5G • Spectrum
CSI-RS
Channel State Information Reference Signal
Downlink reference signals used by the UE to measure radio channel quality and report feedback (CQI, PMI, RI, CRI) to the gNodeB.
Technical Explanation
CSI-RS signals are transmitted by the gNodeB to facilitate multi-antenna channel estimation and beam management. The UE measures CSI-RS and feeds back Channel State Information to the gNodeB, including Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), Rank Indicator (RI), and CSI-RS Resource Indicator (CRI) for beam selection. CSI-RS is also configured for Layer 1 RSRP beam reporting, mobility measurements, and beam failure recovery.
Key Functions
- Precise estimation of DL channel matrix for Massive MIMO precoding
- Adaptive Modulation and Coding (AMC) link adaptation feedback (CQI)
- Fine beam management and tracking for UE mobility
- Beam failure detection and candidate beam identification
Specifications
3GPP TS 38.211, TS 38.214
Interfaces
Uu Physical Layer
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