I. INTRODUCTION
In the last decade the attention for environment-friendly solutions has drastically increased. Especially due to the de-bate concerning climate change every emerging technology is scrutinously evaluated on its carbon footprint. This is also the case for information and communication technologies (ICT).It is estimated that ICT is accountable for 2 – 4% of the worldwide carbon emissions. The power consumption during the use phase of the equipment accounts for roughly 40 –60% of the carbon emissions. By 2020 these emissions are expected to double if no initiatives are taken to reduce this footprint. A significant part of these emissions, about one sixth, is attributed to telecommunication networks [1].