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DARPA Wants Wireless Devices That Can Blast Through the Noise
coondoggie writes "What if your wireless communications just absolutely, positively have to be heard above the din of other users or in the face of massive interference? That is the question at the heart of a new $150,000 challenge that will be thrown down in January by the scientists at DARPA as the agency detailed its Spectrum Challenge — a competition that aims to find developers who can create software-defined radio protocols that best use communication channels in the presence of other users and interfering signals."
Mother-in-law.
You gotta use multi-phasic shifting!
Make it so.
The actual DARPA page, with rules/etc., is here.
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
Not when the signal is below the noise floor.
Spread-spectrum should fix this. Hell, OLIVIA (slow as ass) can be used even when below the noise floor, provided you are listening for it.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
I'm not an engineer.. but some random thoughts?
1) Can you use out of band communications to trigger a special mode of the router (assuming you control it)? (e.g., A special listening mode that gives certain devices priority)
2) Rather than use typical QAM type of modulation, can you use a more limited constellation but BOOST the power so you can punch it through the noise? (which would also allow you to make very good use of forward error correction (FEC); again assumes that you are able to program both the sender and the router.
Assuming you can't alter the Network Stack on either device than you have to look at the communications itself
3) Other than that, it would seem you would need to use a programmable antenna/software antenna, Etc. turning your own Antenna into a high directional Antenna with as much gain as possible. Basically find the WIFI router you want (geo locate it, perhaps triangulation with the help of friendly nearby devices) and the push all your signal towards (a dynamic Yagi antenna that auto-magically maintains it's "aim" at the router even as the sender and/or the receiver move about.
4) If you did have some control over the router and you were sure that you could depreciate other traffic then the router would also get the same auto-magical antenna system and the two devices would "focus" on each other.
http://www.hawknest.com/
The goal is to "engineer software-based radios that transmit data faster than a competitor using identical hardware".
The goal isn't to develop fancy new hardware, or to use an overwhelming amount of power. The goal is to develop fancy new software.
With frequency-hopping and time-hopping techniques, if you can intelligently adapt to the local interference, and transmit in the time and frequency gaps where the interference doesn't occur, then you can transmit more data for the same amount of power. That's the goal.
They want the BEST solution.
Seriously, as others have pointed out, there are obvious ways to solve the problem.
DARPA is challenging the community to come up with optimal or at least more-optimal-than-everyone-else ways.
The only "downside" I can see is that the competition is in a controlled environment. I say let's do the tests in an "uncontrolled" environment, much like an outdoor sporting event where neither the competitors nor the officials get to control the weather. Play the "game" several times in several "representative" environments such as large cities, small towns, rural areas, and during several different times of day or night, etc. Then use a pre-determined, pre-published scoring rule to determine not only the "overall winner" but the "winners" in various categories, e.g. "best in big cities," "best at night," etc.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
The rules aren't available on the site yet, but I assume they're interested in resistance to jamming. From a theoretical perspective, as long as the receiver isn't saturated, there should be some data rate at which transmission is possible. This follows from Shannon. Noise can be overcome with redundancy, at the cost of data rate.
You can usually do better than that by moving around the spectrum to quieter areas. That's what frequency-hopping systems do. Jammers can be agile too, but unless the jammer is in a direct line between sender and receiver, the jammer is always at a time disadvantage due to speed of light lag. Very fast frequency hopping can overcome agile jammers.
What DARPA wants, I suspect, are systems that package up all this into a system that takes care of any noise problems automatically and will get a message through if it is physically possible. DoD has had systems for that for decades, but the technology tended to assume that the opposition didn't know the details of how it worked. It may be possible to have jam-resistant systems that work even if the opposition knows the technology.
The only probable solution would be to dedicate specific channels for their use and have rigidly enforced laws in place which forbid usage by consumer devices.
I'm not sure how you rigidly enforce laws in battle field situations. If you could, why not just make a law against the enemy carrying weapons?
There are two key requirements in the Darpa Challenge:
1) High priority radios in the military and civilian sectors must be able to operate regardless of the ambient electromagnetic environment, to avoid disruption of communications and potential loss of life.
2) Response operations, such as disaster relief, further motivate the desire for multiple radio networks to effectively and efficiently share the spectrum without requiring direct coordination or spectrum preplanning.
In the end I suspect that the winning entry will pay little heed to the regulatory frequency allocations, and fall back on the FCC standard of non-interference by instantaneously finding unused frequencies over a wide spectrum and pushing messages through those spaces in small encrypted bursts so short that licensed users of that bandwidth would not even notice it. Alternatively you might be able to embed your transmission within already widely used frequencies for digital television, AM /FM radio, by using the gaps between allocated frequencies.
Sig Battery depleted. Reverting to safe mode.
No. Because the point of this is the ability to get a signal through in an RF-unfriendly environment. The solution will have down-sides (higher power than optimal, lower bandwidth than optimal). So id everyone did this in shared spectrum, then we'd end up with lower bandwidth and higher power usage. We can do that now in 2.4. The point of licensed spectrum is that it's optimal. The noise floor should not change, and the bandwidth will be higher. The shared combative solution is a tragedy of the commons situation. The more who use it, the less there is to share.
Learn to love Alaska
PPM (pulse position modulation) seems to be pretty resilient. Picking up mode-S transponder signals from planes as far away as 200km with a stock DVB-T antenna and a really cheap SDR (rtlsdr), which has very poor dynamic range. Even when the signal barely gets above the noise threshold.
Shannon's mathematics are valid only so long as the assumptions behind them are true, and the main assumption is that there is *a* communications channel. They do not apply when you are using multiple independant or semi-independant channels, such as in a MIMO radio setup or using multipath communcation. The succesful candidate may well have so many antennas it resembles a sea urchin on a stick.
The 'Turn up to eleven' approach could work for stationary equipment, but it isn't practical for things like field radios - which are exactly the sort of thing that a hostile force may want to jam prior to and during an ambush, to keep the targets from calling for backup.
I have a feeling that people might use this research to blast their data packet on the existing crowded frequencies.
The stuff about "disaster relief" is entirely bogus. They are asking people to work on an entirely military application for very little gain...