5G NR MIMO 4x4 in DL

Oh, got it.
Then UE will need to be camped on two SSB beams?

I think those are dedicated user beams i.e PDSCH ones, not cell beams like SSB.

I think I understand the text in book now.
In its example, basically antenna array is 8 elements (4 +45 + 4 -45).
Author is suggesting that 1st UE is being served 4x4 layer using 4 +45 polarization and 2nd UE being served 4x4 using 4x -45 polarization.
I had long discussion on similar topic with a colleague long time ago and we sort of agreed that +45/-45 polarization of 1 antenna element actually points in same direction.
This book is suggesting otherwise.
I cannot confirm this.

I think i found the answer in Sharetechnote (@Jaeku_Ryu) page that each stream of MIMO is generated by a sub-array and not by all antenna elements.
Please see attached picture and the link here:

https://www.sharetechnote.com/html/5G/5G_CSI_RS_Codebook.html

Hope this clarify all the doubts.
So if there are 8 streams for 8x8 DL MIMO there will be 4 subarrays generating them each subarray having a +45 and a -45.
Don’t know what was written in that book and I am not trying further to understand…

Hi @Dan_s.
If we have 128 AE (64 T64R) ie 64 (+45) and 64 (-45) then considering case of dual stream.
I think all 128 AE will use for steam generation ie 64 for one steam and 64 for second stream.
How to decide which AE to used out of 128?

I also think the same that for 2x2 DL MIMO layers will be 2 streams one +45 from 64 AE and another -45 from 64 AE.
I don’t know what priprietary algos decide which AE to be used for that but I think it has to do with N1, N2, O1and O2 numbers and number of CSI-RS ports as written on sharetechnote page.

Yes same apply for 5G NR active antenna as well.

UE will know type of antenna like explained here.

@Dan_s, above picture given for TM9 mode?
Or 5G NR you referring?

Is 5G from same page Sharetechnote.

As I know, ur give feedback about their condition, if the condition is bad, gnb try to change direction to another degree of beam for that UE…