Multi-Path Routing and Wavelength Assignment (RWA) Algorithm for WDM Based Optical Networks

In this paper we consider the routing and wavelength assignment problem in a wavelength routed all optical network. Inspired by techniques from artificial intelligence, in particular the Blocking Island (BI) abstraction, we propose a simple and intelligent routing and wavelength assignment (RWA) algorithm: BI_RWA. This algorithm can be used in arbitrarily connected optical networks. In addition, it is general enough such that with some simple modifications, it can be applied to different optical networking scenarios: static or dynamic traffic, single or multiple fiber links between node pairs, with or without wavelength converters. We have conducted simulation experiments to evaluate the performance of our algorithm. The simulation is carried out in two parts: static traffic and dynamic traffic. The results will demonstrate that our RWA algorithm outperforms state-of-the-art related algorithms.

Transparent All Optical Networks carry huge traffic and any link failure can cause the loss of gigabits of data; hence protection and its guarantee becomes necessary at the time of failure. Many protection schemes were presented in the literature, but none of them speaks about protection guarantee. Also, in all optical networks, due to absence of regeneration capabilities, the physical layer impairments(PLI) accumulates along the lightpaths (LP) which causes sharp degradation of the Quality of Transmission (QoT), as measured by signal bit error rates (BER). The problem of protection with QoT issues was rarely studied in the literature. In this work, a novel protection backup path ensured, QoT aware Routing and Wavelength Assignment (RWA) algorithm called “Virtual Lit –Exhaustive Highest Q factor” (V-Lit EHQ) is presented which exhibits desirable qualities for reliable network operation. The results of the proposed work are compared with the standard QoT aware versions of the Shortest Path-First Fit schemes for both lit and dark protection. The blocking probability (BP) and BER are taken as the performance matrices and the proposed algorithm found to be outperforming as shown through simulations.

In this paper, we propose a new ant-based algorithm for the dynamic routing and wavelength assignment (RWA) problem in optical WDM networks under the wavelength continuity constraint. Unlike conventional approaches, which usually require centralized global network information, our new RWA algorithm constructs the routing solution in a distributed manner by means of cooperative ants. To facilitate the ants’ foraging task, we adopt in our algorithm a probabilistic routing table structure for route selection. The new algorithm is highly adaptive in that it always keeps a suitable number of ants in the network to cooperatively explore the network states and continuously update the routing tables, so that the route for a connection request can be determined promptly by the current states of routing tables with only a small setup delay. Some new schemes for path scoring and path searching are also proposed to enhance the performance of our ant-based algorithm. Extensive simulation results upon three typical network topologies indicate that the proposed algorithm has a very good adaptability to traffic variations and it outperforms both the fixed routing algorithm and the promising fixed–alternate routing algorithm in terms of blocking probability. The ability to guarantee both a low blocking probability and a small setup delay makes the new ant-based routing algorithm very attractive for both the optical circuit switching networks and future optical burst switching networks

WDM networks are increasingly gaining popularity as the backbone networks all over the world. In WDM network planning, electronic equipments like ADMs contribute heavily towards the capital expenditure of the network (Each ADM costs $50,000-$200,000). In WDM rings, determining minimum number of ADMs is NP-Hard. All the previous works have focused on Wavelength Assignment problem by keeping the routing fixed. In this paper, we suggest an integrated topology independent procedure called M3AWI (Minimum Average Minimum Weight Minimum Intersection). M3AWI is used to solve problems on four different types of routing namely, clockwise routing, Anti-clockwise routing, shortest-path routing, and hybrid routing. Our experimental results show that the combined Routing and Wavelength assignment (RWA) algorithms on an average save around 10% of the ADMs.We have also shown that the distribution of lightpaths is an important parameter to the service providers for selecting a routing policy.

Routing and wavelength assignment vs. EDFA reliability performance in optical backbone networks: An operational cost perspective

In order to transmit data efficiently over an optical network, many routing and wavelength assignment (RWA) algorithms have been proposed. This work presents a genetic algorithm that aims at solving the RWA problem, which consists of choosing the most suitable lightpath (i.e., a combination of a route and a wavelength channel) between a source-destination pair of nodes in all-optical networks. A comparison to some already known approaches in terms of blocking probability was made. Results show a reasonable performance, since the average blocking probability achieved by the genetic algorithm was lower than or relatively equivalent to the standard approaches compared.

As one of the core technology of ASON (automatically switched optical network), the dynamic routing and wavelength assignment algorithm is the key for ASON to reflecting its intelligence. In this paper, a new distributed heuristic algorithm based ant colony optimization for dynamic RWA (routing and wavelength assignment) that is adapted to the environment of ASON networks was put forward. The route selecting and the wavelength assignment process were combined with as whole using multilayer-graph model. The algorithm implements in distributed way using local information stored in a pheromone matrix and will be refreshed on the way of searching path. Compare with shortest-path+first-fit algorithms, it can reduce communication overhead cost of networks and the simulation computing showed lower blocking probability and more balanced wavelength resource assignment.

A wavelength-routed optical network consists of a number of cross-connects which are interconnected by optical fibers. Transparent optical networks allow signals to bypass extensive electronic signal processing at intermediate nodes. The quality of an optical signal degrades as it travels though several optical components along its lightpath. It is essential to incorporate imapact of the physical impairments in the routing and wavelength assignment (RWA) problem in transparent optical networks. This work compiles a comprehensive survey, from various research publications, of the proposed algorithms that address this issue. The physical layer impairments classification in optical networks are initially presented followed by physical layer impairments (PLI) RWA algorithms and algorithmic approaches for the PLI-RWA problem. Performance metrics for evaluating the performance of the proposed PLI-RWA algorithms are presented at the end of the work. Further research topics are presented in this study.

Adaptive FEC-based lightpath routing and wavelength assignment in WDM optical networks

A routing and wavelength assignment (RWA) algorithm against high-power jamming based on software-defined optical networks (SDONs) is proposed. The SDON architecture is designed with power monitors at each node, which can collect the abnormal power information from each port and wavelength. Based on the abnormal power information, a metric, the weighted attack probability (WAP), can be calculated. A WAP-based RWA algorithm (WAP-RWA) is proposed considering the WAP values of each link and node along the selected lightpath. Numerical results show that the WAP-RWA algorithm can achieve a better performance in terms of blocking probability and resource utilization compared with the attack-aware dedicated path protection (AA-DPP) RWA (AA-DPP-RWA) algorithm, while providing a protection comparable with the AA-DPP-RWA algorithm.

We develop a time conflict resolving window division algorithm which places a given set of sliding scheduled lightpath demands within their allowed interval and two routing and wavelength assignment (RWA) algorithms, and study their performance.

Translucent optical networks use sparsely located regenerator nodes to increase the optical reach, otherwise limited by the physical layer impairments. Routing in translucent networks often causes the lightpath to traverse a fiber more than once, requiring the use of multiple wavelengths on a fiber for the same lightpath. Most of the routing and wavelength assignment (RWA) algorithms for static demand in translucent networks (termed static RWA) require loop-free routes for shortest path routing and also are agnostic to traffic load. In this paper, we address the problem of static RWA in translucent networks without using physical layer information and show how to route lightpaths on paths with a loop (i.e., not a simple path). We propose integer linear programming formulation to get the exact solutions to the static RWA problem. This work is the first one to optimally solve the static RWA problem for non-simple paths, providing the lower bound on the number of wavelengths and regeneration needed for static lightpath establishment when regeneration facilities are limited. We propose a heuristic algorithm based on the concept of Wardrop equilibrium, to adaptively equalize the mean delay along all the lightpath routes from source to destination. The proposed heuristic can not only accommodate the correlation between feasible lightpath routes but also account for the fact that alternate routes correspond to different levels of choice randomness. Wavelength assignment is done using graph coloring with branch-and-price method. Numerical results demonstrate that the proposed heuristic reduces the number of regenerators and wavelengths required to satisfy a given demand.

In this paper a novel approach for modelling Routing and Wavelength Assignment (RWA) problem in wavelength-routed Dense Wavelength Division Multiplexing (DWDM) optical networks is proposed. A new idea based on Artificial Bee Colony (ABC) algorithm is introduced for solving RWA problem which is known to be an NP-hard problem. In the proposed ABC-RWA approach every food source represents a possible and feasible lightpath between each original and destination node pair in demand matrix. The positions of food sources are modified by some artificial bees in the population where the aim is to discover the places of food sources. The food source with the highest nectar value seems to be a solution which is evaluated by the fitness function. The simulation results demonstrate the ability and efficiency of proposed approach for solving RWA in real-world optical networks. The proposed approach could be extended for dynamic RWA schemes in real-time applications and employed by network resilience architectures.

We develop on-line routing and wavelength assignment (RWA) algorithms for WDM bidirectional ring and torus networks with N nodes. The algorithms dynamically support all k-allowable traffic matrices, where k denotes an arbitrary integer vector [k/sub 1/, k/sub 2/,... k/sub N/], and node i, 1 /spl les/ i /spl les/ N, can transmit at most k/sub i/ wavelengths and receive at most k/sub i/ wavelengths. Both algorithms support the changing traffic in a rearrangeably nonblocking fashion. Our first algorithm, for a bidirectional ring, uses [(/spl Sigma//sub i=1//sup N/ k/sub i/)/3] wavelengths in each fiber and requires at most three lightpath rearrangements per new session request regardless of the number of nodes N and the amount of traffic k. When all the k/sub i/'s are equal to k, the algorithm uses [kN/3] wavelengths, which is known to be the minimum for any off-line rearrangeably nonblocking algorithm. Our second algorithm, for a torus topology, is an extension of a known off-line algorithm for the special case with all the k/sub i/'s equal to k. For an R /spl times/ C torus network with R /spl ges/ C nodes, our on-line algorithm uses [kR/2] wavelengths in each fiber, which is the same as in the off-line algorithm, and is at most two times a lower bound obtained by assuming full wavelength conversion at all nodes. In addition, the on-line algorithm requires at most C - 1 lightpath rearrangements per new session request regardless of the amount of traffic k. Finally, each RWA update requires solving a bipartite matching problem whose time complexity is only O (R), which is much smaller than the time complexity O(kCR/sup 2/) of the bipartite matching problem for an off-line algorithm.

This paper studies the routing and wavelength assignment (RWA) in wavelength-routed all optical Wavelength Division Multiplexing (WDM) networks. A conception named Link Multiplexing Degree is introduced in our research and a novel adaptive RWA algorithm named MinSum is proposed following our theory analysis. MinSum considers more network state information than other adaptive RWA algorithms while the calculation process is more reasonable. The simulation result shows that MinSum performs better than its counterparts and the network performance can be improved significantly by this novel algorithm.