Twisted Radio Beams Could Untangle the Airwaves

Urchin writes "The radio frequency spectrum available for wireless communication is becoming increasingly crowded thanks to new wireless technology. A solution to the shrinking space might be to put a spin on radio beams during their transmission, to produce a twisted beam, according to Swedish physicists. In theory, huge amounts of data could be sent in the pitch of the twist, which is distinct from the amplitude and frequency of radio waves — the features used at the moment to send information."

Comments

damn

[geekoid]

Damn, this is so obvious now. I should have thought this up years ago.

Re:damn

[Anonymous Coward]

Am I missing something?

These guys are proposing polarizing wireless transmissions. Polarization gets affected by ALL kinds of boundary irregularities, such as nearby cars light poles, traffic signal loops and, in buildings, conducting objects like nails, hinges, pipes, etc.

This seems so noisy as to be useless.

Re:damn

[Anonymous Coward]

The article suggests the technique only works really for point-to-point transmission. Regular amplitude/phase modulation (QAM) is still the best generally I'd imagine.

Re:damn

[ceoyoyo]

You are aware that digital radio techniques all use amplitude, frequency or phase modulation, right? The difference is that the modulation is digital (or thereabouts) rather than analog.

Re:damn

[johanwanderer]

This is slightly different than simple polarization, see here: http://www.newscientist.com/article/mg18224515.000 -- full article requires log-in. Or here: http://www.physics.gla.ac.uk/Optics/play/photonOAM/ The point here is that a "pulse" can now encode more than just an "on/off" state. Instead, a pulse now encodes a "twistiness" level of states (can be 1, 2, 3, or up to 250 as in the NS article.) So, a 2GHz signal can now carries, let's say, 2x8 = 16 Gb/s. The trouble, it seems, is to construct a receiver capable of correctly identifying the pulses.

Two questions

[jandrese]

1. How practical is this technology? Could you mass produce cheap low power receivers to put in every car/computer/etc...? How complex is the transmit circuitry?
2. How resistant is this to atmospheric and other interference? In theory it should be pretty resistant, but in practice who knows.

Needing multiple antennas to get this done sounds like a rather big limitation to me.

Obligatory

[Bovius]

Do a barrel roll!

Sorry, couldn't resist.

Re:in this house we obey shannon's theorem

[ceoyoyo]

Shannon's law is a tricky piece of work. It doesn't actually tell you how much data you can transmit given a particular amount of bandwidth. It tells you how much data you can transmit given a particular amount of bandwidth and particular noise characteristics over a given channel.

Now, you can play various games with that. If you limit yourself to, say, frequency modulation, you just measure the noise, run it through Shannon, and get your result. But what if you polarize the signal and encode data in that? Have you broken Shannon's law? No. You can account for things like that by counting it as a separate channel, or by changing your noise estimate to account for the additional, independent modulation technique.

These guys' modulation technique is another independent channel.

The article does say it's probably not going to work very well for things like cell phones though, since you need an antenna array. It might be useful for things like microwave towers though.

It's not about polarization

[Doug Merritt]

Am I missing something? These guys are proposing polarizing wireless transmissions.

Yes, you are, and no, they aren't.

This is about modulating the orbital angular momentum of photons, a property that wasn't even discovered until 1992.

Each photon can have an integer quantity of orbital angular momentum (0, 1, 2, 3...) without obvious limit (or in the opposite direction, -1, -2, -3...). In principle, and increasingly in experiment, it is possible to encode information by modulating the orbital angular momentum carried. This provides and entirely separate channel with its own bandwidth in addition to traditionally understood modulation. They're right to be excited about it; it has the potential of being just as big in scope as was the invention of radio.

See http://www.physics.gla.ac.uk/Optics/play/photonOAM/

Re:It's not about polarization

[johncadengo]

This provides and entirely separate channel with its own bandwidth in addition to traditionally understood modulation. They're right to be excited about it; it has the potential of being just as big in scope as was the invention of radio.

Isn't one of the hugest factors in the Fermi Paradox the "Great Silence" aka that if life in the universe is so abundant why don't we hear their radio transmissions?

Now, how many other "channels" out there do you think exist that we simply have no grasp or knowledge of?

Does this open up a new potential medium for listening?

Re:No

[Doug Merritt]

Nope, this absolutely is not about polarization.

This is about modulating the orbital angular momentum of photons, a property that wasn't even discovered until 1992.

Each photon can have an integer quantity of orbital angular momentum (0, 1, 2, 3...) without obvious limit (or in the opposite direction, -1, -2, -3...). In principle, and increasingly in experiment, it is possible to encode information by modulating the orbital angular momentum carried. This provides and entirely separate channel with its own bandwidth in addition to traditionally understood modulation. They're right to be excited about it; it has the potential of being just as big in scope as was the invention of radio.

See http://www.physics.gla.ac.uk/Optics/play/photonOAM/

This NOT already done

[Doug Merritt]

Nope, that's not what they're doing; this particular "twist" is absolutely not identical to previously well-understood phase modulation.

They're using physics that wasn't even discovered until 1992.

See http://www.physics.gla.ac.uk/Optics/play/photonOAM/