5G • RAN
Layer Indicator (LI)
MIMO Layer Indicator
CSI reporting parameter identifying which spatial layer experiences the strongest SNR for phase noise tracking.
Technical Explanation
Introduced in 5G NR for multi-layer MIMO, the Layer Indicator (LI) identifies which spatial transmission layer possesses the highest channel gain. When Phase Tracking Reference Signals (PT-RS) are enabled, the gNodeB maps PT-RS to the specific antenna port indicated by the LI to optimize phase noise compensation.
Key Functions
- Identifies the strongest spatial MIMO layer for phase tracking
- Directs PT-RS mapping to optimal antenna port in multi-layer MIMO
- Reported alongside RI, PMI, and CQI in CSI reports
Specifications
3GPP TS 38.214
Interfaces
Uu
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