5G • 5G-Advanced (Rel-18)
Coherent Joint Transmission (CJT)
Rel-18 Multi-TRP Coherent Distributed Massive MIMO
Transmits data phase-coherently from multiple geographically separated base station panels (TRPs), boosting cell-edge SINR by up to 10 dB.
Technical Explanation
While Rel-16/17 supported Non-Coherent Joint Transmission (NC-JT), Rel-18 standardizes Coherent Joint Transmission (CJT). In CJT, multiple distributed Transmission-Reception Points (TRPs) achieve tight sub-nanosecond synchronization and mutual phase alignment, combining RF waveforms constructively at the UE receive antennas to eliminate inter-cell interference.
Key Functions
- Combines RF waveforms constructively in space from geographically distributed radio panels
- Eliminates cell-edge interference by turning interfering towers into cooperating transmitters
- Boosts cell-edge spectral efficiency and 5th-percentile data rates by 8 to 10 dB
- Requires sub-nanosecond over-the-air time synchronization and phase calibration over Fronthaul
Specifications
3GPP TR 38.859, TS 38.214 (Rel-18)
Interfaces
UuF1-C/UeCPRI (Fronthaul)
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