How gNB initiates an PDCCH order incase of UL sync loss?

Question

gNB can intiate RACH procedure for PDCCH order. But If UE is configured with NUL and SUL , then How UE comes to know for which UL carrier it has to initiate PDCCH order.

Answer 1

Hi Chara,

PDCCH order can be initiated be gNB by DCI. gNB send an optional preamble to UE by DCI to initiate an RACH to acquire UL sync.
Please refer RACH section of 38.321 for more information.