Flexible slot format means flexible resource allocation in many possible ways. It could mean:
- TDD self contained slot where opportunity for DL or UL scheduling, DL or UL data, and acknowledgement or SRS are all in the same slot.
Data centric slot where DL or UL scheduling in few symbols followed by DL or UL data in the rest.
Mini slot where 2, 4 or 7 symbols are used for URLLC type traffic
Blank slot for future use cases
Slot Format Indication (SFI) is used to indicate details of the slot (DCI/RRC is used to convey)