Hi JPL,
.mat is really just a complicated container format for all kind of matlab data
-- GNU Radio can't directly deal with that, although with SciPy you could
create something that will be able to parse .mat files; but that is quite
useless, as you could as well use Matlab to write something that can be
directly used with other software.
So to answer question (1.), I'd agree with Nathan: Best way to do it is using
the existing GNU Radio OFDM tools, not writing code that has already been
written several times, and start with something that already works. Thereby
dropping Matlab as your signal processing framework, and only using it for data
analysis and visualisation.
To comment on (II): GNU Radio has blocks like "file_sink". They will just save
the samples to a file, in this case, in the format of raw float32s (1 for real, 1 for
imag part) one after another.
To answer (III): If you really want to do that, see the GNU Radio source tree,
gnuradio-core/src/utils/read_{float,complex,...}_binary.m. There is the same with "write"
instead of "read".
Greetings,
Marcus
On 10/18/2013 06:53 AM, West, Nathan wrote:
On Thu, Oct 17, 2013 at 11:14 PM, JPL <[email protected]
<mailto:[email protected]>> wrote:
Hello,
We have used Matlab to generate *.mat file, a file around 1966240 complex
number OFDM samples.
Thinking to (I) transmit between two USRPs, (II) let the receiver side
saving data into file, and later (III) putting the file on Matlab for
demodulation.
1. What is the best way to do it? like create GRC blocks? or UHD example?
2. How can I make sure that the TX part will stop when those 1966240
samples are sent. and RX part will stop when completely receiving those 1966240
samples?
3. Should the file type be the *.dat?
Sincerely,
JPL
I'll attempt to respond to both questions since they are really the same thing.
First, this is kind of a weird way to use GNU Radio. GNU Radio provides you an environment
to do all of the signal processing you want to do in c++ or (if you want) python. The
flowgraph of file -> transmit antenna --> over the air --> receive antenna ->
file followed by signal processing in Matlab is sort of not the point of GNU Radio. There's
nothing saying you cannot do this, but you might look in to implementing whatever signal
processing you are doing in GNU Radio. This will reduce the round trip time of testing and
make the whole experience a little better. ( you're basically doing an even slower version
of what we call flying blind:
http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#Flying-Blind )
Re: your other email and question about GR file sink/source:
About the file sinks...
http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#What-is-the-file-format-of-a-gr_file_sink
Basically it's a binary file just like you would expect if you open a file with
'b' flag in most languages I'm familiar with. If you're dumping complex floats
in there then you'll need to read two float values.
2. There is a block called head. It takes a number of samples to pass through
and then quits. But again, you might consider your approach here.
3. I've never actually looked in to the format of a .mat file, but connecting
that (regardless of data inside the file) to a UHD source would be spewing
garbage out. The .dat extension you might see in GR literature is just a
convention we use to denote it's data; it's not really a special format.
-Nathan
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