As well known, NR is using slot based scheduling which is with 14 OFDM symbols & it’s duration scales with the subcarrier spacing.
But also, in NR we have what is called Type B scheduling “mini-slot”
Interviewer: what is the mini-slot in NR?
Interviewee: it the minimum scheduling unit in 5G with 2, 4, 7 OFDM symbols.
Interviewer: What is the gain of using it?
This provides fast transmission opportunities, for example, URLLC traffic that is not restricted by slot boundaries. Thus, mini-slots provide a viable solution to low-latency transmissions irrespective of sub-carrier spacing.
In the example of resource allocation shown, you can see a Mini-slot of 4 OFDM symbols allocated to URLLC User Equipment: one symbol in red to carry the PDCCH and 3 symbols (orange) for data traffic transmission.
And hence Mini-slot can over-write a longer allocation & also allows multiplexing of MBB and URLLC use cases.
Interviewer: so how the mini-slot is defined?
Mini-slot is defined by:
K –> identifies the slot
S –> identifies the starting symbol relative to the start of the slot
L –> identifies the number of consecutive symbols counting from S