As internet traffic increases tremendously, energy consumption of networks is expected to increase accordingly.Traffic grooming using optical WDM is regarded as one of the solutions to save energy consumptionbecause traffic flows along optical paths.
Most of the previous researches on traffic grooming have assumed that the energy consumption of network equipment is proportional to the amount of traffic load. However, current research groups reveal that network equipment does not consume energy proportionally due to traffic load, and a large portion of energy is consumed even though the network equipment is in an idle state. In this regard, we consider the impact of the device energy efficiency index (EPI) defined as the ratio of the load-dependent power consumption to the maximum power consumption as an important measure. We show that a new cross layer design with energy consumption analysis requires as high as possible energy proportionality for practical network devices.
In order to analyze energy consumption of networks effectively, cross-layered design between electrical and optical network architectures and their power consumptions are modeled. Especially, the traffic grooming for energy efficient cross-layered optical networks is expressed using the integer linear programming (ILP). With a broad range of EPI assumptions varied from the realistic level for network equipment to the ideal level of which guarantees pure proportionality of energy consumption, it is verified that increasing energy proportionality of network equipment can contribute to energy savings of the networks. In addition, energy consumption of networks with or without wavelength converters is compared. Conditions when wavelength converters may contribute to energy saving of networks are inferred.