Configured grant vs dynamic grant

Dynamic Scheduling and Its Latency Cost

In the default dynamic scheduling mode, every uplink transmission requires an explicit grant from the gNB. The UE first sends a Scheduling Request on PUCCH to signal that it has data waiting. The gNB processes the request and responds with a DCI uplink grant on PDCCH. Only then can the UE transmit its data on PUSCH using the allocated resources. This SR-to-grant cycle provides maximum scheduling flexibility because the gNB can optimize resource allocation in real time, but it introduces two to ten milliseconds of additional latency depending on SR periodicity and processing time.