What happen if after HARQ max retrans, UE still report NACK?

Hi all, what happen if after HARQ max retrans, UE still report NACK?

If you reach upto maxharqdl parameter then arq will start at rlc layer.
If its not successful then packet will discard.

Max harq dl ~ 5 times, arq max retrans often 32, right?

Yes we can put t16, t32.

In HARQ retrans, MAC layer has some mechism to ensure transmission quality such as: reduced MCS, RIV, increased RB.
But RLC does not have special mechism, right?

Yes harq have procedure like RV version like incremental or chase combining.
Adaptive or non adaptive retransmission.
Rlc used segmentation , resegmentation, concatenation.

So, if RLC retrans a packet, it may do segmentation of the original packet to some SO?

Yes SO used but I think it’s for NR RLC I find some differences from RLC 4g layer.

After RLC max retrans, RRC reestablishment or reset?

Rrc connection reestablishment with cause maxrlcretxthtrshold.

So, if UE no reply with rrc recfg complete, then release drb, srb?

It depends on.
Considering your second question item you are refering from enodeB to UE. Right?
If so the UE is considered as lost/unreachable and the rrc is released this also can happen in data connection and for that rab is released.

I think u mean rrc connection reestablishment complete sent from UE to enodeb …below is sequence
Ue to enodeb : rrc connection reestablishment request
Enodeb to ue : rrc connection reestablishment accept
Ue to enodeb : rrc connection reestablishment complete