Energy Savings in Mobile Networks Based on Adaptation to Traffic Statistics

Traditionally mobile communication networks have been designed for maximum throughput and maximum spectral efficiency. With the introduction of new access technologies (e.g. UMTS HSPA and LTE) and with the strongly rising data volume in mobile communication networks operators have rolled out more and more equipment into the field. Today, energy demand for a major mobile network is in the order of several 1000GWh/year, e.g. Vodafone's global energy consumption was about 3000GW/h in 2007/8 [1]. At rising energy prices this has led to a situation where energy cost makes up around 18% of the network operational cost in European markets and even more in developing countries where diesel is used to power off-grid radio base stations [1]. Besides this operator cost issue the rising energy consumption of mobile networks also contributes to the global emission of greenhouse gases and to the global warming. Mobile network infrastructure (without mobile devices) has emitted 64Mtonns of CO2 in 2002 and this is expected to increase until 2020 to 178Mtonns [2]. Both, cost and climate issues of mobile networks have recently drawn significant attention to the improvement of their energy efficiency [3, 4, 5, 6]. Network operators have announced reduction plans for their energy usage [7] and equipment manufacturers have reported significant increase in base station power efficiency [8, 9]. The major power consumption of mobile networks stems from the radio base stations [10]. Therefore, power saving methods developed and deployed today mainly focus on three areas: increasing the power amplifier efficiency [11], minimizing the up to 50% feeder losses in the RF cable between the power amplifier