USRP for GPS

GNU Radio
1

hi,

i was wondering whether the usrp can be used as a “gps receiver”. if so,

  1. how can i achieve this?

  2. any link you could provide for me to read?

  3. what daughterboards should be used?

  4. Can the usrp be used with OpenGTS (for example) for tracking (usrp as
    a gps receiver)?

thanks in advance,
walter

2

Hi Walter,

My group is using the USRP to record raw RF data at GPS and GLONASS
frequencies. We do all of our signal processing in post right now, but
are
interested in developing a stand alone receiver. If you search the
mailing
list you’ll find some other folks who are implementing GPS receivers on
the
FPGA. What kind of performance metrics are you hoping to obtain? As
far as
the daughter boards go, we use the RFX1200 and RFX1800. I’ve also heard
of
people using the SBX.

I have no answer to your question regarding OpenGTS: I’m fairly new to
this
system as well. If you’re going to do real time tracking your best bet
is
probably to modify the FPGA for performance considerations. Hope this
helps!

Ryan

3

Hi Ryan,

Thanks very much for your answer! You mean you are inetersted in
developing a stand alone receiver “with” the USRP?

I’m sorry, what do you mean by performance metrics?

thanks again,
Walter

4

Walter,

Currently the receiver that triggers our USRPs to record the RF data is
quite expensive. We don’t use all of its features, but it has a few key
parameters that are used in our trigger threshold calculation. If we
deploy
this same system to another location we’d like to have a USRP function
as
the trigger. In that sense we are interested in using the USRP as a
GNSS
receiver, but our goal isn’t to get a position solution.

As far as performance metrics go, you need to define a few parameters
for
your receiver before settling on the USRP as a host. The two that pop
into
my mind right away are: 1.) which GPS signal(s) do you want to use and
2.)
how many channels do you hope to track? If I recall correctly, there’s
a
thread somewhere on this list where a group used the old USRP1 and
modified
the FPGA to do 4 channel tracking with fast acquisition.

Regards,
Ryan