What does it mean when NDI = 1 and RV could be 0, 2, 3 or 1?

Hi Experts.

In DCI there is RV field.
What does it mean when NDI = 1 and RV could be 0, 2, 3 or 1?

I know that NDI = 1 means new data but then what does it mean to have redundancy RV = 2 and NDI = 1?
Since it’s new data what is the redundancy for?

NDI 1 alone doesn’t represent new data.
It’s only when the NDI bit is toggled for a HARQ ID, the transmission along with that toggled NDI represents new data

RV is basically redundancy versions.
Each RV contains different parity bits which help with increasing the probability of successful decoding.

So, say the NDI is toggled and the UE is expecting new data.
What is the indication of an RV = 2 if the data is fresh?

I guess I was thinking RV indication makes sense only for retransmissions.

This is not expected.
If this is happening, then there is a network issue.
RV 0 and 3 are self decodable but 2 isn’t.
So, RV2 can only be used when combined with RV0.

So new data would (which toggled the NDI) can come to there with RV 0 or 3 only.
A retransmission can come with RV = 0 2 1 or 3?

Yes, normally, it starts with RV0.
Retransmission with RV2, 3, 1.

Thank you.
I didn’t know RV0 is self decodable.
That makes sense!

The default value is 0,2,3,1 but you can configure 2,3,0,1 also (manually value).

I thought we can’t start with 2 since it’s not self decodable.

See above: