February 26, 2011 – A blank slate is both a challenge and opportunity. Just ask GreenTouch, a consortium founded to improve telecom energy efficiency 1,000-fold by 2020 – even when that means the new technologies require forklift upgrades that could be a hard sell to operators and vendors.
At a February 1 event in London, the consortium marked its one-year anniversary by discussing and demoing some of its initial projects. One is the Large-Scale Antenna System, which dramatically scales up the multiple input, multiple output (MIMO) antenna technology already used in some Wi-Fi and cellular networks to improve data rates and resistance to interference.
Although the prototype at the London demo featured only a 16-antenna array, GreenTouch envisions far more antennas – perhaps 100 or more – when the technology is finally commercialized. (Hence its unofficial moniker: “Massive MIMO.”) Regardless of the exact number, the concept remains the same: More antennas allow the cellular base station to better focus its signal on each user device, instead of the current, brute-force alternative of simply cranking up the power. That’s where the energy efficiency comes in.
“The base station power goes down by a factor of 16,” Dan Kilper, Alcatel-Lucent Bell Labs member of technical staff, optical communications research, told ScreenPlays before the London event. “That means the power for each individual antenna element goes down by 16 squared.
“If you have a 100-element array, the power for each antenna element is down a factor of 10,000 from what you’d have for a single antenna,” Kilper said. “It really puts you into a different regime in terms of getting rid of power amplifiers and going with low-power electronics throughout.”
And therein lies one of the challenges: Although Massive MIMO is still very much on the drawing board, it already appears that real-world implementations might require forklift upgrades because GreenTouch isn’t working within the boundaries of existing designs and standards. “We’re targeting a redesign of the entire cellular network with this approach,” Kilper says.
For Massive MIMO and its other technologies, GreenTouch is developing pre-standards, which standards bodies – such as the International Telecommunication Union, which GreenTouch is already working with – then could choose to adopt or adapt. As a result, the real-world energy-efficiency benefits will depend on the amount of tinkering by the operators and vendors that make up those standards bodies.
The standardization process is one factor that will affect when Massive MIMO and other GreenTouch technologies make their commercial debut. The consortium isn’t estimating when its technologies might be ready for commercialization. But in the case of wireless, the ideal time could be when the industry is gearing up for 5G because forklift upgrades are a given at that point anyway.
“We’re not tying it to any existing standard,” Greg Wright, an Alcatel-Lucent researcher working with GreenTouch, told ScreenPlays. “We’re not ruling out retrofitting it into LTE, but we’re allowed to look at things that are beyond any current standard.”
Meanwhile, other GreenTouch working groups are ferreting out power savings elsewhere. For example, the core switching and routing group is developing designs for single-chip line cards that would go into routers, which are big energy consumers in wireline core networks.
“Quite a bit of energy is lost as the signal moves from one chip to another throughout that line card,” Kilper says. “We’re looking at approaches where we can bring things down to smaller processing elements in a single-chip environment to get rid of these interconnect losses.
“[We would] do as much processing as possible on a single chip, as well as use the latest silicon photonic technology to bring the optics straight into this single-chip environment [to] minimize the interface losses, as well.”
Where’s the Benefit?
A growing number of operators and vendors worldwide are already investing in energy-efficient technologies, but in some cases, the green benefits are a happy byproduct rather than the primary motivation.
For example, many operators have aggressively deployed fiber simply to keep up with bandwidth demands. But that upgrade also has green side benefits, such as 73 percent lower power requirements for FTTx residential triple plays, as the United Arab Emirates operator Etisalat found after replacing its copper infrastructure. And Tellabs says optical line terminals can cut power usage by up to 80 percent in enterprise deployments.
GreenTouch’s Massive MIMO demo featured a speedometer-style gauge to illustrate performance. At one point, the presenter covered the phone with his hand, and the needle shot to the right, suggesting that the technology actually works best when conditions are worst. That boost could be a major selling point for operators and vendors.
Although Massive MIMO is focused on base station efficiency, there should be a side benefit on the device side, too. Because the base station can pick up weaker signals coming from the device, the device doesn’t have to crank up its power just to maintain a connection.
That would help extend battery life, which is increasingly stretched thin because screen sizes and processers keep getting bigger. So the less power that the device’s radio needs, the more that’s left for other components. That could turn out to be a compelling benefit for operators, given that smartphone reviewers and buyers typically scrutinize battery performance.
Those smartphones – along with over-the-top video devices such as Apple TV and Google-equipped TV sets – are increasingly popular with consumers and a major reason why GreenTouch was created in the first place. When the consortium was founded, telecom networks produced 3,000 tons of CO2, the equivalent of more than 50 million vehicles.
“Today the network consumes more energy than it did last year,” said Gee Rittenhouse, GreenTouch Consortium chairman and vice president of research at Alcatel-Lucent Bell Labs. “The exponential increase in data is growing faster than the percent reductions year over year in energy. The problem is even more relevant than it was last year.”