Mobile communications are increasingly contributing to global energy consumption. The EARTH (Energy Aware Radio and neTworking tecHnologies) project tackles the important issue of reducing CO2 emissions by enhancing the energy efficiency of cellular mobile networks. EARTH is a holistic approach to develop a new generation of energy efficient products, components, deployment strategies and energy-aware network management solutions. In this paper the holistic EARTH approach to energy efficient mobile communication systems is introduced. Performance metrics are studied so to assess the theoretical bounds of energy efficiency and the practical achievable limits. Moreover, various deployment strategies focusing on their potential to reduce energy consumption are studied, whilst providing uncompromised coverage and user experience. This includes heterogeneous networks with a sophisticated mix of different cell sizes, which may be further enhanced by energy efficient relaying and base station cooperation technologies. Finally, scenarios leveraging the capability of advanced terminals to operate on multiple radio access technologies (RAT) are discussed with respect to their energy savings potential.
The IP (Internet Protocol) core network operated by TeliaSonera in Sweden has been studied according to a described definition (system boundary) and extrapolated to a national level for Sweden. A top-down and a bottom-up data collection approach have been used to quantify network equipment and energy consumption. The electricity consumption of the IP core network was about one fourth of the total energy consumption of the connected mobile and fixed access networks. The use stage results for the Swedish IP core network is about 0.08 kWh per GB (Gigabyte) of data traffic corresponding to about 19 g CO2e/GB when applying a Swedish electricity mix. If instead a global average electricity mix is used, the resulting greenhouse gas emission would be about 64 g CO2e/GB. A method is also proposed where the amount of data traffic is used to allocate the IP core network on different usage. The method is exemplified by the 3G mobile broadband data traffic in Sweden.
There is a need for verification of the sustainability potential of an increasing number of smart city initiatives. This paper discuss a set of requirements necessary to consider when developing a methodology intended to evaluate the environmental and socioeconomic sustainability impact of Information and Communication Technology (ICT) solutions at a city level. A smart city definition is chosen and a model of the city is proposed, dividing the city into service sectors where ICT solutions are expected to be implemented. Requirements on a quantitative methodology for assessing the sustainability potential of ICT solutions in cities are listed, including transparency in selection of city boundary and results, and the importance of setting realistic scenarios and using publicly available data. The methodology activities presented include defining system boundaries, building scenarios and assessing the solution at a city level, and scaling the solution between cities.
The presented LCA-based method can be used when assessing the potential CO2e emission reduction from introducing an ICT-based service. The method was used to analyze the CO2e emissions from the communication networks in Sweden as well as on the effects of introducing smart work solutions at TeliaSonera. For TeliaSonera the CO2e reductions resulting from smart work sum up to about 40% per employee, or over 2.8 ton CO2e per employee and year. The total reduction potential due to smart work in the world was estimated to be 2 % - 4% of global CO2e emissions, if reductions of 20% - 40% can be achieved per employee in a 10 - 20 year timeframe.
Use of life cycle assessment (LCA) methodology for information and communications technology (ICT) equipment, networks, services and organizations is growing in importance. The complexity of conducting LCA for ICT has led to several initiatives (e.g. by ITU-T and ETSI) to develop standardized methodologies. LCA is an important methodological platform for understanding environmental impact of various product systems and is found to provide a good basis for prioritization of a company's environmental work. However, results of an LCA are always model-based representations of the real environmental impact, and the absolute impact of a certain equipment, network, service or organization is beyond reach. LCA results are only valid under the assumptions of the study and are still associated with substantial uncertainty, which needs to be considered to the extent needed to understand the study results. This paper demonstrates that by examples related to uncertainty and variability of scenarios and data.
This paper discusses the suitability of different standardized approaches for product compliance assessments of low power radio base stations with respect to general public whole-body radiofrequency exposure limits. Using numerical simulations, two standardized procedures based on spatially averaged field strengths, for comparison against the reference levels, and based on SAR assessments, for comparison against the basic restrictions, are evaluated in the frequency range 300 MHz - 5000 MHz. It is shown that the currently standardized whole-body SAR measurement procedure is overly conservative for small phantom-antenna separation distances and may lead to unphysical results. To avoid these problems, a new distance dependent correction factor is proposed to account for effects of tissue layering. Furthermore, a new box-shaped phantom for child whole-body SAR measurements is proposed which may be used to obtain more accurate whole-body SAR results compared with currently standardized procedures. The proposed approach is shown to produce conservative results with respect to numerical simulations using the anatomical child phantom Roberta from the Virtual Classroom set of phantoms.
Current standardized procedures for measurements of the Specific absorption rate (SAR) of mobile phones and radio base station antennas include a volumetric scan of the electric field strength induced in a head or body phantom. Assessment of multi-band and whole-body SAR requires repeated volumetric scanning over a large part of the phantom and is time-consuming. In order to reduce the total evaluation time, different methods have been proposed to estimate the SAR from measurement data based on sparse volumetric scanning and surface scanning. These methods rely on data fitting with underlying assumptions about the spatial distribution of the fields. In order not to be biased by previous or current antenna design, and to be able to use currently available assessment systems, a model-independent dual-plane-scan method is investigated based on amplitude measurements of the electric field components. The amplitude of the electric field components are measured in two planes close to the phantom surface, and the phase is recovered using an iterative process. The plane wave spectrum of the resulting complex electric field components is then used to propagate the field into the phantom. The measurement time is typically reduced by a factor 5 and in some cases even more. Furthermore, the plane wave spectrum is utilized for fast calculation of the mass-averaged local SAR values. A numerical tolerance study, using single and multi- peak fields with relevant errors superposed, is performed to demonstrate the robustness of the method. The resulting errors in the estimated SAR values are below 1% for realistic positioning errors and signal to noise ratio. Comparisons with measurements in a flat phantom are also made. Moreover, the underlying algorithm can be applied to curved surfaces.
This paper discusses how energy consumption can be significantly reduced in mobile networks by introducing discontinuous transmission (DTX) on the base station side. By introducing DTX on the downlink, or cell DTX, we show that it is possible to achieve significant energy reductions in an LTE network. Cell DTX is most efficient when the traffic load is low in a cell but even when realistic traffic statistics are considered the gains are impressive. The technology potential for a metropolitan area is shown to be 90% reduced energy consumption compared to no use of cell DTX. The paper also discusses different drives for the increased focus on energy efficient network operation and also provides insights on the impact of cell DTX from a life cycle assessment perspective.