DARPA Wants Extreme Wireless Interference Buster

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.'"

Comments

What can they hope for

[bugs2squash]

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.

Re:What can they hope for

[russ1337]

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

Re:What can they hope for

[mattj452]

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.

Re:What can they hope for

[rcw-home]

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.

Do NOT open this link!

[majorme]

Guys, do NOT open this link, under no circumstances. Fucking gay pr0n :(

Flag semaphore and interference cancellation

[Catbus]

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.

Re:I've got one for them!!!

[Anonymous Coward]

its immune to EM interference using that computer

Re:Use a wired connection?

[f3rret]

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