Interference Unlocks Faster Mobile Data
Intentionally combining radio signals from different transmitters could allow mobile devices to download at much higher speeds.
- Wednesday, August 3, 2011
- By Tom Simonite
While demand for wireless data grows exponentially, the supply of available radio spectrum remains stubbornly fixed. A new technology could get more from that precious resource by turning a conventional piece of engineering wisdom on its head.
"Every other wireless system up to now has avoided interference," says Steve Perlman, founder of technology incubator Rearden Labs, based in San Francisco. "This embraces it."
Perlman's team is testing a new kind of wireless network that he says can fit thousands of times more data into the same amount of radio spectrum as a conventional one. The approach is known as DIDO, for distributed input distributed output, and is currently being tested around Palo Alto, California, and in rural Texas.
Today, wireless data is most constrained on cell-phone networks, which are struggling under demand from growing numbers of increasingly capable mobile devices.
All wireless systems have access to a fixed portion of radio spectrum, and hence a fixed capacity for transmitting data, known as bandwidth. Today's wireless networks, like those that serve data to cell phones, share that bandwidth among the gadgets connected to the network. The more devices that connect, the smaller the slice for any individual user, and the slower the download speeds. By contrast, a DIDO system, says Perlman, "can offer the full bandwidth available to the network to every user."
DIDO involves intentionally combining signals from multiple transmitters, exploiting interference to create a bubble of crystal-clear reception around every user. Each signal that leaves an individual transmitter is incomprehensible until it encounters, and interferes with, other DIDO signals near a device connected to the network.
This approach removes the need to share bandwidth, says Perlman, because each bubble covers a small area and can occupy all the spectrum available to the network. The size and shape of the bubbles varies depending on the number of antennas broadcasting to a device, says Perlman.
Designing radio signals that will interfere with one another in just the right way takes complex mathematics and careful coordination among the different DIDO transmitters. "The computational requirements are very large, but we solved that by using a cloud server," says Perlman.
When a device wants to connect to a DIDO network, it contacts the nearest tower and sends information on the local radio conditions back to the server. The server combines that information with data from other nearby devices to design signals that will combine in the right way. Perlman says tests involving up to 10 devices downloading at the same time have been successful. Individual devices can't easily take advantage of DIDO's design when uploading, however, so sending data in that direction would be slower.