CSI-RS ports

Hello Experts,

I know that max is 32 but usually 8 ports are configured.
Anyone know the reason why usually 8 ports are configured?


Can this limit to 8 DL transmission layer?

Nope, we should not confuse number of csi-rs ports with mimo layers.

See @Jaeku_Ryu explanation at:

5G | ShareTechnote.

Transition from MIMO layers to CSI-RS ports is done by precoding matrix, like explained in the picture above.
In Drive Test CSI-RS ports is not always 8.
Depending on vendor can be also 4.
But I have not seen values like 16 or 32.

Yes, thanks.
And I will read this article and come back if any.

Number of DMRS = PDSCH layer in precoder and this precoder is the input to beam forming used by CSI RS port mapping.
Number of CSI RS port depends on SSB beam & refined beam.
For example 4x4 MIMO need 4 CSI RS port?
Sso usually 8 port is for 8x8 MIMO.
Am I correct?

No, it is not like this.
MIMO layers has nothing to do with CSI-RS ports.
CSI-RS ports are the number of radiating elements (or group of antennas) of an active antenna unit.
So there can be 4x4 MIMO with 8 CSI-RS ports with 16 CSI-RS ports or with 4 CSI-RS ports.
Are not related with each other.
Only conditions is that MIMO layers cannot be higher than CSI-RS ports.

Few more questions on the same topics.
1 SSB = 4 CSI RS refined beam need 4 logical port to transmit and RANK is calculated based on CSI RS reporting?
Is this correct?

Rank is calculated based on SVD (single value decomposition) of a matrix (precoding matrix).

Yes, this is right explanation, thanks. :+1::+1::+1:

Ericsson in 20Q2 version onward will support 16 CSI-RS ports.
With 19Q4, which is mostly active in Ericsson networks there are 8 CSI-RS ports support.
Because of 8 ports, beam is wide and rare or say less chances of MU MIMO.

Great that Ericsson will start using 16 CSI-RS ports starting 20Q2 onward.

Some trail to increase CSI RS port from 8 to 16/32.
Observed good gain MUBF and beamforning performance in NR.

Does anyone knows how many CSI ports are supported by Ericsson 20Q1?
And what is the minimum that has to be configured in the NR cell?

Minimum depend on type of row selected i.e. row1.
If we configured other type then other row can be selected.
I mean minimum 1 port.

In latest release Ericsson support row16 and 17 also.
Meaning it supports upto 32 ports.

32 port for mmWave only, right?

We can configure this in midband too.