Fwd: MIMO with LimeSDR

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"

Regards,

Dave

---------- 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.3.8.3.1). 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,

Evgeny

From:	Dave Miller
Subject:	Fwd: MIMO with LimeSDR
Date:	Tue, 2 Nov 2021 13:55:04 -0400