MIMO Config Interpretation

RAN
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22

Tx antenna in 5G is given by csi-rs ports.
Max 32 possible.
Usually 8 csi-rs ports.

23

Thanks, good info. :+1:

24

So which DL message should Itrack to know the Tx antenna port count?

25

RRC Reconfig for NSA look for nzp-csi-rs with highest number of ports.
Also same number can be deducted from codebook config n1-n2 and multiply by 2.
For example, if n1-n2 is two-one than csi-rs is 2 x 1 x 2 = 4 csi-rs ports.

26

Ok, I’ll check this.

Meanwhile, I got it directly as below:

image

From MAC PDSCH info.
And since this is mentioned as Rx Ant Num I’m a little doubtful of how I’ll get Uneven Tx Rx signals like 4x2 or 8x2.
Here all I have is 2x2, in 5G which is the expected one.

And UL I have SISO like this:

image

27

This is the number of PDSCH layers.
This is not the number of Tx antenna of gNodeB.

28

Isn’t it the layer number given as 1 & 2 which is the PDSCH layers?

29

Yes, it is but still could come from 8 Tx ports.
Tx transmitting elements of gNodeB is given by csi-rs ports.

So you can have 8x4 MIMO DL with 1, 2, 3 or 4 layers.
Where 8 is csi-rs ports.
4 is UE Rx antenna.
And 1, 2, 3 or 4 layers can be changed in any TTI.
Based on DCI 1_1.

30 
nzp-CSI-RS-ResourceId 6,
                      resourceMapping 
                        frequencyDomainAllocation row1 : '0010'B,
                        nrofPorts p1,
                        firstOFDMSymbolInTimeDomain 5,
                        cdm-Type noCDM,
                        density three : NULL,
                        freqBand 
                          startingRB 0,
                          nrofRBs 68

nrofPorts p1,
Is this the line you are referring to?

And max value I find among diff res id is nrofPorts p2.

nzp-CSI-RS-ResourceId 30,
                      resourceMapping 
                        frequencyDomainAllocation other : '010000'B,
                        nrofPorts p2
31

There must be another one with no of ports 4 or 8 or 16.
There are several of them.
Pick the one with highest no of ports.

32

Highest is 2.

33

Then this is the one.

34

Ok that was from NSA log.

In SA I have 4 as below:

image
image779×420 71.2 KB

35

Check also codebook. What is n1 and n2?

36

2 x 1 x 2 = 4?

image
image962×252 57.9 KB

37

Yes 4 csi-rs ports in this case.

38

How different is this 4G MIMO config derived from L1 PDSCH demod info which states it is the number of antennas?

image

39

It means eNodeB transmits with 2 antenna and UE receives with 4 antenna.

40

So why the similar PDSCH config for 5G doesn’t mean the same?
2x2 here.
Addon query: For a 8T8R antenna config, will eNB or gNB share the total number of antenna ports (8) info in downlink to the UE or just the antenna ports (4x4 for e.g.) it will be using to communicate with the UE only?

image

41

Antenna ports and layers is sent to UEin 5G in dci1_1.
But in RRC UE is also informed about number of csi-rs ports 8, 12, 16, etc.