Routing , Modulation Level And Spectrum Allocation Research Articles

Improved dynamic routing algorithms in elastic optical networks

The considered Routing, Modulation Level and Spectrum Allocation (RMLSA) problem covers path length minimization while still meeting the spectrum continuity constraints, non-overlapping spectra constraints, spectrum contiguity constraints, and choice of modulation level. In this problem, the relationship between spectrum connection and bit rate of the incoming request has been taken into account. In this paper, two algorithms have been proposed. The first one is based on a set of shortest paths whose lengths are determined by the number of links in the network. The second one is a modified version of Dijkstra’s algorithm. Modification of this algorithm is based on introduction of weights of the network links depending on the utilization of the links and the introduction of a aggregated spectrum of the path that is being selected. Extensive research has shown that algorithms reject the lower traffic volume as compared to well-known algorithms proposed in literature.

New Distance-Adaptive Modulation Scheme for Elastic Optical Networks

Elastic optical networks enter as a promising technology for the future of high-capacity networks. Its features provide flexibility and superior scalability in spectrum allocation following the growing demands of Internet traffic. In this letter, we propose a novel approach to address the routing, modulation level, and spectrum allocation (RMLSA) problem through the use of a distance-adaptive modulation scheme that enables the routing of traffic through multiple hops in virtual topology, enabling smoothing out the spectrum continuity and transmission distance constraints. The results showed that the use of the proposed scheme provide a gain of up to 82% in the bandwidth blocking rate using 7% less spectral resources in the network compared with the literature. This proposal opens a new avenue for future research, allowing new solutions for RMLSA problem.

Efficient Routing and Spectrum Allocation Considering QoT in Elastic Optical Network

In recent years, Orthogonal Frequency Division Multiplexing (OFDM)-based elastic optical network (EON) has drawn increasing attention in both academia and industry. Compared to traditional optical Wavelength Division Multiplexing (WDM) network, EON is capable of supporting variable data rate, accommodating traffic demands flexibly with finer provisioning granularity, and utilizing spectrum more efficiently. Accordingly, the resource management in EON is different from that in WDM networks and addresses new challenges in network design and control. In this paper, we study the routing, modulation level and spectrum allocation (RMLSA) problem in EON. We propose an efficient link-based mixed integer linear programming (MILP) model with the objective to optimally utilize the spectrum resources while considering the constraint on Quality of Transmission (QoT). Then, the performance of the proposed model is evaluated and analyzed through case study.

Influence of Physical Layer Configuration on Performance of Elastic Optical OFDM Networks

We study how the physical layer characteristics and novel digital impairment mitigation techniques impact the performance of elastic optical OFDM networks. The relationship between bandwidth blocking ratio (BBR) and fiber type, span length, dispersion management, FEC and intra-channel nonlinearity compensation are evaluated through cross-layer network simulations, which integrate closed-form expressions of quality of transmission into routing, modulation level and spectrum allocation (RMSA). An adaptive FEC assisted RMSA is proposed and proved to improve the network performance by optimizing the FEC overhead assignment for individual paths. Numerical simulations also show considerable performance improvement by deploying shorter span-length fiber links without dispersion management, and imperceptible influence of intra-channel nonlinearity compensation for flexible grid networks under very heavy traffic. These results provide valuable suggestions for physical layer fiber deployment and application of novel impairment mitigation techniques on elastic optical networks, such as intra-channel nonlinearity compensation as well as soft-decision FEC.

Dynamic routing, modulation level and spectrum allocation (RMLSA) in FWDM with modulation format conversion

This paper proposes a dynamic routing, modulation level and spectrum allocation (RMLSA) scheme in the flexible optical wavelength-division multiplexing (FWDM) networks with modulation format conversion ability. The scheme considers the modulation format conversion at the intermediate nodes and addresses the fragmentation problem by avoiding appearance of them. The influence of routing to the emergence of the fragmentation is quantified, which is referenced to decide which one route of k-paths to use. Simulation results demonstrate efficient reductions in blocking rates and improvements in failure recovery rates for the scheme in the network.

Elastic Bandwidth Allocation in Flexible OFDM-Based Optical Networks

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique for optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments. We consider the planning problem of an OFDM optical network, where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers and choosing an appropriate modulation level, taking into account the transmission distance. We introduce the Routing, Modulation Level and Spectrum Allocation (RMLSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, prove that is also NP-complete and present various algorithms to solve it. We start by presenting an optimal ILP RMLSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RMLSA into its two substituent subproblems, namely 1) routing and modulation level and 2) spectrum allocation <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$({\rm RML}+{\rm SA})$</tex></formula> , and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all the connections in the traffic matrix. In the sequential algorithm, we investigate two policies for defining the order in which connections are considered. We also use a simulated annealing meta-heuristic to obtain even better orderings. We examine the performance of the proposed algorithms through simulation experiments and evaluate the spectrum utilization benefits that can be obtained by utilizing OFDM elastic bandwidth allocation, when compared to a traditional WDM network.