GreenTouch unveils mobile network concept boasting 1000-fold energy saving

After nine months of work, the GreenTouch Consortium today revealed the first fruits of its network power efficiency work at an event in London, showing a proof-of-concept base station that could feasibly reduce energy consumption on the network by a factor of 1000. By stringing together as many as 100 antennas, GreenTouch scientists found that the energy needed to power each antenna dropped significantly resulting in overall energy savings before unimaginable in the wireless industry—without sacrificing the range and capacity of the cell.

The key to the concept is an old industry standby, multiple-input multiple-output, or MIMO, smart antenna technology, which has long cut its teeth and WiFi and is now a key component of new WiMax, long-term evolution (LTE) and high-speed packet access plus (HSPA+) networks. That doesn’t mean that MIMO networks are inherently more energy efficient. MIMO is used today to increase network capacity, using dual or quadruple antennas to send multiple yet differing data streams over the same frequencies. Those multiple transmissions, in turn, require multiple power amplifiers and more energy consumption.

But GreenTouch has turned the equation around. Rather than using those multiple antennas to pile on capacity, it’s using those multiple antennas to reinforce the same transmission. It’s found that more antenna elements it combines, the amount of power required by each element drops dramatically, resulting in a system that consumes extremely low amounts of energy compared to today’s base station and cell site designs, said Dan Kipler, a Bell Lab optical networks scientist who chairs the GreenTouch technical committee.

“You can drop the total power of the base station proportionally to the number of antennas used,” Kipler said. “In a 10-antenna system, each antenna uses 100 times less power than a single antenna system. In 100-antenna system, each antenna uses 10,000 times less.”

By focusing all of those low-power transmissions at a subscriber, the technology creates a single strong beam that can support the same range and bandwidth as the single antenna radio technologies today, said Greg Wright, a Bell Labs wireless researcher working on GreenTouch’s mobile communications working group.

“Our baseline is to create a single path to the user, instead of trying to multiple capacity,” Wright said. “By not focusing on capacity we’re instead able to focus on lower power.”

At the London event, which GreenTouch webcast earlier today, GreenTouch scientists had a live demo on hand. Starting with a single antenna, scientists successively turned on more antennas demonstrating sizable drops in total power consumption with each new antenna activated. GreenTouch was founded by Alcatel-Lucent’s (NYSE:ALU) Bell Labs last year as an effort to combat the exponential growth in telecom power consumption in recent years. But since then its ranks have swelled to include researchers and engineers from all over the telecom industry, attracting even direct competitors to Alcatel-Lucent such as Huawei and Samsung. The wireless array research became one of GreenTouch’s first big projects, starting with Bell Labs’ expertise in MIMO, but drawing scientists from Samsung, Huawei, Freescale Semiconductor, Orange (NYSE:FTE) and Imec.

While the telecom industry has made significant strides in reducing the energy footprints of its equipment, many of those gains have been measured in double-digit percentages, for instance dropping average base station power amplifier consumption from 800 Watts to below 400 Watts. While those energy-saving efforts are laudable, the overall energy footprint of the telecom industry still is increasing exponentially. New demands for mobile and wireline data drive demand for more capacity, which in turn drives the installation of more routers, more fiber, more cell sites, more carriers—all of which are successively sucking more electricity out of the grid. The current gains in network efficiency quickly are being wiped out by the dramatic increase in capacity and usage, Kipler said. (Connected Planet explored this issue in depth as part of our Mobile Data Paradox interactive feature.)

The basic problem, Kipler explained, is that the telecom industry has almost single-mindedly focuses its considerable research and technical expertise in maximizing capacity—shoving more and more bits into the same pipe. While energy savings have emerged as a byproduct of that innovation, green networks were never the industry’s main goal, Kipler said. GreenTouch was formed to approach network innovation from a completely different point of view, one in which low energy consumption was paramount over capacity, Kipler said.

The antenna array project is the perfect example of that philosophy, Kipler added. It takes an established technology like MIMO and applies it to reducing the network’s energy footprint rather than applying it boosting bandwidth.

Still, GreenTouch has produced a proof-of-concept, not a commercial product. The horizon for GreenTouch’s development is distant. Most of its technologies are not being targeted for standardization or commercialization for another 5 to 10 years. In order to make the MIMO array a reality, GreenTouch must overcome several technical obstacles.

The first is the complexity of the array itself. Mounting 100 antennas on a cell site is a daunting project, and each antenna must precisely be spaced apart at distance of half a wavelength of the spectrum being used. But Wright pointed out that while the array may be complex, the demands placed on each individual antenna will be far less. They’ll be transmitting at very low power and won’t need to be the ruggedized elements we see mounted on towers today. An array conceivably could be printed out on a roll using basic industrial materials, Wright said.

“Take a roll of antennas, cut out the length you want, peel off the sticky stuff on the back and stick it on the side of a building,” Wright said.

The second is the complexity of the power amplification system. Each of those antennas will require a separate power amplifier, meaning 100 antenna array will need 100 distinct amps. But Wright said this problem can also be overcome with currently available technologies. Today power amps are big powerful affairs, pumping out hundreds of watts. The amps in these array networks will be measured in kilowatts, which can easily run off of off-the-shelf hardware. “You can really start talking about running these base station power amplifiers off of ordinary chips,” Wright said.