Forum: GNU Radio Overflows in benchmark_rx.py

Hi,

I was running the benchmark scripts with the following set of parametrs

-f 915M -r 5000000 -m psk -8

with 30 dB gain set on both Tx and Rx. I was getting cluttered overflows
and packet received during that time are in error.. Like I'm receiving
about a 1000 packet without error and then then system runs into 
overflow
and about then quite a large number of packets are received in error.

Output is posted

Demodulator:
bits per symbol:     3
RRC roll-off factor: 0.35
FLL bandwidth:       6.28e-02
Timing bandwidth:    6.28e-02
Phase bandwidth:     6.28e-02
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes

UHD Receiver:
UHD Args:
Freq:        915MHz
Gain:        30.000000 dB
Sample Rate: 3.33333Msps
Antenna:     None
Spec:        None

Demodulator:
bits per symbol:     3
RRC roll-off factor: 0.35
FLL bandwidth:       6.28e-02
Timing bandwidth:    6.28e-02
Phase bandwidth:     6.28e-02

Receive Path:
modulation:      psk_demod
bitrate:         5Mb/s
samples/symbol:  2.0000
Differential:    True
Using Volk machine: avx_64_mmx
ok =  True  pktno =    1  n_rcvd =    1  n_right =    1
ok =  True  pktno =    2  n_rcvd =    2  n_right =    2
ok =  True  pktno =    3  n_rcvd =    3  n_right =    3
.
.
.
ok =  True  pktno = 2953  n_rcvd = 2953  n_right = 2953
ok =  True  pktno = 2954  n_rcvd = 2954  n_right = 2954
ok =  True  pktno = 2955  n_rcvd = 2955  n_right = 2955
ok =  True  pktno = 2956  n_rcvd = 2956  n_right = 2956
ok = False  pktno = 2957  n_rcvd = 2957  n_right = 2956
ok = False  pktno = 2959  n_rcvd = 2958  n_right = 2956
ok = False  pktno = 2961  n_rcvd = 2959  n_right = 2956
ok = False  pktno = 2963  n_rcvd = 2960  n_right = 2956
ok = False  pktno = 2965  n_rcvd = 2961  n_right = 2956
ok = False  pktno = 2967  n_rcvd = 2962  n_right = 2956
.
.
.
ok = False  pktno = 3838  n_rcvd = 3369  n_right = 2956
ok = False  pktno = 3841  n_rcvd = 3370  n_right = 2956
ok = False  pktno = 3843  n_rcvd = 3371  n_right = 2956
ok =  True  pktno = 3845  n_rcvd = 3372  n_right = 2957
ok =  True  pktno = 3846  n_rcvd = 3373  n_right = 2958
ok =  True  pktno = 3847  n_rcvd = 3374  n_right = 2959
ok =  True  pktno = 3848  n_rcvd = 3375  n_right = 2960
.
.
.


Any idea how to avoid these overflows???

On Fri, Feb 15, 2013 at 9:46 PM, Manu T S <manu.t.sree@gmail.com> wrote:

>
> -- Current send frame size: 1472 bytes
> bits per symbol:     3
> Using Volk machine: avx_64_mmx
> ok = False  pktno = 2957  n_rcvd = 2957  n_right = 2956
> ok = False  pktno = 3843  n_rcvd = 3371  n_right = 2956
> --
> Manu T S
>

This is usually a problem due to the receiver not being able to keep up
with the flow of samples from the UHD device. Try running at a lower
bitrate. If you're seeing overflows temporarily and then things are
correcting themselves, it looks like you might be right on the edge of 
your
system's capabilities. In this case, it's like some other process/task 
is
taking some time away from your app, causing it to slow down just enough 
to
cause problems, but then things look like they come back. You could also
try to run with realtime privileges enabled to make sure your process 
gets
priority.

On the other hand, the output you show here doesn't have any overflow
indication. Are you sure that this is what's happening? You're running 
at
915 MHz, the center of the 900 MHz ISM band (depending on where you 
are).
It's likely to have other signals in it. Maybe this is just a case of
interference?

Tom

Hi Tom,

Thanks for the reply.. I teed the output at the Rx to a file. It showed 
O's
on my screen, but the file had no O's. I came to know from a friend of 
mine
that the O's may be going into the stderr and the file had only stdout
output. But the errors you see there were actually preceded by O's. I 
will
run them again after making the changes you suggested.

Thank you