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# Wireless breakthrough: one frequency, multiple signals

A team of Italian radio boffins – and one Swede – have one-upped their pioneering countryman Guglielmo Marconi by demonstrating a method of simultaneously transmitting multiple signals on the same frequency. "This novel radio technique allows the implementation of, in principle, an infinite number of channels in a given, fixed …

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1. #### huh?

/me looks at picture of mangled dish antenna.

/me looks at calendar, date 3/1/12, not 4/1/12.

/me repeats the above several times before continuing the article.

2. #### Yer, circular polarization, right?

http://en.wikipedia.org/wiki/Circular_polarization

1. #### Re: Yer, circular polarization, right?

It's hard to say, it certainly doesn't look like it. However I'm not sure if that's just a mangled translation, or some basic lack of understanding by the experimenters

The interesting question is if there are any serious publications on it. That would distinguish nutjobs from serious researchers.

My guess is that even if this is true, it's not much better than classical MIMO systems.

1. #### Re: Yer, circular polarization, right?

No, it's not the same as circular polarization. But it's actually equivalent to MIMO, as in it is exactly the same thing. See link to paper below.

1. #### Re: Yer, circular polarization, right?

You didn't read the paper either:

<i>"[O]ne can obtain...distinct channels on the same frequency by [using the circular] polarization (SAM), which is independent of [our magic technique] OAM. A further five-fold multiplicative factor from implementing multiplexing would yield a total of 20 channels on the same frequency. <u>The utilization of multiport techniques (e.g. MIMO) could increase the capacity further.</u>"</i>

And for everybody else: this is not mistranslated; they know what they are talking about. Angular momentum is composed of two components - the circular polarisation (which corresponds with a constantly rotating electromagnetic field vector, or the ±1 intrinsic spin of the "photons") and an "orbital component" around the axis of travel. It's the latter they are exploiting. So, at the classical level, imagine a helical path about which the field vector rotates as it travels.

2. #### Re: Yer, circular polarization, right?

No, it's not just circular polarisation.

Comments and the article need the original article links.

Institute of Physics web-site published full article from New Journal of Physics here:

http://iopscience.iop.org/1367-2630/14/3/033001/article

Direct download link for full article is here:

http://iopscience.iop.org/1367-2630/14/3/033001/pdf/1367-2630_14_3_033001.pdf

Same article is in Nature Physics (behind a pay-wall).

This is a possible additional wave analysis analogous to quadrature wave phase shift keying. Whether it has a practical application in hand-held devices such as smartphones is moot - the demonstrated antennae configuration is not practical in small devices.

So while interesting, I'd agree with others that last mile fibre optics is the future.

1. #### Moving on a little in the real world .....

So while interesting, I'd agree with others that last mile fibre optics is the future......Posted Saturday 3rd March 2012 00:12 GMT

The future to Novel Virgin Source, AC, in NEUKlearer HyperRadioProActive ITs AI in Live Operational Love Environment Energy Fields? There's an Orgy of HyperRadioProActive Resident Talent there, Field WareFare Testing. :-)

So preposterous it is most likely perfectly true too. How clever.

3. #### Re: Yer, circular polarization, right?

Try http://en.wikipedia.org/wiki/Light_orbital_angular_momentum &

http://en.wikipedia.org/wiki/Light_spin_angular_momentum

3. #### How Does This Increase Channel Capacity ??

If I understand this contraption, it is merely a mechanism of toggling the transmit antenna from one receiver antenna to the other. That does not increase bandwidth, but merely split it spatially.

Actually *doubling* can only be achieved using to spatially separated transmitters or receivers which use one dish, as seen by modern sat antennas.

Methinks the days of Italian innovation have been during the time of Leonardo da Vinci. Modern Italians can't even build petrol-powered carriages properly.

1. #### Re: How Does This Increase Channel Capacity ??

The way I understand it is that you can have many channels on the same frequency. The difference being that each one is twisted slightly and delayed. As a circle can be infinitely divided up that is how many channels theoretically can share the same frequency. Use another frequency and repeat. I maybe wrong though.

1. it would seem they could also change timing of multiple signals and have spirals layered within spirals

2. #### Re: How Does This Increase Channel Capacity ??

Well the same way MIMO does. You try to get several channels which are as independent as possible. If you can somehow send out photons in different ways and detect those photons independently, you can get several channels instead of one.

However I currently don't think this is more than just some basic misunderstanding.

3. #### Re: Italian cars

Care to explain how the modern Italians cannot build petrol-powered carriages such as Ferrari, Lamborghini, Maserati, Pagani, Alfa Romeo or even Lancia?

4. #### Re: How Does This Increase Channel Capacity ??

It doesn't increase the capacity for a given transmitter/receiver pair, but it allows more than one transmitter/receiver pair to use the same carrier frequency at the same time without interference from each other. Currently they would create interference and neither could communicate, but with this technique they would be able to filter out the correctly polarised signal and ignore the other signals.

4. #### Sounds like their reinventing...

Tesla's wireless system, which could do the same thing (lots of unique non interfering channels), only he did it without using transverse waves.

5. #### It'll never catch on*

Where's the monetisation, the competitive flogging of bandwidth spectrum etc..?

* i.e. Ofcom won't like it

1. #### Re: It'll never catch on*

You don't think that they'd find a way to sell it over and over again, each time with a different angle (or whatever)

2. #### Re: It'll never catch on*

Nor the FCC who are busily killing Bandwidth developers like ---- Light Squared http://www.forbes.com/sites/danielfisher/2012/03/02/lightsquared-battle-heats-up-as-politico-reveals-dod-e-mail/ and ------ Dish http://www.reuters.com/article/2012/03/03/dish-fcc-idUSL2E8E2EG520120303

1. #### Re: It'll never catch on*

Yes, but Light Squared rely on being allowed to go mental next to the GPS allocation. Oddly enough, the rest of us aren't too keen on that

3. #### Re: It'll never catch on* (@ David Gosnell)

I can't see final user's devices using this. On the other hand, if a pair of these rotating antennas can carry as much bandwidth as an optical cable, Cable companies could probably save lots of dough by using them for everything but the last mile. Maintaining a cable network is a pain in the ass, and laying new cable is costly, slow and full of potential trouble.

6. #### History is written by the winners..

"Since Marconi first demonstrated wireless communications in 1895,"

J.C. Bose, my all time science hero, arguably got there first:-

http://www.tuc.nrao.edu/~demerson/bose/bose.html

1. #### Re: History is written by the winners..

...and the web page celebrating the work of Mr Bose appears to be rendered in hundred year old HTML as well.

1. #### Re: History is written by the winners..

Well there''s always Wikipedia then :-/

http://en.wikipedia.org/wiki/Jagadish_Chandra_Bose

or:-

http://www.minhas.net/culture/indianpeople/jcbose.htm

2. #### Re: History is written by the winners..

And, of course, they are Hertzian waves anyway

7. Unless the signals are orthogonal they will interfere with each other. It still will not take away the fact that one fibre can currently carry 300,000 times the bandwidth of ALL the radio frequencies. Hit a bandwidth limit then run another fibre. Have another go folks. Bert

1. To my way of thinking, they should all be orthogonal or equal in the same way that all frequencies of sine waves are orthogonal or equal. So, I suppose that means that this essentially operates like a three dimensional representation of a sine wave or a three dimensional version of radio frequency.

So, I'd guess that this would actually square the entire available wireless bandwidth. Since they won't actually get an infinite number of overlapping signals. I'm sure there will be some issue with noise that will limit the actual number of available channels that can be used. However, that will probably still be enough wireless bandwidth for a decade, maybe even two.

2. #### @bert_fe

They don't need to be completely orthogonal. There is a broad range between completely orthogonal channels (which would double the capacity) and the same channel.

3. #### Re: run another fibre

If you can lay fibre between your end-points, you shouldn't be using wireless.

This development is surely aimed more at people like satellite operators. It might be aimed at other mobile uses, but it seems to require a specific relationship between the antennae of the sender and receiver, which might limit its applicability somewhat.

8. While I wouldn't mind seeing Shannon's communications theory or the second law of thermodynamics disproven, I do not have high hopes for this.

1. If it is a distinct channel, Shannon doesn't apply.

An earlier post suggested that the technique only works between matching antennae, so sender A can only be heard by receiver A, and sender B only by receiver B.

9. #### The same as MIMO

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 area?" http://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=2062936&fileOId=2339120 [lub.lu.se]

10. This post has been deleted by its author

11. #### Circular? I don't think so

It's been awhile since I did any serious wireless engineering, but the purpose of a parabolic reflector is to concentrate the signal, and to me it looks like the only thing that they accomplished was to detune the reflector and disperse the signal.

12. #### I like it

I often wonder about what would happen if you had an antenna shaped like a spiral or "the golden rule" that is if it would provide for multi-frequency use as it's size (being a spiral starting small and getting bigger) already runs though different wave lengths. Would it be like an sea shell in receving etc

The only way I understand is time-slicing two modulated sources, but this seems to be suggesting some kind of bleedover. What happens when the spectrum is full already and bleedover disrupts neighboring emissions? They need to pick a spot in the spectrum and test.

13. #### Another way to do spatial reuse

GPS supports up to 30 (24 typ) simultaneous transmissions all at L1 (~1.5 GHz). It uses orthogonal Gold codes to separate the 30 simultaneous signals. To a receiver there are 29 received sources of noise and 1 desired signal when "Gold-tuned" to the desired signal... I know this is not OAM but still in the domain of spatial reuse..

http://en.wikipedia.org/wiki/GPS_signals

14. #### Spatial reuse

GPS supports up to 30 (24 typ) simultaneous transmissions all at L1 (~1.5 GHz). It uses orthogonal Gold codes to separate the 30 simultaneous signals. To a receiver there are 29 received sources of noise and 1 desired signal when "Gold-tuned" to the desired signal... I know this is not OAM but still in the domain of spatial reuse..

http://en.wikipedia.org/wiki/GPS_signals

1. #### @videoguy

Bit of multipath going on there, I reckon.

2. #### Re: Another way to do spatial reuse

But the GPS system only splits the existing bandwidth into 30 parts (so each part has less that 1/30 of the available bandwidth) to allow 30 transmitter/receiver pairs to share the same carrier; it doesn't increase the total information carrying capacity of the signal.

15. #### Perhaps it opens-up Shannon's Law by 3dB

I suspect that the same basic concept was discussed on the 'rec.radio.amateur.antenna' newsgroup about ten years ago (circa 2001/2002). :-)

The suggestion at that time was related to H/V linear and RH/LH circular polarization from (for example) communications satellites. The concept discussed is to add a small communications window using *differential* circular/linear (!) polarization.

For example: Adding a differential RH/LH circular signal to a linear satellite. The linear receivers would never see it, but it would open-up an additional communication path. But probably just a wee little (3dB SNR tall) Shannon window.

I'd be (very pleasantly) surprised if this new idea opens anything larger in the Shannon domain than as discussed above.

16. #### looks like cartoon version of time division multiplex

No I didnt read the paywall article, paywalls are obscene for personal use... looks like some type of pipe switching MX sceme with an analog path (or really good codex) with the paths being switched a a high enough rate that the individual channels do not cross-mod on each other, the rolling of the propagation time probably helps cross-mod distortion a bunch... as this is analog, I wish them well... NOTE= ATT hit the wall of diminishing returns for Analog Radio when it took 120 watts of microwave power spread over 2 polarities of 12 Rf frequencies, each fm modulated at 6mhz to go 30 miles without cross-mod distortion on the rcvg end killing the signals on the channels... we added 5db rcvg waveguide amps at the far end... no improvement in cross-mod= we were at the limits of physics... MY THOUGHTS= AM Stereo was trialed several years ago, channel separation was quite good, perhaps 2 separate channels per freq possible with the help of this propagation time thing... Multi-path distortion will still kill complex signals, and by definition these are... Getting more than 1 commercial quality signal per rf channel is a HUGE monetary reward... Good Luck guys !

17. #### I do hope it works

so we can set up a proper working internet from our rooftops if acta goes ahead.

18. #### It will never work

The Italians will be too bust boffin each other

19. #### PS: Huge FAIL for a demo with just two signals

Also...

Frequency reuse of 2:1 via orthagonal polarization is completely and utterly standard. These guys deserve a slap upside the head for not creating a demo with at least THREE independant channels. Two proves nothing.

"We have invented a car that can move in any direction, forward... backward... or sideways at any angle. We will now demonstrate it with an amazing prototype car that can move either forward, or in reverse."

20. #### ah, think I finally get it.

So, currently it isn't unusual to transmit via HP and VP on the same frequency at the same time, this concept takes the principle further by using a whole range of angular polarisations between HP and VP. Possibly.

Can't see how that will work in the real world where any refelections of the signals will start causing interference between them and a loss of orthogonality.

21. #### So this is basically...

a conical scan where each "channel" is effectively the lobe at the same angular point? To those of us used to ancient military radar systems its simply lobe switching?

Or am I missing something stunningly obvious here?

1. #### Re: So this is basically...

Bad form replying to your own post but this is going to be virtually impossible to utilise in anything other than fixed comms for a good long while due to multipath propagation.

I can't see the interest in it for fixed comms either - you tunnel stuff via TDM over microwave links now and lobe switching is much the same.

Solution looking for a problem I think. Shannon doesn't need to start spinning yet ;)

22. #### So it will work perfectly...

...assuming you align your own split-parabolic dish to EXACTLY the same angle as the broadcasting one?

I can't see any problems with that, carry on.

23. #### I am suprised this is news

This technique of using different orthogonal or non-orthogonal polarizations of the incoming wave for a second channel is trivial. It is nearly the same as isolating linear polarized waves using orthogonal polarizations for each channel you are interested in (assuming the transmit and receive pairs have fairly large cross polarization rejection). What works much better is well established in many communications schemes is QAM, personally, I have seen at least 256 communications channels in one RF channel.

24. #### Science....

...it kicks ass.

25. #### Yes, ...

So, helical polarisation by another name ?

http://en.wikipedia.org/wiki/Helical_antenna

Don't I seem to remember that the receive antenna should be the opposite hand helically ?

26. #### Breakthrough

This would be a real breakthrough if they could send more signals point to point along the same line, but they can't. They are effectively splattering the signal across a wider area and using some phase jiggery-pokery to send different bits of the signal to different places. They're using a new spatial encoding trick but it doesn't change the basic physics.

More complex spatial antennas could always send more stuff, the trouble is they're spatial so don't expect one built into in your mobile phone. To get the sort of bandwidth that you can get from a strand or two of fibre out the chunk of spectrum a telco might hold, you'll need an antenna the size of a city and a massive amount of cables and electronics to drive it. Which is kinda what's happening, when you think about it.

27. In the late 90s when the bubble was expanding a Californian start-up called SilkRoad made all sorts of outlandish claims (that amounted to nothing) for optical fibre transmission and when I read this I was reminded of the similarity in language used. That's all I can say about this latest news as I have no deep understanding of radio.

The SilkRoad brochure was hilarious and included a history of optics/physics with a lineage that basically went from Da Vinci to Newton to Einstein to the founder of SilkRoad.

http://www.pcmag.com/encyclopedia_term/0,2542,t=SilkRoad&i=51365,00.asp

Despite what PC mag says, the prototype systems were not impressive and 15 or so years later fibre optics is busy plundering existing radio techniques to increase bandwidth and there's not even a hint that there was anything more to the SilkRoad hype than encouraging investors.

28. #### Nothing new

I get that on Talk Sport frequencies every night.

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