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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