Open fronthaul (7.2x split)

User and Control Planes

The open fronthaul interface between O-DU and O-RU uses the 7.2x functional split, defining four planes. The U-Plane (User Plane) carries IQ sample data — in downlink, O-DU sends frequency-domain samples after coding and modulation, while O-RU performs iFFT, cyclic prefix insertion, beamforming, and digital-to-analog conversion. In uplink the flow reverses. The C-Plane (Control Plane) carries scheduling and beamforming commands from O-DU to O-RU, including PRB allocations, beamforming weights, and timing advance values for each slot.