Dynamic Elastic Optical Networks Research Articles

Reducing blocking probability and QoT violation in dynamic elastic optical networks via load-aware margin selection

In this paper, we study the effect of load-aware margin selection on the performance of elastic optical networks (EONs) in dynamic service provisioning. First, a mixed-integer linear programming (MILP) formulation is proposed as a benchmark for dynamic routing, modulation level, spectrum, and power assignment (RMSPA). In this formulation, nonlinear interferences (NLIs) in optical fibers and the noise of amplifiers are considered. In addition, a margin which is calculated based on the network load is considered to estimate the additional noise which may degrade the signal quality of transmission (QoT) during its life time. The objective of this formulation is to minimize the spectrum usage and impairments of/from the signal which is optimized by choosing the optimum channel among a number of pre-calculated channels based on the QoT constraints. In order to reduce the RMSPA run time, heuristic algorithms are also proposed. The algorithms employ K-least weighted paths for routing. The defined weights are distance, the amount of traffic load, and a mixture scheme. Furthermore, the algorithms try to minimize the spectrum usage by choosing the highest possible modulation level while considering a specific criterion. The assumed criteria are: i) choosing the lowest possible power spectral density (PSD) in a discrete set, ii) selecting the optimum power among the set, iii) obtaining maximum SNR. We simulated the proposed algorithms and the MILP, and compared their performances on NSFNET and US Backbone topologies. The results reveal that the constrained best SNR scheme has the best performance among the heuristics and its performance is close to MILP, especially in higher loads. Moreover, results show that considering the links congestion leads to blocking reduction. We also simulated the first-fit based algorithms without considering NLIs which assign the modulation based on: i) considering only amplifier noise and self-channel interference (SCI), ii) experimental distance thresholds, and iii) overestimating the NLI. The results imply that the proposed MILP and heuristic algorithms outperform the other algorithms in terms of the summation of outage (probability of QoT violation) and blocking probability.

Impact of Amplification and Regeneration Schemes on the Blocking Performance and Energy Consumption of Wide-Area Elastic Optical Networks

This paper studies the physical layer’s impact on the blocking probability and energy consumption of wide-area dynamic elastic optical networks (EONs). For this purpose, we consider five network configurations, each named with a network configuration identifier (NCI) from 1 to 5, for which the Routing, Modulation Level, and Spectrum Assignment (RMLSA) problem is solved. NCI 1–4 are transparent configurations based on all-EDFA, hybrid Raman/EDFA amplifiers (with different Raman gain ratio $\Gamma _{R}$ ), all-DFRA, and alternating span configuration (EDFA and DFRA). NCI 5 is a translucent configuration based on all-EDFA and 3R regenerators. We model the physical layer for every network configuration to determine the maximum achievable reach of optical signals. Employing simulation, we calculate the blocking probability and the energy consumption of the different network configurations. In terms of blocking, our results show that NCI 2 and 3 offer the lowest blocking probability, with at least 1 and 3 orders of magnitude of difference with respect to NCI 1 and 5 at high and low traffic loads, respectively. In terms of energy consumption, the best performing alternatives are the ones with the worst blocking (NCI 1), while NCI 3 exhibits the highest energy consumption with NCI $2\,\,\Gamma _{R}=0.75$ following closely. This situation highlights a clear trade-off between blocking performance and energy cost that must be considered when designing a dynamic EON. Thus, we identify NCI 2 using $\Gamma _{R}=0.25$ as a promising alternative to reduce the blocking probability significantly in wide-area dynamic EONs without a prohibitive increase in energy consumption.

Performance Comparison of Dynamic Elastic Optical Networks with Optical Regeneration

We have investigated optical regeneration issues and application in elastic optical networks that are capable of providing dynamically optical paths with flexible bandwidths. We have analyzed the impact of optical regeneration in elastic optical networks and clarified various usage scenarios. We have then evaluated and compared the performance, in terms of the overall blocking probability and the total accommodated traffic volume, of three possible network scenarios with regeneration capability including (i) no regeneration, (ii) 3R regeneration, and (iii) 4R regeneration for practical network topologies. Numerical simulation proved that deployment of optical regeneration devices can exploit elastic optical networking to enhance the network performance for provisioning dynamically bandwidth-flexible lightpath services. It is also demonstrated that using re-modulation function while regenerating optical signals (4R regeneration) can further improve the network performance. However, due to the high cost of optical regeneration devices, especially all-optical ones, and more functional regenerators, the trade-off between the performance enhancement and the necessary number of regenerating devices needs to be carefully considered.

Introduction to the Special Issue on Optical Network Design and Modeling

The ONDM 2016 Special Issue is a collection of outstanding optical networking papers, chosen among the ONDM 2016 most highly ranked papers. The papers in this special issue cover a broad range of topics including dynamic elastic optical networks, network virtualization, next-generation optical access networks, spatial division multiplexing networking, and multi-layer design.

On Spectrum Efficient Failure-Independent Path Protection <italic>p</italic>-Cycle Design in Elastic Optical Networks

High spectrum efficiency and fast restoration speed are highly desired for survivable elastic optical networks (EONs). In this paper, we take the advantages of failure-independent path-protecting preconfigured cycles (FIPP p -cycles) and investigate how to realize spectrum efficient resilience design with them. We first study the problem of offline service provisioning with FIPP p -cycles. We formulate an integer linear programming model and prove that the problem is $\mathcal{NP}$ hard. Then, several time-efficient heuristics are designed for FIPP p -cycle formulation and related routing, modulation format, and spectrum assignment. Extensive simulations on offline provisioning verify that the heuristics can obtain near-optimal solutions. Next, we consider online service provisioning with FIPP p -cycles in dynamic EONs. In order to overcome the decrease of protection efficiency during dynamic network operation, we propose a p -cycle reconfiguration scheme to reoptimize protection structures on-the-fly. Simulation results demonstrate that the proposed algorithms can improve spectrum efficiency and reduce bandwidth blocking probability simultaneously.

Service Availability Oriented p-Cycle Protection Design in Elastic Optical Networks

In this paper, we develop a theoretical model to precisely analyze the service availability of networks with preconfigured cycles (p-cycles). By considering the dependence among protection domains and all the scenarios when a lightpath is available, our model can estimate the service availability more precisely than those in previous work. Then, based on the availability analysis, we propose a service availability oriented p-cycle configuration algorithm for dynamic elastic optical networks (EONs), namely, the number of relevant links (NRL)-based p-cycle design algorithm (NRL-p-cycle). The simulations compare the proposed algorithm with two benchmark p-cycle design algorithms that are based on the protection efficiency of p-cycles. Simulation results show that the proposed algorithm can effectively improve the service availability in EONs while keeping the blocking probability almost unchanged.

Optimal Route, Spectrum, and Modulation Level Assignment in Split-Spectrum-Enabled Dynamic Elastic Optical Networks

The spectrum fragmentation effect in elastic optical networks is one of their main limitations. Multiple techniques have been proposed to address this problem, with the split spectrum approach (SSA) being a very interesting candidate among them. This technique is based on splitting a demand into smaller sub-demands when a blocking situation arises. In split-spectrum-enabled networks, the route, spectrum, and modulation level assignment (RSMLA) problem that appears in elastic optical networks is further complicated due to the signal splitting operation. In this paper we present novel mechanisms to optimally attack this problem; various possible implementations of the SSA are also discussed. We highlight the benefits of the proposed mechanisms through illustrative results and compare the various implementation solutions in terms of average network cost.