5G • 5G-Advanced (Rel-18)
Early Data Transmission (EDT)
Rel-18 Small Data Transmission in RRC Inactive Mode
Allows IoT devices to transmit small data payloads directly in Message 3 or MsgA during random access, without transitioning to full RRC Connected state.
Technical Explanation
Transitioning from RRC Inactive to RRC Connected requires dozens of signaling messages, consuming more battery power than transmitting the actual sensor data. Rel-18 EDT / Small Data Transmission (SDT) allows an eRedCap device to attach its sensor payload directly to the PRACH random access message, receiving an acknowledgment and returning to sleep in under 20 ms.
Key Functions
- Transmits sensor telemetry payloads directly within initial random access messages
- Eliminates complete RRC Connected state transition signaling overhead
- Reduces over-the-air communication duration from 150 ms down to under 20 ms
- Saves over 70% of energy consumed per sensor data reporting transaction
Specifications
3GPP TS 38.300, TS 38.321 (Rel-18)
Interfaces
Uu (PRACH / Msg3 / MsgA)
Related 5G Concepts
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