5G • RAN
SFI
Slot Format Indicator
Dynamic control signal carried by DCI Format 2_0 indicating symbol-by-symbol transmission direction in TDD.
Technical Explanation
The Slot Format Indicator (SFI) is broadcast to a group of UEs using DCI Format 2_0 scrambled with SFI-RNTI. It dynamically signals the direction of each OFDM symbol across one or multiple slots as Downlink (D), Uplink (U), or Flexible (F). This allows real-time adaptation of TDD link direction to match fluctuating traffic demands.
Key Functions
- Dynamically assigns symbols as Downlink, Uplink, or Flexible
- Broadcasts slot format tables via DCI Format 2_0 using SFI-RNTI
- Allows instantaneous adaptation to asymmetric DL/UL traffic bursts
Specifications
3GPP TS 38.213
Interfaces
Uu
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