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Re: [Discuss-gnuradio] Wideband Random Noise Cypherpunk Guerrilla Radio

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] Wideband Random Noise Cypherpunk Guerrilla Radio - Doc Req
Date: Sun, 29 May 2016 19:09:35 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

Hi grarpamp,

nice idea, would be a shame if it was already being used, and partly
obsoleted ;)

What you describe, ie. spreading the signal over a large bandwidth is
World War II era innovation, and is nowadays called spread spectrum; and
current implementations use pseudorandom bit sequence generators to do
exactly that. For example, most UMTS/3G networks  and WiFi following the
IEEE802.11b standard do that. And as you might know, 4G is superseeding
3G (there's a lot of brain and money mobilized to develop 5G right now),
and 802.11b has been constantly superseeded by 802.11g and 802.11n
networks. All these technologies are based on OFDM to make use of a high
bandwidth. There's good technical/physical reasons for that, and looking
at these would be a nice, involved discussion that I can't possibly
squeeze in today. Basically, for communications to work, you need
modulations that are robust to a number of channel influences, and it
turns out that direct sequence spread spectrum (DSSS) as done by code
division multiple access (CDMA) systems mention before has serious
problems as soon you have more than one transmitter active at a time in
a typical, urban or indoor environment.

If you spread it extremely wide and basically put the power level, you
get what is called Ultra Wide Band. It's been an ongoing argument for
years whether that technology is dead by now or isn't. As a matter of
fact, it never made it to wide adoption, because of different, partly
political reasons. Also, its technological realization isn't possible to
combine with the type of SDR that GNU Radio does, most of the time.

Best regards,

On 29.05.2016 18:56, grarpamp wrote:
> Imagine noise radiator capable of making your spectrum analyzer
> look like /dev/urandom across the board. There's no center frequency,
> no clock, no freq hopping, no spreading, no observables, no off the
> shelf wireless hardware or reference design... it's not based on that.
> To any viewer, it's just background noise. To you and your peers
> who hold, say, a shared XOR key for data and a seed for DRBG noise,
> it looks like data... lots of data ;-) With achievable datarate,
> error correction, and unjammability governed by the range of spectrum
> you can generate noise over. You could even mimic within existing
> spectra if need be. And its nature is highly reistant to location.
> The amplifiers and radiators to cover the spectrum are hardware.
> Everything else is SDR.
> There is at least one good paper on this, particularly involving
> GNURadio style SDR as the enabling basis, but I forgot the magic
> search terms to find it again.
> While not the paper in mind (and not necessarily from the new SDR
> guerrilla / cypherpunk / darknet radio crowd), these are somewhat
> relavant...
> Digital Chaotic Communications
> https://smartech.gatech.edu/bitstream/handle/1853/34849/michaels_alan_j_200908_phd.pdf
> Synchronization in Cognitive Overlay Systems
> http://lib.tkk.fi/Dipl/2012/urn100685.pdf
> Covert Ultrawideband Random Noise papers by Jack Chuang and Ram Narayanan...
> https://etda.libraries.psu.edu/files/final_submissions/3142
> Can you link to some better docs, whether philosophy, theory or
> application, using SDR along the main topic above? Thanks.
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> Discuss-gnuradio mailing list
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