DCI & UCI

Technical Explanation

• DCI (Downlink Control Information): Transmitted by the gNodeB on the PDCCH (Physical Downlink Control Channel). DCI instructs the UE which time-frequency resource blocks to listen to for downlink data (PDSCH) or when and how to transmit uplink data (PUSCH). It also controls power, BWP switching, and beam indication (TCI). • UCI (Uplink Control Information): Transmitted by the UE on PUCCH or multiplexed onto PUSCH. It delivers HARQ ACK/NACK feedback, Channel State Information (CQI, PMI, RI), and Scheduling Requests (SR).

Key Functions

• DCI dynamically schedules resource allocation, modulation, and antenna precoding
• UCI provides real-time channel quality feedback (CSI) and HARQ ACK/NACK responses
• DCI triggers fast BWP (Bandwidth Part) and beam configuration switching
• UCI triggers uplink scheduling requests (SR) when UE has buffer data