text:
Vortex radio waves could boost wireless capacity "infinitely"
- By Sebastian Anthony on March 2, 2012 at 7:07 am
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After four years of incredulity and not-so-gentle mocking, Bo Thide of the Swedish Institute of Space Physics and a team in Italy have finally proven that it's possible to simultaneously transmit multiple radio channels over exactly the same wireless frequency. In theory, according to Thide, we could potentially transmit an "infinite number" of TV, radio, WiFi, and cellular channels at the same time over the same frequency, blasting apart our highly congested wireless spectrum.
Thide's approach is rather simple. Basically, electromagnetic waves can have both spin angular and orbital angular momentum (OAM). If you picture the Earth-Sun system, spin momentum is the Earth rotating on its axis (producing the day-night cycle), and orbital momentum is the Earth rotating around the sun (producing the seasons). In standard wireless communications — radio, TV, WiFi — we only modulate the spin angular momentum of waves. For years, Thide had theorized that orbital angular momentum could also be added to wireless signals, effectively creating a spiral signal that looks like fusilli pasta; or, in the words of Thide, a "radio vortex."
Now, in an experiment in Venice, Thide and his Italian colleagues have transmitted two signals at the same time, on the same frequency, over a distance of 442 meters (1450ft). Pictured on the right is the antenna that the team used. No, your eyes don't deceive you: To create these radio vortices, all you have to do is make a cut in a standard parabolic reflector and twist it slightly. If you imagine a corkscrew of radio signals being continuously transmitted from the outside edge of the antenna, that's effectively what's occurring. On the receiving end, there are two "normal" TV antennae (Yagi-Uda) set apart by the same angle as the break in the transmitter. These antennae "decode" the vortex, and voila: Two radio signals transmitted over the same frequency.
It is hard to put into words just how significant Thide's discovery could be. If the vortex preserves other aspects of wireless communications, such as multiplexing, then in the short term we could be looking at a wireless spectrum that can carry 10 or 20 times as much data. In the long term, as our understanding of orbital angular momentum grows, our wireless spectrum could effectively be infinite. To be honest, this is such a huge twist for wireless communications that the full repercussions are not yet known.
With radio and TV, and now cellular networks, wireless spectrum is one of humanity's most valued resources. It is because airwaves are so clogged that companies like Verizon or Vodafone pay billions of dollars for just a few megahertz. If Thide's discovery pans out, not only would wireless spectrum lose most of its value, but the trouble and strife surrounding LightSquared, international roaming, LTE rollout, white space wireless, and digital TV simply cease to be.
Read more at New Journal of Physics
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http://twitter.com/standaloneSA Matt Simmons
If it's this easy to create spin, I imagine it's just as easy to introduce noise. Or at least, to have noise interfere.
Presumably there would be less "spun" noise than standard noise, and once could use similar techniques for noise reduction and error correction as for normal signals
http://twitter.com/bothide Bo Thidé
OAM, that we have now shown can be utilised to pack mor information in – and extract more information from – radio waves, has nothing to so with spin (which is polarisation). OAM is a physical observable in its own right.
David Kuehling
Sounds like they're only inventing a new name for (long known) MIMO communication systems (as already used by LTE).
http://www.mrseb.co.uk Sebastian Anthony
The paper mentions that MIMO could be combined with this — so I don't think it's the same thing.
It is the same thing as MIMO, see the following paper, published in IEEE Transactions on Antennas and Propagation, titled "Is orbital angular momentum (OAM) based radio communication an unexploited area?"
It is not the same thing as MIMO, how can you say that? You have obviously not understand what OAM is about. The paper pick distinct parts of the OAM technique and generalize it, it does not cover the OAM science at all, only a small subset of it. Based on the conclusions you draw from small subsets of OAM you say that it is the samr thing as MIMO? Please come on, even an amateur radio like me see the difference clear, stop being so ignorant to this breakthrough in radio science.
http://profiles.google.com/enigmav8 Chris Kleczynski
http://twitter.com/bothide Bo Thidé
OAM, which is a fundamental physical observable which relates to rotation and torque action, is completely separate from current MIMO techniques which rely entirely on translation and force action. In fact, using MIMO techniques on the new physical OAM states, will allow an even higher information content.
http://www.mrseb.co.uk Sebastian Anthony
Welcome, Mr Thide!
Not buying this "breakthrough" at the moment. This just sounds like circular polarization. I don't at all see how a purely mechanical change like cutting a reflector is supposed to impart some heretofore unforeseen effect on the e-m field. Show me a peer-reviewed paper, then we'll talk.
There's a link to the peer-reviewed paper in the article.
Touché! So let's talk, then :)
http://twitter.com/bothide Bo Thidé
The so far relatively unknown vorticity (orbital angular momentum) is completely separate from the well-known polarisation (spin angular momentum). In fact, combining vorticity and polarisation the information carrying capacity can be doubled. This has been amply demonstrated in opitcs where the results have been articles published in top-level journals (Nature, Science,…)
http://pharaohtechblog.blogspot.com/ Conan Kudo (ニール・ゴンパ)
This looks like it could be the foundation of fifth-generation cellular wireless technology. It'll just need a decade of refinement… :)
Paolo Pistolato
Come on guys, how not to understand that this is a scientific fraud ? How can one only think that a parabolic antenna manually modified with a cutter can generate and propagate an e.m. vortex !!! And what about the "experiment" : an analog transmission in a multipath environment to mask a trivial crosstalk as a "new era of the digital transmission". And finally what about the main authors: all italian …
http://pulse.yahoo.com/_HUHWX4TIAZRFNFYCWUE43OZDUQ 7LeagueBoots
Have you read the peer reviewed article linked to in the article, and this this a field of which you have some particular knowledge?
Sorry, but I'll put my money on the guys who did the work, not on an internet commentator. .
http://twitter.com/bothide Bo Thidé
We have developed this step by step. Following a thorough theoretical analysis, the results of which are included in my textbook "Electromagnetic Field Theory", we performed a comprehensive numerical experiment (results published in Physical Review Letters 99(8):087701, 22 August 2007). We then verified these results in a controlled lab experiment in the big, fully shielded Angstrom Lab anechoic antenna chamber in Uppsala (results published in Applied Physics Letters, 99(20):204102, 16 November 2011). Step three was to repeat the verify that the lab results can be achieved also in an real-world setting and this is what we have published now. All our publications have been subject to anonymous peer reviews and approved before being published. Please be careful to use the term "fraud" unless you can substantiate it!
Bo Thidé
Professor, Co-author
http://twitter.com/bothide Bo Thidé
By the way, I am not Italian, I am Swedish. We all know that Italian so called "physicists" such as Galileo Galieli, Enrico Fermi and Nicola Cabbibo and so called "engineers" such as Leonardo da Vinci and Guglielmo Marconi were all frauds and never contributed anything at all to "real" physics and "real" engineering… Never!
Bo, thank you for your contribution. My question is the multiplexing part of this technology. Can I assume that current multiplexers may by insufficient to handle this or am I mistaken?
I'm also curious as to what level of precision of antenna angling and spacing is required on the Yagi side and how far apart the antennas have to be for specific distances. Is it possible to use the parabolic dish at a matching position?
Paolo Pistolato
Come on guys, how not to understand that this is a scientific fraud ? How can one only think that a parabolic antenna manually modified with a cutter can generate and propagate an e.m. vortex !!! And what about the "experiment" : an analog transmission in a multipath environment to mask a trivial crosstalk as a "new era of the digital transmission". And finally what about the main authors: all italian …
There were some numerical results showing this *could* be possible (http://prl.aps.org/abstract/PRL/v99/i8/e087701, Utilization of Photon Orbital Angular Momentum in the Low-Frequency Radio Domain).
I do not see how the momentum pattern gets preserved after the receptors antenna, do we need a bunch of twisted antennas, one per mode?
There were some numerical results showing this *could* be possible (http://prl.aps.org/abstract/PRL/v99/i8/e087701, Utilization of Photon Orbital Angular Momentum in the Low-Frequency Radio Domain).
I do not see how the momentum pattern gets preserved after the receptors antenna, do we need a bunch of twisted antennas, one per mode?
There were some numerical results showing this *could* be possible (http://prl.aps.org/abstract/PRL/v99/i8/e087701, Utilization of Photon Orbital Angular Momentum in the Low-Frequency Radio Domain).
I do not see how the momentum pattern gets preserved after the receptors antenna, do we need a bunch of twisted antennas, one per mode?
So basically take a Dish, cut a radius out, and corkscrew it?
Sometimes complicated problems really do have simple solutions.
http://twitter.com/bothide Bo Thidé
What do you mean by "complicated problems"? That electromagnetic fields may contain angular momentum is well-known by physicists and something that is covered in most textbooks on electromagnetism. It is only that the typical radio engineer that designs radio systems overlook this fact or perhaps does not even remember it from his EM course.
How about the part where everyone is paying billions over what could become near infinite? Everyone interested in spectrum is fighting for it, and with bigger and bigger piles of cash. Theoretically, the hoarding of spectrum is going to be a bit useless now…
http://www.seven-sigma.com/ Jeff Dickey
Which is the most powerful argument yet why large-scale implementation of Dr. Thidé's technique is years off, if not decades. There is so much money and organisational politics tied up with the status quo that those in a position to make the change happen will fight it tooth and nail. What's one of the greatest boons to human civilisation if it comes at the possible risk of power, prestige and money?
If you're the most efficient company on the market and can cut your prices in half, yet still raise profit, you'll do it. Consumers will demand better and better things, and companies will have no choice but to comply. The first ones to comply will get a surge in business, and the slower ones will want to be first on the innovation the next time, so that they have the "next big thing".
All it really takes is one company to start using these spiral radio waves and claim that essentially no signal can interfere with it. They'd get a big boost in business, and the other companies will rush to catch up before they lose everything.
comparing this to pearlman's DIDO wireless tech its not all to impressive, that's the one I'm really hoping will become an international wireless standard
comparing this to pearlman's DIDO wireless tech its not all to impressive, that's the one I'm really hoping will become an international wireless standard
Actually, Qualcomm has been been effectively doing this (frequency re-use) for 20 years. It is commonly known as Code-Division-Multiple-Access (CDMA). Perhaps this "OAM" will add a new twist to further increase cell capacity.
Jeff Jones
So how are they inserting these two radio signals, on the same frequency, using a single transmitter? The picture looks like there is only one transmitter and one wire leading to it, so it makes me think they are just doing something like multiplexing.
http://twitter.com/bothide Bo Thidé
We used two transmitters. In fact, as you can see for yourself by downloading our paper from the journal web page iopscience.iop.org/1367-2630/14/3/033001/pdf/1367-2630_14_3_033001.pdf
we write
"Two identical WiFi FM transmitters, each with an output power of 2W and driven by a signal generator, were tuned to the carrier frequency of 2.414 GHz to feed two antennae."
Bo Thidé, co-author
Dear Bo,
How well is OAM orthogonality maintained under multi-path conditions?
http://twitter.com/bothide Bo Thidé
We performed our Venice experiments (we ran them for a month before the big demo on 24 June) in a multipath condition and saw no problems despite a rough water surface, ships passing by etc. Since angular momentum is a conserved quantity (constant of motion) it will always be preserved. This is not true for polarization which is the spin part of the angular momentum and is not a conserved quantity. Neither is the orbital angular momentum alone. But the sum is. This is one of the neat things with angular momentum. Guns are designed so that the projectile will have angular momentum when it leaves the barrel. This way the trajectory is stabilised
Yep. An unspun bullet has less net kinetic impact velocity than a spinning bullet. Although the mass of the bullet remains constant, the imparted forward kinetic push is multiplied by the angular spin force which results in a kinetic force increase when the bullet impacts the target.
Jeff Jones
So how are they inserting these two radio signals, on the same frequency, using a single transmitter? The picture looks like there is only one transmitter and one wire leading to it, so it makes me think they are just doing something like multiplexing.
Why is no one exploring longitudinal EM (Tesla/scalar) waves? Is anyone familiar with the early Raymond C Gelinas patents sold to Honeywell and buried? They state non-interference with TEM transverse waves, and the ability to determine distance and direction.
Robert Syputa
Broadly disproved. If you don't believe that, never brought forward to commercial use and thus totally irrelevant fantasy.
There are much more valid theories that could have dramatic impact that remain valid if not yet practical.
Among these are new signal acquisition and encoding methods that seemingly violate Shannon-Harley but arguably work with it but starting at a lower level than MIMO-AAS. Among the segment is single-cycle or limited-repetitive cycle fractal encoded waveforms. The theory has been around for several years. Somewhat analogous to MIMO, this has remained impractical due to the high level of highly sensitive receiver input sampling and real-time low level signal processing processing required. However, it does not violate laws of physics, it just performs richer encoding at the deepest level of signaling possible.
Higher order relationships, such as phase-angle modulation or complex multiple signal propagation differentiation modulation, can have their place if they are made practical. Tesla/scalar are debunked in the literature.
http://www.facebook.com/manouu Mt Nicolas
Pure Awesomeness
Robert Rockey
I wonder, what would the rate of rotation be called as I dout it would also be called frequency. I can also see how this can be adapted for security by dynamically
changing the "frequency" of the vortex spiral similar to how frequency
hopping works…
http://twitter.com/bothide Bo Thidé
In fact it can be called the rotational frequency as opposed to the "usual" frequency that is the oscillation frequency. So, with OAM/vorticity the frequency axis has been expanded to a frequency plane.
http://twitter.com/bothide Bo Thidé
In fact it can be called the rotational frequency as opposed to the "usual" frequency that is the oscillation frequency. So, with OAM/vorticity the frequency axis has been expanded to a frequency plane.
http://www.facebook.com/mike.hughjass Mike Hugh-jass
I wonder if SETI will be looking at "noise" from space in different ways now.
It is important to keep pushing the boundaries of knowledge
and experimenting with new ideas, even in a classical field such as radio-wave
communications. I read the NJP paper and I do not doubt the results. However,
my first impression is that this looks
like using a 'sum' and 'difference' beam to transmit the two signals (using two pairs of
antennas). The 'difference' pattern is produced by the 'cut' parabolic dish and
the 'sum' one by the second Tx antenna
(Yagi?). Nice experiment but not really
'revolutionary'; this is just antenna pattern/phase diversity. Also, trying to extend this to higher-order phase-pattern
modes will be practically very challenging (will need complex antennas).
Finally, this scheme will work well only for high-directivity line-of-sight
links. Multipath reflections (in buildings for example) will destroy the phase orthogonality. Nevertheless, this is still nice work …
Robert Syputa
This is hardly revolutionary. on the surface it looks like another Italian farce.
Encoding multiple channels differentiated by higher order phase channel relationship is a possibility well known in the field. What makes sense to carry beyond theory comes down to practical application. That starts with an understanding of the practical impacts, such as whether the differentiation can be delivered in small antenna and can work well with lower level signal modulation and multiplex channel antenna, time-phase and modulation coding methods.
Can higher order/level phase angle modulation methods be used? Of course. Can they be made practical? Perhaps but in the meantime there are many methods that are exposed in LTE-Advanced that have yet to be implemented that are proven to work well using commercially available antenna size/isolation properties in conjunction with low level signaling and higher level spectrum access methods.
Kick this one to the curb until they show vast improvements in viable adaptation and consensus for adoption.
This is my own update:
I have looked at the Laguerre-Gaussian (LG) modes more closely. It all seems to relate to the exp(j*l*phi) term that is there to ensure mode orthogonality in the azimuth. If this is what OAM is all about then I totally confirm my first impression that the Venice experiment is just a 'sum' (l=0) and 'difference' (l=1) pattern diversity encoding. Higher order beams will need to generate and encode the exp(j*l*phi) term for l>1. We are talking about establishing orthogonal beams in free space and there is nothing 'revolutionary' here at all ! MIMO includes the case of using orthogonal beams. If I am not mistaken these LG beams are used in optics to demonstrate 'optical tweezers' where perhaps the 'angular momentum' notion is meaningful. In the radio experiments all this is not very relevant or meaningful (I do not see what quantum mechanics has to do with the Venice experiment….).
This is actually a subset of MIMO, which is already widely used in WiFi
and other wireless networks. Thus it will, regrettably, not give access
to any additional bandwidth. The details on the equivalence is in a
paper from IEEE Transactions on Antennas and Propagation, titled "Is
orbital angular momentum (OAM) based radio communication an unexploited
http://twitter.com/bothide Bo Thidé
We have read the paper and I am sorry to say that the author has misunderstand the very concept of OAM. The article in question is merely a mathematical model analysis of the linear momentum (not the angular momentum) of what is known as phase modes. it essentially only repeats the results that we published in our Physical Review Letters paper already in 2007 where we showed that such phase modes may, in certain cases, contain the fundamental physical observable OAM and that therefore already existing radio technology can be used to produce, at least approximately, OAM radiation eigenmodes. However, not all phase mode contain OAM and vice versa. There are many more and better ways to create OAM than to use phase modes. This is totally overlooked in the IEEE paper mentioned. The author also overlook that OAM is a quantised property and therefore allows for a much higher information density (bits per photon) than current MIMO techniques.
Radio antenna technology as we know it today is solely based on linear momentum and force, i.e. on the translational, typically oscillating, motion of electric charges (Newton's second law). OAM is most effectively produced by "antennas" that instead work on the principle of anuglar momentum and torque (Euler's second law). Very interesting results in this area have been obtained by Bill Phillips, Nobel Laureate in Physics 1997, at NIST (http://en.wikipedia.org/wiki/William_Daniel_Phillips) and others but this atomtronics technology is not yet applicable in the low-frequency radio range. However, as mentioned above, using the phase modes that we discuss in our 2007 PRL paper to produce OAM eigenstates to a good approximation in low-frequency radio, we already today have a means to investigate OAM radio experimentailly. Another one is demonstrated in the Venice results where we used a monoithic antenna to generate OAM rather than a phase mode antenna array.
A step in the direction of atomtronics "antennas" for radio are spintronics "antennas" currently studied intensively by many groups. In such antennas the elctrons do not move at all as in the antennas that are used in radio today. I.e. the conduction property is not used. Instead it is the spin property of the electrons that moves and constitute an almost perfect super-current. That such currents do indeed radiate in microwave despite the fact that the electrons do not have any translational/oscillatory motion whatsoever have recently been experimental demonstrated. The results have been published in Science, Nature, and elsewhere. The generalisation to include not only the spin degree of freedom but also the orbital degree of freedom, i.e. to expand from spintronics to atomtronics to use the both spin currents and orbit currents, is in principle straightforward but it will take time before this technology will be available for angular momentum radio applications. Until then we will in our OAM radio experiments use phase mode antenna arrays, sprialised parabolic antennas (as in our Venice experiments) and several other not yet published techniques.
One thing we show
in our paper is that the OAM generating technique in your 2007 paper is
equivalent to MIMO.
If you
instead choose to generate the OAM modes by classical phase plates, either transmissive or
reflective, flat or parabolic, then you need one such specially designed
antenna-phaseplate combination for each OAM channel you are going
to use. I.e. for four channels you need four antennas at each end of the link. Traditional
MIMO already gives four channels for four antennas at each end. Thus you will not gain anything over MIMO by using these designs either for generating OAM modes.
http://twitter.com/bothide Bo Thidé
As I wrote in my earlier long comment, we purposedly used conventional radio techniques, encompassed in MIMO. to show that the resulting radiation contains OAM. More specifically, we deliberately chose a circular array of a well-known type that is used in many different situations, including aircraft navigation, to show that the radiation contains not only linear momentum (Poynting vector) but also angular momentum. This is in itself important since when a radio beam contains OAM there appears a new type of Doppler effect:
(see Courtial, J., Robertson, D. A., Dholakia, K., Allen, L. & Padgett, M. J. Rotational Frequency Shift of a Light Beam. Phys. Rev. Lett. 81, 4828, 1998) that may implicate the navigation reliability if the aircraft is banking, say. At least it is essential that this effect is studied. But without us showing that the particular, conventional circular antenna array that we studied may contain OAM we would not be aware of this possible jeopardy.
Please note that a circular array is not NECESSARY to produce OAM. What we showed, though, is that is it SUFFICENT, which is an entirely different thing! And please do not mix up an antenna engineering trick (MIMO) with a deeply fundamental physical phenomenon and property (OAM).. OAM is not a matter of combining antenna currents; in fact, as I also wrote in my earlier long comment: To produce OAM modes you should preferably avoid antennas of the type that is used in MIMO.
However if, for some reason, one chooses to use conventional
conduction current antennas to produce OAM modes, this is a significantly more efficient use of the array than MIMO. This is due to the quantum properties of OAM. For instance with 10 conventional conduction current antennas it should be possible to produce somewhere between 500 and 1000 independent OAM transmission channels whereas MIMO can at most produce 100 (10×10) such channels. In Italy, with its proud radio (Marconi) and physics (Fermi, Majorana) tradtitions it might be possible to experimentally verify this and this is what we are working on right now (I am typing this from my low-cost hotel in Padova…)
Furthermore, atomtronics-based detectors, optically cooled to sub micro-Kelvin temperatures, have between 60 and 90 dB less inherent noise than even the best conventional conduction current antenna detectors available. Unfortunately, we do not have enough funding to follow up this lead ourselves but have been forced to give the idea away to our colleagues in Europe and the US where OAM research is not discriminated but gets its fair share of funding.
Ove Edfors
Regarding dimensionality: Achieved capacity grows linearly with dimensionality and the number of independent channels that can be created is therefore very important. With 10 antenna elements/ports (on each side I assume) Bo Thidé claims that 500 to 1000 independent OAM channels can be created. Unfortunately, I do not find the arguments that lead to these numbers and they seem way too high. I think extreme claims require extreme evidence and choose to wait for a more detailed explanation. The corresponding number of 100 channels given for MIMO (10×10) is however incorrect. It is only possible to create 10 independent channels (on "the same frequency"). The number of channels in MIMO is limited by the the number of transmit antenna elements or the number of receive antenna elements, whichever is smaller.
Regarding signal-to-noise ratios (SNRs): Achieved capacity only grows logarithmically with SNR and it is therefore a much more difficult way of increasing the capacity. With extreme cooling of the detectors down to sub micro-Kelvin, as discussed by Thidé, it would be possible to increase the SNR and the capacity. I do, however, think that this is beyond the point when putting this forward as something that can improve WLAN and TV transmissions.
http://twitter.com/bothide Bo Thidé
Based on our analyses we are convinced that we can substantiate our claims and provide experimental confirmation of them in terms of capacity. But in order to do so we need funding. Without funding these expensive experiments will be impossible to perform and since you and/or your radio engineer colleagues constantly refuse to recommend funding in your peer reviews of our proposals to the Research Council, we will not be able to provide the proofs you require and therefore you will not recommend funding and therefore we cannot provide proofs and therefore… Catch 22 – the really vicious circle version – at play!
Comments such as "OAM is not physics – it's nonsence" are not meant to build confidence and respect. This is why we seek funding and collaboration outside Sweden.
If any scientist claims that he or she has the final solution to all problems in a field of physics then I, and most other colleagues, will get really suspicions. With all respect, we may not necessarily share your almost religious belief that MIMO solves every existing and future problem in electrodynamics and that therefore no other research than MIMO is worth funding anymore..
Ove Edfors
Dear Bo, I hope that some of us, including you, can still have a serious debate on the core topic. I also hope that I have not written anything that can be interpreted differently. You may confuse me with someone else when you say things like "your almost religious belief that MIMO is the final answer". I don't think that I have ever said or written anything that can be interpreted that way, anywhere or anytime. I can also, without hesitation, say that I have never stated that "OAM is not physics – it's nonsence".
What I have said, througout this debate (maybe not 100% clearly everywhere), is that OAM does exist and it can be used to carry information in the RF range of frequencies. I also agree that the OAM can be as high as one may wish. This is not where the debate is. I say that transmitting information using OAM works. I just can't find the arguments that will convince me that this is something fundamentally different from what can be done with traditional MIMO. Both you and I have shown the similarities and how OAM can be generated using MIMO technology where simple antennas that do not generate OAM themselves are combined. I even showed that the well known methods for analysing/designing MIMO systems gave exactly the same transmitter structure as the one you use in your 2007 paper to show that you can create EM fields with a certain OAM. I just cannot see how they are fundamentally differ from each other.
Again, I hope that this makes my position more clear.
Hi Ove! I fail to understand how you can misunderstand everything Bo Thidé writes, and do it so fataly.
Your unwillingness to understand is showing in your comments and it is revealing you,
you're just trying to discredit Bo Thide's work.
Dear AndersJJ, I read your paper in the IEEE Transactions on Antennas and Propagation and I do like it! It makes a lot of sense. Trying to use free-space naturally orthogonal beams (Laguerre beams, as done in optics for radio waves is not very practical either: Needs line of sight, careful alignment (imagine if the 'vortex/null'in the middle is aligned with one of the Rx antennas…). The beauty of MIMO is that it does not require orthogonal 'beams' to work, just independent ones which are revealed through the SVD process. Part of these misunderstandings are due to the different 'language' used by engineers and scientists. MIMO is not a 'trick' really, from the physics point of view it does what the orthogonal beams do (Laguerre or even Hermite if you like) but in a much more general way: With any antennas (not special ones to generate the required beam patterns) and under any environment (in buildings with multipath, with line-of-sight or not etc.)….However, people should keep trying to push the enevope and this is a nice attempt…
Dear AndersJJ, Bo Thidé's work is absolutely not a "subset of MIMO". That is a ridiculous conclusion and you know it! You do all you can trying to take credit for the work of Bo Thidé's team.
Thomas Menzel
But if this work is so groundbreaking, why does this site seem to be more or less the only one where it is discussed?
This is actually a subset of MIMO, which is already widely used in WiFi
and other wireless networks. Thus it will, regrettably, not give access
to any additional bandwidth. The details on the equivalence is in a
paper from IEEE Transactions on Antennas and Propagation, titled "Is
orbital angular momentum (OAM) based radio communication an unexploited
Yony Torres
Would this increase or at least make more feasible for waves to produce health problems due to the highly saturated "air" with radio signals?
http://natanael.posterous.com/ Natanael L
Health issues can only be caused by EM radiation if it interacts with the body. This does not increase the energy in the EM radiation by itself, and I see no reason to believe that the OAM properties themselves would make the body respond harmfully to the EM radiation (radio signals). Molecules would have to be broken, created or stimulated in some way by it to have an effect.
Kyle Mink
The use of a parabolic reflector means this can only be employed directionaly. Not so well suited for cell phone networks, transmitting TV, or any other omni-directional type of broadcast. Unless I'm missing something…
http://twitter.com/skyfoxx skyfoxx
Cell phone towers use directional antennas set up in a triangular configuration. Each of the three sections provides 120 degrees of coverage to provide 360 degrees of coverage for the area the tower services. It's certainly possible that this could be used for cellular networks.
志平 李
clear allclose allclc%
lam = 3e-2;r1 = lam;r2 = 2*lam;
num1 = 8;num2 = 16;
delta1 = 2*pi./num1;delta2 = 2*pi./num2;
phi1 = 0:delta1:(2*pi-delta1);phi2 = 0:delta2:(2*pi-delta2);
X1 = r1.*cos(phi1);Y1 = r1.*sin(phi1);
X2 = r2.*cos(phi2);Y2 = r2.*sin(phi2);
figure(1)plot(X,Y,'o','LineWidth',2,'MarkerEdgeColor','k','MarkerFaceColor','g','MarkerSize',10)axis equal;grid on;
%OAM Orderl1 = 2;l2 = 2;w1 = exp(j*phi1*l1);w2 = exp(j*phi2*l2);W = [w1,w2];
%sum patternN_theta = 64;N_phi = 128;theta = linspace(0,pi./2,N_theta);phi = linspace(0,pi.*2,N_phi);for p=1:N_theta for q = 1:N_phi u = sin(theta(p)).*cos(phi(q)); v = sin(theta(p)).*sin(phi(q)); U(p,q) =u; V(p,q)=v; Pattern(p,q) = sum(W.*exp(j*2*pi./lam.*(u.*X+v.*Y))); endend figure(2)contourf(U,V,abs(Pattern))axis equal;
志平 李
I have simulated the radio vorticity in RF band.The fact is right and clear , but how can the "normal" TV antenna (Yagi-Uda) decode the vortex? how can be the receving OAM mode order given to the normal antenna?
cl maxwell
Wow…..pardon the twisted Italian pun….But, this is bigger than sliced pizza! Climbing roof now and taking slice out of dish =p
But the real work of develope simulations of vortex radio waves have been done by a student that prof.Bo Thidé lied in front of when Siavoush called "Sia" Mohammadi did his graduate paper at the Institut for Space physics (IRF) at Uppsala University here in Sweden 2006.
Siavoush "Sia" Mohammadi was "shadow" postgraduate during 2 years when Mr.prof.Bo Thidé sad that "Sia" would get his postgraduate employment and nothing hapened.
Siavouch Mohammadi have reported prof.Bo Thidé to postgraduate representative at Uppsala University where postgraduate board have taken up Siavoush Mohammadi case.
Prof.Bo Thidé is weill known to make this in system for let postgraduate students to get very low payment or not getting an really postgraduate employment.
Elettra Mari
Have you some scientific argument about the paper?
Or do you want to talk about Prof. Bo Thidè?
Does he pay his students enough?
His office in Uppsala is definetely too big!
Is his haircut nice?
Don't you think that his house is too much for a Professor?
Please, be serious. That is not a personal war.
This is a discussion about a scientific paper.
It you translate this article in swedish to your language, you can read about that professor Bo Thidé have made it systemtically to
ignore postdoctorate students payment and take postdoctorate students work and call it his work.
"Sia was shadow postdoctorate for 2 years" says the title.
Prof.Bo Thidé is professor at Institut of Space physics (IRT) which is a part of Institution of Physics and Astronomy at Uppsala University.
It was Siavoush "Sia" Mohammadi who made the basis of this about vortex radio waves.
Prof.Bo Thidé does not mention Siavoush Mohamamdi as the individe who made the basis work of vortex radio waves.
Why, do you think?
Elettra Mari
Again, we are discussing about a paper, not about Prof. Bo Thidè.that's it.
So when prof.Bo Thidé have taken "his" idea from a postdoctorate work it does not matter!
http://natanael.posterous.com/ Natanael L
In a scientific discussion, it does not. It has zero effect on the value, meaning or usefulness of the science.
If you want to discuss him as a person, do that elsewhere. Maybe in a discussion about if he's worthy the funding, but not in here.
It is just in a discussion about prof.Bo Thidé "idea" this discussion about WHO have really done the basic work for vortex radio waves at Institut.for Space Physics at Uppsala University here in Sweden.
In the academic research world stolen ideas is very common because the academic levels of is based on prestige.
So it is just HERE this shall be knowned.
Vortex radio waves will anyway be more long lasting
than Malmoe vortex skyscraper Turning Torso that now
is for sale.
HSB Malmoe do not want to own it.
Turning Torso will no one acknowledge in future!
As Bo has already explained, OAM were known before their first application to radio transmissions, but their physical nature was debated. The most recent original theoretical work on them was done by Fabrizio Tamburini and Bo Thide. They demonstrated that OAM is a property of the EM field and not of individual photons. However, much theoretical work, many numerical simulations and many laboratory experiments were done just at the University of Padova by Fabrizio, Gabriele Anzolin, Elettra Mari, Anna Sponselli, and, in part, also by myself . In particular, the first telescope experiments using star light were carried out at the Asiago Observatory (Padova University).
Fabrizio Tamburini was a student of mine and I soon noticed his geniality. Sometimes people who possess geniality and have new ideas find any kind of obstacles in their life even when one like me does his best to help. Fortunately, sometimes, intelligence prevails. Here, nobody has exploited anybody else!
We all have worked as much as possible. And we are proud of it!
In all cases, I have enough scientific credit and experience to immediately recognize a fake !
So translate this swedish article from Uppsala University students news item "Ergo" to Italian.
Academics in Italy have of course much more of this than we have here in Sweden.
Elettra Mari
Hi all.
I'm reading all the comments and that someone even arrived to personally attack Prof. Bo Thidè, or to discredit the paper just because the main authors are all italian.
Well, shall we coming back to Physics?
In this paper we have demonstrated a principle: it is possible to encode information in OAM states, in the same frequency.
OAM is a degree of freedom of the EM field, MIMO is an engineering trick. They are deeply different.
In optics there are a lot of peer reviewed papers about OAM, with developed theory, experimental tests and applications in several fields. There are several groups working on OAM, but the studies are usually within the visible bandwidth.
As Maxwell's equations are equally valid for all wavelengths, OAM can be carried also in radio frequencies. Based on this fundamental principle we have studied diffractive optics in the radio domain, presenting the first experimental evidence of a radio vortex.
( http://apl.aip.org/resource/1/applab/v99/i20/p204102_s1 )
Venice experiment exploited the results of this first experimental paper.
We have shown a new possibility in radio communication based on a physical quantity(OAM). Of course the development of the technology is open, Venice experiment was just the first step.
Elettra Mari – co-author
Ove Edfors
I think engineers are up to more than performing tricks. Your statement that "MIMO is an engineering trick" made me believe that there may be some differences in how we (I'm an engineer) understand MIMO. Let me try to put this into some perspective.
If it is possible to use OAM to carry information, in the RF range of frequencies, is very possible and not what is debated. This has been shown both theoretically and experimentally. To be able to transmit and detect OAM states in the optical range, we use e.g. spiral phase plates. This way we can create the OAM states by successively delaying parts of a beam with azimuthal angle. The "receiver" on the other side could use a spiral phase plate, with the spiral in the other direction, thus converting the corresponding OAM state to a planar laser beam. This is what we would call a "matched filter receiver", as engineers. To create beams with different OAM states, we need different phase plates. This is, in a wide sense, what was demonstrated in Venice by using a modified parabolic antenna acting as a reflective "phase plate". This is what I would call a "geometrical" way of introducing the increasing delays with azimuthal angle (where we use properties of materials and geometrical shapes).
In the optical range of frequencies we do not have many choices but to use "geometrical" devices to introduce a linearly increasing delay with azimuthal angle. In the RF range of frequencies, however, we can control and detect both amplitude and phase very accurately. It is therefore possible to use several "geometrically" simple antenna elements where we control, most importantly, the phase/delay on the signal delivered to each antenna element. The combined EM field from these antennas can then be made to show the wanted OAM properties. We only need enough antenna elements. This is what Thidé et al did in the 2007 PRL paper. In particular, you can generate any OAM state, and any combination of them (at the same time) using the same fixed array of "geometrically" simple antenna elements. You don't need to fabricate specific antennas to create each OAM state with a different geometry. The accurate control of the phase of input signals to each antenna element is what makes it possible to to this in the RF range and not in the optical range of frequencies. From an engineers point of view, this is the beauty of it. At the same time, this particular way of precisely controlling phase and amplitude to multiple antenna elements, has been thoroughly investigated and we already know which phase/amplitude combinations on the different antenna elements that give us the best capacity of information transfer. This is the core of MIMO, that you call an "engineering trick". As was shown in the a paper by me and a co-author in th the February issue of IEEE Antennas and Propagation, it is only for very specific configurations that the linear phase delay with azimuthal angle (i.e. OAM) is the optimal one. In almost all situations, except for the artificial one we created, other solutions are better.
I hope this made our point somewhat clearer.
Thank you for your explanation. Obviously, there are many technical problems that are, in fact, actually addressed by Fabrizio and Bo, and I'm sure that they will consider the work you made.
However, I wish to stress the fact that the Venice experiment came after having achieved a better physical interpretation of OAM states. Some simple aspects of the phenomenon, and of the transmission itself, were not so obvious before.
The physical interpretation of OAM states has also produced new applications in astrophysics (how to detect Kerr black holes) and in nano technologies (with the collaboration of prof. Filippo Romanato). A correct theoretical interpretation can often suggest the appropriate solutions to some of the many technical problems. Besides this aspect, technology is sometimes unpredictable…
http://twitter.com/bothide Bo Thidé
The correct and complete description of the dynamical state of a physical system (billiard balls, electrons, the atmosphere, sound fields, electromagnetic fields, etc, etc) requires that one specifies both the system's translational and its rotational state (i.e. both its linear motion and its rotational motion) . The fundamental physical law that describes translational motion is the famous Newton's second law, a.k.a. the acceleration law (and variations of it), which states that in order to change the translational state – i.e. the LINEAR momentum – of a system, one has to apply a force. The fundamental physical law that describes rotational motion is the equally famous Euler's second law, a.k.a. as the law of momentum (and variations of it), which states that in order to change the rotational state – i.e. the ANGULAR momentum – of a system, one has to apply a torque. The linear momentum is, in the general case, totally independent of the angular momentum, so one has to use BOTH to fully characterize and control the system. This fundamental law of nature was proved already 1776 by Euler. No engineering tricks or techniques, not even MIMO, can invalidate this hard fact. Mathematics or clever engineering can never outsmart Nature.
So, a correct and complete description of the dynamics of a charge has to include both its linear momentum and the angular momentum of the charge. The same is true for the photons that are generated by the charge in question. Hence specifying, controlling och manipulating only the electromagnetic linear momentum (to which MIMO is currently constrained) is NO sufficient to get the maximum information. Angular momentum provides the missing part. This is what our research is all about. If we find time, and above all funding, we will pursue this to learn more about OAM. One thing we want so do is to show how MIMO tricks (multiport techniques) can be applied also to the orbital angular momentum modes of radio waves. What's so frightening about this? Why must our OAM research be stopped at any cost? Scientific censorship and does not belong in a modern society!
Ove Edfors
If I understand your argumentation above correctly, you implicitly say that the circular antenna array used in your 2007 PRL paper (which is a perfectly good example of a traditional MIMO transmitter array) cannot generate OAM? This makes me somewhat confused. I thought that your 2007 paper actually shows that, by using a configuration of simple antenna elements fed with the proper signals, you can generate EM fields with OAM.
What our 2007 PRL paper shows is that in certain special cases (including radiating into free space and not into a medium) a circular array may generate *approximate* OAM states (you got that right in your IEEE article). At the same time this array will generate ordinary linear momentum (Poynting vector) modes but with different characteristics and properties. These two co-exisitng modes do not even propagate in the same direction! And one can in fact construct a generalised version of this kind of array radiate essentially only OAM so that your MIMO antennas would not pick up very much signal at all whereas we would have no problems with that with our OAM sensors (let me iterate once again that "antennas" that use angular momentum current directly would be preferable). This discovery of us thus opened the possibility to detect OAM radiation from space by using existing and upcoming distributed radio telescopes (LOFAR, SKA, LOIS). If we would have been able to do so in Sweden, we believe that this first for Swedish physics would have reflected positively on Swedish science. I am not convinced that the constant mocking of our project and stubborn refusal to give it funding necessarily reflects only positively on Swedish research policy.
A quote from the congratulation speech by professor Sir Michael Berry (http://www.phy.bris.ac.uk/people/berry_mv/index.html) on the occasion of our OAM radio experiment in Venice, Italy, 24 June, 2011, as recorded on YouTube (http://www.youtube.com/watch?v=xTSuECvAMoA&feature=related
at about 05:40 into the recording):
"We are celebrating a beautiful but rather strange experiment. It's beautiful especially to me as physicist, because your local astronomerFabrizio Tamburini and his colleague Bo Thidé from Sweden here have invented a new way to transmit radio waves using a fundamental property of all waves.
Well, as well as being a clever invention for radio – here in the land of Marconi of course it's very appropriate – this illustrates somethingfundamental about science. It's a collective as well as an individual creative activity. And different people have very different imagination, so you can never predict how an idea will suddenly reappear. I'm delighted with this unexpected application of wave vortices and I want to congratulate you Fabrizio, and you Bo, on theirinvention. It's a great honour to be invited here to celebrate this demonstration this evening and I thank you."
Ove Edfors
I have no real knowledge about how OAM detection can assist in the understanding of the universe, when applied in the area of radio astronomy. I therefore refrain from making any comments on that, beyond that it may very well be an extraordinary contribution in that area.
My questions are entirely related to the wireless communications applications. I hope you do not find them to be a "constant mocking". I'm merely trying to understand if and how this may revolutionize wireless communications, as do many others in my field of research.
Maybe you can start by explaining: "And one can in fact construct a generalised version of this kind of
array radiate essentially only OAM so that your MIMO antennas would not
pick up very much signal at all whereas we would have no problems with
that with our OAM sensors (let me iterate once again that "antennas"
that use angular momentum current directly would be preferable)." In your Venice demonstration you used two Yagi antennas, where you combined the received signals to decode the two channels (measuring the OAM by exploiting the phase difference between the two received signals). This seemed to work pretty well and I would call this a pretty "standard" MIMO receiver.
http://twitter.com/bothide Bo Thidé
I will refrain from discussing antenna technology and other engineering aspects. We do physics research that can oopne the doors to more efficient communications, not designing prototypes for such systems. We are physicists – not engineers.
Ove Edfors
I'm sorry to hear that you are
refraining from continued discussion on the wireless communications
(engineering) aspects of this. I have interpreted your multiple press
releases and appearances in media over the last few years, with
claims about revolutionizing wireless communications, as an
invitation to a constructive dialog with researchers in that area. I
guess that was an incorrect interpretation.
Bo Thidé: I am not aware of the articles you refer to, that show that wireless communications has experienced a revolution through the introduction of OAM, if we by wireless means RF and not optical systems. I would be most interested if you could provide me with some references.
http://twitter.com/bothide Bo Thidé
Those claims are not mine or ours. We have essentially only cited articles where these claims have been substantiated again and again in well-designed experiments. If you think that those articles in Nature and other similar journals that show that wireless communications has experienced a revolution due to the introduction of OAM modes are wrong you should write articles in Nature, Science that prove them to be wrong..
Dear Bo, FYI – In the early 90's I was informed that a 'Torsion based' communication system had been created which enabled communications to be sent directly through the earth rather than around it or carried through the atmosphere. Fundamentally, the system enabled a call from one mobile device to be received by another on the opposite side of the earth. The connection going directly 'through' the planet. Am wondering if you have ever heard of this, even though it was never announced publicly!
http://twitter.com/bothide Bo Thidé
If you familiarise yourself with astrophysics and radio astronomy you will find that the potential for extremely interesting discoveries is very high by analysing the vorticity of radiation from the Universe since this vorticity would make it possible to obtain much better understanding of the physical processes in the Universe. And it is for this kind of important research we seek funding every year – not to design radio communication prototypes or to forbid MIMO research…
Ove Edfors
Can you please give me some references to "articles in Nature and other similar journals that show that wireless communications has experienced a revolution due to the introduction of OAM modes"? I was under the impression that most such articles were discussing the optical frequency range, not the RF frequency range we are discussing. I may have missed something here.
http://www.facebook.com/people/Jeff-Cauhape/100000703239998 Jeff Cauhape
If the polarization of the two test signals was induced by the shape of the same antenna, then both signals would have the same polarization and nothing really has been proved. I think a better solution would be to used 2 yaggies on each end, at 90 degrees to each other. Then each signal would be fed with a different phase delay, and then you would truly have different polarization being sent.
Elettra Mari
We used two antennas for transmission: yagi antenna for the "normal" signal, i.e. without OAM, and the cutted parabolic antenna for OAM-signal.
Anyway, polarization has nothing to do with OAM.
Yes, believe or not, polarization has nothing to do with OAM !
Elettra, I don't feel like we should repeat it once again.
Instead, I do think that you and especially Bo have already given quite exhaustive answers to all the main questions asked.
For now, "That's what it's all about".
The Italian researcher group who don´t beliave that professor Bo Thidé have done something ugly against his postdoctorae students as he have done against Mr. Siavoush "Sia" Mohammadi can translate this article from the Ergo paper as Uppsala University students paper.
http://profile.yahoo.com/BWQYWJ7F2HRKNLTWTK5BYZUBGY TAB
Sounds great and I hope it works out. Probably just the fearful in me, but I wonder if the end result will fry goats, cows, and humans(?) : ).
http://natanael.posterous.com/ Natanael L
No, you don't add (much, or any) additional energy to the signals to do this.
Have there been any tests to see what biological effects are possible from such waves?
See www2.i-med.ac.at/medphysik/tweezerpage.html
Fabrizio Tamburini
I am sorry to say as we see that some people really need to come back to study electromagnetism in the high school at least.
Maybe a pedagogical introduction to the invariants of the EM field might be useful.
It is interesting how many people do not understand the difference between spin polarization and orbital angular momentum, for example. Or to misunderstand phase tuning of mobiles with a physical principle. It is funny.
In the meanwhile, if someone is not an expert of the field, he could try to read the papers and book by Fuschich and Nikitin.
Moreover, a physical principle is not a technique. MIMO is not a physical principle but can use partially a physical principle. The cited IEEE paper is valid only in a small set of assumptions, it can be trivially shown with simple mathematics and this will be the subject of our forthcoming work, as better explanations are needed, as I can see.
Ove Edfors
I totally agree with you, that "many people do not understand the difference between spin polarization and orbital angular momentum". I would not go as far as saying that those "people" should go back to high school. If those who have the knowledge give proper answers to misunderstandings, everyone will gain in the end. Anything that can bring more light on this topic is good.
I do understand your point that "physical principle is not a technique", but still fail to find any convincing argumentation why OAM cannot exist in MIMO. I believe that it is there, it is just that engineers have not bothered to use the OAM terminology before to describe it. What you have done is to show a physical principle that MIMO systems can use. From my point of view, engineers have done this without explicitly knowing which property of the EM field they have used. Now you and your colleagues have explained it in terms of OAM. This is very nice and increases the understanding of the basic mechanisms.
No, I am sorry to say but you are wrong. When you say "From my point of view, engineers have done this without explicitly knowing which property of the EM field they have used", that is like saying: "Some of our ancienstors invented the wheel millions of times when they where throwing rocks down the hill, without knowing that they did!". Engineers have NOT used the physics of OAM to their benefit when they have tried squeeze speed with the help of MIMO. They might accidentially by coincident have used more than 1 OAM state, but they havn't taken advantage of it. Bo Thidé and the others do demonstrations (for the purpose of demonstration!) using common electronics, and emediately you jealous people attack him and claim his research is a fraud or whatever you are trying to say?. Read the papers again, OAM is not a subset of MIMO or whatever you guys are trying to make it look like. Shame on you! … but in the end, time will tell! You can't talk down Einsteins relativity theory. If OAM is as real and genious as I know it is, it will only be you who are constantly trying to talk it down who will suffer for your own words in the future!
My view on the claim that vortex radio waves could boost wireless capacity "infinitely" is the following:All macroscopic EM-phenomena including antennas and radio channels can be described completely by classical electrodynamics, and the classical description should be a good approximation of a quantum description. An antenna system consisting of N transmittingports (assuming that the power to the antennas is delivered via coaxial cables) and M receiving ports can, in principle, be described completely from classical electrodynamics(using eg vector spherical waves) and is well understood.In this framework, it is possible to describe the physical limitations that exists regarding the information capacity between the transmitter and the receiver when all the transmitting and receiving signals are seen from the respective antenna ports. The physical limitations of these antenna systems are well-known in MIMO communication theory and are based on Shannon information theory. Here, it is fundamental that the maximum number of independent "information channels" is equal to the "rank" (=number of non-zero singular values) of the channel between the transmitter and the receiver, at each frequency. This number is, as someone has commented earlier, always less than or equal to min(M,N). Furthermore, at very large distances between the transmitter and the receiver, as the direct path will be the dominant signal path and there are no multi-path components, the rank of an electromagnetic antenna channel must ultimately be equal to 2 (two independent states of polarization). I think this is well known in satellite communications. Hence, at a very long distance, there cannot be more than two channels at each frequency. This is fundamental, and I cannot see how it (or the other MIMO capacity constraints) could be bypassed by using the OAM states. I agree with previous comments that there is nothing wrong with the OAM states, they certainly exist and they can be used for radio-communication. It is just that they could not possibly violate the physical limitations on information capacity that is well known and relies on MIMO information theory as well as on classical electrodynamics, in particular as the OAM-theory itself also rely on classical electrodynamics?
http://natanael.posterous.com/ Natanael L
Are you talking about Shannon's theorem? Isn't that limited per channel? This creates several channels per frequency.
http://geek.com sal cangeloso
Sorry about the broken commenting on this page (for about the last hour). I've fixed it!
http://profiles.yahoo.com/u/BSZ4ON6UOA4M7M5V5AINDR2V4Y Matt
I think this is real. However I think it's going to be very difficult to separate the higher angular momentum modes with a simple antenna design. Moreover you are going to get cross-mode leakage just as you get cross-polarization leakage.
The similalrity to MIMO is there, but standard MIMO typically relies on the existence of multipath in the radio channel. This does not, and in fact multipath will not be your friend.
Ove Edfors
In fact, MIMO can be used in free space conditions as well, as long as the transmitting and receiving antenna arrays are close enough. They need to be closer than the Rayleigh distance. At high frequencies this distance may be quite substantial even for physically small arrays. Free-space or geometrical MIMO, as the technique is called, has been investigated in different forms for almost a decade. We recently published a paper showing that under certain such conditions, OAM modes identical to those demonstrated by Thide et al in 2007 are the "optimal" waves, derived using standard MIMO theory. See the link provided by AndersJJ earlier in this discussion and references therein.
"If Thide's discovery pans out, not only would wireless spectrum lose most of its value, but the trouble and strife surrounding LightSquared, international roaming, LTE rollout, white space wireless, and digital TV simply cease to be."
I still adhere to the belief that there is between a given hertz,and another hertz several thousand 'channels'of bandwidth,that there is not exactly the precicision in the transmitters,or receivers to differentitate between them. And that being so,the entire planet "should'have their own wavelength in order to communicate-given that problem is solved. IT is on one side of this,. But the physics is still on the other conclusive.
http://profiles.google.com/alien8752 Mark Fergerson
Ping Bo Thidé: your "brute force" use of a cut and twisted dish reflector is brilliant and blatantly equivalent to phase plates and y-fork gratings etc. used in the optical part of the EM spectrum. I can't imagine how anyone would confuse this with mere polarization or MIMO "antenna tricks".
I have some questions:
If the depth of the gap in your reflector were to be mechanically varied dynamically during transmission, would the OAM of the emitted radiation be modulated?
Is the OAM of light quantized such that certain gap values would result in transmissions "between" quantized values, and therefore forbidden?
Is this applicable to metamaterial research?
Can OAM-light be amplified so as to preserve its angular momentum- an OAM laser?
Do natural sources of OAM exist, or would its detection by radio astronomers be the long-awaited LGM signal?
http://natanael.posterous.com/ Natanael L
"If the depth of the gap in your reflector were to be mechanically varied
dynamically during transmission, would the OAM of the emitted radiation
be modulated?"
IIRC, it's only integers (whole numbers, no decimals). Which means there are only certain "depths" that you can use. So I assume that means you'd have to do quick jumps, not gradual changes.
I think OAM is "generated" by any rotating object, IIRC.
http://twitter.com/bothide Bo Thidé
Actually, electromagnetic (radio/photon) OAM can take any value (even a complex number). In the lab experiment in Uppsala in 2010 that preceded the one in Venice las summer, we actually used a twisted reflector that produced an OAM of -1.12. Nature of course emits OAM modes of arbitrary value all the time; integer OAM values are a pure conicidence or exception. it is only that nobody has bothered to try to observe this natural OAM radiation utnil now. All radio astronomy telescopes, for instance, are built for receiving linear momentum only. This is now changing.
Also, a circular array, which is one contraption out of very many providing a vast number of very different ways to synthesise OAM radiation, does of course not have to produce pure phase modes (multiples of 360 degrees in the phase variation around a full circuit). Any phase variation (larger than 180 degrees) will produce radiation of, what in the OAM community is called non-integer OAMi and radio voritces. The reflector that we used in the Uppsala lab experiment actually produced a total phase variation of 403.2 degrees and still worked fine to produce OAM.
OAM has an enormous flexibility and adaptability. You realise this once you study it at depth.
I am currently attending a workshop in Vienna, arranged by professor Anton Zeilinger ( http://www.quantum.at/zeilinger/ )
and today, over the lunch break, we carried out another successful OAM radio experiment over some 700 wavelengths. It is so simple to do so you can't believe it. This was also the feeling of the collected world expertise on OAM and its use in communications…
http://twitter.com/bothide Bo Thidé
Explicit answers to your questions.
1 – Yes
2 – No (see my other reply)
3 – Yes
4 – Probably (would be surprised if would not)
5 – Yes, indeed. Turbulent plasma in labs and in space, rotating black holes, pulsars, etc.
Let me explicitly point out a few misunderstandings of what OAM is and what it is not:
1. Helical states are something entirely different from the physical quantity angular momentum and OAM in particular. However, some helical modes may contain an amount of OAM. We showed precisely this in our 2007 Phys. Rev. Lett. paper where we used standard interferometry, a technique that outdates MIMO by almost two centuries. In our 2011 paper in Nature Physics we showed that EM radiation from near a black hole contains OAM. Hence, the OAM generation process is a very fundamental physical process, completely separarate from – and independent of – any antenna engineering tricks.
2. OAM is not limited to the antenna near-field. It is a conserved quantity like for instanc energy and propagates all the way to infinity. It can be focused and collimated just as the linear momentum (Poynting vector) can. Comments on "low antenna efficiency" statement are statements about the linear momentum (Poyntingvector, intensity) part of the radation , not about the OAM part of it.
3. Heisenberg's uncertainty principle for position and linear momentum requires that antennas emitting linear momentum (Poynting vector) must be separated in configuration space (or spacetime) by at least half a wavelength (see a quantum mechanics textbook). This has the consequence that a MIMO antenna becomes rather voluminous. Heisenberg's uncertainty principle for angle and angular momentum is completely different (again see a quantum mechanics textbook) and does not require the OAM emitting devices (let's, for simplicity, call them "antennas" too) to be separated in configuration space (in fact they should preferably not be separated at all in configuration space). However, it sets a fundamental limitation on the OAM "antennas" in angular space.
4. OAM has nothing to do with spherical wave expansions per se. OAM is described by a straightforward, exact, closed-form formula describing a measurable, fundamental physics quantity and not by some approximate expansions. OAM is a physical observable in its own right just as length, time, mass, temperature, velocity, acceleration, force, pressure, stress, frequency etc. are!
5. There seems to be a general misconception that the number of independent OAM channels is equal, or linearly proportional, to the number of OAM states. This is not correct.
Ove Edfors
On the web pages of Nature, Bo Thide has commented on our 2012 A&P paper where we argue against revolutionizing wireless communication with OAM. In a response I have posted the comment/letter below on the same web page (http://www.nature.com/news/adding-a-twist-to-radio-technology-1.10160).
Since much of the open discussion about OAM revolutionizing wireless communications has taken place on this page, I have chosen to publish the comment/letter here as well:
Dear Bo Thide,
I agree that our 2012 A&P paper does not provide a complete and absolutely irrefutable argumentation for the general case. It was intended as a clear and pedagogical illustration of the fact that OAM is contained within standard MIMO theory, in particular when using the type of antenna arrays you use in your 2007 PRL paper. Let me, in an attempt to remedy this, provide a more general, but consequently more abstract, argumentation that I suggest leads to the same general conclusions. I will continue to assume that we are in free space, but will now allow completely arbitrary transmitting and receiving "devices".
For any technology to revolutionize wireless communications, we need the transmitting and receiving devices to be practical. I hope we can agree on the following (very forgiving, I would say) limitations:
(1) Both transmitter and receiver must be of finite size,
(2) the time-delays incurred by our system must be finite, and
(3) the receiver must be permitted to operate at "a reasonable temperature" (possibly very low, but still non-zero Kelvin).
With these limitations, it is possible to show that OAM-based communication (or any other EM propagation based communication) is covered by traditional MIMO theory and that the large capacity gains you are predicting cannot be realized.
The more detailed argumentation is as follows:
Limitation (1) implies that we can use spherical vector wave expansions of the EM field outside some finite spheres enclosing transmitter and receiver, respectively. This leads to a complete and linear relation between the expansion coefficients of the outgoing transmitted EM field and the incoming received EM field, including any of its OAM properties.
Limitation (2) implies that only a finite number of the modes in the spherical vector wave expansion can be used for communication (possibly very high, but still finite), since the bandwidth of higher order modes quickly approach zero and the corresponding time-delays therefore grow out of bounds.
Limitation (3) implies that a receiver cannot detect the incoming field perfectly and therefore the detected expansion coefficients at the receiver side will contain some non-zero noise.
Hence, the three limitations lead to the following conclusions, which are very similar to what we illustrate in the 2012 A&P paper:
(A) There is a traditional MIMO description of the communication between the two spheres, transmitter-side to receiver-side expansion coefficients, of the type y = Hx +n. Hence, all existing MIMO theory applies.
(B) The rank of the linear relation H, between transmitter-side and receiver-side expansion coefficients, is limited and will approach rank two when the distance between transmitter and receiver increases. One dimension per polarization direction (spin angular momentum), both with OAM=0, when we separate transmitter and receiver. See [1] for an illustration.
I believe this closes our argumentation against OAM providing something beyond traditional MIMO, under very reasonable limitations.
Ove Edfors
[1] S. Nordebo at al. "On the Capacity of the Free Space Antenna Channel", In Proc. IEEE International Symposium on Antennas and Propagation in Albuquerque, pp. 3105-3108, NM, USA, 2006.
http://profile.yahoo.com/7NSJWZQBEK24NQLTKAF42D6GWI Vladimir
I have a question to those who understands OAM. How do you multiplex multiple channels with their corresponding OAM states into a single EM beam? For example, let's say we have two transmit and two receive antennas. Theoretically, I can transmit and receive two OAM states: 0 and +/-1. In the OAM=0 state, both TX antennas are fed the same signal (let's call it channel 0) with the same phase (let's say 0 degrees). In the OAM=1 state, both TX antennas are fed the same signal (channel 1 in this case) with 180-degree phase difference (let's say antenna 1 gets 0-degree phase and antenna 2 gets 180 degree phase). Do I understand it correctly that the channel multiplexingin this example looks like this:
TX antenna 1: channel 0 (0 degrees) + channel 1 (0 degrees)
TX antenna 2: channel 0 (0 degrees) + channel 1 (180 degrees)
http://twitter.com/bothide Bo Thidé
I am sorry, but I do not understand your question. Radiation (from antennas or not) comes in (at least) two forms, linear momentum (used in radio today) and angular momentum (not yet used in radio). Both of these physical observables can be used in wireless communications and both have their advantages and disadvantages. Just as we can modulate our linear and/or angular momentum radiation in different ways by using AM and FM say. The fact that there exists one modulation technique (AM) does not mean to say that it AM is optimal in all cases and that one should never use another one (FM). Both have their advantages and disadvantages and both have their use in different situations.
http://profile.yahoo.com/7NSJWZQBEK24NQLTKAF42D6GWI Vladimir
Dear Bo,
Let me explain my question. You claim that OAM states can be used to increase capacity of a microwave link in such a way that each transmitted channel gets assigned a unique OAM state. Right? Here, I use the term "channel" to describe a data stream modulated onto an RF carrier, for example 2.4GHz. The modulation can be any, AM, FM, or both. But, it is the same for all channels. So, all channels have the same carrier frequency (let's pick 2.4 GHz), the same modulation (let's pick FM as an example), the same modulation bandwidth, but different data. The OAM states can be generated by a circular antenna array with a carrier phase shift from antenna to antenna, as described in one of your papers: "Orbital Angular Momentum in Radio – A System Study". So far, all papers on this subject have been discussing how such an antenna array (or a single "twisted" dish antenna as in your most recent paper) generates only one channel with a certain OAM value. They show radiation matterns, discuss propagation properties etc. I am interested to know how multiple channels, as described above, with different OAM states are combined together in a single transmission. In other words, how does a single circular antenna array transmit these multiple channels simultaneously? Are the channels simply added together for each antenna with a corresponding phase shift in the carrier to create a unique OAM state assigned to that channel? After all, we only need these OAM states to be able to pack several channels carying different data into one transmission, right? So, my question is how do you that and how that affects the radiation pattern. For example, in your paper "Utilization of photon orbital angular momentum in the low-frequency radio domain", you use two concentric circular antenna arrays, with the internal array fed one OAM state, and the external array fed another OAM state. Is that how you intended to combine multiple channels: one antenna array per channel? I hope not.
This question can be extended to your most recent experiment in Venice, where you used a helicoidal dish antenna. Obviously, such antenna could transmit only OAM state 1 becuase of the fixed physical dimensions of the displacement at the cut. So, you used another antenna (Yagi-Uda) to transmit OAM state 0. But, in a practical application, to be able to claim a capacity gain, you must show that the same antenna (or antenna array) can transmit more than one OAM state (channel) simultaneously. It is hard to transmit several OAM states simultaneously with your dish antenna. Even if you make moving reflectors so that the same dish antenna can be tuned to a different OAM state, it will still be just one OAM state per a specific position of the reflectors. So, I don't see how such antenna can transmit several OAM states simultaneously. That is why I mentioned the circular antenna array as a more practical way to achive a simultaneous multi-channel transmission. But then, my original question is how do you combine these channels? And what happens to the radiation pattern?
I hope my question is clearer now.
Our experiments have so far been of a fundamental physics "proof-of-principle" nature, and not OAM "antenna" engineering research and development aiming at a final design of commercial products. They have had one purpose and one purpose alone – to prove the feasibility of using OAM for wireless information transfer over long distances also in the low-frequency radio domain. This OAM property has already been amply demonstrated at higher frequencies but it has been claimed by radio engineers that this is impossible in radio; we have now proved them wrong on this account. Believe it or not but it has in fact been claimed by reviewers that electromagnetic OAM does not even exist!
The OAM states are distinct, orthogonal Hilbert states and can therefore be superposed ("summed") precisely as you say and precisely as we showed in our 2007 Phys. Rev. Lett. paper. To achieve this in practice with a single "antenna" (which, by the way, has already been demonstrated in optics – see http://www.phorbitech.eu) is more an engineering problem than a fundamental physics one. Precisely how this will be done in practice is a matter of technology R&D, not a matter of basic physics research into the fundamental properties of OAM that is our task for the moment. The only thing we can say with certainty is that in practical radio communication applications the "antennas" will look very different from the ones we used on our Uppsala and Venice proof-of-principle experiments.
I wroe a long reply a few minutes ago and posted it here. Now it seems to have disappeared!
http://twitter.com/bothide Bo Thidé
It would be very nice if the site manager were able to put the long reply I wrote about an hour ago back on this page again. I do not feel like spending time trying to rewrite my posting from memory…
http://twitter.com/bothide Bo Thidé
I rewrote my reply to you and posted it here once again. Unfortunately it was immediately removed!! So even if I have
tried to answer your questions twice already, the site manager or whomever does not allow me to publish my answers. I really do not like censorship!!!
http://twitter.com/bothide Bo Thidé
I will try to reconstruct a succinct version of my earlier reply that for some reason was erased three times. Here goes (the fourth time I try to reply):
What we have shown, in laboratory and outdoor proof-of-principle fundamental physics experiments in Uppsala and Venice, is that it is indeed possible to use "clean" OAM at low radio frequencies to transfer information wirelessly over long distances, well into the far zone (In fact, this has already been amply demonstrated experimentally at higher frequencies; the literature on this is very abundant. Also consult the web site for the EU funded OAM research project Phorbitech to learn more about electromagnetic OAM and its use in physics, biology, medicine and technology).
With our experiments we disproved the claims made by numerous radio engineers and funding proposal reviewers that it is not possible to use OAM for radio communications (one reviewer even claimed that electromagnetic OAM does not exist!).
As we showed in our 2007 Phys. Rev. Lett. paper it is possible to superpose ("sum") different radio OAM states. However to show something in fundamental physics experiments, is not the same as to have produced a final, optimum engineering solution for a future commercial product, The EU funded project Phorbitech mentioned above have made significant steps in this direction and
has come up with at least one concept for a multi-OAM state "antenna". However, we are currently not doing any substantial amount of antenna engineering R&D ourselves. We focus on theoretical, numerical and experimental investigations into the fundamental properties of electromagnetic OAM and its use in physics and astronomy even though we have an industrial project going too.
The only thing that we can say for certain regarding the engineering and technology is that a commercial product will
definitely not have the same "antennas" that we used in our proof-of-concept experiments in Uppsala and Venice. The technology solution will be entirely different altogether.
http://twitter.com/bothide Bo Thidé
I have tried four times to reply to your questions even though they do not concern the physics but rather the engineering and antenna technology aspects of OAM. However, as you can see, my replies immediately get censored and removed by the moderator of this site. I have no clue why… So I suggest we continue off line. My e-mail is firstname.lastname@example.com. Alternatively we can discuss further on the Nature News web forum. But I am NOT interested in discussing too much possibel future OAM applications within the very limited antenna engineering framework set by today's technology. It feels rather futile…
http://www.mrseb.co.uk Sebastian Anthony
Hey Bo.
No idea what's happening to your reply. It only appeared in my inbox once, not four times. (I have copied/pasted it above, in response to Vladimir).
We are VERY lax on moderating ET comments. We don't delete or edit stuff unless it's incredibly rude or really malicious hate speech.
You probably ran into a Disqus issue, or something. Try copying the post to your clipboard/Notepad before submitting, just in case :)
http://www.mrseb.co.uk Sebastian Anthony
Here is Bo's reply:
I will try to reconstruct a succinct version of my earlier reply that for some reason was erased three times. Here goes (the fourth time I try to reply):What we have shown, in laboratory and outdoor proof-of-principle fundamental physics experiments in Uppsala and Venice, is that it is indeed possible to use "clean" OAM at low radio frequencies to transfer information wirelessly over long distances, well into the far zone (In fact, this has already beenamply demonstrated experimentally at higher frequencies; the literature on this is very abundnant. Also consult the web site for the EU funded OAM reserch project to learn more about electromagnetic OAM and its use in physics, biology, medicine and technology).With our experiments we disproved the claims made by numerous radio engineers and funding proposal reviewers that it is not possible to use OAM for radio communications (one reviewer even claimed that electromagnetic OAM does notexist!).As we showed in our 2007 Phys. Rev. Lett. paper it is possible to superpose ("sum") different radio OAM states. However to show something in fundamental physics experiments, is not the same as to have produced a final, optimum engineering solution for a future commercial product, The EU funded project Phorbitech mentioned above have made significant steps in this direction andhas come up with at least one concept for a multi-OAM state "antenna". However, we are currently not doing any substantial amount of antenna engineering R&D; ourselves. We focus on theoretical, numerical and experimental investigations into the fundamental properties of electromagnetic OAM and its use in physics and astronomy even though we have an industrial project going too.The only thing that we can say for certain regarding the engineering and technology is that a commercial product willdefinitely not have the same "antennas" that we used in our proof-of-concept experiments in Uppsala and Venice. The technology solution will be entirely different altogether.
termenlab termen
Gugliermo Marconi wasn't fluent in italian
but strong in english and bolognese vernacular
Why ? here's the reason :
From Italian Royal Navy to G. Marconi esq.
Dear Sir
it is impossible to transmit wireless
telegraph signals…
termenlab termen
Gugliermo Marconi wasn't fluent in italian
but strong in english and bolognese vernacular
Why ? here's the reason :
From Italian Royal Navy to G. Marconi esq.
Dear Sir
it is impossible to transmit wireless
telegraph signals…
termenlab termen
Gugliermo Marconi wasn't fluent in italian
but strong in english and bolognese vernacular
Why ? here's the reason :
From Italian Royal Navy to G. Marconi esq.
Dear Sir
it is impossible to transmit wireless
telegraph signals…
http://natanael.posterous.com/ Natanael L
First of all, how is buildings related to radios? Or is it actually a radio antenna in secret? :p
Second: It's Sweden's tallest building. I'm sure somebody will want to buy it.
Nobody want to own the vortex skyscraper Turning Torso because it is a symbol of HYBRIS.
When a people´s movement based property motion organisation as HSB is. When their department in Malmoe believe that a small town can be bigger just because of the height of a skyscraper housing.But a small town as Malmoe with less than 300 0000 inhabitans can´t be a city only with a 54-level skyscraper building.
http://natanael.posterous.com/ Natanael L
Now you're just trolling.
Malmoe Totem pole the 54-level skyscraper building will no one acknowledge in 5-years.
termenlab termen
The genius maximus et emeritus in italy was not
Galileo Galilei or Leonardo da Vinci
but Gennaro Capuozzo,
from Neaples the alleged inventor of the fusillo
Nobody told him that twist spaghetti in
a spiral shape was impossible, and he did
termenlab termen
let's get serious now…
as far i understood it, the twisted reflector is
a big bad "phase plate"
and OAM is just generate in phase (SAM) and out
phase (OAM) signals on a
say, a sort of "3-D" plane, and discriminate
on arrival ???
(i apologize for my ignorance i am not a professor
but just a tricky sub-engineeer
and inveterate antenna masher ;-)
Timothy McDonald
When they are doing this with more 4 signals I will be impressed. 2 channels is easily achieved by transmitting and receiving the signal on antennas mounted at 90degrees relative to each other.
http://profile.yahoo.com/S75QHJWRQ3CU4C25RD77U3CHKY Luis
this looks like b******t. circular polarizaton has been in use for the last 20 years, but point to point line of view, and it depends on the antenna geometry. The only addition seems to be the discrimination in thread pitch. Questi sono tutti pazzi
http://pulse.yahoo.com/_YQP5ISWLCDMH2QZIM3PLYT6SCI C4T
An orbit requires a central mass, so i call bullshit as well.
termenlab termen
some suggestion about an antenna scheme
without parabolic ?
to allow perhaps lower frequency operation
where parabolic reflector is not practical..
"Maxwell was a fool, Marconi a cheater and I
invented the warm water !!!"
Perpetual Rabbit
I think with multiple antennas you can do this. A phased array antenna such as LOFAR. It should be possible to pick any number of oam modes AND directions simultaneously.
I just wonder if it will get progressively more difficult to reach the higher oam modes, say for instance l=453920234 ("rotational number")? If not, this oam technique will give a lot of room, but certainly not infinite.
I bet that higher modes are more difficult to reach, and that there are practical or technical limits to the theoretical infinity or oam modes.
I think the Russians have been doing something similar to this for years in
satellite transmissions along with ham operators.
Alexandra Williams
After four years of incredulity and not-so-gentle
mocking, Bo Thide of the Swedish Institute of Space Physics and a team
in Italy have finally proven that it's possible to simultaneously
transmit multiple radio channels over exactly the same wireless
Anthony R King
"and orbital momentum is the Earth rotating around the sun (producing the seasons)."
I just wanted to point out that the seasons aren't determined by the Earth's trek around the Sun, but rather by the tilt of the Earth itself. It's winter in the Northern Hemisphere when the Earth is closest to the Sun because that is when the Northern Hemisphere is tilted towards the Sun… for right now. In thousands of years, that will no longer be true, as the Earth wobbles back the other direction…
http://www.mrseb.co.uk/ Sebastian Anthony
Very true :) Thanks for the clarification.
http://www.gsmbooster.co.uk/?cPath=89_93 vodafone signal booster
This is nice, which can help in any situation to boost your mobile signal in order to make communication. In bad weather this is completely good way to communicate with one other.
http://www.facebook.com/people/John-Cummins/531833267 John Cummins
So, extremely cool and yet another example of why we must NOT think in terms of limited everything. We need politicians like Ron Paul who think in terms of Freedom (not "security) and in human rights terms which will unleash more and more inventions that benefit all. We must have free trade and open, free markets and do away with the dinosaur loser Keynesian Economics.
Sergio Huaman Kemper
Let's see what everybody says now: http://www.extremetech.com/computing/190408-towards-infinite-capacity-wireless-networks-with-twisted-vortex-radio-waves
Nice. Glad to see that people are properly researching SPIN axis in directional space.
The funny thing is that since electromagnetism is a 4th directional force (3 directional space in regards to the Earth has a spherical spin axis which has 1-spin direction with a unique spin velocity, a spherical tilt axis with a spin-direction and spin velocity with is separate from the prime spin, and the ability to move in any angular direction from the centerpoint of the sphere towards any point on the exterior of the sphere) they are only using a few of the 4th-directional spin angles.
A 4th-directional hypersphere interacts with 3D space by expressing force as electromagetism and other "invisible" forces when it interacts upon 3-directional space. For a hypersphere, you get another angular range and another spin-direction in play. To understand easier, think of a 2-directional circle. It has a centerpoint, can be spun either left or right and the circle in 2D space can only move in a direction from the centerpoint towards any point on the radius of the circle. These velocities can be vastly different from the spin velocities, but can only spin in one direction at a time.
An addition to Newton's Law of "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it" would need to be ammended to state, "by an equal or higher directional force". To simplify, a 4-Directional object can enact force upon a 2-Directional or 3-Directional object, but can barely move a 5-Directional (Quantum) object.
5th-Directional Objects (Photons, gravity, etc) can enact huge forces upon 3D objects, but if not operating in a contrary manner, can also enact very minor amounts of action upon lower-directional objects.
Oh, and if I fail to note this, I will feel very bad.
Playing cards.
When thrown like a piece of cardboard without spinning, will have very little kinetic velocity. When a playing card is thrown with an energetic spin, it can embed itself into soft surfaces. The reason is simply that the spin momentum ADDS KINETIC ENERGY to the playing card and as a result, has more stability and kinetic impact force.
Radio waves are not unique in this manner either.
Spin a radio wave and it is more energetic when emitted.
Which means that it can move farther with less dissipation and transmission power can be transferred into wave-spin force with an equal power output if desired.
How to impart force as a signal?
You can transmit on a frequency and modulate the time (telegraph).
You can modulate the energy of that set frequency (AM Radio).
You can modulate the frequency domain of that set frequency (FM radio).
You can modulate both the amplitude and the frequency domain.
You can spin the emitted frequency like a corkscrew at constant spin velocities and blink it on and off like a telegraph.
You can modulate the spin direction (spin + counterspin modulation).
You can modulate the spin velocity for the signal.
You can modulate the energy level of the spin (AM spin modulation).
You can modulate the frequency plus the spin velocity (FM spin).
You can modulate the spin velocity and spin angle (detected by inserting a "circle count of 01 to 15″ stream interrupt and having divided multiplexed antenna and figuring out which number on the circle count pops up first. For example, if the circle count starts with 01 to 16 then you are getting the untilted signal. If you get 08 first then 09 to 15 then 01 to 07 then the signal was modulated at a 45 degree tilt for that packet).
Constant expected signal modulation is another option.
Let us say your expected signal range is 00 to 15.
You expect that the signal is streaming a constant digital repeat of the hexadecimal digits of Pi (3.1415926… in Base 10) for 256 digits.
So you have hexadecimal digits of Pi on constant 256 digit repeat, but ever other digit is a XOR addition of your sent signal. So your signal looks like this.
Hex Pi (Digit 01)
Hex Pi Digit 01 XOR'ed first digital packet result
Hex Pi (Digit 02)
Hex Pi Digit 02 XOR'ed second digital packet result
Hex Pi (Digit 03)
Hex Pi Digit 03 XOR'ed third digital packet result
… and so on.
Since you know what your signal is supposed to be it is easier to decode it.
Now let's say you have no recognizable Hex Pi digits, but you know the signal is encoded in this manner.
Well, what if you kept track of the difference values of Hex Pi digits?
Hex Pi (a few of the first digits)
Difference between the digits.
So if you receive a constant weak signal of Hex Pi of (-2 strength which results in anything equal or less than 2 becoming zero):
The expected Hexadecimal difference between digits becomes:
So your check values with your interleaved signal can tell how weak the signal is, where the digits have dropped off and how much to correct for the Hex Pi and digital XOR'ed signal.


text:
Machida still wants to stay busy, targets Gustafsson if Jones' time off lengthy | News
As it currently stands, UFC President Dana White has declared Lyoto Machida (19-3 MMA, 11-3 UFC) the promotion's current No. 1 contender at light heavyweight. But if the division's champ isn't cleared to fight until the end of the year, "The Dragon" has another plan in mind.
Soares and Machida were in attendance at Saturday night's UFC 159 event, which took place at Prudential Center in Newark, N.J., and featured Jones (18-1 MMA, 12-1 UFC) downing Chael Sonnen in the evening's main event. Machida previously faced Jones in December 2011. "Bones" won the fight by second-round technical submission, and the former UFC light heavyweight champ has pined for a rematch ever since."We just talked about it last night and this morning on the way home, and basically the way Lyoto feels about it is that if Jon Jones is not going to be able to fight until November or December, then Lyoto would rather take the Alexander Gustafsson fight," Machida's manager, Ed Soares, told MMAjunkie.com (UFC blog for UFC news, UFC rumors, fighter interviews and event previews/recaps). "If Jon Jones can fight in like August or September, then Lyoto would love to fight for the title."
The one big variable in the schedule, of course, is Jones' mangled left toe. The UFC light heavyweight champion suffered a fractured big toe during the first round of his record-tying fifth-consecutive light-heavyweight title defense, and the bone wound up protruding through the skin. Fortunately for Jones, he was able to earn a TKO finish before anyone (including himself) noticed the wound, which likely would have led to him being pulled from the fight had it been addressed before the contest was waved off.
Jones was transported to a local hospital after his win, and the toe has since been surgically repaired. Jones on Sunday took to Twitter to proclaim he wouldn't be shelved for long.
Still, MMAjunkie.com confirmed with Jones' team that the champ has yet to receive an estimate on when he may be cleared to fight again. If it turns out to be longer than hoped, the 34-year-old Machida wants to securely entrench himself as the division's No. 1 contender by taking on fellow top-ranked fighter Gustafsson (15-1 MMA, 7-1 UFC)."Screw my big toe, I'm on a mission," Jones wrote. "No time to slow down now."
Of course, there is one more potential hurdle in booking Jones vs. Machida II. Another Soares' client, UFC middleweight champion Anderson Silva (33-4 MMA, 16-0 UFC), is said to be interested in a superfight with Jones, according to White."Lyoto wants to stay sharp, and he wants to fight to support his family," Soares said. "Time is going by, and you can never get back time."
Soares declined to comment on that potential matchup, pointing instead to Silva's UFC 162 bout with undefeated contender Chris Weidman (9-0 MMA, 5-0 UFC) as the lone focus of "The Spider" for the time being.
And so, a little more than two months after downing MMA legend Dan Henderson, Machida's next booking still isn't quite clear. But Jones' next trip to the doctor's office might provide some answers. A short recovery time, and Machida is game for the rematch he so desperately wants. But if Jones is going to need a little extra time to recover, Machida is happy to stand across from "The Mauler."
"Your window of opportunity as a fighter is only so much," Soares said. "Lyoto is here to fight. He's here to his job, to stay sharp and to compete. If Jon needs time to heal, then we'd love to face Gustafsson."

subset: commoncrawl