[USRP-users] packet transmission question

Francois Quitin fquitin at ulb.ac.be
Thu Sep 19 04:53:17 EDT 2013

Hi all, 


We have a little question for you: we use a USRP+WBX with a code derived
from tx_timed_burst.cpp to create our custom transmitter, and we use another
USRP that records the received data to a file. 


When we look at the received signal, we observe a slight small staircase
(around 30 samples long at 10MHz = 3us), as can be seen in the attached
figure. It seems that our actual transmitted packet starts after this
"stair". When we decrease the sample rate to 5MHz, the "stair" is still 30
samples long (6us this time). 


As we are working in a case where timing is very critical, this 3us delay is
a bit of an issue (unless it's constant in which case we can compensate for
it). Any idea where this is coming from ? 






Francois Quitin, Ph.D.


Research Fellow

INFINITUS - Infocomm Centre of Excellence

School of EEE, Nanyang Technological University

50 Nanyang Ave, S2-B4b-05
Singapore 639798 

Phone: +65-8502-3690

Email: fquitin at ntu.edu.sg <mailto:fquitin at ece.ucsb.edu> 


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