Re: [Discuss-gnuradio] How to start with stream tags

[Hoang Ngo Khac]

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

 

On Wed, Apr 23, 2014 at 7:39 PM, Marcus Müller <address@hidden> wrote:

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

On 04/23/2014 06:41 AM, Hoang Ngo Khac wrote:

Thank you Mr. Newman,

I've read (1) GNU Radio Manual on stream tags, (2) slides of Tom Rondeau 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?

3. 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 Newman <address@hidden> wrote:

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

http://bit.ly/1kWXdCl

On Tue, Apr 22, 2014 at 6:29 AM, Hoang Ngo Khac <address@hidden> wrote:

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 Khac 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:  address@hidden

Mobilephone:  +84.163.682.7874

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--
Ngo Khac 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:  address@hidden

Mobilephone:  +84.163.682.7874

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