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Scientists Twist Radio Beams To Send Data At 32 Gigabits Per Second
concertina226 writes Scientists from three international universities have succeeded in twisting radio beams in order to transfer data at the speed of 32 gigabits per second, which is 30 times faster than 4G LTE wireless technology in use today. The researchers, led by Alan Willner, an electrical engineering professor with the University of Southern California Viterbi School of Engineering, successfully demonstrated data transmission rates of 32 gigabits per second across 2.5m of free space in a basement laboratory.
the University of Southern California Viterbi School of Engineering, successfully demonstrated data transmission rates of 32 gigabits per second across 2.5m of free space in a basement laboratory.
They would have tried for 10m, but Mom and Dad told them that the street lights were on, and their little friends would have come up from the basement and go home.
Yeah, I could do with one of those office-space meme's right now.
If all the nay-sayers faux-gasping at the extreme length of 2.5m could shut up, that'd be great.
I'm not sure what people expect these days - this is a major achievement - whether it *can* be extended, or whether it *will* be extended would be different achievements. You could almost apply Jackson's rules of optimisation to this (refresher below) - in that first you *do* it, and only then (if you're an expert) do you try to do it *well*.
Simon
Jackson's rules of optimisation: "The First Rule of Program Optimization: Don't do it. The Second Rule of Program Optimization (for experts only!): Don't do it yet."
Physicists get Hadrons!
The reference to 4G limits has exactly what to do with this story? This was not 32Gb/s over a 4G network, it was 32Gb/s over an unknown protocol at a very short distance. I'm guessing that the basement was isolated from signal noise, which means this pretty much a non story or extremely premature.
There are many people that invent some batshit crazy things that simply don't work in the real world. Honestly that is not an insult directed at the inventors, because their work tends to lead to other developments down the road. It's more an insult at media which focuses on hyping everything possible.
-The wise argue that there are few absolutes, the fool argues that there are no probabilities.
Along with IR and Visible light, unless you are pumping watts into a very small volume you're not going to boil your guts with wifi.
Dear aunt, let's set so double the killer delete select all
Frankly, I am still confused as to why it's not (more simply) "circular polarisation" that has been known about since the early days of radio.
Since you linked to Wikipedia, I'm going to assume that Wikipedia didn't do a very good job at explaining the difference. While OAM and circular polarisation both describe some sort of spinning, they correspond to different phenomena. As you may know, electromagnetic waves are oscillations of the electric (and magnetic) field, with the field at each spatial position varying over time. You may also recall from your high school physics class that the electric field at any position is a vector quantity --- it has both a strength and a direction. The polarisation of a electromagnetic field is a description of the direction that the electric field points, and circular polarisation can be roughly seen as the electric field direction rotating as you travel in the direction of propagation. What OAM is describing is the phase relationship between the oscillations of the field at different positions (whether the oscillation at one point is lagged or ahead compared to a different point); it can be roughly thought of as a spinning motion in the transfer of energy inside an electromagnetic field.
For a rather inaccurate, but perhaps intuitive, analogy, try imagining a giant stream of asteroids coming your way in outer space. If the rocks are following a spiral trajectory as they come at you, then this corresponds to the rocks having "orbital angular momentum". If the rocks are themselves spinning, then this corresponds the rocks being "circularly polarised".
This is a myth. There is nothing special about 2.4 GHz as far as water is concerned. There is a mild absorption peak at 24 GHz, but nothing at 2.4.
As a microwave engineer, I find it unfortunate that it is called "orbital angular momentum" or "twisted beams". It causes confusion for many in the antenna engineering community. It is _not_ circular polarisation, but a form of spatial diversity non unlike MIMO systems. Where it differs from MIMO is, instead of translational spatial diversity, we have angular spatial diversity. The "beams'" phase fronts "twist" at different rates (there is no "twisting" of the direction of the E-field vector, as is the case with circular polarisation). This provides a means to multiplex many signals on the same "beam". Incidentally, you can also exploit polarization on top of the angular spatial diversity to (nearly) double the transmission capacity.