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Shannon's Theory Finally Broken

Posted by Hemos on

Mike Monett writes, "Claude E. Shannon published A Mathematical Theory of Communication in 1948, and his work has successfully resisted all attempts to find a loophole. Since then, the communications industry has been guided by a term called "signal-to-noise ratio," and negative values are frowned upon. This sets the limit for communication in the presence of unwanted noise added to a signal as it is transmitted from one place to another. But a loophole has been finally discovered. I have found a method of recovering arbitrary signals buried in noise. An example is available here. No information on how it is done, but a brief summary of the good and bad features of the discovery. Will it affect you? There is a good possibility. Will the effect be good? Probably. Will my site be taken down by the Slashdot effect? There is a good chance of that also. "

14 comments

  1. Shannon's Theorem by TimoT · · Score: 2

    As I understand it this doesn't break Shannons theorem (and it says so on the page). AFAIK, Shannon's Theorem says that the amount of information sent in a given amount of bits (or in the continuous version combination of bandwidth and time) depends on the quality of the statistical model of the source (and the noise present on the channel).

    An event of probability p requires -log2 p bits to encode in it's most efficient form. There's no lower limit to the amount of bits needed to specify a sequence of events provided that you can estimate the next event's probability close to 1 and succeed every time. If you have a completely accurate model, 0 bits are needed. So this might be an improvement on the statistical model of the source. The theory of information is sound; you can't disprove a mathematical theory once it is proven correct and the proof has no mistakes. The headline has a bit of unwarranted sensationalism :)

    1. Re:Shannon's Theorem by Anonymous Coward · · Score: 0
      >As I understand it this doesn't break Shannons
      >theorem (and it says so on the page).

      You are right.

      As far as I can see from glancing at his page, what he has done is encoding a 50 kHz signal in a 3GHz bandwidth - he is even talking about a "modulation ratio". This is called spread spectrum encoding, and you get an SN increase of log(BW1/BW2), less any noise introduced in the spread spectrum bits. He has a -30dB signal, and spreading the signal by a factor 60000 (3G/50k) gives an SN increase of approx 50dB, which means that the receiver sees a +20dB signal, less some for his crude decoding.

      There are commercial radio sets on the market today which will operate down to -3dB S/N ratio reliably, measured at the antenna. The reason for the modest SN yield taken out of commercial systems are based on not wanting to be a bandwidth hog.

      This is explained much better in e.g. Rohde et al, "communications receivers", McGraw-Hill.

    2. Re:Shannon's Theorem by thogard · · Score: 1

      Isn't the GPS signal at something like -39dB S/N?
      I know that is a small fraction of the normal backround noise at the frequencys it uses.

      GPS transmits at about 50 baud in the 1.[25] GHz range and does some interesting frequnecy hopping. To find the sats signal you have to know where it is and then fiugre out its doppler shift and its offset into its pseudo random jumping so you can start to look for it. And there are $150 hand held devices that do this on 12 channels at once.

  2. Slashdot Effect premature? by Anonymous Coward · · Score: 0

    Well, the topic doesn't seem to be on the front page yet, there are no comments about it yet, but the site is already unreachable!

  3. I'm still skeptical by Alik · · Score: 1

    I don't see anything that makes this obviously impossible, but I'm still not convinced of its truth. Among other things, it's a story submitted by the inventor himself, which smells a bit funny to me. (Then again, if I invented something really cool and wanted to tell the world, I might well use Slashdot.) I think I'm also uneasy about the complete lack of information about how the method works. I suppose it's necessary for patent purposes, but I think it might have been a bit premature to submit "news" that doesn't actually inform us very much.

    Anyway, I hope this is for real, but I'll believe it when I see more than an arbitrary signal trace.

  4. Slashdot != News by morris57 · · Score: 1
    While I have no problem with /. reporting the existence of an invention that might break an established mathematical theory, I find it highly irresponsible that this item is reported as a counter-example to a mathematical theory. If it were, it would be more believable coming from an academic journal. (Anyone remember cold fusion?)

    I hate that this story was put on the science page, because it is Bad Science(TM). However, I'm glad that it is not on the front page, where it might reach a more easily confused audience.

  5. Old news by Lozzer · · Score: 1
    I read about stuff like this in "From Here to Infinity" by Ian Stewart about 8 years ago as a use for Chaos theory. I believe the example in the book talked about recovering voice from a recording contaminated with a noisy air conditioning unit. It said something about considering the voice as the noise, removing it then subtracting what you had left from the original signal...

    Loz

    --
    Special Relativity: The person in the other queue thinks yours is moving faster.
  6. No method? Color me suspicious by Proteus · · Score: 2
    Pardon me for my skepticism, but if no method - or even a proof for the method - is published, how can we know that this is not flawed? I would like to look at some pure data, and a well-structured methodology before I lend any credence to this.

    On a lighter note - even if it doesn't really work, wanna bet it gets a patent? :P

    --
    : remove whitespace to e-mail me

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    We may not imagine how our lives could be more frustrating and complex—but Congress can. – Cullen Hightower
  7. Over the sound of one hand clapping... by WiartonWilly · · Score: 1

    you can hear Mike Monett tooting his own horn.

    When is the IPO, Mike? ;^)

  8. Cant even get the dB voltage to power linear right by aholtzma · · Score: 1

    If his -30dB is really a voltage ratio, then the power ratio is -60 dB. This of course makes the capacity even smaller than what he has with the his strange looking dB to linear calculation.

    Not that I actually believe anything else on his page either. Tons of people have made similar claims and have later been proven incorrect.

  9. Call him and find out! by Ironix · · Score: 1


    Perhaps we need a bit more info... Considering I have found a total lack
    there of on his web page. Try here.



    --
    Still #1 -- Lonely Gay Geek
  10. Journals by Detritus · · Score: 2
    If it is real, he should write a paper and submit it to the appropriate IEEE journal.

    I'll believe it when I read about it in a reputable peer-reviewed journal.

    --
    Mea navis aericumbens anguillis abundat
  11. Re:Cant even get the dB voltage to power linear ri by Anonymous Coward · · Score: 0

    His calculation is incorrect, even if he "rounds". 30dB is a difference of a 1000 in power, not 900. 30=10log10(power_ratio) In any case, this is very cool. I hope the invention is real. Better, I hope that someone publishes details soon.

  12. Yikes! Does nobody check these things? by Spiork · · Score: 2

    Well, it looks like the /. story review board isn't doing a very good job. The guy posting this stuff about having broken Shannon's Theorum is currently being ripped apart by sci.electronics.design regulars.

    His postings are funny, you should deja.com them.

    In short: he hasn't broken the theorum, he has yet to produce code, and the excuses he's serving up are priceless. His announcement message was the kind of thing one reads while chuckling.

    So, sorry, it isn't going to change the world, /., or really anything at all. (as suggested in the news article writeup)