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