows for any kind (partial or full, sparse or ubiquitous) of wavelength conversion and limited number of converters, thus providing a tool for the allocation of conversion resources in the network. Index Termsoptical networks; lightpath routing; virtual and physical topology; wavelength conversion.

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.

Time-efficient optimal wavelength assignment in optical WDM networks with conversion capability

IEEE Communications Letters, 2006

In wavelength-routed optical networks (WRONs), a wavelength assignment algorithm which can optimally utilize wavelength converters is strongly desired. In this letter, for the first time, we propose a novel graph constructed with groups of available wavelengths, called lambda-runs, to obtain the leastconversion lightpaths easily by applying the shortest-path routing Dijkstra's algorithm. Simulations show that our algorithm is much more scalable than an existing optimal algorithm, and significantly improves the blocking performance, compared to modified first-fit algorithm.

Algorithmic aspects of optical network design

Optical network design problems fall in the broad category of network optimization problems. We give a short introduction on network optimization and general algorithmic techniques that can be used to solve complex and difficult network design problems. We apply these techniques to address the static Routing and Wavelength Assignment problem that is related to planning phase of a WDM optical network. We present simulation result to evaluate the performance of the proposed algorithmic solution.

On the routing and wavelength assignment in multifiber WDM networks

IEEE Journal on Selected Areas in Communications, 2004

This paper addresses the problem of routing and wavelength assignment (RWA) in multifiber WDM networks assuming neither a special topology nor wavelength converters. Given a traffic matrix, the number of fibers per link, and the number of wavelengths a fiber can support, we seek to realize the maximum number of connections. We formulate the problem as an integer linear program (ILP), and show that the selected lightpaths by this formulation can indeed be realized by properly configuring the optical switches. An upper bound on the carried traffic can be computed by solving the linear programming (LP) relaxation of the ILP formulation. However, we prove that the bound can be computed exactly by solving a significantly simplified LP, which considers only one wavelength. Consequently, our bound can easily scale to an arbitrarily large number of wavelengths. Although our formulation is path-flow based, we will demonstrate that, even if all, possibly exponentially many, paths are considered, the upper bound can always be computed in polynomial time. Our bound can thus be used as a benchmark against which exact and heuristic techniques are compared. Furthermore, we demonstrate that a simple greedy algorithm provides solutions to the original ILP formulation that are guaranteed to be within (1 − 1 e ) of its optimal solution. As the greedy algorithm considers only one wavelength at a time, it can scale to a large number of wavelengths. Computational results confirm the high efficiency of our proposed algorithm.

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 multifiber WDM networks with non-uniform fiber cost

Computer Networks, 2006

Motivated by the increasing importance of multifiber WDM networks we study a routing and wavelength assignment problem in such networks. In this problem the number of wavelengths per fiber is given and the goal is to minimize the cost of fiber links that need to be reserved in order to satisfy a set of communication requests; we introduce a generalized setting where network pricing is non-uniform, that is the cost of hiring a fiber may differ from link to link.

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.