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DARPA Wants Extreme Wireless Interference Buster

Posted by samzenpus on from the no-down-time dept.

coondoggie writes "This month the Defense Advanced Research Projects Agency will begin looking for technology that will let wireless communications work through the most extreme interference. From the article: 'The CommEx program will assess next generation and beyond jamming threats and then develop advanced interference suppression and avoidance technologies to successfully communicate in the presence of severe, traditional, and novel types of interference that are orders-of-magnitude more severe than what are currently addressed by the most advanced systems, DARPA stated.'"

32 of 105 comments (clear)

  1. distinct lack of content by advocate_one · · Score: 3, Interesting

    in the article... anyone got a better link?

    --
    Donald 'Duck' Dunn: We had a band powerful enough to turn goat piss into gasoline.
  2. What can they hope for by bugs2squash · · Score: 4, Informative

    LDPC, spread spectrum and more EIRP. Or are they hoping to overturn Shannon ?
    Really, the state of the art is fractions of a dB away from theory. There are no further breakthroughs to be found. Unless you count social engineering the bad guys to block the wrong signals.

    --
    Nullius in verba
    1. Re:What can they hope for by russ1337 · · Score: 2, Informative

      exactly. I'd speculate that these techniques have been combined and in use for some time.

      Just look at how long GPS has been around. For those not aware, it uses spread spectrum CDMA, with a signal is well below the noise level. I've speculated (in my mind) that you could easily combine the techniques to transmit and receive reasonable data at a level 'below the noise threshold' for some time. Just like GPS, you just need some reasonable clocks (hand held GPS quality), some decent processing (like an FPGA), and the rest is how far you can push the bandwidth in the real world. You can include other comms techniques, phase, multi-band, etc. it just comes down to processing power and a heap of math that is way above my head.

      the basics of GPS spread spectrum is here: http://alumni.cs.ucr.edu/~saha/stuff/cdma_gps.htm

    2. Re:What can they hope for by Trepidity · · Score: 2, Interesting

      I think that's probably true for algorithms, but it might not be for deployed systems. Current communications devices can't use all the available theoretical techniques over all possible frequencies in all possible configurations, so there might be some significant gains on that front with new transmitters/receivers/etc. For example, most spread-spectrum systems operate over relatively narrow portions of the spectrum, at least compared to the whole electromagnetic spectrum--- nobody is spreading over everything from radio waves to x-rays, or anything close to that. Using larger parts of it has both some technical and operational challenges, since if your spread is over very large parts of the spectrum, parts of your signal are being transmitted on frequencies with extremely different properties.

      --
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    3. Re:What can they hope for by mattj452 · · Score: 2, Informative

      I'd imagine that not only will they look at those techniques (FEC, spread spectrum etc), but also techniques related to intelligent channel switching when a channel is jammed. Also, there are other methods than noise to interfere with the reception. For example, sending out false signals, repeated signals etc which also needs to be considered.

    4. Re:What can they hope for by AK+Marc · · Score: 2, Interesting

      You need signal/noise of some level. Jamming acts like noise. You can't add power past some point, so that means you must subtract noise. How? Well, you can try MIMO techniques that try to essentially lock on to the jamming signal and subtract it out. Or lock on to the generated signal with rejection of the jamming signal. Right there are two possibilities that don't violate the theory and should be able to get real gains. Maybe not the best possible, as moving jammers or moving desired signals would be an issue. But that's just a napkin thought. There are more out there. Jamming may affect the signal like noise, but it isn't.

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    5. Re:What can they hope for by HungryHobo · · Score: 2, Insightful

      they could come up with some kind of missile designed to go after transmitters broadcasting interference, they'd be pretty loud and easy to spot.

      of course this is probably for drone tech so if you armed a drones as such and programmed them to attack the transmitters if their command channel was blocked the first thing any amoral adversary would do would be to stick an interference transmitter in a preschool with a camera crew nearby.

    6. Re:What can they hope for by digitalchinky · · Score: 2, Insightful

      As a former ELINT / EW drone, I'd like to make a correction good sir. I can tell you that the GPS spread spectrum transmissions (actually, all spread spectrum transmissions) are not below the 'noise level' - or noise floor. They are quite distinctive on a spectrum analyzer and the link you posted does show this. I say this sitting at the back end of several 20+ meter satellite dishes and do acknowledge that for some receive systems, the transmissions may indeed be below their noise floor - but, to qualify this, if something is below the noise floor, by extension this means it simply cannot be received. Including spread spectrum.

      You are right about the technology having been around for a long time though - decades : )

    7. Re:What can they hope for by rcw-home · · Score: 3, Informative

      if something is below the noise floor, by extension this means it simply cannot be received. Including spread spectrum.

      No, it doesn't mean that at all. It does mean that your error-free bitrate will be limited to less than the bandwidth (how much less depends on how much more noise than signal you have). GPS uses 1.023MHz of bandwidth (for the civilian signal - 10.23MHz for the military one) and has a bitrate of 50 bits/sec. Typical noise levels are -110dBm and typical signal levels are -130dBm.

  3. Ok, an interesting challenge. by jd · · Score: 4, Interesting

    The conventional approach by NASA is to use Turbo Codes to handle burst errors and Reed-Solomon to handle randomly-distributed errors. You'd need to increase the error correction bits to handle really significant errors, but that seems like a good starting point. If you were to imagine the data as a cube, then produce the error-correction codes for each and every line you could draw through that cube, then each unit within that cube is represented by three sets of error-correction codes.

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    1. Re:Ok, an interesting challenge. by digitalchinky · · Score: 2, Funny

      I remember way back being taught about trellis code modulation - 8am - squeaky white board marker - "Right, today we'll cover a very simple 2 bit trellis code modulation scheme' - I thought I was a frigging rocket scientist back then, 2 bits, heh, some kind of noob joke?! I have to say after 2 minutes I'd actually glazed over, just like everybody else... : )

      Who dreams this stuff up! Seriously! These guys and girls don't actually think like the rest of us.

    2. Re:Ok, an interesting challenge. by jd · · Score: 2, Interesting

      Any given point in a cube exists along three lines - one parallel to X, one parallel to Y and one parallel to Z. If you wish to find a fourth orthogonal axis, please do so. Your TARDIS awaits.

      Regardless, three is plenty. If you want to improve reliability still further, then if turbo codes are mapped onto X, use LDPC (low-density parity-check code) alone -X.

      Since Reed-Solomon is for random errors, you'd probably want to use a conventional ten-bit system - 8 bits of data, 2 bits of ECC. A layout used by a lot of modern electronics. Since turbo codes and LDPC are intended to fix bursty errors, they're useless if the block size used is smaller than the size of burst that you can expect. In the scenario the DoD is interested in, it's extremely hard to say what to do here. If the block size is too big, then the error correction codes have an increased probability of being damaged by such a burst. Thus, not only is there a lower limit but there is also an upper limit.

      NB: If you not only want to ECC each line but also each plane using turbo codes, then you have a further constraint. The line cannot exceed the minimum size but the plane cannot exceed the maximum size.

      My thinking is that each line's turbo codes would also cover the Reed-Solomon codes, and each planar turbo code would also cover all of the turbo codes for each line within that plane.

      Since the same object is mapped from three (or six, using LDPC) different perspectives and the probability of the noise being such that all three/six perspectives are damaged in mathematically identical ways is extremely low, you can generate a set of the most probable original messages at that level. This could be done by combining the probabilities generated from each of the algorithms, a voting system, or some sort of statistical analysis. How doesn't matter that much, so long as you can produce a bounded set of messages that could be described by the codes.

      Here, you can use Reed-Solomon not as an error-correction code but as an error-detection code. You know for a fact that the original pattern will satisfy each and every one of the Reed-Solomon ECCs. Any one of the candidate original messages that does not meet this constraint is incorrect. It has to be.*

      If the slices used are one bit thick and each line drawn has a diameter of one bit, then I see no possible way for any aliasing effect to occur, which means you'll end up with exactly one reconstituted message even if fairly extensively damaged in transit. That's probably still true even if working using byte-sized atoms, but bit-planes have some definite advantages for this kind of work.

      *Ok, it may be possible to inject deliberate corruption such that the resultant turbo codes would produce a candidate solution which aliased onto the Reed-Solomon codes. It'd be better if you could use cryptographic hashes, but those tend to be big and therefore more subject to being corrupted via a wireless connection. You could break the data into fixed-sized chunks, cryptographically hash each chunk, append the hash to that chunk, then do the whole process as outlined for the composite message. If you did this, then you would test the turbo code candidates against the hashes and if they all failed then you'd use the Reed-Solomon to re-fix the messages before testing against the hashes again.

      This method is by no means foolproof, it is not intended to be optimal, it has not been evaluated for every possible scenario to see if it's watertight, it is not FDA-approved and it's likely signals analysts and crypto experts would regard it skeptically. It is not intended as an actual submission to the DoD. What it is intended to do is show that the problem does not require any tools that do not already exist. Indeed, it does not require any tools that aren't already being used by industry to tackle some subset of the problem. There is no novelty in this problem, beyond what combination of tools it will take to defeat deliberate interference of arbitrary nature.

      --
      It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
  4. Faraday FTW! by nacturation · · Score: 3, Funny

    This is so easy. All you need to do is roll out a point to point Faraday cage between the two parties that wish to communicate. To build the Faraday cage, go to your local hardware store and purchase all the rolls of chicken wire they have in stock. Now take the chicken wire and form a loop about 5 meters in diameter. Keep on doing this and stitch the loops together until you have a big enough tunnel to reach from your source to the destination. Remember! There must be line of sight for your wireless to properly function. I recommend getting wooden pallets to smooth out any hills and valleys so that you can see clear through.

    Now the fun part. To make a proper Faraday cage you need to run current through the chicken wire. Experiment with the right voltage, but I find that running a chainsaw through a local wooden power pole will score you a big fat power cable capable of delivering the right amount of juice. Strip the power cable and attach the positive and negative wires to the chicken wire. CAREFUL!!! Make sure you're wearing latex gloves to protect your hands against the current. If you don't have latex gloves, fashion your own gloves out of banana peels.

    Once the power is hooked up, you have now created an impenetrable electromagnetically shielded tunnel through which your wireless transmissions can propagate. Place the transmitter at one end and the receiver at the other and enjoy your interruption free communications!

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    1. Re:Faraday FTW! by angiasaa · · Score: 4, Funny

      I think they could use sandpaper instead of wooden pallets to smoothen out the hills.

      You give a very good textbook solution to the problem.

      Personally, I'd just switch to shielded cables though. :P

      --
      Geekism is your _only_ God!
    2. Re:Faraday FTW! by foobsr · · Score: 3, Funny

      Indeed, and this is to be called ALAS (Advanced Layer Augmented Shielding).

      BTW, IMHO, the outlined approach is a paradigm regards advanced technological solutions: if a given system does not work as demanded, create another layer and hope that the increase in complexity will automagically solve the problems.

      CC.

      --
      TaijiQuan (Huang, 5 loosenings)
    3. Re:Faraday FTW! by L4t3r4lu5 · · Score: 2, Funny

      Is there some way we can get both XML and violence into this situation? They somehow seem appropriate...

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    4. Re:Faraday FTW! by mcgrew · · Score: 2, Funny

      Is there some way we can get both XML and violence into this situation? They somehow seem appropriate...

      Ok, here you go... "XML is the last refuge of the incompetent" -- Salvor Hardin

      --
      Free Martian Whores!
  5. Wireless Engineering by HRbnjR · · Score: 2, Funny

    Just make sure the CommEx program doesn't contract the electrical engineers behind the iPhone 4 antenna - I hear they are looking for work :P

  6. Drones are the future. by Dutchmaan · · Score: 3, Insightful

    This has drone research written all over it! Take out a signal to a drone and it's as good as shooting it down. It's probably easier to mess with a drone signal than shooting it down as well, but that's just pure speculation on my part.

  7. jamming != white noise by tempmpi · · Score: 4, Interesting

    They are looking at intentional jamming, not at white noise. Your solution would be almost perfect for white noise channels but not for channels with jamming.
    E.g.: No jammer will be able to distribute its noise evenly in both time and space. You should be able add a nice bit of performance if you are able to predict the behaviour of the jammer to some extend. So spread spectrum with non-uniform frequency distribution of the signal energy could be a topic. Some jammers might not even send real noise but pseudo random noise. Then you could try to subtract the jammer from your received signal.

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    1. Re:jamming != white noise by Aceticon · · Score: 3, Interesting

      And then let's not forget the spatial dimensions in addition to the frequency dimension - jamming signals originate from one or more sources at specific locations so this could also be used in eliminating interference from jammers.

      I remebers from reading a bit of the GSM spec that mobile phones includes adaptative antenna and algorithms that allow retrieving a usefull signal not just from the direct line of sight transmission (from the mobile tower) but also from multiple reflections with different path lengths. Could not the same techniques be used to, instead of boosting a signal, offset that signal?

  8. I've got one for them!!! by syousef · · Score: 2, Interesting

    It's called cat5e.

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    1. Re:I've got one for them!!! by L4t3r4lu5 · · Score: 2, Interesting

      Wrap your Cat5 in a coil made of the power lead to your PC, then turn your PC on. Tell me it's immune to EM interference using that computer.

      If it catches fire, that counts as "successfully blocked signal".

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    2. Re:I've got one for them!!! by Anonymous Coward · · Score: 2, Informative

      its immune to EM interference using that computer

  9. The technology exists.... by Kaptain+Kruton · · Score: 3, Funny

    IP over Avian Carriers. (IPoAC). With the pigeons, you don't have to worry about EM radiation interrupting the signal. http://en.wikipedia.org/wiki/IP_over_Avian_Carriers

    1. Re:The technology exists.... by L4t3r4lu5 · · Score: 2, Funny

      They would indeed be impervious to the jamming effects of EM interference.

      However, unlike EM waves, they are totally at the mercy of buckshot.

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  10. Re:Suppression? by nacturation · · Score: 2, Funny

    For advanced interference, you might want this: http://en.wikipedia.org/wiki/Wicked_Weasel

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  11. Frequency Hopping.... more? by NouberNou · · Score: 5, Interesting

    Not really sure what they can advance on besides frequency hopping routines that are quicker and cover a larger spectrum. SINCGARS, HAVE QUICK I/II and SATURN are pretty good at counter-jamming already, as long as the sequence can not be easily predicted and the fills are updated regularly (every 24 hours or so) then jammers will have to invest quite a bit into the infrastructure of their broadcasting equipment. It certainly wouldn't be portable, and it'd be loud and easy enough to find and take out by more traditional means.

    The only thing, like I mentioned above, is moving to waveforms that are spread across larger frequency ranges (which can be problematic) and are faster so the jamming equipment can't keep up with the normal signal. Beyond that, digital data over RF can be reinforced by better packet correction and error handling.

    Of course you could always just overpower every other signal on your band, but I do not think battery tech has reached that level yet for portable radios, and well... Most soldiers prefer not to be cooked alive if they have a choice.

  12. Flag semaphore and interference cancellation by Catbus · · Score: 2, Informative

    Flag semaphore remains highly resistant to electromagnetic interference. http://en.wikipedia.org/wiki/Flag_semaphore There is more to be done with interference cancellation techniques using active multiple-antenna systems, that can place a null toward the source of interference.

  13. Re:Use a wired connection? by f3rret · · Score: 2, Informative

    I think there's a practical problem with running wires to Predator or Global Hawk drones...

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  14. Re:Do NOT open this link! by FatdogHaiku · · Score: 2, Funny

    Gyro cooking?

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  15. Active cancelation of interference with anti phase by tarpitcod · · Score: 2, Funny

    Antiphase? Have a receiver transmitter pair that receives the interference and then transmits the 180 degree out of phase equivalent - hopefully cancelling it out. For extra points deploy multiple stations, and for a bonus credit, don't evern transmit your signal, just modulate your antiphase to leave your signal as a remanant. Physics Problems: Can you near instaneously send the anti phase (those radio waves travel quite quickly)... What happens for moving receivers.....