This is not correct.
MIMO references is transmit and receive antenna.
So when you see 4x2 mimo means 4 tx antenna and 2 rx antenna.
Don’t know what is represented in this picture.
I got it from LTE Transmission Modes and Beamforming - White Paper.
From R & S
Look at the first picture. Does it seem to you it is 2xN MIMO?
It looks more like an 8xN transmission because it has 8 distinctive TX antenna.
It is not clear what R&S says until you read: Each “polarization column” (blue or red) represents an antenna element that can transmit a different signal.
Then indeed that picture is for 2xN transmission scheme.
MIMO MxN means M transmit antenna and N receiving antenna.
Here N may be UE receive antenna since for eNB or gNB TX =Rx usually.
Indeed, but there is MIMO for UL and MIMO for DL.
Specifically whenever we speak about DL MIMO M is TX of BTS and N is Rx of UE.
We have seen 8 x 2 in TM9 for one carrier - which uses beamforming in LTE.
What R&S wanted to say with first picture 2xN is that 4 transmission antenna +45 degree are beamforming one tx layer.
And the other 4 antenna of -45 degree are beamforming the other tx layer.
I think we should call it Antenna elements.
Each vertical column is an antenna according to the picture.
It is but antenna ports is only 2
Rest are just phase shifts of same signal, not a different signal.
This is why mapping of layers to antenna ports will have only 2 ports for first picture.
Either way R&S naming of antenna is wrong.
Antenna for massive mimo are nominated by n1 and n2 values as per 3GPP recommendations.