Agree, even in Nokia also it is a parameter as per radio design.
The more csi-rs ports, the narrower the beam and higher the gain.
8 port csi rs beam can generate more directional beam.
But we need csi rs reference signal per layer and that can be generated from x port based on that directivity and gain change, right?
I think there is csi-rs reference signal for each csi-rs port 3000s.
csi-rs beams are different, are transmitted in different direction and different time and different frequency.
one csi-rs beam is generated using all csi-rs ports to have a high gain and narrow beam.
In 64 csi-rs beams, 4 csi-rs beams transmitted in a slot.
All 64 will cover the whole sector while 4 are expected to cover an SSB.
3 terms here:
- CSI-RS signal
- CSI-RS beam
- CSI-RS ports
UE will measure CSI-RS signal to report csi, let’s say there are 4 layers.
Then UE will report csi by measuring CSI-RS signal.
But how many ports for csi-rs used, is the open question now.
In my view 4 ports will be used.
So 16 SSBs assumed here?
Yes, assumed is the word.
I don’t have the config file to check in params.
Or the SSB bitmap.
8 is max limit for FR1.
The idea is: 16 ssb beams cover whole cell, for eg 128°, initial access UE and gNB know which SSB index, can locate UE within 8° of each SSB.
Then in connected, locate UE within 2° of each csi-rs beams?
Refined beam possible with FR1 only.
What you need to understand for csi-rs ports is this:
A PDSCH layer is sent to each of the csi-rs port (let’s say 16 of them) and each csi-rs port will apply a different weight so all 16 signals will reach a speciifc Ue antenna (no 3 let’s say) so will sum up to reach maximum level.
Followings short notes for each process.
This is very well explained in Sharetechnote:
A -> B : This is the process of the raw data (data with DMRS) to CRS-RS antenna port. This mapping is done by multiplying the data with PMI matrix(codebook). The number of columns of this matrix is same as the number of layers (i.e, the number of DMRS antenna ports) and the number of raws of this matrix is same as the number of CSI-RS antenna ports. This mapping can be illustrated as follows.
FR2 also have refined beams.
Really? In my understanding it’s with digital beamforming only.
I think beam forming is target of FR2.
All mmWave I have seen had Csi beams.
Hope this is what you meant by refined beams.
I think FR1 has digitial beamforming while FR2 has analogue beamforming.
But most vendors use hybrid versions of AAU where both analog and digital beamforming is used.
Yes, I mean refined beams only valid with FR1 only.
Yes, correct. Hybrid beamforming is future concept as of now.
I think we have discussed this with some logs long time back, where I have shared snaps of 4 refined beams in mmwave DT csi-rsrp of the best refined csi beam was chosen.
Maybe was this discussion: Beam Management, Beam Switching and Beam Refinement in 5G NR - #22 by ankgitm
Very well explained, thanks!
Anyone can share idea about CSI resource?