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<p>On Thu, 22 Sep 2016 11:30:52 +1000<br>
"Matt Ames matt.ames7bc@gmail.com [op25-dev]"<br>
<op25-dev@yahoogroups.com> wrote:<br>
<br>
> Hi Alex,<br>
> <br>
> Some of those ideas/tasks date back to 2008 when the project was its'<br>
> initial embryonic stages. The idea back then was to find a way to<br>
> track a P25 station geographically - for example, using multiple time<br>
> and frequency sync'd USRP's (with GPSDO for location and time sync)<br>
> to do time difference of arrival type location determination, or even<br>
> a Roanoke Doppler style of receiver.<br>
> <br>
> Since then, Motorola TRBO and DMR has become very popular, and with<br>
> it, services such as LRRP are transmitting data over some of these<br>
> networks. I know that some of the Motorola APX and TRBO series radios<br>
> can be set up to transmit their GPS locations in the clear, which<br>
> could be easily read over the air. This has been done in other<br>
> projects with TRBO, but not with P25 to my knowledge.<br>
> <br>
> These are just a few ideas I threw around, Balint (with some<br>
> assistance from me) implemented a great SDR Doppler RDF. It wasn't<br>
> tuned for P25 but it did work well on whatever it was tuned to..<br>
> Balint since went to California and worked on another setup using a<br>
> USRP and an algorithm called MUSIC that worked very well...<br>
> <br>
> In short, there are many ways of determining the direction an RF<br>
> signal is coming from, and then using this to triangulate a position..<br>
> <br>
> Cheers,<br>
> Matt<br>
> <br>
<br>
Hi Matt,<br>
<br>
Thank you for that detailed explanation. I am a DSP neophyte, but I am<br>
absolutely interested in helping out in any way I can with this. In<br>
fact, I just ordered a B200 with GPSDO from Ettus and will be<br>
experimenting with it when it arrives.<br>
<br>
I have read up on cyclostationary signals and am currently trying to<br>
implement SPECCOA to determine a TDOA for multilateration.<br>
Unfortunately, I am having difficulty understanding some of the math.<br>
Are you familiar with SPECCOA, or do you know anyone I could talk to<br>
off-list who can answer some questions I have?<br>
<br>
-- <br>
Alex<br>
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