Forum: GNU Radio USRP Delays

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04a562aa0bb96f564cf5134a32d63c2d?d=identicon&s=25 sri ram (Guest)
on 2008-11-28 21:48
(Received via mailing list)
Hi everyone,
                  I am interested in knowing the delay jitter of the
transmission time of a packet/waveform. Specifically, I want to know the
time between the time the flowgraph is tsarted in python ( or
tb.start) and the time that the first sample is transmitted into the air
from the USRP hardware. I want to know if I can reduce the jitter in
time (across runs) to as low a value as possible.

I use with gnuradio-3.1.2 to transmit a square waveform
try to start the flowgraph at a precise time x (in microseconds) by
y=x-time.time() and time.sleep(y) and then tb.start(),time.sleep(0.1)
tb.stop(). I also use an interp of 32 at the Tx. I have a receiver that
all data (with -d 64). I observe the samples just out of the usrp

For transmissions that are precisely spaced in time using appropriate
x, the inter transmission delay measured at  the receiver is off by a
> than 2 ms.
(despite using nice to increase the priority of this process).

1. Is it possible to reduce the jitter between successive Tx.delay
measurements to be few 10's of microseconds or lesser?

2. Is there a way to run the usrp_siggen code as a kernel module to
the delay jitter performance?

Thanks in advance for your help,
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