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Re: MIMO with LimeSDR

From: Evgeny Hahamovich
Subject: Re: MIMO with LimeSDR
Date: Wed, 3 Nov 2021 16:24:04 +0200

Thanks Dave, read your previous post, indeed this is something similar to what I did.
Eventually I found the problem... I am used to LimeSDR having an automatic channel selection (L/W/H), and it appears that for channel B, you actually need to select one on your own :) After doing so, it works well!

Now I just need to figure out what to do with those two parallel streams :)
Saw a nice lecture from the last conference by Matt Ettus: https://youtu.be/Qx8uFhumgGM?t=26826
Will try to follow that and see how it goes.

On Tue, Nov 2, 2021 at 7:56 PM Dave Miller <dave.todd.miller@gmail.com> wrote:
Hi Evgeny,

A few months ago, I had I believe a similar situation with the LimeSDR-mini you describe below and show in your attached spectrum plots. Although not a MIMO configuration.

For me the solution was to not use the gnu radio in-tree modulation blocks in gnuradio version 3.8 with the LimeSDR sink block.  I used my own modulator blocks for BPSK and later QPSK with the LimeSDR block.  I sent a square wave pulse shape baseband signal to the input of the LimeSDR-mini.

The full discussion and solution for this work-around with flowgraphs and spectrum plots is on a Lime Myriad RF site thread in August that I established to get some input from the Lime Microsystems folks: "LimeSDR-Mini GR-3.8 Block Transmit Distortion"


---------- Forwarded message ---------
From: Evgeny Hahamovich
Date: Thu, Oct 28, 2021 at 11:57 AM
Subject: MIMO with LimeSDR
To: <discuss-gnuradio@gnu.org>

Hi all,

I am interested in checking the MIMO (well, actually it's SIMO for now) work mode for my LimeSDR with GNURadio (v. Getting into the MIMO mode was simple by setting RxChannel = A+B, but I got stuck just after this...

In the attached screenshots you can see the spectrum and constellations I got for QPSK. As you can see, one of the channels offers terrible performance :( Have you encountered something similar? This is strange to me, I didn't expect such a major difference between the 2 channels performance. Maybe I'm doing something wrong...

Also, can you advise on some blocks I can use for 2 antenas detection to improve performance or point me to some documentation or examples for using this mode?

Thank you,

Thank you,
Evgeny Hahamovich

Cell: +972-55-6633583
Biomedical Imaging and Sensing Laboratory
Technion - Israel Institute of Technology

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