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. >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> [email protected] >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected] >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
