Ok lets explain a little bit more what actually you observe. Each burst
is a training sequence that has a duration of 64 samples and then 1000
zero samples. This is generated using a vector source block repeatedly.
As you can see in the ok.jpeg all sequences are exactly the same. In the
other plot however the sequence constantly changes. To me, it seems that
parts of the actual sequence are randomly cropped or re-arranged. This
happens only when two different B210 are used. We also tried to transmit
the sequence from a third device with the same results.
And yes we have tried to receive from both devices each one working on a
separate flowgraph. The result was exactly the same.
On 06/13/2017 06:05 PM, mle...@ripnet.com wrote:
I'm having a hard time seeing a significant functional difference
between the two. Could you perhaps explain?
Also, maybe a diagram showing the two configurations?
Do you get any error messages during a run?
Are you doing reception on the two USRPs within a single flow-graph,
or two separate processes?
On 2017-06-13 10:51, Manolis Surligas wrote:
Hi Marcus,
yeah we have updated the UHD on the latest version and the problem
still persists. I have started to debug the UHD and we suspect some
kind of inconsistency between the device pointers of the different
devices. Perhaps a race condition is hidden somewhere.
I also attach two plots. The first one is the problematic with two
different USRPs and the second the expected signal transmitting and
receiving using the same USRP.
On 06/13/2017 05:30 PM, mle...@ripnet.com wrote:
Thanks, George.
Two things:
Could you try updating to the most recent UHD version?
It would be helpful if you provided your .dat files in the form of
plots or graphs, highlighting the areas you consider "distortion".
This will help us help you.
On 2017-06-13 07:23, George Vardakis wrote:
Good evening,
I attach three captures to show you the problem, one with the
reference signal i transmit, one with the received samples when
using the same device for TX and RX and one with the received
samples of the one device, when the second one transmits. I also
attach the flowgraph i used for this capture. The sampling rate
i use is 1MHz. The specific captures are done with the USRPs
over USB-2 ports, but i have also tried over USB-3 and observed
the same behavior.
Thank you for your time
same_tx_rx_device.dat
<https://drive.google.com/file/d/0BxyASy57xNmqV2pLd2xUVWRRRU0/view?usp=drive_web>
refference.dat
<https://drive.google.com/file/d/0BxyASy57xNmqT1JQd2xfWjF6SjQ/view?usp=drive_web>
different_tx_rx_device.dat
<https://drive.google.com/file/d/0BxyASy57xNmqMVhqd29NTmdiMDA/view?usp=drive_web>
On Tue, Jun 13, 2017 at 12:04 AM, Marcus D. Leech
<mle...@ripnet.com <mailto:mle...@ripnet.com>> wrote:
On 06/12/2017 03:53 PM, George Vardakis wrote:
Hello all,
I have two USRP B210 devices which i use in my MIMO
application. When i use the two of them concurrently in
a flowgraph - or different flowgraphs - i notice that
the signal received by the streams of one of the devices
(the one whose serial number is last in lexicographical
order) is distorted. Because i transmit a known training
sequence, i know what to expect, and i observe that
sometimes the real or imaginary part of the signal has
flipped its sign (i see the signal mirrored compared to
the known one), or other times it is completely
distorted. When i use each device separately, everything
works fine. The UHD driver i use is the v3.9.5 one.Any
ideas about it?
Thank you!
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COuld you perhaps share a very-simple flow-graph that shows
the issue? What sample-rate are you using? Is this over
USB-2 or USB-3?
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