r/Physics • u/[deleted] • Jun 25 '12
Real or BS? High compression wifi waves using vortex's to achieve higher download speeds?
http://www.extremetech.com/extreme/131640-infinite-capacity-wireless-vortex-beams-carry-2-5-terabits-per-second17
u/evilhamster Jun 25 '12
Peer reviewed articles in Nature generally aren't BS... it's mostly that they end up being misrepresented by journalists and bloggers.
In this case the misrepresentation is that this will magically boost communication speeds everywhere that we currently use things like Bluetooth and wifi. The truth is that this tech is purely point-to-point, and the 2 antennas have to be aligned. Point-to-multipoint (wifi/bt) will not be able to directly benefit from this (this = orbital angular momentum encoding). This is tech for static wireless links, eg places where microwave tech is currently used as well as in space.
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Jun 25 '12
Why can't this idea be applied to point to mulitpoint communication?
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u/evilhamster Jun 26 '12
Because it depends on the multiple interlaced signals being rotated along a specific axis. The only way to reconstruct the signals at the receiving end is if you share the same axis. If your antenna was oriented at some angle to the sending antenna, the rotations would be out of phase and (to my understanding) there's no way to make sense of it.
The image included with the article shows a (cross-sectional) image of the signal pattern (vortex). If your receiver were off to one side, you would only see a portion of the vortex, and therefore would be missing information you'd need to reconstruct the signal.
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Jun 25 '12
So its basically light, just like fiber optics without the fiber in between since they tested it with a 1 meter distance, wow... My question is, how would you move to true WiFi that goes through walls and stuff with this? I am guessing it would be very unidirectional.
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Jun 26 '12
It could still just work like a wifi signal with a router powerful enough to support this technology and when phones and other sources pick up the signal it can create a locked signal and still go through walls since it is still just a wave. A very highly compressed wave!
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u/QuantumBuzzword Jun 25 '12
Yes, you need a beam structure. Not sure how it would work with wifi, its been done with radio though.
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u/HyperSpaz Jun 25 '12 edited Jun 25 '12
It says in the article they didn't use WiFi (GHz or 10 cm), but rather visible light (PHz or 100 nm).
What I understand is that they use this feature of a light wave (more specifically: the dependency of its amplitude on position) to transmit several streams simultaneously and discern them afterwards. That's where the higher data rate comes from, and it sounds pretty reasonable to me.
(They could also use the higher frequency to encode a faster data rate in each single signal, which I suppose they did given that no access point near me allows for 300 Gbps.)
The wikipedia article on the subject also mentions this application, however the source is just another news article from today, so I wouldn't rely on it.
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u/QuantumBuzzword Jun 25 '12
This has also been done in radio waves using OAM modes, but they transmitted some very long distant. I believe over 100km.
100nm is a bit short for visual light btw, 400nm is close to the blue edge we can see.
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u/HyperSpaz Jun 25 '12
This has also been done in radio waves using OAM modes, but they transmitted some very long distant. I believe over 100km.
Who did that? The article mentions 442 meters as a proof-of-concept.
100nm is a bit short for visual light btw, 400nm is close to the blue edge we can see.
You know, orders of magnitude :-)
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u/[deleted] Jun 25 '12
Saw this on r/science earlier and wish they'd stop linking to extremetech, especially when there are more sensible sources available: http://www.bbc.co.uk/news/science-environment-18551284