Design of green optical networks with signal quality guarantee

Energy consumption of communication networks is growing very fast due to the rapidly increasing traffic demand. Consequently, design of green communication networks gained a lot of attention. In this paper we focus on optical Wavelength Division Multiplexing (WDM) networks, able to support this growing traffic demand. Several energy-aware routing and wavelength assignment (EA-RWA) techniques have been proposed for WDM networks in order to minimize their operational cost. These techniques aim at minimizing the number of active links by packing the traffic as much as possible, thus avoiding the use of lightly loaded links. As a result, EA-RWA techniques may lead to longer routes and to a high utilization on some specific links. This has a detrimental effect on the signal quality of the optical connections, i.e., lightpaths. In this study we quantify the impact of power consumption minimization on the optical signal quality. and address this problem by proposing a combined impairment and energy-aware RWA (IEA-RWA) approach. Towards this goal we developed a complete mathematical model that incorporates both linear and non-linear physical impairments together with an energy efficiency objective. The IEA-RWA problem is formulized as a Mixed Integer Linear Programming (MILP) model where both energy efficiency and signal quality considerations are jointly optimized. By comparing the proposed IEA-RWA approach with existing RWA (IA-RWA and EA-RWA) schemes, we demonstrate that our solution allows for a reduction of energy consumption close to the one obtained by EA-RWA approaches, while still guaranteeing a sufficient level of the optical signal quality.

1. Introduction

T^HERE is a rising concern about the energy consumption figures of communication networks [1]. For this reason every network segment, i.e., from the access to the core, has been the target of optimization studies aimed at reducing power consumption. One important result that was found for core networks is the possibility to considerably reduce power consumption by relying on optical transmission technologies [2]. In fact, transmission in the optical layer allows for a transparent flow of data from source to destination without the need for any opto-electrical-opto (0-E-O) conversion, with an evident gain in terms of energy consumption. For this reason, in order to make further improvements, energy efficiency in the optical layer has attracted a lot of attention and a wide range of topics are addressed in the literature. Energy-efficient strategies for network design [3] as well as for static [4] and for dynamic [5], [6] provisioning have been proposed to minimize the power necessary to support the traffic demands. Similar studies addressed also the issue of the power consumed by the provisioned protection resources [7]–0.