In this paper, we discuss energy-efficiency improvements in core networks obtained as a result of work carried out by the GreenTouch consortium over a five-year period. A number of techniques that yield substantial energy savings in core networks were introduced, including (i) the use of improved network components with lower power consumption, (ii) putting idle components into sleep mode, (iii) optically bypassing intermediate routers, (iv) the use of mixed line rates, (v) placing resources for protection into a low power state when idle, (vi) optimization of the network physical topology, and (vii) the optimization of distributed clouds for content distribution and network equipment virtualization. These techniques are recommended as the main energy-efficiency improvement measures for 2020 core networks. A mixed integer linear programming optimization model combining all the aforementioned techniques was built to minimize energy consumption in the core network. We consider group 1 nations' traffic and place this traffic on a US continental network represented by the AT&T network topology. The projections of the 2020 equipment power consumption are based on two scenarios: a business as usual (BAU) scenario and a GreenTouch (GT) (i.e., BAU + GT) scenario. The results show that the 2020 BAU scenario improves the network energy efficiency by a factor of 4.23 x compared with the 2010 network as a result of the reduction in the network equipment power consumption. Considering the 2020 BAU + GT network, the network equipment improvements alone reduce network power by a factor of 20 x compared with the 2010 network. Including of all the BAU + GT energy-efficiency techniques yields a total energy efficiency improvement of 315 x. We have also implemented an experimental demonstration that illustrates the feasibility of energy-efficient content distribution in IP/WDM networks.

Presents information and current topics of interest to the global communications industry.

We summarize the various techniques developed by the GreenTouch consortium over the past 5 years to minimize core network power consumption. Adopting GreenTouch techniques can potentially improve the energy efficiency by 316x in a 2020 reference network compared to the state of the art in 2010.

Currently transforming all spheres of human activity, at a level greater than the industrial revolution, the Information and Communication Technology sector (ICT) is emerging in the 21st century as the dominant driver of sustainability, with the potential to reconcile economic growth, environmental protection and societal benefits. It is a key tool in the fight against climate change as it can enable a 20 percent reduction in global greenhouse gas emissions by 2030. However, achieving such outcomes will require a holistic approach to the proper design, broad application, widespread adoption and social acceptance of ICT products and solutions. As such, this “green” potential of ICT requires a complete rethinking of how not only we design but also how we use ICT in a sustainable fashion. It is a huge challenge that can only be satisfactorily addressed by bringing together the research community, ICT equipment and solution providers, practitioners in various ICT vertical markets, the standards community, and public policy and regulatory influencers and decision makers.As IEEE is the world’s largest technical professional organization dedicated to advancing technology for the benefit of humanity, the Green ICT initiative is committed to providing leadership on these issues. In this context, the mission of the IEEE Green ICT Initiative, launched in January 2015 by the IEEE Future Directions Committee and the IEEE Communications Society, has been defined as “build a holistic approach to sustainability by incorporating green metrics in various IEEE technical domains”. Viewed through the triple bottom line of sustainability (economic, environmental and …

After about a decade of intense research, spurred by both economic and operational considerations, and by environmental concerns, energy efficiency has now become a key pillar in the design of communication networks. With the advent of the fifth generation of wireless networks, with millions more base stations and billions of connected devices, the need for energy-efficient system design and operation will be even more compelling. This survey provides an overview of energy-efficient wireless communications, reviews seminal and recent contribution to the state-of-the-art, including the papers published in this special issue, and discusses the most relevant research challenges to be addressed in the future.

Climate change is one of the defining topics of our generation. At the heart of the issue is a growing understanding of the impact of human activities on our planet and the desire to balance the evolution of human technology to meet our needs with the preservation of natural resources for current and future generations. Global energy consumption, especially the use of fossil fuels, has been dramatically increasing since the industrial revolution and increases with each technological revolution. Every single industry sector is facing this challenge and the information and communications technologies (ICT) sector is no different. The ICT sector, however, is in a very unique position as it both contributes to carbon emissions and enables reductions of carbon emissions in other industry sectors.

Rate adaptation technologies aim at establishing a linear relationship between power consumption and traffic load in packet networks. They rely on power profiles of network elements, which map system configurations and traffic loads onto power consumption levels, for the selection of network resources to place into low-power states and to identify new system designs with high power-saving yields. We introduce a methodology for profiling the power consumption of network systems that reconciles modeling accuracy with cost containment and rapidity in the preparation and execution of power measurements. We apply the methodology to network systems from multiple vendors and find it capable of delivering a clear message: the power savings enabled by protocol and system software upgrades that support demand-timescale rate adaptation are worthwhile, but also largely inferior to those attainable with a new generation of hardware platforms that pervasively deploy packet-timescale rate adaptation.

We analyze the performance of TCP and TCP with network coding (TCP/NC) in lossy networks. We build upon the framework introduced by Padhye et al. and characterize the throughput behavior of classical TCP and TCP/NC as a function of erasure probability, round-trip time, maximum window size, and duration of the connection. Our analytical results show that network coding masks random erasures from TCP, thus preventing TCP's performance degradation in lossy networks. It is further seen that TCP/NC has significant throughput gains over TCP. In addition, we study the cost of improving the goodput per user in a wireless network. We measure the cost in terms of number of base stations, which is highly correlated to the energy cost of a network provider. We show that increasing the available bandwidth may not necessarily lead to increase in goodput, particularly in lossy wireless networks using TCP. We show that using protocols such as TCP/NC, which are more resilient to erasures in the network, may lead to a goodput commensurate with the bandwidth dedicated to each user. By increasing goodput, users' transactions are completed faster; thus, the resources dedicated to these users can be released to serve other requests, consequently reducing the cost for the network providers.

We study the cost of improving the goodput, or the useful data rate, to user in a wireless network. We measure the cost in terms of number of base stations, which is highly correlated to the energy cost as well as capital and operational costs of a network provider. We show that increasing the available bandwidth, or throughput, may not necessarily lead to increase in goodput, particularly in lossy wireless networks in which TCP does not perform well. As a result, much of the resources dedicated to the user may not translate to high goodput, resulting in an inefficient use of the network resources. We show that using protocols such as TCP/NC, which are more resilient to erasures and failures in the network, may lead to a goodput commensurate with the throughput dedicated to each user. By increasing goodput, users' transactions are completed faster; thus, the resources dedicated to these users can be released to serve other requests or transactions. Consequently, we show that translating efficiently throughput to goodput may bring forth better connection to users while reducing the cost for the network providers.

Power-load proportionality is a necessary feature in networks that aim at maximizing energy efficiency. Even in networks that handle near-capacity loads very efficiently, energy savings increase substantially if the power consumption closely follows the offered load. Rate adaptation is a common denomination for a set of technologies that operate at different timescales to establish power-load proportionality. To propel their deployment, it is useful to assess how compatible they are with existing network systems and identify the design upgrades that can maximize their energy savings in future networks. The formulation of accurate energy profiles for current equipment is a first step in this direction. We run extensive power measurement experiments to compile the energy profiles of five network systems from multiple vendors. Our results show only negligible signs of power-load proportionality in all five cases: to really make a dent in the carbon footprint and operational cost of packet networks, future system designs must pervasively deploy rate adaptation technologies, especially those that control power state transitions at the packet timescale.

We present a TCP mobility solution for the mobile Internet which enables seamless session end-point migration across multi-provider network environments. The solution can be applied by mobile devices to conduct energy-efficient network selection and dynamic spectrum sharing or by data centers to facilitate service migration across IP domains. We leverage MPTCP's in-band signaling protocol to provide the necessary robustness against firewall- and middle-box policies encountered in these environments. The mobility solution builds on a lightweight MPTCP proxy function which is inserted into the data path and performs header rewriting without packet buffering or stream assembly. The proxy is therefore easily integrated into mobile devices, network routers or data center nodes hence facilitating fast deployment. We discuss the use cases, deployment scenarios and algorithmic challenges of the proxy design. We also present a Linux implementation, demonstrate its functionality and prove the proxy's interoperability with native MPTCP transport-layer implementations.

We propose an efficient encoding algorithm that considers multiple neighbors as next hop candidates for a packet, while searching for an optimal packet combination to transmit. Our algorithm, based on bipartite graphs, lets a node exhaustively search its queue to identify the maximum set of packets that can be combined in a single transmission. This algorithm can be easily integrated with a routing scheme in which a node considers multiple neighbors before choosing to forward a packet to one of them. We demonstrate this by integrating our algorithm with delta routing. Throughput benefit offered due to network coding is often hampered by congested nodes in a network. Delta routing improves throughput of a network by helping packets circumnavigate congestion. We demonstrate how our packet encoding algorithm can be coupled with such a routing mechanism in order to leverage the benefits offered by an efficient encoding scheme and enhanced routing both.

We study the cost of improving the goodput, or the useful data rate, to user in a wireless network. We measure the cost in terms of number of base stations, which is highly correlated to the energy cost as well as capital and operational costs of a network provider. We show that increasing the available bandwidth, or throughput, may not necessarily lead to increase in goodput, particularly in lossy wireless networks in which TCP does not perform well. As a result, much of the resources dedicated to the user may not translate to high goodput, resulting in an inefficient use of the network resources. We show that using protocols such as TCP/NC, which are more resilient to erasures and failures in the network, may lead to a goodput commensurate the throughput dedicated to each user. By increasing goodput, users’ transactions are completed faster; thus, the resources dedicated to these users can be released to serve other requests or transactions. Consequently, we show that translating efficiently throughput to goodput may bring forth better connection to users while reducing the cost for the network providers.