How to start with stream tags

GNU Radio
1

Dear List,

I want to make time synchronization for implementation of two-way
relaying
network. Each node contain both RX chain and TX chain but they should
not
run simultaneously (half-duplex mode). Therefore, the TX chain is on
when
it is needed to transmit, and off when the transmission is over. I found
that stream tags is the key solution to perform that.

My question is, how should I start to learn about* stream tags*, where
can
I find tutorial of stream tags?

Thank you so much.

Best Regards,
Hoang

–
Ngo K. Hoang
Faculty of Electronics and Telecommunications -
University of Engineering and Technology (UET) - Vietnam National
University, Hanoi (VNU)
Vice-president of Student Association of UET
Alternative email: [email protected]
Mobilephone: +84.163.682.7874

2

Try:

http://gnuradio.org/doc/doxygen-3.7/page_stream_tags.html

or

http://gnuradio.org/redmine/attachments/download/252/06-rondeau-stream_tags.pdf

or even

3

Thank you Mr. Newman,

I’ve read (1) GNU Radio Manual on stream tags, (2) slides of Tom R.
and (3) Block Coding Guide about stream tags in
http://gnuradio.org/redmine/projects/gnuradio/wiki/BlocksCodingGuide#Stream-Tags.
They are general and I would like to find some specific example. Anyway,
I
have some questions.

  1. In (3), they give the example codes for reading/writing stream tags.
    Where should these codes be inserted?

  2. sob and eob are inserted to the data frame. Does the USRP Sink remove
    these redundant data before transmitting?

Best Regards,
Hoang

On Tue, Apr 22, 2014 at 9:27 PM, Tim N. [email protected]
wrote:

should not run simultaneously (half-duplex mode). Therefore, the TX chain

Discuss-gnuradio mailing list
[email protected]
Discuss-gnuradio Info Page

–
Ngo K. Hoang
Faculty of Electronics and Telecommunications -
University of Engineering and Technology (UET) - Vietnam National
University, Hanoi (VNU)
Vice-president of Student Association of UET
Alternative email: [email protected]
Mobilephone: +84.163.682.7874

4

Hi Hoang,

aha! Now you’re mentioning USRPs, we know what platform type you refer
to. What USRP are you using?

  1. as you can see, these instructions belong into the work function of a
    block that you write. You’ll have to work through the GNU Radio guides
    on the gnuradio.org start page, after which you’ll be able to design
    your own functionality.
  2. ?
  3. The USRP sink only sends the samples to the device; there is no data
    in the sample stream (which I hope you understand, if you’ve understood
    Tom’s presentation – you can query if there are tags for a specific
    sample range, but there is no in-band data added).

All in all, it seems you’re at the very beginning of understanding GNU
Radio, and you’ve picked up that stream tags might be a suitable tool
for you. They are, but you need some experience writing basic GNU Radio
applications before you can use them.
Although that is currently work in progress, so far you can not instruct
the USRP sink using stream tags – the USRP source just adds a rx_time
tag on certain events.

Hope that was a little insightful,
Greetings,

Marcus

5

Dear Mr. Müller,

I have 3 USRP1s (https://www.ettus.com/product/details/USRPPKG), each
contains one RFX2400 daughter board and one VERT2450 antenna. I found
that
most people here use USRP N210 in their project.

I’ve installed GNU Radio 3.7.0 and made some flow graphs in GNU Radio
with
provided blocks by GNU Radio and coded blocks by other developer. These
flow graphs run well. I’ve learn some basic about how to make new blocks
by
in out-of-tree modules (
http://gnuradio.org/redmine/projects/gnuradio/wiki/OutOfTreeModules).
What
I coded is just very simple: reverse a sequence, combine two sequences
and
separate one sequence into two sequence.

I want to implement a two-way relaying model applying network coding and
using OFDM technique with these USRPs and GNU Radio. Up to now, I built
the
flow graphs for two end nodes and the relay node. They work but without
any
time synchronization. If I want to turn on/off a chain, I press the
button.
I want a method to control the TX chain, and stream tags is the key. I
have
just one more month to make the synchronization done.

Thank you for your answers. Do you have any suggestion for me in my
problem? Can you expand “the USRP source just adds a rx_time tag on
certain
events”?

Best,
Hoang