How Can We Achieve Low Latency for URLLC Use Cases?


URLLC use cases can have very stringent latency requirements, as low as 5 ms for end-to-end latency. Taking into consideration the various factors of the end-to-end network, the budget for the air interface delay can be very tight (for instance, 1 ms or even less). To reach low latency, every and each step of the data delivery has to be optimized. 

The latency components in each step of a downlink (DL) data transmission and the corresponding mechanisms to reduce the latency as below:

The Key techniques in the PHY/MAC layer to reduce the latency: 
• Frequent transmission opportunities that minimize waiting time.
• Flexible/short transmission duration.
• Short UE processing time.
• Short next-generation NodeB (gNB) processing time.
• Grant-free (or configured grant) UL transmission.
• Flexible frame structure for TDD.

Source: 5G Americas