For Ultra-Reliable Low Latency Communication (URLLC) 5G provides two mechanisms:
- preemptive scheduling,
- minislots.
Normally for a channel, one slot could be assigned starting from a specific point in time and in regular intervals. Such slots consist of 7 OFDM symbols and are scheduled in advance of the transmission. This is not fine for URLLC communication.
Waiting with data for the next scheduling phase could lead to unacceptable delays. To resolve that it was agreed that every slot could be interrupted with high priority data at any given moment. The receivers for normal and high-priority data will get information about that afterward. This is called preemptive scheduling.
To achieve more flexibility slots for URLLC data are usually smaller than normal ones. They could be 2,4 or 7 OFDM symbols long. Thanks to such minislots only one normal slot could be corrupted and dropped by the receiver.
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