GreenTouch Shows Low Power Wireless

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Large scale antennas start GreenTouch Consortium on its way to cut network power 1,000-fold

The GreenTouch Consortium, launched a year ago with the mission of reducing network energy demands by a factor of 1,000, has shown its first technology: a large scale antenna system which focusses radio signals.

The antenna system, known as Massive MIMO during development, uses multiple antennas instead of a single antenna on the base station tower, and creates a precise beam to phones, instead of wasting energy in all directions.

Many cheap antennas save power

Despite its ambitious target, the consortium is on target, said Gee Rittenhouse, founder and chairman of GreenTouch, and the director of research at Alcatel Lucent’s Bell Labs.

“Our goal is to demonstrate key technologies to achieve a 1,000-fold reduction in network power, within five years,” he said at an event in London, where the large scale antenna was demonstrated.

“Normally most of the energy from a cell tower is wasted,” said Rittenhouse, as it sends signals across a wide sector.

In the demonstration one antenna sent a signal to a mobile phone, and then fifteen more were switched on. The power used fell to a fraction of the original level, as the antennas used superposition to create a tight beam.

“The power drops sixteen-fold with sixteen antennas,” Greg Wright of Alcatel Lucent, demonstrating the technology,”and we’re not limited to that. We could use hundreds of antennas.”

At the request of eWEEK Europe the demonstration was repeated, with the phone being moved, to show that the beam could actually move and follow the handset.

Tom Marzetta, group leader of Bell Labs’ communications and signal processing research group in New Jersey, who described the technology to eWEEK Europe, was at the London demonstration and said the GreenTouch involvement had been crucial to the move to a concrete demonstration.

The technology can be seen in a video on the GreenTouch site.

Overall, the GreenTouch programme is focusing on new technologies such as the antenna array, and more simple ideas such as making network equipment go to sleep when it is not in use.

“Home routers use 10W to 20W,” said Rod Tucker of the University of Melbourne. “We can reduce this by putting the modem to sleep when it is not being used.” Beyond that, more network functions could be hosted at the telephone exchange where power is used more efficiently, he said, creating “virtual modems”.

GreenTouch also wants to see the cellular networks’ signalling systems separated from their data carrying networks. “The signalling network uses low power,” said Tucker, pointing out that if the two were separated, then the data network could be shut down except where individual phones are using it.

GreenTouch also wants to reduce the chip count in network equipment, including a proposal for a single-chip line card for use in telephone exchanges, which combines a photonics and electronics in a hybrid chip.

Consortium gathers strength

The consortium now has 35 members including operators, universities, hardwave vendors and chip makers, and is co-ordinating 25 research programmes, which cover different aspects of the network.

One company noticeable by its absence was BT, a major operator which has taken a strong green stance, and advised other companies to do the same, even taking the UK government to task for its level of support for on-site renewable power sources.

Despite not actually signing up, BT has been very supportive of GreenTouch, said Rittenhouse, adding that the consortium has benefitted from BT’s verbal support outside the consortium.

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