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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."
Does this have implications for enhanced wireless security? A wireless signal that can only be received in a specific location seems like a valuable thing.
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.
The article says their implementation should be sensitive enough to deal with movement, even driving. Not sure if that claim will hold up but at least they're thinking about it.
How do you come up with signals that not only constructively and destructively interfere in precisely the right spot in precisely the right way to deliver data to a device, but also for those same signals to simultaneously interfere at other points to deliver different data?
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.
Oh! The cloud. I thought he might dodge the question with some hand-waving. But he's got the cloud on it.
Where do I sign up? And how do I make sure the guy sitting next to me isn't stealing my signal?
In other words, phased arrays. It'd be really cool if he could deploy it for wireless communication though. There's a lot of wasted wireless bandwidth to recoup.
Higher Logics: where programming meets science.
Bingo. It sounds like he's trying to take a "cloud-sourced" approach to MIMO, with a little meshiness thrown in for good measure.
Plus I think the whole "support for non-stationary receivers is a huge issue" and "needs to avoid interference that's not of its own making" aspects will make this a non-starter. Good luck getting that spectrum, or finding a big enough group of fixed-wireless customers to make this either useful or profitable.
WiMAX and LTE are already doing MIMO and beamforming (perhaps to varying degrees), so the only thing novel about this is how massively it can fail, and just how smoothly he managed to weave the ever-magical "cloud computing" buzzword into it.
Again, Ciscos can do this. I don't care much for the company, but I've a client with more money than brains and they have a HUGE deployment of these things. The WiFi is actually faster than the wired lan, despite having 300+ clients.
-Billco, Fnarg.com
Waves don't only interfere constructively at one point. They interfere constructively at many points, to varying degrees. What happens when two devices are using mirrored interference points?
Instead of targeting specific devices, what about dividing the landscape into many physical regions, using constructive interference to cover an area rather than a single device. It would be like space-division multiplexing.
My biggest concern with this tech is not transmission from towers to individual devices, but rather the return call. What are the computational requirements for a receiver using this technology?
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.
Which is a variant on "steerable null" - a multi-antenna hack that lets the antennas at a cell site send out beams configured such that, at each active remote device paired with the site, the signals intended for all the OTHER active receivers cancel out. (Ditto with those coming FROM the remote devices to the cell: A combination of the multiple antennas' signals is computed for each remote terminal, in such a way that the signals from all the OTHER remote terminals cancel.)
This one seems to be a 3-D version of the above. Instead of a tight cluster of antennas at a site making beams with nulls pointed at all-but-one of the remote termals, it uses an array of synchronized transmitters to give each partner a signal distribution that has a dead spot on each of the other partners.
Both require (at least) as many cooperating antennas as remote partners, by the way. You can't generate more than one spectrum of signal from each antenna.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way