Sofie Lambert

Trends in worldwide ICT electricity consumption from 2007 to 2012

Information and Communication Technology (ICT) devices and services are becoming more and more widespread in all aspects of human life. Following an increased worldwide focus on the environmental impacts of energy consumption in general, there is also a growing attention to the electricity consumption associated with ICT equipment. In this paper we assess how ICT electricity consumption in the use phase has evolved from 2007 to 2012 based on three main ICT categories: communication networks, personal computers, and data centers. We provide a detailed description of how we calculate the electricity use and evolution in these three categories. Our estimates show that the yearly growth of all three individual ICT categories (10%, 5%, and 4%, respectively) is higher than the growth of worldwide electricity consumption in the same time frame (3%). The relative share of this subset of ICT products and services in the total worldwide electricity consumption has increased from about 3.9% in 2007 to 4.6% in 2012. We find that the absolute electricity consumption of each of the three categories is still roughly equal. This highlights the need for energy-efficiency research across all these domains, rather than focusing on a single one.

Worldwide electricity consumption of communication networks

There is a growing research interest in improving the energy efficiency of communication networks. In order to assess the impact of introducing new energy efficient technologies, an up-to-date estimate for the global electricity consumption in communication networks is needed. In this paper we consider the use phase electricity consumption of telecom operator networks, office networks and customer premises equipment. Our results show that the network electricity consumption is growing fast, at a rate of 10 % per year, and its relative contribution to the total worldwide electricity consumption has increased from 1.3% in 2007 to 1.8% in 2012. We estimate the worldwide electricity consumption of communication networks will exceed 350 TWh in 2012.

Dynamic Resource Provisioning for Energy Efficiency in Wireless Access Networks: A Survey and an Outlook

Traditionally, energy efficiency aspects have been included in the wireless access network design space only in the context of power control aimed at interference mitigation and for the increase of the terminal battery lifetime. Energy consumption of network components has also, for a long time, not been considered an issue, neither in equipment design nor in network planning and management. However, in recent years, with the user demand increasing at nearly exponential pace and margins rapidly shrinking, concerns about energy efficiency have been raised, with the objective of reducing network operational costs (not to mention the environmental issues). Installing more energy-efficient hardware does not seem to fully solve the problem, since wireless access networks are almost invariably (over)provisioned with respect to the peak user demand. This means that efficient resource management schemes, which are capable of controlling how much of the network infrastructure is actually needed and which parts can be temporarily powered off to save energy, can be extremely effective and provide quite large cost reductions. Considering that most of the energy in wireless access networks is consumed in the radio part, dynamic provisioning of wireless access network resources is crucial to achieving energy-efficient operation. The consensus on this approach in the research community has been wide in the last few years, and a large number of solutions have been proposed. In this paper, we survey the most important proposals, considering the two most common wireless access technologies, namely, cellular and WLAN. The main features of the proposed solutions are analyzed and compared, with an outlook on their applicability in typical network scenarios that also include cooperation between both access technologies. Moreover, we provide an overview of the practical implementation aspects that must be addressed to achieve truly energy-efficient wireless access networks, including current standardization work, and trends in the development of energy-efficient hardware.

Trimming of silicon-on-insulator ring resonators with a polymerizable liquid crystal cladding

We demonstrate the trimming of silicon-on-insulator ring resonators with a cladding layer of polymerizable liquid crystal. An electric field is applied over the cladding layer to tune the resonance of the ring resonators, which is then fixed by UV illumination of the polymerizable liquid crystal. A range of 0.56 nm is obtained. We provide the material properties of the polymerizable liquid crystal, give a description of the tuning mechanism and present experimental results. This method opens up possibilities in the field of low-cost trimming of photonic devices.

Energy efficiency analysis of high speed triple-play services in next-generation PON deployments

In this paper, the energy consumption of high speed access services up to 1Gb/s per customer is estimated for different passive optical network (PON) technologies. While other studies on PON power consumption typically assume a fixed split ratio, we also consider a greenfield approach, where the split ratio can be optimized for each technology, taking full advantage of its capacity and reach. The split ratio optimization takes into account Quality of Service (QoS) in terms of bandwidth availability and packet loss for triple-play services (voice, television and Internet). This paper includes an in-depth discussion of our split ratio dimensioning approach and our power consumption model for an optical access network in a major city. The obtained results show that statistical gain provided by dynamic bandwidth allocation as well as power splitting ratio optimization in PONs are key factors for achieving energy efficiency. For access rates up to 900Mb/s, XG-PON1 turns out to be the most energy efficient option. For higher access rates up to 1Gb/s, the optimal technology depends on split ratio restrictions. If an existing optical distribution network (ODN) with split ratio 1:64 is used, XG-PON1 remains the most energy efficient technology. If higher split ratios up to 1:256 can be achieved, TWDM PON becomes the most energy efficient solution for access rates up to 1Gb/s.

Energy efficiency analysis of next-generation passive optical network (NG-PON) technologies in a major city network

Ever-increasing bandwidth demands associated with mobile backhaul, content-rich services and the convergence of residential and business access will drive the need for next-generation passive optical networks (NG-PONs) in the long term. At the same time, there is a growing interest in reducing the energy consumption and the associated cost of the access network. In this paper, we consider a deployment scenario in a major city to assess the energy efficiency of various PON solutions from a telecom operators perspective. We compare five next-generation technologies to a baseline GPON deployment offering similar bandwidths and Quality of Service (QoS) for best-effort high speed connectivity services. We follow two approaches: first, we consider a fixed split ratio (1:64) in an existing Optical Distribution Network (ODN); next, we consider an upgraded ODN with an optimized split ratio for the specific bandwidth and QoS values. For medium bandwidth demands, our results show that legacy PONs can be upgraded to 10G PON without any ODN modification. For future applications that may require access rates up to 1 Gb/s, NG-PON2 technologies with higher split ratios and increased reach become more interesting systems, offering the potential for both increased energy efficiency and node consolidation.

Power consumption evaluation for next-generation passive optical networks

In this paper, we assess the energy efficiency of various optical access solutions including both the telecom operator and the end user side. We compare different next-generation passive optical networks (NG-PONs) to a baseline GPON deployment offering similar bandwidths and Quality of Service (QoS) for best-effort high speed connectivity services. For the operator side, we follow two approaches: first, we consider a fixed split ratio (1:64) in an existing optical distribution network (ODN); next, we consider an upgraded ODN with an optimized split ratio for specific bandwidth and QoS values. For medium bandwidth demands, our results show that legacy PONs can be upgraded to XG-PON without any ODN modification. For future applications that may require access rates up to 1 Gb/s, NG-PON2 technologies with higher split ratios and increased reach become more interesting systems, offering the potential for both increased energy efficiency and node consolidation. For the user side, we consider power consumption of the optical network unit (ONU), installed at the customer premises, incorporating several energy saving mechanisms. Combining our results for the central office and ONU side, we see that XLG-PON (using a bit-interleaving protocol) and TWDM-PON (using a standard protocol) consume the lowest power per user among the different NG-PON2 technology candidates.

Towards energy efficiency in optical access networks [Invited]

A continual increase in bandwidth consumption stimulates the need for next generation optical access (NGOA) networks, which should also conform to the societal green agenda. Currently, the access segment consumes a major fraction (about 67%) of the energy consumption in end-to-end fiber-to-the-home (FTTH) based telecommunication networks, and thus the energy consumption of access networks remains a crucial concern. In this paper, we present a thorough analysis of energy consumption in various NGOA technologies. In this analysis, we have also accounted the effects of low power modes (e.g., sleep modes) and the use of optimal split ratios for the considered technologies on the energy consumption.

Road to energy-efficient optical access: greentouch final results

The growing energy footprint of communication networks has raised concern about the sustainability of future network development. The GreenTouch consortium was founded to help counter this trend by developing and integrating green network technologies from the access to the core. In order to evaluate these technologies, an end-to-end network power model was developed in the form of the Green Meter, a tool to assess the overall impact and overall energy efficiency benefits of an entire portfolio of solutions. In this paper, we describe the methodology of the Green Meter for the residential fixed access portion, which was extended to include metro aggregation. A baseline architecture for optical access and metro aggregation networks is defined, and is adapted to other scenarios integrating future technologies. The performance is evaluated each time through a mathematical model that captures the energy savings at the component level and has the ability to compute the overall system-level energy savings. We show that energy efficiency can be improved 29-fold over a decade (2010-2020) with businessas- usual trends, and with the added effort of introducing GreenTouch solutions, this could be further improved to achieve a 257-fold increase in energy efficiency. The results confirm that an emphasis on green network design can indeed have a huge impact on reducing the energy consumption of an optical access infrastructure.

How sleep modes and traffic demands affect the energy efficiency in optical access networks

An ever-increasing bandwidth demand is the main driver to investigate next-generation optical access (NGOA) networks. These networks, however, do not only have to comply with increasing data rates, but they should also meet the societal green agenda. As the access part consumes a major fraction of the energy consumption in today’s fiber-to-the-home-based telecommunication networks, the energy efficiency of NGOA networks should be an important design parameter. In this paper, we present a detailed evaluation of the energy consumption in different NGOA technologies. Furthermore, we analyze the effects of (1) introducing low power modes (e.g., sleep and doze modes) in the various NGOA technologies and (2) using optimal split ratios adjusted to the traffic demands so that the energy consumption is optimized for the desired quality of service level.