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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."
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.
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.
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.
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.
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
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