Forum: GNU Radio Questions on stream tags

D41d5d1b903f356b90da0c2c8842b41b?d=identicon&s=25 Hoang Ngo Khac (Guest)
on 2014-05-05 09:57
(Received via mailing list)
Dear List,

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

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?
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?

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...

Sorry if my questions are silly.

Thanks,
Hoang
B4ffbc711addde4c649b1ed526df6157?d=identicon&s=25 Martin Braun (Guest)
on 2014-05-05 14:59
(Received via mailing list)
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
Bc47c4eec3c22199dd203fc7145231d7?d=identicon&s=25 Hoang Ngo Khac (Guest)
on 2014-05-06 04:45
(Received via mailing list)
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).
B4ffbc711addde4c649b1ed526df6157?d=identicon&s=25 Martin Braun (Guest)
on 2014-05-06 09:37
(Received via mailing list)
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
Bc47c4eec3c22199dd203fc7145231d7?d=identicon&s=25 Hoang Ngo Khac (Guest)
on 2014-05-06 12:21
(Received via mailing list)
Sorry, I didn't really get what you meant by "pipe the tagged stream
straight into the uhd sink".
B4ffbc711addde4c649b1ed526df6157?d=identicon&s=25 Martin Braun (Guest)
on 2014-05-07 09:43
(Received via mailing list)
On 06.05.2014 12:18, Hoang Ngo Khac wrote:
> Sorry, I didn't really get what you meant by "pipe the tagged stream
> straight into the uhd sink".

If you put tagged streams into the UHD sink it'll understand that (and
add eob automatically).

M
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