In the two-USRPs scenario, one of the USRPs is transmitting, and one is
receiving?
Are they "through the air" or over a cable. If over a cable, how much
attenuation has been added to the cable.
On 2017-06-13 11:16, Manolis Surligas wrote:
> 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 [2]
> refference.dat [3]
> different_tx_rx_device.dat [4]
>
> On Tue, Jun 13, 2017 at 12:04 AM, Marcus D. Leech <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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[2]
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