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Carriers gearing up for 3G networks might sit up and take notice of a recent discovery by scientists at Lucent's Bell Labs (www.bell-labs.com).

Bell Labs physicists Michael R. Andrews and Partha P. Mitra, along with Robert deCarvalho, a Harvard University (www.harvard.edu) grad student, proved that through electromagnetic polarization and the use of specialized antennas and signal-processing techniques, a 3-fold increase in channel capacity can be obtained, relative to the conventionally assumed capacity of dual-polarized radio signals. The scientists presented their research in an article published in the Jan. 18 issue of Nature (www.nature.com).

The experimental technology takes advantage of the scattering of radio signals that takes place in dense urban areas or indoors. Under direct line-of-sight transmission conditions, the electric field of a radio wave must be perpendicular to that line, deCarvalho said.

“That means the electric field can point sideways or up and down. It's a 2-component vector,” he said. “Now, the idea rests on answering how to pack more information into that slice of radio spectrum.”

The Bell Labs experiment proved that, within a scattering environment, special antennas can take advantage of a third polarization.

“We were re-examining the assumption that two polarization states in free space didn't hold in scattering environments, where waves are bouncing off of buildings and cars and mountains,” Andrews said. “What that led to is the realization that there are really six polarization states. And each one of those can be used as an independent channel to some extent.

“What we were considering is how polarization figures into this multiple-antenna business,” he said. “Previously, people were thinking more about using arrays of antennas spread out over space, whereas we are talking about some kind of compact antenna that could measure fields in space. We found that you can measure six polarization states, not two. That ratio of 6:2 gives you this tripling of information capacity.”

This approach could conceivably be used by engineers building new wireless systems to take advantage of this extra capacity. A Lucent spokesperson said the company had no immediate plans to integrate the discovery into its network equipment.