In LTE/5G, before a UE can send any uplink data, it needs permission from the network — that’s the Uplink (UL) Grant.
- Sent by the gNB/eNB via DCI on the PDCCH
- Tells the UE exactly: which resource blocks, what MCS, how much power, and when to transmit
- Without it, the UE simply can’t transmit on PUSCH
Think of it as air traffic control for the uplink — no takeoff without clearance.
Two flavors worth knowing:
Dynamic Grant — allocated per transmission, most flexible
Configured Grant (Grant-Free) — pre-allocated resources, cuts latency for URLLC use cases
Small signaling detail, huge impact on network efficiency and latency. 
Why is UL Grant needed?
MSG2 (RAR) MAC PDU Structure
UL Grant field breakdown (27 bits)
UE Processing Flow
Time-frequency resource mapping (MSG3 on PUSCH)
Practical example
Key takeaways
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