Marcus, Thanks again. Very helpful as always. Of course those are 2 completely different approaches, but this one can also be useful to me. I'll start looking in to it right now.
Thanks! 2016-03-15 18:02 GMT+02:00 Marcus Müller <marcus.muel...@ettus.com>: > That is direction finding, not distance estimation based on signal power. > Two totally different approaches. You'll need at least two antennas for > direction estimation. > > Meny, you're an engineer, read up on the theory; it's actually fun to see > these signal and geometric equations fall into place. > > In this case, Walter Kaminsky (who made that device from the video) holds > a granted patent [1] on this specific device, and as a skimming of the > abstract of that patent shows, direction finding is done by phase > comparison. You'll find more details in the patent and if you look up > direction finding in the literature/the internet. > Direction finding through phase difference isn't such a complex concept > mathematically, but non-trivial to implement in hardware (which is why > Walter was granted a patent on a device that implements a rather well-known > application); but if you have phase-coherent receivers, also not impossibly > hard to build such a system with GNU Radio. It all boils down to writing a > direction estimator. There's a *lot* of approaches and algorithms out > there, but I'd recommend you start with something intuitive – maybe finding > the relative phase of a received signal by estimating the phases of > signals, and based on these phase relationship estimate the angle of the > wavefront relative to your antenna array. > > Best regards, > Marcus > > [1] http://www.google.de/patents/US6239747 > > > On 03/15/2016 03:17 PM, Meny Sidar wrote: > > Thank you for your comments. > Marcus, sorry for bugging you with this issue. > I am well aware of the previous discussions with you, and have learned > from them as well as from other people. > however, when i come across something like this for example: > https://www.youtube.com/watch?v=ZUqzdrB1o2U > i keep thinking that there is some kind of heat signature in the spectrum > that the cellular produces (please correct me if im wrong) > how else can you explain this works? > > I know my approch is not ideal, and i'm not ruling out opening a bts base > station, > but i cant find a way to make phones register to my station automatically.. > > thanks again for your comments guys, > really appreciate it. > > Meny > > 2016-03-15 4:11 GMT+02:00 Nikos Balkanas <nbalka...@gmail.com>: > >> Indeed, there is phone locator protocol, and a service offered as by some >> companies. They work through provider contracts. The problem is that you >> have to know the phone number beforehand and the carrier. Not very useful >> in a disaster case :( >> >> BR, >> Nikos >> >> On Mon, Mar 14, 2016 at 5:50 PM, Marcus Müller < >> <marcus.muel...@ettus.com>marcus.muel...@ettus.com> wrote: >> >>> True, at least unless you send them something they have to react to. >>> Which the phone will only do if you're the infrastructure, and usually >>> implies you authenticate as such[2]. Which will hence most likely only work >>> if the cellular providers cooperate with you. >>> >>> [...snip...] >>> >>> >>> >>> On 03/14/2016 03:54 PM, Meny Sidar wrote: >>> >>> Hi guys, >>> >>> I am currently working on a project for my university, where i'm trying >>> to locate cellular phones using SDR (USRP B210). >>> The idea of the project is to be able to find survivors/victims in >>> disaster areas, such as earthquakes, by assuming they have their cellular >>> on them. >>> >>> What i did so far, is a program that calculates and outputs in a loop >>> the power transmitted from a cellular phone from it's uplink channel. that >>> can tell me my distance to it. >>> problem is, that cellular phones are usually in idle mode and not >>> transmitting at all. >>> So it works, but only if the phone is currently transmitting to the >>> network (phone call, internet, etc..) >>> >>> I'm trying to find a solution for this, >>> There has to be a way of knowing that some kind of RF >>> transmitter/receiver is near me... >>> If anyone can shed some light on this subject, what can i do or if i >>> need to go in another way, i'll be very grateful! >>> right now i'm stuck. >>> >>> Thanks a lot, >>> Meny >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing >>> listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > >
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