How many transmission schemes available in 5G for PDSCH?

Hello Experts,

How many transmission schemes available in 5G for PDSCH?

As far as I know there is only 1 transmission scheme is available and that can go up to 5 to 8 layers with 2 Codeword and 1 to 4 layer with 1 codeword.

Only 8 layers are possible with 2 codewords so in 5G maximum, 4 UE can be paired with 2*2 MIMO is this right?

Yes correct.

If 4*4 UE there then with MU MIMO 2 UE can be paired considering 8 SSB.

If we increased SSB > 8 then also layer will 8 only as per transmission scheme 1?
Why is the limit of maximum 8 layers with 2 codeword?
What are the challenges?

Sorry mentioned wrong.
With MUMIMO upto 16 MIMO stream in DL so upto 8 UE 2 * 2 can be in pairing.
Upto 4 UE 4 * 4 MIMO DL can be in pairing.

Correct @ankgitm.
That’s why the question is how 16 MIMO layer is possible as transmission scheme is supporting 8 layers only?
What is the relation of transmission scheme 1 and MIMO layers?

Limit is 8 layers with 2 codewords as per 3gpp for one UE.
Even now in drivetest you hardly see rank 4 in drivetest and as of today no UE supports 8x8 dl mimo (rank8).
But gNodeB can provide up to 16 layers in DL for MU-MIMO and this number of 16 will increase in future releases.

Thanks @RFSpecialist.
Which parameter configuration defined mu MIMO layer in gNB?
And which L3 in drive test.

It is not in layer3.
It is in dci format1_1.

Ok got it thanks.
Any parameter to be configured for it?

It is different for each vendor.
Basically needs to configure proper antenna type if 8T8R or 32T32R or 64T64R, etc.

Yes understood it’s different for each vendor.
In Huawei which parameter?
8T8R, 32T32R and 64T64R are antenna design specifications, ok.
I just wanted to know parameter setting that control maximum dl mimo layers.
As you said currently it’s 16 layers.

With Huawei, MNOs have to purchase license for each MIMO layer.
That means you cannot activate 16 layers without purchasing 2 layers license.
8 licenses are required.
Per cell.

Ok thanks no problem, I will read Huawei documentation.
16 layers can be possible now DL MIMO layers.
Now for example 1 SSB can have 4 CSI RS beam and with polarization 8 DL layers per SSB can be possible?
Is this sentence correct?

According to Huawei:
maxmimolayernumDL for PDSCH with 64T64R and 32T32R -16 layers are supported.

Yes, 16 Layers.

Not sure about this.
We should not confuse csi-rs ports (max 32) with csi-rs beams (I think no limitation in number but i’ve seen a case with 64 csi-rs beams in mmwave).
To my understanding csi-rs beam each points toward a different direction in space.

Please read this:

Thanks @RFSpecialist.
Let me re-define my question: 1 SSB beam can have 4 CSI-RS beams?
Each CSI_RS beam must have a separate antenna port?
For example we have different raw index up to 32 port as per 3gpp, correct?


1 SSB = 4 CSI-RS beam and these beams can be scheduled to UE /TTI?
Is this correct?

I think you wrongly understood that picture.
Each color represents a SSB beam with different location in time and in space.
Don’t know why you mention 4 CSI-RS beams associated with a SSB beam, where in 3GPP it is menytioned this?

Each csi-rs port has a different TRP point (max 32 possible) like explained here:

You are very right, as per color represents SSB Beam not CSI RS in above picture.
I have interpreted wrongly.
3gpp i have mentioned is for CSI RS port mapping.

For FR1 1 ssb = 4 csi rs beam if we enable csi rs beam related parameter.

Now my question is 1 SSB = 4 CSI RS beam what is the meaning of this sentence?
Which beam carry PDSCH, SSB or CSI RS?