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

[Marcus Müller]

Indeed, I should've mentioned GPS :) Especially since it's a pretty
popular field for SDR implementation nowadays! Now, it wouldn't ever
lend itself to any relevantly high data rate – Shannon's channel
capacity just doesn't allow that.
Anyway, grarpamp, what's up with the funny subject line? What's
Cypherpunk Guerilla about any of this?




On 29.05.2016 19:36, Marcus D. Leech wrote:
> On 05/29/2016 01:09 PM, Marcus Müller wrote:
>> 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
> Hedy Lamar was granted the patent in 1947 (AFAIR) for a form of FHSS,
> designed for torpedo control via sonar.  But it established
>    the foundation of all SS systems that followed, including DSSS. She
> was an avante-garde actress of the time, and a helluva
>    smart lady.  I wish we had been contemporaries...
>
> The most famous extant example of DSSS is of course GPS, which spreads
> the signal below the noise floor of receivers--you need
>   to figure out the position in the spreading code to even "see" it. 
> Unlike CDMA, it's not going away any time soon :) :)
>
>
>> 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,
>> Marcus
>>
>> 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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>>
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