K. D. R. Assis

Hybrid Algorithms for Routing and Assignment Wavelengths in Optical Networks

This paper presents a strategy for the solution of the WDM optical networks planning. Specifically, the problem of Routing and Wavelength Allocation (RWA) in order to minimize the amount of wavelengths used. In this case, the problem is known as the Min-RWA. Two meta-heuristics (Tabu Search and Simulated Annealing) are applied to take solutions of good quality and high performance. The key point is the degradation of the maximum load on the virtual links in favor of minimization of number of wavelengths used; the objective is to find a good compromise between the metrics of virtual topology (load in Gb/s) and of the physical topology (quantity of wavelengths). The simulations suggest good results when compared to some existing in the literature.

Deadlock avoidance under incremental traffic in the elastic single link

The paper investigates the conditions that lead to deadlocked resources in a single link that services an incremental traffic of requests for a variable number of contiguous slots. The paper shows that such deadlocks result from a mismatch between the traffic profile and the number of available slots for assignment in a spectral void. For each traffic profile with no demand for single slots, a set of forbidden void sizes that inevitably lead to deadlock is identified, so deadlock-avoiding spectrum assignment algorithms must avoid them whenever starting from a non-forbidden void size.

Flexgrid optical networks design under multiple modulation formats

This paper proposes an MILP (Mixed Integer Linear Programming) formulation for the design of flexgrid optical networks under multiple modulation formats and noise constraints. The proposed MILP benefits from the flexibility of using multiple modulation formats, each of which with its spectrum efficiency and individual noise constraints, to properly perform routing and spectrum assignment of the demanded traffic. The model is capable of maximizing the amount of traffic that is established in the network for a limited number of slots per link. Cases studies are carried out in order to analyze the benefits of the proposal as well as the basic properties of the formulation.

Fast spectrum exhaustion under incremental traffic in the elastic single link

The paper discusses the mean time to exhaust the spectrum of a single link under an incremental traffic of requests for connections with a variable number of slots. It is shown that optimal assignment policies exist under awareness of the traffic profile. For instance, if the traffic rates decrease with the number of requested slots, greedy policies that accept all requests that may be accommodated will speed up the spectrum exhaustion. On the other hand, if the traffic rates increase with the number of requested slots, spectrum exhaustion is favored by wholesale policies that accept only requests for the entire available spectrum. An optimal algorithm is derived for any given traffic profile.

Spectrum-sliced elastic optical networking

Current communication environments present a wide range of traffic granularities, making it hard to use the optical spectrum efficiently under the WDM framework. In elastic networking, the WDM rigid frequency grid is replaced by a more flexible structure, in which the spectrum is organized in frequency slots, and each traffic flow is assigned to an appropriate set of contiguous slots. The classical RWA problem is then replaced by a Routing and Spectrum assignment (RSA) problem, which presents different characteristics when compared to the former. In this paper, we discuss a novel approach to tackle the spectrum assignment problem in elastic networks.

Routing in EON networks under mixed static and dynamic traffic

This paper proposes heuristics, which can maximize the number of remaining available routes and minimize the number of transceivers used in Elastic Optical Networks (EON). The aim of the proposal is to preserve the open capacity for the accommodation of future unknown dynamic demands. Case studies are carried out in order to analyze the performance of the heuristics over two networks. The results suggest that it is feasible to preserve enough open capacity to avoid blocking of future requests in EON with scarce resources.

An analytical defragmentation bound on the performance of the elastic single link with dynamic traffic

This paper discusses an analytical calculation of the blocking performance of the defragmented elastic single link, given a multi-class traffic profile. This performance bound is then compared with the performance of several spectrum assignment algorithms, thus yielding an evaluation of the potential gains imparted by defragmentation in each case.

SimRSA: An education tool for network planning in Spectrum-sliced Elastic Optical Path Networks

This paper presents the SimRSA tool, an educational network planning tool for Spectrum-sliced Elastic Optical Path Networks. It includes a set of heuristic algorithms for solving RSA problem. The input parameters to the planning problem are the network physical topology, the traffic matrix and some technological constraints like the number of sub-carriers per link or slots. The tool is implemented as a JAVA program. The set of heuristic algorithms can be easily extended. A graphical interface is provided to plot the results obtained from different heuristics and compare them.

Efficient traffic routing for current and future demands in optical networks

We propose a linear formulation for traffic routing in optical networks after the Virtual Topology Design (VTD). The formulation maximizes the amount of traffic the network is able to accept, through minimizing the residual capacity in established lightpaths. The results suggest that it is feasible to preserve enough open capacity to avoid disruption of connections and blocking of future traffic demands in networks with scarce resources.

A New Strategy for Energy Saving in Spectrum-Sliced Elastic Optical Networks †

In this paper, we propose a new approach for energy saving in Elastic Optical Networks (EONs) under physical impairments based on MILP solving instances. First, we seek to maximize the attended traffic on the network whereas the blocking probability is maintained below a defined limit. Hence, the next step is to minimize the power consumption on the network. The proposed MILP-based algorithm models the RMLSA problem and considers transponders, optical cross-connects (OXCs), and optical amplifiers as the physical components with influence on network optimization. The results show that our approach offers, on average, a reduction of up to 7.7% of the power consumed on the four moderate networks analyzed.