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Alex alex323@gmail.com [op25-dev] op25-dev at yahoogroups.comOn Thu, 22 Sep 2016 11:30:52 +1000 "Matt Ames matt.ames7bc at gmail.com [op25-dev]" <op25-dev at 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/op25-dev/attachments/20160921/8e359edc/attachment.htm>