The components that make up today’s traditional communication networks were built primarily with performance, not energy efficiency, in mind. As more of everything comes online, the energy consumption of cellphone towers, set-top boxes, routers, and the rest of the infrastructure, to say nothing of data centers, is rising—and so is the cost of running a network.
Some operators already have energy bills of more than US $1 billion annually. And socially conscious consumers and governments are demanding that the environmental impact of such systems be reduced drastically.
Finding ways to increase the energy efficiency and shrink the carbon footprint of communication and data networks, including the Internet, was the mission of the GreenTouch consortium. This precompetitive research consortium, launched in 2010, is composed of experts from 48 information and communication technology (ICT) companies, as well as academia and nongovernmental organizations. GreenTouch members include Bell Labs/Alcatel-Lucent (now part of Nokia), China Mobile, Huawei, Orange, the Politecnico di Milano, Swisscom, the University of Leeds, and the University of Melbourne.
The group set a lofty goal: improve by 2020 the energy efficiency of communication networks by a factor of 1,000 compared with those in use in 2010 (the year GreenTouch was launched), all without compromising performance and while supporting the larger traffic volumes expected. The group also committed to deliver a road map by last year of what architectures and technologies would accomplish the feat and to demonstrate the key technological contributors.
“We ran studies and found that a factor of 1,000 improvement in energy efficiency would be a bold but feasible grand challenge,” says Thierry Van Landegem, who chaired the consortium.
“Achieving that factor of improvement was one important objective,” explains IEEE Member Thierry Klein, who led the consortium’s technical committee. “But more importantly we wanted to go after a new way of looking at networks. We gave ourselves the freedom to think differently to achieve this ambitious goal.”
GreenTouch not only met the goal, it exceeded it. The group announced in June that it found ways to improve the energy efficiency of mobile access networks, which connect cellphones and other mobile devices, by a factor of 10,000. The group delivered on its promise of detailing the architectures, specifications, and technologies that could help lower power consumption. Its research results are expected to enable significant improvements in areas that include fixed-access networks for residences and businesses that use copper or fiber access, and the IP and optical core networks making up the regional and national interconnects that are the backbone of the Internet.
“We asked ourselves what we could do from a hardware, software, architecture, and algorithms perspective if we put energy efficiency at the forefront of network design,” Klein says. “We weren’t saying make the network more efficient at the expense of decreased performance and reliability. Maintaining high throughput, high performance, and high capacity was a given. Energy efficiency should be achieved on top of that.”
A BROAD VIEW
GreenTouch conducted Green Meter, a comprehensive, first-of-its-kind study to assess the overall energy efficiency of everything the group’s members were interested in: technologies, architectures, components, devices, algorithms, and protocols. The study didn’t quantify the energy benefits of just a single technology but had an end-to-end network perspective to capture the combined and the relative energy-efficiency benefits of different technologies. The study took into account traffic growth until 2020.
For its baseline, the researchers used the most energy-efficient commercially available mobile, fixed-access, and core network technologies that existed in 2010.
According to Klein, if networks supporting the traffic volumes of 2020 were to be built using technologies from the GreenTouch portfolio, they would consume 98 percent less energy than those of 2010. If implemented, the corresponding annual energy savings would be equivalent to eliminating the greenhouse-gas emissions of 5.8 million cars. And the networks would handle more traffic.
The study found there would be a 10,000-fold increase in energy efficiency in the mobile access networks compared with 2010, with an estimated traffic growth of 89 times; a 254-fold increase in energy efficiency in residential fixed access networks, with an estimated traffic growth of 8 times; and a 316-fold increase in energy efficiency in core networks, with an estimated traffic growth of 12 times.
NEW TECHNOLOGIES
Here are a few examples of the energy-saving technologies that GreenTouch members have developed, evaluated, and demonstrated.
Mobile-access networks—cellphone towers and base stations, which are often located a kilometer away from the caller—could be replaced with low-power radio-access nodes that operate in licensed or unlicensed spectrum with ranges of 10 to 100 meters. The smaller cells use the radio spectrum more efficiently and cover the same geographic area but provide better service. They can be located in homes, buildings, and public access spaces, like coffee shops and airports, as well as outdoors.
“These are inherently more efficient because the signal doesn’t have to travel as far,” Klein says. “Small cells have a small footprint but provide a lot of capacity in a more energy-efficient way.”
For residential access networks, the group has proposed that the dedicated set-top boxes in each home be replaced by a virtual gateway in the cloud. “We could host them on a single machine that performs the same functions virtually for everybody,” Klein explains. “By moving to the cloud, you can share the resources more effectively and turn the services on only when you need them.”
Turning to routers and transponders, the core networks’ main power consumers, the GreenTouch group found that optical interconnects and improved digital signal processors with voltage and frequency scaling can lower power consumption. It also has suggested that sleep modes of components be programmed with traffic patterns in mind, saving more energy, along with energy-optimized caching and content distribution algorithms.
“The GreenTouch technologies and results pave the way to a more energy-efficient future and ensure that communication networks remain environmentally and economically sustainable,” Klein says. “ICT technologies are increasingly being used to reduce carbon emissions in other industry sectors and are vital to bridge the digital divide and connect the unconnected in the world. Energy efficiency and our results are key contributors and enablers to a more productive and sustainable future for all of us.”
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