Energy Efficiency Analysis in Adaptive FEC-Based Lightpath Elastic Optical NetworksJournal of Circuits, Systems and Computers

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Authors
Fábio Durand, Taufik Abrão
Year
2015
DOI
10.1142/S0218126615501339
Subject
Hardware and Architecture / Electrical and Electronic Engineering

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Energy E±ciency Analysis in Adaptive FEC-Based

Lightpath Elastic Optical Networks¤

Fabio Durand†

Department of Electrical Engineering,

Technological Federal University of Parana,

UTFPR Cornelio Procopio-PR, 86300-000, Brazil fabiodurand@utfpr.edu.br

Tau¯k Abrão

Department of Electrical Engineering,

The State University of Londrina,

UEL, Londrina-PR, 86.057-970, Brazil taufik@uel.br

Received 21 December 2014

Accepted 28 May 2015

Published 10 July 2015

In this paper, an energy e±ciency (EE) analysis for elastic optical networks (EONs) considering the adaptive allocation of the transmitted power, spectrum bandwidth, modulation format and forward error correction (FEC) type has been proposed. The trade-o® between the FEC coding types and the optical layer EE (OL-EE) was investigated considering the capacity of information transmission and power consumption. The power consumption model considers elements involved in the lightpath establishment, namely transmitter, receiver, bandwidthvariable optical crossconnect (BV-OXC), optical ampli¯ers and network control. Numerical examples have demonstrated EE increasing for the lightpaths when adaptive FEC coding is deployed; furthermore, the EE varies with the distance of the optical network nodes and hop count. In this sense, it is observed that the EE decreases with the increasing of FEC energy per bit consumption; however, an operation region is veri¯ed in which the overall EE network with

FEC is superior to the system without FEC coding. After this point, the increases in the FEC energy per bit consumption will a®ect negatively the EE metric. For instance, with the proposed

OL-EE model it is possible to determinate the maximum energy consumption allowed to the

FEC codes without OL-EE system degradation.

Keywords: Elastic optical network; energy e±ciency (EE); optical layer energy e±ciency (OL-EE); power consumption; forward error correction (FEC). *This paper was recommended by Regional Editor Kshirasagar Naik. †Corresponding author.

Journal of Circuits, Systems, and Computers

Vol. 24, No. 9 (2015) 1550133 (22 pages) #.c World Scienti¯c Publishing Company

DOI: 10.1142/S0218126615501339 1550133-1

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TY o n 08 /2 5/ 15 . F or p er so na l u se o nl y. 1. Introduction

The rapid increase in the tra±c demand motivated by the development of highde¯nition video communications, e-learning, cloud computing, as well, the Internet tra±c, has resulted in a high bandwidth demand in the optical core networks.

Therefore, the optical transmission and networking technologies are moving toward more e±cient, °exible and scalable solutions.1 In this context, the technology of elastic optical network (EON) based on orthogonal frequency divisionmultiplexing (OFDM) has experienced remarkable advancements.2 The main EON characteristics, such as allocation of variable bandwidth and modulation format are very attractive, in contrast to the conventional, ¯xed-grid, rigid-bandwidth wavelength division multiplexing (WDM) network.2 OFDM is a multicarrier transmission technology, based on digital signal processing (DSP), which is able to transmit high-speed data streams by splitting them into multiple parallel low-speed subcarriers.1 The adoption of DSP techniques, such as equalization and forward error correction (FEC) codes, as well as coherent detection, can o®er far greater °exibility in signal generation and decoding allowing compensation of signal distortions and/or utilization of advancedmodulation formats, which are inherently more tolerant to the ¯ber distortion e®ects.3,4

In EONs, the requested tra±c is transported by end-to-end lightpaths, which are established by algorithms responsible to routing, assigning dynamical (adaptive) modulation order and spectrum bandwidth, while maintaining an acceptable level of optical power for an appropriate optical signal-to-noise ratio (OSNR) along the optical network.5,6 The modulation order is given by M , where M ¼ 2m is the number of symbols in the constellation diagram and m is the number of bits that can be transmitted in each symbol. Note that in an adaptive transmission context, modulation order can be updated dynamically— from low to high order and so on— depending on the optical channel condition or equivalently on the instantaneous

OSNR level. Besides, an e®ective approach to compensate the OSNR degradation is with low hardware investment cost and high error-correction performance is the FEC coding technique.4,7 This technique is based on adding redundant information previously to the modulation and transmission processes. The FEC techniques can be classi¯ed into three generations.8 The ¯rst generation of FEC was based on the hard decision decoding technique that uses block codes, of which a typical example is the

Reed–Solomon (RS) codes, such as RS (255, 239). The second generation of FEC mainly focused on the concatenated codes as RS and Bose, Chaudhuri and Hocquenghem (BCH) codes, e.g., RS (255, 239)/BCH (1023, 963). The third generation of FEC is based on more powerful soft-decision codes such as low-density paritycheck code (LDPC) and Block Turbo codes. The improvement in the FEC performance is based on the growth of coding overhead, at the expense of the bandwidth occupied by the code.7,8

In this sense, the FEC bandwidth consumption motivated the development of

FEC attribution schemes aiming to optimize the system transmission capacity, such

F. Durand & T. Abr~ao 1550133-2

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TY o n 08 /2 5/ 15 . F or p er so na l u se o nl y. as in Ref. 7 in which an adaptive approach was proposed to choose the most e±cient

FEC type (RS, RS/BCH and LDPC) for di®erent lightpaths based on their individual OSNR. The simulation results indicated that compared to the non-adaptive case, using the proposed adaptive FEC selection scheme could signi¯cantly reduce the required FEC overhead. However, only ampli¯ed spontaneous emission (ASE) was considered in OSNR model, while nonlinear ¯ber e®ects were unvalued. Furthermore, the relationship between bandwidth blocking ratio and ¯ber type, span length, dispersion management and FEC compensation has been discussed in Ref. 4.