Slot based scheduling:
In LTE if a sub frame is configured for DL or UL then all the symbols will be for DL or UL.
But in 5G NR, the symbols inside a slot can be used for UL or DL depending upon the slot format.
In 5G, there is no need to use all the symbols inside a slot.
A single slot can be divided in such a way that it can transmit DL, UL or Flexible (F).
Since we can have multiple combination of such combination, 3GPP has defined 61 pre-defined combination.
Below table has been taken from TS 38.213 Table 11.1.1-1
The reson behind these combination is to provide different types of scheduling.
For example:
“format 28” can be used for DL heavy scheduling with UL control.
“format 34” can be used for UL heavy scheduling with DL control.
“format 0” can be used for DL-heavy transmission for eMBB with slot aggregation.
“format 1” can be used for UL-heavy transmission for eMBB with slot aggregation.
Slot aggregation means, the transmission can be spanned to two or more slots inorder to achieve traffic requirements.
Mini slot scheduling:
WKT a slot will have 14 OFDM symbols. This enables slot based scheduling.
A mini slot occupies 2, 4, or 7 OFDM symbols.
With this a user can be allocated with mini slot that is less than 14 symbols.
They can be placed asynchronously rather than the beginning of a standard slot. This is used where we need to achieve very low latency. Cannot be used for eMBB, can be used for URLLC.