5G • 5G-Advanced (Rel-18)
Unified TCI Framework
Common Transmission Configuration Indicator for Downlink and Uplink
Unified beam indication signaling framework where a single TCI state dynamically controls both Downlink (PDSCH/PDCCH) and Uplink (PUSCH/PUCCH) beams.
Technical Explanation
In earlier 5G releases, downlink beam indication (via TCI) and uplink beam indication (via Spatial Relation Info) were separate, protocol-heavy mechanisms requiring separate MAC CE and RRC commands. Release 18 unifies them: a single 'Unified TCI' state indicated in DCI immediately configures both downlink receive beams and uplink transmit beams across the UE.
Key Functions
- Replaces disconnected DL TCI and UL Spatial Relation Info with a single unified framework
- Reduces beam switching latency from tens of milliseconds to sub-frame DCI speeds
- Drastically decreases over-the-air RRC and MAC CE beam management signaling overhead
- Supports common beam indication or joint/separate DL-UL beam configurations
Specifications
3GPP TS 38.214, TS 38.331 (Rel-18)
Interfaces
Uu (DCI)MAC CE
Related 5G Concepts
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