Hello Experts.
If I configure 4 RF ports on RU (4 antennas configured).
And fully attenuate (at max attenuation) 2 antennas out of 4.
Then shall UE see 2 antennas and report RI 1 or 2 with num of layers 2 (and not RI 3)?
Yes.
In your case 2 ports attenuated.
So max layers 2.
So RI can be 1 or 2 as per radio condition SINR.
Thanks, I understand.
So RI 1 or RI 2 according to SINR.
But when like UE decides to report RI 1 and when RI 2?
Like what is SINR ranges for RI 1 and RI 2?
When UE reports RI 1 means UE sees two anntenas but num of layer is 1, is it?
No such defined tables.
In theory generally you can say from SINR 30 to 2 it’s like RI2 and less then 2 tend to RI1.
Main point is to improve RI2 sample to improve SINR in cluster by reducing overlapping.
Yes I understand, thanks.
But trying to understand when RI 1 means one layer and RI 2 means 2 layers?
Or even with RI 1 still num of layers 2?
RI will be always higher or equal to number of layers. Ie you can never have more layers than is your rank. RI is basically saying how many uncorrelated channel paths UE can see. If lets say you have RI=2 then you can transmit one OR two layers. If you are close to BTS in good radio conditions, typically you will be using two layers to maximize your THPUT, if you are far away but still can see two paths, you might be transmitting only one data layer over two paths (diversity) to improve your communication reliability. Actual thresholds are hidden as they are vendor/chipset dependent, but if you do large drive tests you can start extracting some data… for example I have seen reports with SIMO to MIMO switching around 10-12dB (SINR).
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