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Twisted Radio Beams Could Untangle the Airwaves

Posted by ScuttleMonkey on from the only-the-flying-spaghetti-monster-would-know-for-sure dept.

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."

24 of 183 comments (clear)

  1. damn by geekoid · · Score: 4, Funny

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

    --
    The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
    1. Re:damn by Anonymous Coward · · Score: 5, Interesting

      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.

    2. Re:damn by Anonymous Coward · · Score: 5, Informative

      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.

    3. Re:damn by ceoyoyo · · Score: 5, Informative

      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.

    4. Re:damn by johanwanderer · · Score: 4, Informative

      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.

    5. Re:damn by ceoyoyo · · Score: 3, Informative

      Check out the wikipedia page for OFDM: http://en.wikipedia.org/wiki/OFDM

      First paragraph: "Each sub-carrier is modulated with a conventional modulation scheme (such as quadrature amplitude modulation or phase shift keying)."

      You're right, analog transmissions are generally less efficient for transmitting data. Your AM radio vs. digital radio example isn't quite fair, since the digital radio is compressed - that is, it isn't actually transmitting as much information as the analog channel.

      Your overall point is flawed. It is not the type of modulation (AM or FM) that is at fault, but rather the analog nature of the transmission. This new technique actually sounds like it would NOT lend itself naturally to analog transmissions - it would be far more likely to be used with digital encoding.

      In fact, you could probably use OFDM if you want to, just like it is commonly used with amplitude modulation.

  2. Two questions by jandrese · · Score: 4, Interesting

    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.

    --

    I read the internet for the articles.
  3. Obligatory by Bovius · · Score: 4, Funny

    Do a barrel roll!

    Sorry, couldn't resist.

  4. As Dr. Egon Spengler once said by auric_dude · · Score: 3, Funny

    Don't cross the streams.

  5. No by rcw-home · · Score: 3, Informative

    The article appears to be referring to right or left circular polarization, as opposed to horizontal or vertical polarization. A horizontally-oriented dipole transmitting near a vertically-oriented dipole will be heard much more faintly - 20db+ quieter. Similarly, a left-polarized antenna won't interfere with a right-polarized antenna. But a circularly-polarized antenna will still interfere with a horizontally or vertically polarized antenna - it'll only be 3db weaker.

    1. Re:No by Doug+Merritt · · Score: 5, Informative
      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/

      --
      Professional Wild-Eyed Visionary
  6. does satellite internet already do this? by steak · · Score: 3, Interesting

    I install wildblue satellite internet and we have two type of transceivers right hand and left hand polarization. after rtfa I am curious if this is the same thing or something different?

    --
    lose != loose
    1. Re:does satellite internet already do this? by scerruti · · Score: 3, Interesting

      I don't know about wildblue, but when I was working with satellite about 10 years ago DirecTV was circularly polarized DirecPC was not.

  7. FM is polarized as it is for a reason by Anonymous Coward · · Score: 3, Informative

    There is a reason that FM is polarized in the direction it is: any other direction is relative.

    FM is vertically polarized because that means that a car needs only have a vertical antenna to catch the signal, if they polarize it horizontally then the antenna on the car needs to rotate every time the car turns.

    At least this is what I was told in my RF/microwave design class.

  8. Twisted Radio Waves by komische_amerikaner · · Score: 3, Informative

    AFAIK (yes, I did RTFA), this is tantamount to adding another method of data transmission using more of the envelope. You still have the frequency being used and still have a portion of the carrier plus sideband transmitted, no matter what type or method of transmission is used. This may be used to embed something similar to a sub-carrier, or a unique identifier. More directivity and narrower beamwidth during point-to-point transmissions will do wonders to keep the RF floor down.

    --
    Don't spend your life lamenting your life.
  9. Re:in this house we obey shannon's theorem by ceoyoyo · · Score: 5, Insightful

    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.

  10. It's not about polarization by Doug+Merritt · · Score: 5, Informative

    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/

    --
    Professional Wild-Eyed Visionary
    1. Re:It's not about polarization by johncadengo · · Score: 4, Interesting

      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?

      --
      My page.
  11. Incorrect by Doug+Merritt · · Score: 3, Informative
    Nope, that's not what they're doing. They're using physics that wasn't even discovered until 1992.

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

    --
    Professional Wild-Eyed Visionary
  12. NOT 140 years late by Doug+Merritt · · Score: 3, Insightful
    Nope, that's not what they're doing; it's not polarization. They're using physics that wasn't even discovered until 1992.

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

    --
    Professional Wild-Eyed Visionary
    1. Re:NOT 140 years late by Doug+Merritt · · Score: 3, Informative
      As far as you can tell? Why don't you just go look at the link I provided?

      It won't take but a second for you to stop guessing that it's about polarization once you see their clear explanation that it's different.

      --
      Professional Wild-Eyed Visionary
  13. This NOT already done by Doug+Merritt · · Score: 4, Informative
    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/

    --
    Professional Wild-Eyed Visionary
  14. FM is circularly polarized, not vertically! by NixieBunny · · Score: 3, Interesting

    Actually, broadcast FM is nearly always circularly polarized using a multi-bay antenna with a bunch of 3/4 circle center-fed elements, each with one end pointing up and the other down.

    If you weren't aware of this, go look atop an FM tower with binoculars some day.

    Good luck finding the published theory on these antennas, since they're all proprietary designs!

    --
    The determined Real Programmer can write Fortran programs in any language.
  15. Orbital Angular Momentum versus Polarization by TheSync · · Score: 3, Informative

    This article has a good explanation of the difference between Orbital Angular Momentum and Polarization of EM waves.

    If you look at the cross section of a "normal" polarized EM beam, the electric field amplitude and direction at every point of the cross section are in the same phase - although that direction may be up, down, or rotate over time depending on the polarization.

    In an EM beam with orbital angular momentum, the electric field amplitude at different points on the cross section are in different phases - although it is my understanding they are usually all in the same polarization.