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Re: Issue with USRP signal reception when stream is produced by a Vector
From: |
Marcus Müller |
Subject: |
Re: Issue with USRP signal reception when stream is produced by a Vector Source |
Date: |
Tue, 8 Jun 2021 19:07:50 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 |
Just from very quickly over your attached images:
Your receiver is clipping, you can see that: the receive waveform should never
even touch "1".
You need to substantially reduce gain, potentially both in your receiver and
transmitter.
Best regards,
Marcus
On 08.06.21 16:32, Γιώργος Γιώργος wrote:
> Hello to everyone on the list,
>
> To begin with, my overall goal is to build an adaptive modulation scheme
> using GnuRadio
> and USRPs. Concept-wise, this will be implemented by calculating the BER at
> the receiver,
> feeding this data to the transmitter, and switching between two different
> modulation
> schemes based on threshold BER values.
>
> I am currently working on an 8DPSK modulation format. After succesfully
> building and
> testing the flowchart in simulation, I split the transmit and receive chain
> in order to
> actually test the setup using two B210 USRPs.
>
> After a little bit of experimentation, transmission is great when using a
> random source at
> the transmitter. The FFT plot and the Constellation appear as expected.
> However, when
> using a vector source, which is mighty helpful for my purpose since I have a
> known bit
> sequence to compare at the receiver, my ouputs are unexpected (screenshots
> attached). This
> is baffling because the only thing that changed is the bit sequence and
> nothing in the
> actual signal processing chain (to be frank a packed to unpacked, and upacked
> to packed
> block were used after the vector source, but I'm getting pretty much the same
> results
> without them). I have experimented with different parameters but to no avail.
> It is
> important to note, that the simulations were working fine, regardless of the
> source that
> was used.
>
> Any thoughts on why this is happening? I have also attached screenshots of
> the flowcharts.
>
> Thank you very much for all the effort you are putting into the project.
>
> Best regards,
> George
>
>