[USRP-users] USRP under run when when trying to send messages in a low rate

Martin Braun martin.braun at ettus.com
Thu Mar 24 19:32:40 EDT 2016


If you're sending non-contiguous samples, the last packet of every burst
needs to be tagged as 'end of burst'. If you're using GNU Radio, add a
tag on the last sample of the burst with key 'tx_eob' and a non-negative
value (e.g. PMT_T). If you're using straight UHD, set the eob field in
the tx_metadata to true.

Cheers,
Martin

On 03/23/2016 06:19 PM, Damindra Bandara wrote:
> Martin,
> 
> I do not know about end of burst packets. If possible could you please
> give me more details on what I should do.
> 
> Thank you
> Damindra
> 
> On Wed, Mar 23, 2016 at 1:46 PM, Martin Braun via USRP-users
> <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>> wrote:
> 
>     Damindra,
> 
>     this looks like bursty transmission, are you sending end-of-burst
>     packets?
> 
> 
>     M
> 
>     On 03/22/2016 08:22 AM, Damindra Bandara via USRP-users wrote:
>     > Hi Marcus,
>     >
>     > Thank you for getting back to me. Here is the description of my application.
>     >
>     > I want to get the user messages and transmit it via USRP. Since the
>     > messages are infrequent I am use a beacon message to keep the message
>     > stream  alive. I use QPSK as the modulation scheme. A beacon message is
>     > transmitted in every second. At the receiving end I extract the
>     > application level message and output it. I am using Etuss USRP N200 to
>     > test the setup.
>     >
>     > The problem is that I do not receive the message at the other end. When
>     > I observe the constellations at the receiver  it shows that the QPSK
>     > demodulator does not remain synchronized. Also I observed  'UUUUUU'  at
>     > the transmitter end.(which is due to an under run at the USRP).
>     >
>     >  If I transmit a file using this setup it works fine. But when I
>     > transmit messages it is not transmitting.
>     >
>     > The transmitter end: application-->packet encoder --> QPSK modulator -->
>     > USRP sink
>     >
>     > Receiver end: USRP source --> Synchronization blocks --> QPSK
>     > demodulator  --> Packet decoder --> application
>     >
>     > Let me know if you need further information. I really appreciate if you
>     > could help me to solve this issue.
>     >
>     > Thank you
>     > Damindra
>     >
>     > On Tue, Mar 22, 2016 at 4:05 AM, Marcus Müller
>     > <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>
>     <mailto:usrp-users at lists.ettus.com
>     <mailto:usrp-users at lists.ettus.com>>> wrote:
>     >
>     >     Hi Damindra,
>     >
>     >     it's a bit too much guesswork involved if you don't share *what*
>     >     kind of application in GNU Radio you're designing. And a few
>     >     parameters would be helpful too: something like sampling rate
>     of the
>     >     USRP, which USRP type you're using.
>     >
>     >     Generally, an underrun means your computer wasn't fast enough at
>     >     providing samples to your USRP.
>     >
>     >     Best regards,
>     >     Marcus
>     >
>     >
>     >     On 22.03.2016 04:06, Damindra Bandara via USRP-users wrote:
>     >>     Hi,
>     >>
>     >>     I am creating an application using GNURadio that transmits a
>     >>     message every second. When I try to do this the transmit USRP
>     >>     indicates that is is under run and I was not able to recover the
>     >>     message at the receiving end.
>     >>
>     >>     When I use the same setup to transmit a file it works fine and
>     >>     able to recover it.
>     >>
>     >>     Is there any procedure that should be followed when transmitting
>     >>     infrequent messages? I appreciate if I could get any help.
>     >>
>     >>     Thank you
>     >>     Damindra
>     >>
>     >>     --
>     >>     Damindra Savithri Bandara,
>     >>     PhD in Information Technology (Candidate)
>     >>     George Mason University,
>     >>     Fairfax,
>     >>     Virginia
>     >>
>     >>
>     >>     _______________________________________________
>     >>     USRP-users mailing list
>     >>     USRP-users at lists.ettus.com
>     <mailto:USRP-users at lists.ettus.com>
>     <mailto:USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>>
>     >>     http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>     >
>     >
>     >     _______________________________________________
>     >     USRP-users mailing list
>     >     USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>
>     <mailto:USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>>
>     >     http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>     >
>     >
>     >
>     >
>     > --
>     > Damindra Savithri Bandara,
>     > PhD in Information Technology (Candidate)
>     > George Mason University,
>     > Fairfax,
>     > Virginia
>     >
>     >
>     > _______________________________________________
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>     >
> 
> 
>     _______________________________________________
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> 
> 
> 
> 
> -- 
> Damindra Savithri Bandara,
> PhD in Information Technology (Candidate)
> George Mason University,
> Fairfax,
> Virginia





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