Hi Experts,
I am confused about one slide: go to slide4math.com chose beam management then chose csi-rs report 1. Then play with green arrows left and right. You will get picture like this:
My doubt is why UE1 measures rsrp of csi-rs user 2 ( blue color) and not rsrp of csi-rs user 1 ( magenta color)?
I am not clear if those are csi-rs beams (beamformed) or csi-rs reference signals (from one single antenna port).
I tend to believe are csi-rs beams as they point in different directions.
Another question: we have seen that csi-rs beams are enabled only when reportquantity=cri-RSRP for one resource nzp-csi-rs. How does Nokia deliver data when this is not active? They have to do it via Grid of beams with PMI, right?
So there are 3 options to cover the whole sector with pdsch beams:
1st one is weights based on srs.
2nd one is GoB based on csi-rs beams.
3rd one is GoB based on PMI.
1st & 3rd switching: based on Ul SINR threshold.
But this is only Huawei.
When srs UL SINR is lower than -10 dB it switches to PMI based weights, till then it uses srs based weights.
Yes, they even recommend -20 dB.
Not sure how GnodeB can decode something at -20 dB.
Param is called srspresinrjudgethld.
But on some projects it is -15 dB in others is -10 dB.
Hat I am trying to understand is how srs ports work. For example if csi-rs ports = 8 and UE has 4 antenna then the air interface matrix H will be 8 x 4.
But UE is 2T 4R.
How gNodeB can constitute a H matrix of 8 x 4 from srs since UE can transmit only on 2 antenna srs signals not on 4 antenna srs signals.
So gNodes B has 8 csi-rs ports to measure srs signals but UE does no have 4 srs transmitting antenna only 2 of them.
So how does gnodeB makes the matrix of 8 x 4 from 2 srs signals?
This problem does not happen in DL PMI because gnodeB has 8 antenna ports and UE has 4 rx antenna so it is easy to constitute the 8 x 4 air interface matrix from csi-rs signals.
And then UE from the air interface matrix H = 8 x 4 can calculate the PMI matrix.
In this case, I think We’d better check UE capability on its layer number. Its maximum layers should be 2. Generally in this case UE has 4 rx antennas but only 2 RF trx front end chains and the smart antennas technology is used to select best two Rx antennas.
I remember they said it is based on srs if UE supports Tx antenna selection - meaning that each time UE transmit srs signal over 1 tx antenna port and turn next.
On one UE log that I have I see supportedSRS-TxPortSwitch = 7 corresponding to 4T4R.
Meaning that now we have UE with 4T4R.
Meaning 4 srs ports are possible yet not for all UEs.
I thought there are no UEs on the market with 4T4R but I was wrong - there are.
Your UE support 2Tx 4Rx that’s why you are getting Rank 4.
But even if UE have 2 TX used for 1Tx for 4G 1Tx for 5G and how about 4TX, 2 antenna each for 4G and 5G.
In NSA.
…never seen such solutions!
