Physical/MAC | DL synchronization | Doppler shift, long delay | Pre-/Post-compensation of Doppler shift, common offset |
UL synchronization (TA, RACH) | TA variation, long delay, long procedure (4-step RA) | Common timing/frequency offset, use of UE/Satellite position information, 2-step random access, Enhanced PRACH formats/preamble sequences |
UL scheduling | Long delay | SR/BSR/Grant procedure optimization |
Retransmission issue | HARQ | Long delay, need more HARQ processes | UL HARQ ACK disabling, UL retransmission disabling |
RLC/PDCP | Timer | Long delay | Longer timers: t-Reassembly, discardTimer, t-Reordering |
SN | Large window size | Longer RLC/PDCP SN |
Mobility | Tracking area | Frequent TA change | Handover, TAU, Paging |