File sink problems

GNU Radio
1

Dear all,

I have simulated an OFDM transmission chain. I generated data file with
1000 samples and save it to file “random_1k_source”. I did ofdmmod and
then ofdmdem. Finaly I saved the demodulated samples to the file
“random_1k_sink”. I compared the files with gr_int_plot. The
“random_1k_source” file has 1000 samples and the
“random_1k_sink” file has only about 750 samples. Do I make somthing
wrong? There is no difference between the file sink option unbuffered on
or off.
Thank for you help
A. Baier

2

On Fri, Sep 13, 2013 at 12:27:51PM +0200, Baier wrote:

Dear all,

I have simulated an OFDM transmission chain. I generated data file
with 1000 samples and save it to file “random_1k_source”. I did
ofdmmod and then ofdmdem. Finaly I saved the demodulated samples to
the file “random_1k_sink”. I compared the files with gr_int_plot.
The “random_1k_source” file has 1000 samples and the
“random_1k_sink” file has only about 750 samples. Do I make somthing
wrong? There is no difference between the file sink option
unbuffered on or off.

Most likely this is connected to packet sizes (granularity of packets).
Which blocks were you using?

MB

–
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin B.
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu

KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

3

On Mon, Sep 16, 2013 at 09:08:53AM +0200, Baier wrote:

Most likely this is connected to packet sizes (granularity of packets).
Which blocks were you using?

MB

I dont’t have any packet data transmision. I generate 1000 samples and I use
OFDM mod(fft 128, ot 100, cp 16) from GRC. It is only streaming.

That still uses packets. When you increase the amount of generated data,
does that help?

MB

–
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin B.
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu

KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

4

On Tue, Sep 17, 2013 at 10:01:36AM +0200, Baier wrote:

If I generate 100000 samples the source file has 400 kByte and the sink file
after the ofdmmod und demod has only 95,7 kByte.
I think it could be a buffer problem.
A. B.

Well yes, but it could also be a problem of packet granularity. I’m not
sure how large the packets in OFDM mod are.

Also, try and and remember answering to the list.

MB

–
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin B.
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu

KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association