CBG (Code Block Group) parameters for L1 retransmissions in UE capabilities

5G NR
1

Question about UE capability 5G/NR: why we never see CBG (code block group) parameters for L1 retransmissions in UE capabilities?
I know are not mandatory to be mentioned, but how does UE work with CBG without informing NW about CBG parameters?

I am speaking about these UE capab:

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Also if we search for “codeblock” string in logs, almost nothing is found.
How does 5G NW and UE operate together without exchanging info about codeblockgroup CBG?

2

These cbg used for harq process that instead of sending whole tb only chunk need to retransmit.

3

Yes, but why no info about them is exchanged between NW and UE?

My huntch is that it operates with some default values for CBG.
But where to find those default values for how many CBG are?
For example you have a TB that is more than 1Mb for 1 TTI/slot.
This one will be divided in 4 layers.
So one layer data will be like 250 Kb.
In how many CBG blocks will be divided?
There are many parameters about codeblock in 3GPP, but in UE logs we find none.

4

Need to check. Is it related to some flag value to be enabled?

5

I think simply UE is not configured to work with CBGs.

Idea is that not all UEs support it:

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So when UE does not report anything about CBG it simply does not support it.
And it will not work with CBG.

I think this is what we need to understand.