Harnessing Interference For Faster Wireless Data
holy_calamity writes "Inventor of the Quicktime codec Steve Perlman has unveiled a new wireless technology he claims can deliver thousands of times more bandwidth to mobile devices than existing technology. Each user is served by multiple transmitters, which send out waves carefully designed to combine into a data signal only at a device's location. That technique enables every user to be targeted with a signal with the same total bandwidth that would usually be shared between users, says Perlman."
802.11n already does this, they call it "beam-forming". Cisco features it in their high-end access points, using multiple antennae to send the same payload but with varying phase shift, which recombine at the receiver to produce a stronger coherent wave.
I love how the summary introduces him as the "inventor of the Quicktime codec". Yeah, he provided the RPZA ("road pizza") codec, which is so damn simple it made Bink Video look like fine art, back in the day.
-Billco, Fnarg.com
Not mentioned in this article, but called out elsewhere in the press surrounding this, is that this new interference formula only works where nobody else is broadcasting. This can't be used in the existing wi-fi spectrum, for example, because the interference from non-DIDO devices will corrupt his receivers. Unlike FM, for example, which grabs the strongest local signal, this tries to grab and combine all signals under the belief that they will combine properly. If anyone else is emitting on that same spectrum (intentionally or not), it will be troublesome.
According to the whitepaper, the coefficients to weight each transmitter signal to constructively interfere at your location sets up mathematically orthogonal channels (at lease orthogonal to some SNR, with some leakage from other channels depending on the number/location of devices and antennas).
The device can send a signal back which will interfere with other devices, but incoming signals at the antennas can be weighted by the same coefficients (or at least derived from the same) to again cancel all the other signals but your own.
Mathematically, the channel can go both ways with full bandwidth.