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Re: [Discuss-gnuradio] Questions on stream tags


From: Martin Braun
Subject: Re: [Discuss-gnuradio] Questions on stream tags
Date: Tue, 06 May 2014 09:36:28 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

On 06.05.2014 04:44, Hoang Ngo Khac wrote:
Hi Martin, and all,

I meant, I want to add tx_sob and tx_eob to tell the USRP Sink to
start/stop the TX chain. I intend to add tags before the modulation,
where data type is /byte. /Since the provided block PDU to Tagged Stream
takes message as input, I guess I need to make my own block(s).


On current master, you can also pipe the tagged stream straight into the uhd sink.

M

On Mon, May 5, 2014 at 7:57 PM, Martin Braun <address@hidden
<mailto:address@hidden>> wrote:

    On 05.05.2014 09:56, Hoang Ngo Khac wrote:

        Dear List,

        I'm new to stream tags. Could someone help me to understand
        about stream
        tags and know how to use it?


    Remember that we have a lot tag debugging tools available, such as
    the QT GUI Time Sink and tag debug.


        1. In GNU Radio Manual: "A stream tags is generated by a block's
        work
        function and from there on flows the downstream...*until it
        reaches a
        sink*...".

        If we use tags to tell the USRP Sink to start/stop the TX chain,
        do we
        need to modify the USRP Sink block?


    Probably not... are you talking about tx_sob and tx_eob?


        I found that gr_uhd_usrp_sink.cc file contains the
        get_tags_in_range()
        function. However, this file is not, at first, in the GNU Radio
        3.7.0
        source folder. How to add this to project and make it work with
        USRP Sink?


    Look in gr-uhd/, there it is.


        2. I am implementing a model of ofdm-based two-way relaying network
        apply network coding. Up to now, each single transmission in one
        time
        slot are done, but the model runs without any timing
        synchronization.
        For this, I need to use TDMA, and stream tags is the solution. I
        list
        here the steps to make TDMA with stream tags. Could you leave some
        comments if I miss some thing?
        + Add tags to stream; using provided block such as PDU to Tagged
        Stream,
        or custom block.
        + Write a block for error checking, repeat request...


    Seems right. You shouldn't need other blocks to control UHD.

    M


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