The steadily rising energy cost and the need to reduce the global CO2 emission to protect our environment are today's economical and ecological drivers for the emerging consideration of energy consumption in all fields of information and communication technology (ICT). In Germany alone, the energy consumption of core and access networks amounts to more than 6000 GWh per year, and that of data centers to around 10000 GWh per year, according to a 2009 Fraunhofer study. These essential ICT infrastructures already today exceed the yearly net energy output of one typical nuclear power plant.

Because of society's desire to communicate more globally, in real-time, and at ever-greater data rates, ICT infrastructures will continue to expand in geographic and functional terms and their energy consumption is expected to substantially increase in the near future under current operations and management practices. NLE recognizes the vital need for new approaches that are able to achieve ecologically sustainable communication infrastructures, which contribute a significant portion to the whole of ICT's energy consumption. Building on NLE's extensive experience in network research, development, and standardization, the labs investigate novel operations and management technologies for current and future communication systems.

NLE focuses on designing innovative communication and management technologies that increase the efficiency of optical networks, radio access networks, and high-performance switching networks in modern data centers.

The labs' research activities are tightly coupled with relevant standardization activities. The labs are contributing Internet draft standards for energy management within IETF's network working group and specifications for energy savings management in telecommunication networks within 3GPP's TSG SA WG5.

NLE also actively participates in workshops, conferences, and journals that focus on energy-efficient networking and communications topics. The labs are the major organizer of the IEEE workshop series on green communications, TPC member and panelist of ACM SIGCOMM e-Energy, and guest editor of IEEE Communication Society's Network magazine.

Energy Saving SON Functions for EUTRAN

In mobile telecommunication networks, a large part of the total energy is consumed in the radio access network. In order to reduce its energy consumption, NL-E developed a set of energy saving SON functions for EUTRAN. When introducing energy saving mechanisms it is important to maintain network performance as well as operational cost-efficiency. Research work has been targeted at improving the energy consumption of base stations, which cause the highest energy expenditure for network elements. The particular focus is on urban areas where the network is designed to accommodate peak hour traffic conditions with relatively dense arrangements of base stations that often are idle out of business hours.

The SON algorithms are based on coordination between network elements introducing the notion of energy partitions - associations of powered-on and powered-off base stations - to deliver energy saving with the objective of matching offered capacity with the traffic demand in a flexible manner using shared knowledge of load and coverage information.

Energy Saving SON Functions for EUTRAN: Energy Saving Reconfiguration.

In essence, such coordination permits higher quality energy solutions since network elements collectively contribute in energy decisions providing algorithms with load and coverage information beyond local scope providing flexibility for further energy partition adjustments based on alternation of traffic conditions. Instead of reacting to increased load by simply powering on BSs in certain locations, our aim is to balance such load by re-configuring the energy partitions and have the optimal base station take over coverage for its assigned partition.

Energy-Efficient Data Center Networking

Data centers play an essential role in today's global ICT infrastructures by serving as the backbone for many kinds of electronic services. In order to operate a data center more energy-efficient under varying load, many approaches were proposed, ranging from physical DC design to the use of efficient equipment to sophisticated virtualization approaches.

While site infrastructure and servers make up a large part of the energy consumption, exploiting the potential in powering off network elements not only leads to a more energy-efficient network, but also reduces the power needed by cooling and auxiliaries for the NW equipment. Joint optimizations between network infrastructure and data servers lead to additional energy savings both on the side of NW and IT.

Energy-Efficient Data Center Networking: Virtual Machine and Network Flow Consolidation

NLE investigates joint energy management in data centers by developing mechanisms and protocols that reduce the energy consumption of both NW and IT resources in a consistent way. In the basic concept of virtual machine and network flow consolidation, virtual machines and traffic flows are relocated in such a way that both IT and NW resources and optimally, complete IT and NW segments, can be powered down without impacting service performance. Exploiting NEC's flexible and high-performance OpenFlow switching technology, NLE's DC energy management system is highly efficient, scalable, and can be seamlessly integrated with other DC management components.

Energy Saving in Optical Networks

Energy saving in optical networks is NLE's current effort to deliver energy-efficient communications in fixed networks on a broad geographic scale. The labs' focus is on mechanisms that power off network elements using efficient design methods, on the network level through energy-aware traffic shaping, routing algorithms and protocols, and on the deployment level employing power-aware design and cooperative networking.

Energy-aware traffic shaping adapts the transmission rate to exploit well defined time intervals where certain interfaces may sleep, reducing the amount of on-off transitions. Incoming traffic is shaped into bursts at the edge of the network allowing sufficient sleeping periods for core routers in order to profitably be powered off.

Energy Saving in Optical Networks through Traffic Shaping.

Energy-aware routing aims to power off intermediate nodes while still guaranteeing connectivity among source-destination nodes with certain service quality. This is accomplished by aggregating the service load among a few routes (e.g., via a so-called Steiner-tree) that satisfy quality of service constraints allowing certain routers to sleep.

Energy Saving in Optical Networks through Energy-aware Routing.

Besides network level energy solutions, NLE also considers energy conservation traffic policies in an effort to introduce specific service targets within limited energy expenditure.

K. Samdanis, D. Kutscher, M. Brunner: Dynamic Energy-Aware Network Re-Configuration for Cellular Urban Infrastructures, 3rd International Workshop on Green Communications, December 2010.

J. Quittek, R. Winter, T. Dietz, D. Dudkowski: Definiton of Managed Objects for Energy Management. Internet Draft, Version 1,
Network Working Group, IETF, April 22, 2010.

3GPP TR 32.826, Telecommunication management; Study on Energy Savings Management (ESM), (Release 9), March 2010.

3GPP TS 32.551, Energy Saving Management (ESM), Concepts and requirements; (Release 10), June 2010.

NEC, Green Radio - NECs Approach towards Energy-efficient Radio Access Networks. White paper, February 2010.

K. Samdanis, D. Kutscher, M. Brunner: Self-Organized Energy Efficient Cellular Networks. IEEE PIMRC, Istanbul, September 2010.

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